In this preliminary study, we identify two pathways through which invasive dreissenid mussels can transfer microcystin to higher trophic levels: either directly, through consumption by benthivorous fish such as the round goby; or indirectly, through their biodeposits which are an important food source for benthic invertebrates. Our results suggest that dreissenid mussels represent a potentially important benthic pathway for the food web transfer of microcystin. Environ Toxicol Chem © 2013 SETAC

In this study, we took advantages of the supply of naturally contaminated oysters and investigated how the subcellular metal distribution and the metal burden in prey affected the transfer of metals to a marine fish, the grunt Terapon jarbua. The oysters Crassostrea hongkongensis with different contaminated histories were collected and separated into three subcellular fractions (metal-rich granules, cellular debris and a combined fraction of organelles, heat-denatured proteins and metallothionein-like proteins, defined as the trophically available metal, TAM). These purified fractions showed a wide range of metal concentrations and were fed to the fish for a period of 7 days at a daily comparable feeding rate of 3% of fish body weights. After 7 days of exposure, the newly absorbed metals were mainly distributed in the intestine and liver, indicating a significant tissue-specific trophic transfer, especially for Cd and Cu. The trophic transfer factors (TTFs) showed a sequence of cellular debris >TAM > metal-rich granules, suggesting the impact of subcellular distribution in prey on metal bioavailability. However, significant inverse relationships between the TTFs and the metal concentrations in diets were also found in this study, especially for Cd and Zn. The subcellular metal compartmentalization might be less important than the metal concentration in prey influencing the trophic transfer. Our results have important implications for bioavailability and environmental assessment of dietary metals. Environ Toxicol Chem © 2013 SETAC

The bioconcentration factor (BCF) of neutral and weakly polar organic chemicals in fish is modeled using independently calibrated models of chemical partitioning (φ_sys, K_FW), respiratory exchange (k₁, k₂ = k₁/K_FW), and biotransformation (k_M) as BCF = φ_sysK_FW/(1 + k_M/k₂). Existing k₁ models tend to overestimate for chemicals with logK_OW < 3.5, which constituted 30–50% of the examined chemicals. A revised k₁ model covering a wider logK_OW range (0–8.5) is presented k₁ = (5.46 × 10⁻⁶MW + 0.261/K_OW)⁻¹, where MW is the molecular weight. The biotransformation rate constant k_M is modeled using biota internal partitioning and Abraham parameters as reactivity descriptors. The reductionist model was tested using 3 different BCF data sets (EPI, n = 548; Hertfordshire, n = 210; Arnot-Gobas, n = 1855) and compared to 3 state-of-the-art models: (i) the EPI Suite BCFBAF module, (ii) CAESAR, and (iii) the EPI/Arnot mechanistic kinetic model. The reductionist model performed comparably with the alternative models (RMSEs = 0.72–0.77) with only 5 fitting parameters and no training against experimental BCFs. Respiratory elimination and biotransformation dominate the total depuration (i.e., (k₂ + k_M)/k_T ≥ 0.8) for approximately 98% of the data entries, thus validating the reductionist approximation. Mechanistic models exhibit greater insights and sensitivity to biological variation. The present study shows that a streamlined mechanistic model of BCF is possible for assessment purposes. Environ Toxicol Chem © 2013 SETAC

A growth and reproduction test using the nematode Caenorhabditis elegans was recently standardized by the International Organization for Standardization. Performing the ISO 10872 protocol (2010) revealed some drawbacks when applied to soil or soil mixed with complex matrices. We propose some modifications to the current protocol in order to normalize the test conditions. An appropriate range of moisture conditions was determined as a percentage of the water holding capacity (WHC) of the soil. According to our results, C. elegans tests can be performed in the range of 60–100% WHC. To ensure that the modifications of the protocol did not affect the organisms' recovery, extraction ratios for the juveniles were subsequently estimated. The modified protocol was found to be as reliable as the standard one concerning juveniles' recovery (over 80%). The protocol was also applied to several chemicals, to investigate their potential as reference chemicals for soil toxicity tests. Boric acid, copper chloride, and nickel sulfate showed deleterious effects in a concentration-dependent manner for C. elegans' growth and reproduction. Finally, the modified protocol was used to assess C. elegans' growth and reproduction in soil amended with a limed sewage sludge. We conclude that the C. elegans modified protocol is a promising tool for the assessment of soil toxicity as well as that of mixtures with complex matrices. Environ Toxicol Chem © 2013 SETAC

Future shifts in climatic conditions may impact watershed mercury (Hg) dynamics and transport. We apply an ensemble of watershed models to simulate and evaluate the responses of hydrological and total Hg (Hg_T) fluxes from the landscape to the watershed outlet and in-stream Hg_T concentrations to two contrasting climate change projections for a watershed in the southeastern Coastal Plain of the US. Simulations are conducted under stationary atmospheric deposition and land cover conditions to explicitly evaluate the effect of projected precipitation and temperature on watershed Hg export (i.e., the flux of Hg at the watershed outlet). Based on downscaled inputs from two global circulation models that capture extremes of projected wet (CCSM3) and dry (ECHO) conditions for this region, we estimate an approximate 19% decrease in ensemble-averaged mean annual watershed Hg_T fluxes using the ECHO climate change model and an approximate 5% increase in Hg_T fluxes with the CCSM3 model. Ensemble-averaged mean annual ECHO in-stream Hg_T concentrations increased 20%, while those of CCSM3 decreased by 9%, between the baseline and projected simulation periods. Watershed model simulation results using both climate change models suggest that monthly watershed Hg_T fluxes increase during the summer, when projected flow is higher than baseline conditions. Our multiple watershed model approach underscores the uncertainty associated with climate change response projections and their use in climate-change management decisions. Thus, single-model predictions can be misleading, particularly in developmental stages of watershed Hg modeling. Environ Toxicol Chem © 2013 SETAC

The Canadian Council of Ministers of the Environment (CCME) Reference Method for the Canada-Wide Standard (CWS) for Petroleum Hydrocarbons (PHC) in Soil provides chemistry analysis standards and toxicity guidelines for the remediation of contaminated sites. However, these methods can co-extract natural biogenic organic compounds (BOCs) from organic soils, causing false exceedences of toxicity guidelines. This 300-day microcosm experiment used CWS PHC Tier 1 soil extraction and Gas Chromatography Flame Ionization Detector (GC-FID) analysis to develop a new Tier 2 mathematical approach to resolving this problem. Carbon fractions F2 (C10-C16), F3 (C16-C34), F4 (>C34) and sub-fractions F3a (C16-C22) and F3b (C22-C34) were studied in peat and sand spiked once with Federated crude oil. These carbon ranges were also studied in 14 light to heavy crude oils. The F3 range in the clean peat was dominated by F3b, while the crude oils had approximately equal F3a and F3b distributions. F2 was non-detectable in the clean peat but was a significant component in crude oil. The crude oil spiked peat had elevated F2 and F3a distributions. The BOC-adjusted PHC F3 calculation estimated the true PHC concentrations in the spiked peat. The F2:F3b ratio of less than 0.10 indicated PHC absence in the clean peat, and the ratio of greater than or equal to 0.10 indicated PHC presence in the spiked peat and sand. Validation studies are required to confirm if this new Tier 2 approach is applicable to real case scenarios. Potential adoption of this approach could minimize unnecessary ecological disruptions of thousands of peatlands throughout Canada, while also saving millions of dollars in remediation costs. Environ Toxicol Chem © 2013 SETAC

On December 22, 2008 a dike containing coal fly ash from the Tennessee Valley Authority Kingston Fossil Plant failed and resulted in the largest coal ash spill in U.S. history. This study was designed to determine sediment metal concentrations at multiple site locations and to determine if site-specific bioaccumulation of metals existed in tetragnathid spiders. Selenium and nickel were the only two metals to exceed the EPA sediment screening levels. Selenium concentrations in spiders were significantly higher at ash-affected sites than those from reference sites. The ratio of methyl to total mercury found in spiders was found to be similar to other organisms (65–75%) and highlight the potential use of tetragnathid spiders an indicator species for tracing contaminant transfer between the aquatic and terrestrial ecosystem. Environ Toxicol Chem © 2013 SETAC

The biomagnification potential as well as the substance and tissue specific distribution of perfluoroalkyl substances (PFASs) in market-size rainbow trout (Oncorhynchus mykiss) was investigated. Rainbow trout with an average body weight of 314 ± 21 g were exposed to perfluorobutane sulfonate (PFBS), perfluorohexane sulfonate (PFHxS), perfluorooctane sulfonate (PFOS), perfluorooctanoic acid (PFOA), and perfluorononanoic acid (PFNA) in the diet for 28 d. The accumulation phase was followed by a 28-d depuration phase, in which the test animals were fed with non-spiked trout feed. On days 0, 7, 14, 28, 31, 35, 42, and 56 of the study, fish were sampled from the test basin for PFAS analysis. Biomagnification factors (BMF) for all test compounds were determined based on a kinetic approach. Distribution factors were calculated for each test compound to illustrate the disposition of PFASs in rainbow trout after 28 d of exposure. Dietary exposure of market-size rainbow trout to PFASs did not result in biomagnification; BMF values were calculated as 0.42 for PFOS; > 0.23 for PFNA; > 0.18 for PFHxS; > 0.04 for PFOA; and > 0.02 for PFBS, which are below the biomagnification threshold of 1. Liver, blood, kidney and skin were identified as the main target tissues for PFASs in market-size rainbow trout. Evidence was shown that despite relative low PFAS contamination, the edible parts of the fish; the filet and skin, can significantly contribute to the whole-body burden. Environ Toxicol Chem © 2013 SETAC

As the production and applications of nano silver (nano Ag) increase, it is essential to characterize fate and effects in environmental systems. Nano Ag materials may settle from suspension, therefore, our objective was to utilize environmentally relevant bioassays and study the impact, bioaccumulation, tissue distribution, uptake and depuration of nano Ag on a sediment-dwelling invertebrate, Lumbriculus variegatus. Hydrodynamic diameters of uncoated 30, 80, 1500 nm nano Ag powders and a polyvinylpyrrolidone (PVP) nano Ag suspension, were measured utilizing dynamic light scattering in freshwater media (0–280 µS/cm). Aggregation for 30, 80, and 1500 nm silver increased with conductivity; however, was minimal for PVP silver. Lumbriculus variegatus were exposed to nano Ag or silver nitrate (AgNO₃) spiked into sediment (nominally 100 mg/kg) and water (PVP 30 and 70 nm Ag, nominally 5 mg/L). Uptake was assessed through inductively coupled plasma mass spectroscopy (ICP-MS) and hyperspectral imaging. Particle sizes were examined through field flow fractionation-ICP-MS (FFF-ICP-MS) and ICP-MS in single particle mode (spICP-MS). Lumbriculus variegatus were also depurated for 6, 8, 24, and 48 hours to determine gut-clearance. Bioaccumulation factors of sediment-exposed L. variegatus were similar regardless of particle size/coatings. The FFF-ICP-MS and spICP-MS detected nano Ag up to 48 hours post depuration. The present study provides information on bioaccumulation and interactions of nano Ag particles within biological systems. Environ Toxicol Chem © 2013 SETAC

It has been suggested that Xenopus laevis is less sensitive to some chemicals than other amphibians and therefore, the Frog Embryo Teratogenesis Assay-Xenopus (FETAX) may have limited use in risk assessments for other amphibians. However, comparisons are mostly based on results of FETAX which emphasizes embryos. Larval X. laevis may be more sensitive to chemicals than embryos and may serve as a better life stage in risk assessments. The present study was conducted to determine the lethal and sublethal effects of three insecticides (malathion, endosulfan, and α-cypermethrin) on X. laevis embryos and larvae, and to compare toxicity of X. laevis to other amphibians. All three insecticides have different modes of action, and they caused mortality, malformations, and growth inhibition in both developmental stages. Compared to embryos, larvae were more sensitive to endosulfan and α-cypermethrin but not malathion. Xenopus laevis larvae had low sensitivity to endosulfan, median sensitivity to malathion, and high sensitivity to α-cypermethrin/cypermethrin relative to other larval amphibians. Our results suggest that X. laevis larvae may generate more protective toxicity estimates in risk assessments than embryos. Xenopus laevis may have limited use in evaluating risk of organochlorine insecticides to other amphibians but may provide useful toxicity thresholds for pyrethroid and maybe organophosphorus insecticides. Environ Toxicol Chem © 2013 SETAC

Following a 120 hours exposure period to three concentrations of oil dispersions (0.022, 1.8 and 16.5 mg L⁻¹ + controls) generated from a North Sea crude oil, and a subsequent 21 days recovery, mortality and several reproduction endpoints (egg production rates, egg hatching success, fraction of females participating in reproduction) in Calanus finmarchicus were studied. Concentration-dependent mortality was found during exposure, averaging to 6, 3, 15 and 42% for the controls and three exposure levels, respectively. At the start of the recovery period mean egg production rates of surviving females from the highest concentrations were very low, but reproduction subsequently improved. In a four-day single female reproduction test starting 13 days post exposure no significant differences in egg production rates or hatching success between reproducing control and exposed copepods were found. However, a significant lower portion of the surviving females from the highest exposure participated in egg production. The results indicate that although a short-term exposure for oil-polluted water after an oil spill can induce severe mortality and temporarily suspend reproduction, copepods may recover and produce viable offspring soon after cessation of exposure. The results may imply that for C. finmarchicus populations the impact from short term exposure to an oil spill may be predicted from acute mortality and that delayed effects have limited contribution to population decrease. Environ Toxicol Chem © 2013 SETAC

Knowledge about how toxicity changes with temperature is important for determining the size of safety factors used when extrapolating from standard laboratory conditions to variable field scenarios. In this study we evaluated the toxicity of Cu and Cd to the potworm Enchytraeus crypticus at six temperatures in the range of 11–25°C. For both metals, reproductive toxicity decreased approximately 2.5-fold with increasing temperature. This is contrary to what has been found for most other studies. Measurements of the bioavailable fraction of the metals in the soils and the internal metal concentrations in the worms over time showed that the major cause for the change in toxicity with temperature for Cu was the ability of the worms to regulate internal concentration at high temperatures. Uptake of Cd increased with time at all temperatures and with higher rates at high temperatures. Hence, the lower toxicity of Cd is proposed to be due to the E. crypticus being more efficient at immobilising Cd and/or repairing damages at high compared to low temperatures. The study concludes that no consistent relationship between metal toxicity and temperature across species can be made, but that the metabolic dependence of the species in terms of regulating metal uptake, excretion, immobilisation, damage and repair processes will be crucial factors in determining species susceptibility to metals at varying temperatures. Environ Toxicol Chem © 2013 SETAC

Solid phase microextraction (SPME) has often been used to estimate the freely dissolved concentration (C_free) of organic contaminants in sediments. A significant limitation in the application of SPME for C_free measurement is the requirement for attaining equilibrium partition that is often difficult for strongly hydrophobic compounds such as DDT. A method was developed using SPME with stable isotope-labeled analogues as performance reference compounds (PRCs) to measure C_free of DDT and metabolites (DDTs) in marine sediments. Six ¹³C-labeled or deuterated PRCs were impregnated into polydimethylsiloxane (PDMS) fiber before use. Desorption of PRCs from PDMS fibers and absorption of DDTs from sediment were isotropic in a range of sediments evaluated ex situ under well-mixed conditions. When applied to a historically contaminated marine sediment from a Superfund site, the PRC-SPME method yielded C_free values identical to those by a conventional equilibrium SPME approach (Eq-SPME), while the time for mixing was reduced from 9 d to only 9 h. The PRC-SPME method was further evaluated against bioaccumulation of DDTs by Neanthes arenaceodentata in the contaminated sediment with or without amendment of activated carbon or sand. Strong correlations were consistently found between the derived C_free and lipid-normalized tissue residues for DDTs in the worms. Results from the present study clearly demonstrated the feasibility of coupling PRCs with SPME sampling to greatly shorten sampling time, thus affording much improved flexibility in the use of SPME for bioavailability evaluation. Environ Toxicol Chem © 2013 SETAC

The use of pesticides may lead to environmental problems, such as surface water pollution, with a risk for aquatic organisms. In the present study, a typical vineyard river of western Switzerland was first monitored in order to measure discharged loads, identify sources and assess the dynamic of the herbicide glyphosate and its metabolite AMPA. Second, based on river concentrations, an associated environmental risk was calculated, using laboratory tests and ecotoxicity data from the literature. Measured concentrations confirmed the mobility of these molecules with elevated peaks during flood events, up to 4970 ng/L. From April to September 2011, a total load of 7.1 kg was calculated, with 85% coming from vineyards and minor urban sources and 15% from arable crops. Compared with existing literature, this load represents an important fraction (6–12%) of the estimated amount applied, due to the steep vineyard slopes (∼10%). The associated risk of these compounds towards aquatic species was found negligible in our case, as well as for other rivers in Switzerland. A growth stimulation was nevertheless observed for the algae Scenedesmus vacuolatus with low concentrations of glyphosate, which could indicate a risk of perturbation in aquatic ecosystems, such as eutrophication. Combining field and ecotoxicity data allowed to perform a realistic risk assessment for glyphosate and AMPA and should be applied to other pesticide molecules. Environ Toxicol Chem © 2013 SETAC

We compared two spiking methods and evaluated nickel (Ni) partitioning during a series of toxicity tests with eight different freshwater sediments having a range of physico-chemical characteristics. A two-step spiking approach with immediate pH adjustment by addition of NaOH at a 2:1 molar ratio to the spiked Ni was effective in producing consistent pH and other chemical characteristics across a range of Ni spiking levels. When Ni was spiked into sediment having a high acid-volatile sulfide (AVS) and organic matter content, a total equilibration period of at least 10 weeks was needed to stabilize Ni partitioning. However, highest spiking levels evidently exceeded sediment binding capacities; therefore, a 7-d equilibration in toxicity test chambers and 8 volume-additions/day of aerobic overlying water was used to avoid unrealistic Ni partitioning during toxicity testing. The 7-d pre-test equilibration allowed “excess” spiked Ni and other ions from pH adjustment to diffuse from sediment pore water and promoted development of an environmentally relevant, 0.5 to 1-cm oxic/sub-oxic sediment layer in the test chambers. Among the eight different spiked sediments, the logarithm of sediment/pore water distribution coefficient values (log K_d) for Ni during the toxicity tests ranged from 3.5 to 4.5. These K_d values closely match the range of values reported for various field Ni-contaminated sediments, indicating that testing conditions with our spiked sediments were environmentally realistic. Environ Toxicol Chem © 2013 SETAC

We evaluated the chronic toxicity of nickel-spiked freshwater sediments to benthic invertebrates. A two-step spiking procedure (spiking + sediment dilution) and a two-stage equilibration period (10 weeks anaerobic + 1 week aerobic) was used to spike 8 freshwater sediments with wide ranges of acid-volatile sulfide (AVS; 0.94–38 µmol/g) and total organic carbon (TOC; 0.42–10%). Chronic sediment toxicity tests were conducted with 8 invertebrates (Hyalella azteca, Gammarus pseudolimnaeus, Chironomus riparius, Chironomus dilutus, Hexagenia sp., Lumbriculus variegatus, Tubifex tubifex, and Lampsilis siliquoidea) in 2 spiked sediments. Nickel toxicity thresholds estimated from species-sensitivity distributions were 97 µg/g and 752 µg/g (total-recoverable nickel; dry wt. basis) for sediments with low and high concentrations of AVS and TOC, respectively. Sensitive species were tested with 6 additional sediments. Twenty-percent effect concentrations (EC20s) for Hyalella and Gammarus, but not Hexagenia, were consistent with US Environmental Protection Agency benchmarks based on nickel in pore water and in simultaneously extracted metals (SEM) normalized to AVS and TOC. For Hexagenia, sediment EC20s increased at less than an equimolar basis with increased AVS, and toxicity occurred in several sediments with SEM > AVS. We hypothesize that circulation of oxygenated water by Hexagenia led to oxidation of AVS in burrows, creating microenvironments with high nickel exposure. Despite these unexpected results, a strong relationship between Hexagenia EC20s and AVS could provide a basis for conservative site-specific sediment quality guidelines for nickel. Environ Toxicol Chem © 2013 SETAC

In the present study, we investigated the effects of bisphenol A, chlorpyrifos, methylparaben and 2 effluent samples from wastewater treatment plants located in the province of Madrid (Spain) on the mRNA expression of specific genes involved in early development (ESR1, pax6, bmp4 and myf5) and a gene involved in general stress response (hsp70) during Xenopus laevis embryo development. Gene expressions were analyzed after 4, 24 and 96 h of exposure by semi-quantitative RT-PCR. Concentrations ranges of the compounds and dilutions for the samples were selected to cause morphological alterations in embryos after 96 h of exposure. Transcript levels of ESR1, pax6, and hsp70 were differentially altered at early developmental stages with patterns specific to the contaminant and the exposure time. However, further studies are needed to establish transcript levels of specific genes as biomarkers of sublethal effects in an environmental risk assessment framework. Besides, studies including more generic responses, such as genes encoding antioxidant enzymes, together with genes related to embryonic development have to be developed in order to look for a battery of mechanistic endpoints for the evaluation of the chemical exposure at molecular level in a first tier assessment. Environ Toxicol Chem © 2013 SETAC

Use of glyphosate-based herbicides is increasing worldwide. Here we review the available data related to potential impacts of these herbicides on amphibians and conduct a quantitative meta-analysis. Because only a little is known about environmental concentrations of glyphosate in amphibian habitats, and virtually nothing about environmental concentrations of the substances added to the herbicide formulations that mainly contribute to adverse effects, glyphosate levels can only be seen as approximations for contamination with glyphosate-based herbicides. The impact on amphibians depends on the herbicide formulation with different sensitivity of taxa and life-stages. Effects on development of larvae apparently are the most sensitive endpoints to study. As with other contaminants, co-stressors mainly increase adverse effects. If and how glyphosate-based herbicides and other pesticides contribute to amphibian decline is not answerable yet due to missing data on how natural populations are affected. Amphibian risk assessment can only be conducted case-specifically, with consideration of the particular herbicide formulation. We recommend for better monitoring of both amphibian populations and contamination of habitats with glyphosate-based herbicides, not just glyphosate, and we suggest including amphibians in standardized test batteries to study at least dermal administration. Environ Toxicol Chem © 2013 SETAC

Toxic effects of heavy metals on soil microorganisms have been confirmed in a number of laboratory studies. However, most real-field studies do not allow for strong general conclusions due to a range of problems, such as pseudoreplication and confounding factors, which are almost impossible to control for with the most commonly used polluted-vs.-unpolluted or random sampling designs. Effects of metal contamination on soil microbial community traits were measured along two pollution gradients in Southern Poland. Employing an experimental regression design, using two separate gradients, we aimed to control for effects of soil properties and beta-diversity of microbial communities. General microbial activity was measured as soil basal respiration rate (BAS) and substrate-induced respiration (SIR), while microbial functional and structural diversity were analyzed with Community-Level Physiological Profiles (CLPP) and Phospholipid Fatty Acid (PLFA) patterns, respectively. Metal concentrations were normalized to their toxicity and integrated in a Toxicity Index (TI). Microbial activity (BAS and SIR) decreased in both gradients with increasing TI. CLPPs for fungi correlated positively with TI, but no impact of TI on the CLPPs of bacteria was observed. The PLFAs a:15 and i:17 were positively correlated, while 16:1ω9 and 18:2ω9 were negatively correlated with TI. The use of two gradients (Olkusz and Miasteczko Śląskie) allowed us to reveal a clear effect of pollution on general microbial structure and activities, even though we were not able to control completely for all confounding factors. Soil pH, organic matter content and nutrient level appeared to be at least as important as TI in determining microbial community structure and activities. Environ Toxicol Chem © 2013 SETAC

Two factors influencing amphibian population declines are infectious diseases and exposure to anthropogenic contaminants. We examined an emerging fungal pathogen, Batrachochytrium dendrobatidis (Bd), and its interaction with an emerging contaminant, the antimicrobial triclosan. We first conducted, a two x two x four factorial study to examine the interactive impacts of dragonfly predator cues, Bd, and triclosan (0, 10, 100, 1000 µg/L) on Woodhouse's toad (Anaxyrus woodhousii) tadpoles. We measured the lethal and sub-lethal impacts of these stressors on tadpoles over four weeks. All tadpoles in the 100 and 1000 µg/L concentrations of triclosan died within 24 h of exposure, but tadpoles in the low concentration (10 µg/L) survived. Tadpoles exposed to only Bd (no triclosan) exhibited a low survival rate (67.5%) while those exposed to both 10µg/L triclosan and Bd exhibited a high survival rate (91.1%) implying that triclosan inhibits Bd on tadpoles. Bd and predator cue exposure individually increased the developmental rate of the surviving tadpoles but this effect was absent when these factors were combined with triclosan. In a follow-up study we found Bd growth in culture was significantly inhibited at 10 µg/L concentration of triclosan and completely inhibited at 100 µg/L. These findings suggest that interactions among multiple stressors can be complex and require examination in conjunction with one another to evaluate actual impacts to aquatic fauna. Environ Toxicol Chem © 2013 SETAC

We investigated the kinetics of transfer of perfluorooctane sulfonate (PFOS) from water, suspended sediment, and bottom sediment, to a marine benthic fish, the marbled flounder (Pseudopleuronectes yokohamae). Fish were exposed in three treatments to PFOS in combinations of these exposure media for 28 days, and then depurated for 84 days. A major part (37%–66%) of PFOS in the fish was in the carcass (i.e., whole body minus muscle and internal organs). Three first-order-kinetic models that differed in exposure media, i.e., (I) sum of dissolved and particulate phases, and sediment; (II) dissolved phase, particulate phase, and sediment, and (III) dissolved phase only, were fitted to the data assuming common rate constants among the treatments. The uptake efficiency of dissolved PFOS at the respiratory surfaces was estimated to be 3.2% that of oxygen, and the half-life of PFOS in fish whole body 29 to 31 d. The better fit of models (I) and (II) and the values of the estimated uptake rate constants suggested that the PFOS in suspended and bottom sediments, in addition to that dissolved in water, contributed to the observed body burden of the fish. Based on an evaluation of several possible contributing factors to the uptake of PFOS from suspended and bottom sediments, we propose that further investigation is necessary regarding the mechanisms responsible for the uptake. Environ Toxicol Chem © 2013 SETAC

The variability and extent of the intersex condition (oocytes in testes or testis-ova) in fish along an urban gradient, that included major wastewater treatment plant outfalls, was documented in the Grand River, Ontario, Canada. A rapid enumeration of testis-ova method (RETO) was developed and applied that increased the capacity to quantify both intersex prevalence and severity. Male Rainbow Darters (Etheostoma caeruleum) sampled downstream of the first major wastewater outfall (Waterloo) had a significant increase, relative to four upstream reference sites, in the mean proportion of fish with at least one testis-oocyte (t.o.) per lobe of testes (9–20% proportion with ≤ 1 t.o./lobe vs. 32–53% and >1.4 t.o./lobe). A much higher mean incidence of intersex proportion and degree was observed immediately downstream of the second wastewater outfall (Kitchener; 73–100% and 8–70 t.o./lobe) but only 6.3 km downstream of the Kitchener outfall the occurrence of intersex drops to those of the reference sites. In contrast, downstream of a tertiary treated wastewater outfall on a small tributary intersex was similar to reference sites. Estrogenicity, measured using a Yeast Estrogen Screen (YES), followed a similar pattern increasing from 0.81 ± 0.02 ng/L EEq (Guelph), to 4.32 ± 0.07 ng/L (Waterloo), and 16.99 ± 0.40 ng/L (Kitchener) respectively. Female Rainbow Darter downstream of the Kitchener outfall showed significant decreases in gonadosomatic index (GSI) and liver somatic index (LSI), and increases in condition factor (k) relative to corresponding reference sites. The prevalence of intersex and alterations in somatic indices suggest that exposure to municipal wastewater effluent discharges can impact endocrine function, energy use, and energy storage in wild fish. Environ Toxicol Chem © 2013 SETAC

Some aquatic organisms can live in contaminated environment due to their adaptable defense mechanism related to their inducible detoxification and excretion. Recent study showed Glyceraldehyde-3-phosphate dehydrogenase (GAPDH) can modulate different cellular activities including transcription activation and detoxification. In the present study, we report on experiments to test the GAPDH activity of Chironomus riparius towards heavy metals. GAPDH was isolated and purified from Chironomus riparius. The kinetics of the enzyme was measured. The results showed that GAPDH was inhibited by heavy metals including Co²⁺, Cu²⁺, Fe²⁺, Ni²⁺, Pb²⁺, but was activated by zinc ions. The kinetics study of the enzyme showed Vmax of GAPDH increased by 50%. Also the substrate and cofactor affinity increased in the presence of zinc. The GAPDH from Chironomus riparius had maximum activities at pH 8.5 and 37 °C. The protein sequence analysis shows that there are two additional cysteine and histidine residues in the conserved region of GAPDH from Chironomus riparius, which is believed to play an important role in the interactions with heavy metals. The results suggest that exposure to zinc could modulate GAPDH which could be related to response of antioxidant defense to other heavy metals. Environ Toxicol Chem © 2013 SETAC

Belted Kingfishers (Megaceryle alcyon) are predators in many North American aquatic ecosystems, and as such they are prone to bioaccumulation of certain environmental contaminants. In 2002 and 2004, kingfisher eggs collected near the upper Hudson River in New York had elevated concentrations of polychlorinated biphenyls (PCBs), and the kingfisher population in this area was reported to be at risk because of PCB exposure. From 2007 to 2009, we monitored 69 kingfisher nests on the Hudson River to track both nest success and survival of individual nestlings. The study site consisted of two adjacent sections of the Hudson River, one upstream and one downstream of a historic PCB source. We compared models of nest success that differentially incorporated four variables that we deemed most likely to affect reproductive output: 1) river section (upstream vs. downstream of PCB source), 2) year, 3) hatch date, and 4) abandonment by one parent. After ranking models according to Akaike's Information Criterion for small sample sizes it was clear that parental abandonment was the most important of the factors we examined. River section was not an important parameter, and overall nesting success was slightly higher in the PCB contaminated section than in the upstream area. These findings support the conclusion that kingfisher productivity is not adversely impacted by PCB contamination in the Upper Hudson River. Environ Toxicol Chem © 2013 SETAC

The polychaete worm Nereis diversicolor engineers its environment by creating oxygenated burrows in anoxic intertidal sediments. We carried out a laboratory microcosm experiment to test the impact of polychaete burrowing and feeding activity on the lability and methylation of mercury in sediments from the Bay of Fundy, Canada. The concentration of labile inorganic mercury and methylmercury in burrow walls was elevated compared to worm-free sediments. Mucus secretions and organic detritus in worm burrows increased labile mercury concentrations. Worms decreased sulphide concentrations which increased Hg bioavailability to sulphate reducing bacteria and increased methylmercury concentrations in burrow linings. Because the walls of polychaete burrows have a greater interaction with organisms, and the overlying water, the concentrations of mercury and methylmercury they contain is more toxicologically relevant to the base of a coastal food web than bulk samples. We recommend that researchers examining Hg in marine environments account for sediment dwelling invertebrate activity to more fully assess mercury bioavailability. Environ Toxicol Chem © 2013 SETAC

The practical usefulness of biomarkers is limited by the complexity of linking their responses to life-history traits of the organisms (e.g., survival, growth, reproduction) over time. Here we present a first attempt to simultaneously model biomarker responses and survival over time with a toxicokinetic-toxicodynamic approach. Even though more work is clearly needed, the present study provides a novel direction for interpreting biomarker responses and dynamically linking them to life-history traits. Environ Toxicol Chem © 2013 SETAC

Great concern has been raised over the potential impact of environmental contaminants on fish populations that inhabit in the Three Gorge Reservoir (TGR). In the present study, we investigated the endocrine disrupting effects of di-(2-ethylhexyl)-phthalate (DEHP), on the Chinese rare minnow (Gobiocypris rarus), an endemic fish distributing upstream waters in the Yangtze River. Adult rare minnow were exposed to environmentally relevant concentrations of DEHP (0, 3.6, 12.8, 39.4 and 117.6 µg/L) for a 21-d period. Then concentrations of sex hormones in the plasma and relative transcription of various associated genes were measured in the hypothalamic–pituitary–gonadal (HPG) axis and liver of the fish. Exposure to DEHP resulted in greater circulating concentrations of testosterone (T) and lower concentrations of estradiol (E2), which was accompanied by up-regulation of Cyp17 mRNA and down-regulation of Cyp19a mRNA in the gonads of females. In males, increases of T and E2 levels were consistent with up-regulation of Cyp17 and Cyp19a in the gonads. Furthermore, the T/E2 ratio was increased in females but reduced in males. A significant increase in the levels of hepatic vitellogenin (VTG) gene transcription was observed in both females and males. The present study showed that waterborne exposure to DEHP altered plasma sex hormone levels and modulated gene transcription profiles of associated genes in the HPG axis and liver, mostly occurred at higher concentrations (> 39.4 μg/L), which suggest that environmental concentration of DEHP (5.4 μg/L) alone may not likely disturb endocrine system of rare minnow in the Three Gorge Reservoir. Environ Toxicol Chem © 2013 SETAC

A model for whole body in vivo biotransformation of neutral and weakly polar organic chemicals in fish is presented. It considers internal chemical partitioning and uses Abraham solvation parameters as reactivity descriptors. It assumes that only chemicals freely dissolved in the body fluid may bind with enzymes and subsequently undergo biotransformation reactions. Consequently, the whole body biotransformation rate of a chemical is retarded by the extent of its distribution in different biological compartments. Using a randomly generated training set (n = 64), the biotransformation model is found to be: log(HLφ_fish) = 2.2(± 0.3)B − 2.1(± 0.2)V − 0.6(± 0.3) (RMSE = 0.71), where HL is the whole body biotransformation half-life in days, φ_fish is the freely dissolved fraction in body fluid, and B and V are the chemical's H-bond acceptance capacity and molecular volume. Abraham type linear free energy equations were also developed for lipid–water (K_lipidw) and protein–water (K_protw) partition coefficients needed for the computation of φ_fish from independent determinations. These were found to be: (i) logK_lipidw = 0.77E − 1.10S − 0.47A − 3.52B + 3.37V + 0.84 (in L_wat/kg_lipid; n = 248, RMSE = 0.57), and (ii) logK_protw = 0.74E − 0.37S − 0.13A − 1.37B + 1.06V − 0.88 (in L_wat/kg_prot; n = 69, RMSE = 0.38), where E, S, and A quantifies dispersive/polarization, dipolar, and H-bond donating interactions, respectively. The biotransformation model performs well in the validation of HL (n = 424, RMSE = 0.71). The predicted rate constants do not exceed the transport limit due to circulatory flow. Furthermore, the model adequately captures variation in biotransformation rate between chemicals with varying logK_OW, B, and V, and exhibits high degree of independence from the choice of training chemicals. This study suggests a new framework for modeling chemical reactivity in biological systems. Environ Toxicol Chem © 2013 SETAC

The applicability of silicone rubber and low density polyethylene (LDPE) as passive sampling materials for target and non-target analyses of moderately polar and non-polar substances was assessed through a field deployment of samplers along a small polluted stream in Oslo (Norway). Silicone and LDPE samplers of identical surface area (but different volumes) were deployed at six sites in the River Alna for 49 days.

Quantitative target analysis by GC-MS (quadrupole, SIM mode) demonstrated that masses of polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs) and organochlorine compounds (OCs) absorbed in the two polymeric materials were consistent with the current understanding of the control and mode of accumulation in these sampler materials. Some deviation was observed for decabromodiphenyl ether (BDE 209) and may be linked to the large molecular size of this substance resulting in lower diffusivity in the LDPE. Target and non-target analyses with gas chromatography coupled to high resolution time-of-flight mass spectrometry (GC- HR ToFMS) allowed the identification of a wide range of chemicals including organophosphate compounds (OPCs) and musk compounds (galaxolide and tonalid). Semi-quantitative analysis revealed enhanced quantities of the OPCs in silicone material indicating some limitation in the absorption and diffusion of these substances in LDPE. Overall, silicone enables non-target screening analysis for compounds with a wider range of logK_ow values than what can be achieved with LDPE. Environ Toxicol Chem © 2013 SETAC

This study intended to assess the influence of salinity on the effects of copper on two life-stages of Pelophylax perezi. Single and combined effects of salinity (NaCl) and copper on survival, malformations, body length, and biochemical markers (catalase-CAT, cholinesterases-ChE, lactate dehidrogenase-LDH, and glutathione S-transferase-GST) of individuals were evaluated in a multifactorial design. Two experiments were performed, one with embryos and the other with tadpoles. Each of these life stages were exposed to individual and combinations of copper (0.0–7.4 mg/L; 0.0–2.4 mg/L, respectively) and NaCl (0.0–10.2 g/L; 0.0–7.4 g/L, respectively) concentrations. Copper alone exerted a higher lethal toxicity to tadpoles (90%; 2.4 mg/L) than to embryos (65%; 7.4 mg/L). Conversely, NaCl alone exerted a higher lethal toxicity to embryos (100%; 6.9 g/L) than to tadpoles (50%; 7.4 g/L). The four lowest tested NaCl concentrations decreased the lethal effects of copper to embryos and the incidence of malformations, but the same outcome was not observed on tadpoles. Regarding enzymatic activities, though significant interaction, between copper and NaCl, were observed for the activity of CAT and LDH in embryo and tadpole, a consistent pattern on NaCl and copper interactive effects was not observed. Obtained results suggest a life-stage dependency on the effects caused by exposure to the individual chemicals or its combination. Also, it was observed that moderate salinity may have a shield effect against copper lethal toxicity for embryos of P. perezi. These results highlight the need, within ecological risk evaluations, to characterize the sensitivity of amphibian different life stages to individual chemicals but also their combination with other environmental conditions resulting from climate changes. Environ Toxicol Chem © 2013 SETAC

Bio-equivalents (bio-EQs, e.g., 17β-estradiol or dioxin equivalents) are commonly employed to quantify the in vitro effects of complex human or environmental samples. However, there is no generally accepted data analysis strategy for estimating and reporting bio-EQs. Therefore, the aims of the present study are to (I) identify common mathematical models for the derivation of bio-EQs from the literature, (II) assess the ability of those models to correctly predict bio-EQs, and (III) propose measures to reduce uncertainty in their calculation and reporting.

We compiled a database of 234 publications that report bio-EQs. From that, we extracted 3 data analysis strategies commonly used to estimate bio-EQs. These models are based on linear or nonlinear interpolation, and the comparison of effect concentrations (EC_x). To assess their accuracy, we employed simulated data sets in different scenarios. The results indicate that all models lead to a considerable misestimation of bio-EQs if certain mathematical assumptions (e.g., goodness of fit, parallelism of dose-response curves) are violated. However, nonlinear interpolation is most suitable to predict bio-EQs from single point estimates.

Regardless the model, subsequent linear extrapolation of bio-EQs generates additional inaccuracy if the prerequisite of parallel dose-response curves is not met. Taken together, our evaluation indicates that data analysis introduces a considerable uncertainty in the derived bio-EQs. To improve accuracy and transparency of bio-EQs, we propose a novel data analysis strategy and a checklist on reporting Minimum Information about Bio-equivalent ESTimates (MIBEST). Environ Toxicol Chem © 2013 SETAC

Metal toxicity is usually determined at a fixed time point, which may bias the assessment of risks associated with varied exposure time. Time-dependent accumulation and toxicity of nickel in the potworm Enchytraeus crypticus were investigated in solutions embedded in an inert quartz sand matrix. Internal Ni concentration and mortality were determined at seven different time intervals and interpreted from the perspective of toxicokinetics and toxicodynamics. A one-compartment model was used to describe the uptake and elimination kinetics of Ni. At each exposure concentration, Ni concentration in the organisms increased with increasing exposure time, reaching equilibrium after approximately 14 d. Median lethal concentration (LC50) decreased with time and reached an ultimate value of 0.182 mg/L. LC50 values expressed as internal Ni concentrations (LC50inter) were almost constant (16.7 mg/kg body dry weight) at each exposure time. The LC50inter was independent of exposure time, suggesting that internal concentration was a better indicator of Ni toxicity than external concentration. Uptake rate constant was 11.9 L/kg/d and elimination rate constants were 0.325 per day (based on internal concentration) and 0.070 per day (based on survival), indicating not all internal Ni contributes to toxicity. The present study highlights the importance of taking time into account in future toxicity testing and risk assessment practices. Environ Toxicol Chem © 2013 SETAC

Management decisions aimed at protecting aquatic resources following accidental chemical spills into rivers and coastal estuaries require estimates of toxic thresholds derived from realistic spill conditions: acute pulse exposures of short duration (h), information which is often unavailable. Most existing toxicity data (LC50 or EC50) come from tests performed under constant exposure concentrations and exposure durations in the 24–96 h range, conditions not typical of most chemical spills. Short-exposure hazard concentration estimates were derived for selected chemicals using empirical toxicity data. Chemical-specific fifth (5^th) percentile Hazard Concentrations (HC5) of species sensitivity distributions (SSD) from individual exposure durations (6–96 h) were derived via bootstrap re-sampling, and plotted against their original exposure durations to estimate HC5s and 95% confidence intervals (95%CIs) at shorter exposures (1, 2, 4 h). This approach allowed the development of short-exposure HC5s for 12 chemicals. Model verification showed an agreement between observed and estimated short-exposure HC5s (r² adj. = 0.95, p < 0.0001), and comparison of estimated short-exposure HC5s with empirical toxicity data indicated generally conservative hazard estimates. This approach applied to two real spill incidents indicated hazard estimates above expected environmental concentrations (acrylonitrile), and suggested that environmental concentrations likely exceeded short-exposure hazard estimates (furfural). While estimates generated through this approach were likely overprotective, these were derived from environmentally realistic exposure durations providing risk-assessors a tool to manage field decisions. Environ Toxicol Chem © 2013 SETAC

Gamma aminobutyric acid (GABA) and GABA receptors play an important role in neuroendocrine regulation in fish. Disruption of the GABAergic system by environmental contaminants could interfere with normal regulation of the hypothalamic pituitary gonadal axis, leading to impaired fish reproduction. The present study used a 21 d fathead minnow (Pimephales promelas) reproduction assay to investigate the reproductive toxicity of fipronil (FIP), a broad-spectrum phenylpyrazole insecticide that acts as a non-competitive blocker of GABA receptor-gated chloride channels. Continuous exposure to up to 5 µg FIP/L had no significant effect on most of the endpoints measured, including fecundity, secondary sexual characteristics, plasma steroid and vitellogenin concentrations, ex vivo steroid production, and targeted gene expression in gonads or brain. The gonad mass, gonadosomatic index, and histological stage of the gonad were all significantly different in females exposed to 0.5 µg FIP/L compared to those exposed to 5.0 µg FIP/L; however, there were no other significant effects on these measurements in the controls or any of the other treatments, in either males and females. Overall, our results do not support a hypothesized adverse outcome pathway linking FIP antagonism of the GABA receptor(s) to reproductive impairment in fish. Environ Toxicol Chem © 2013 SETAC

Six freshwater species (Chlorella sp., Lemna aequinoctialis, Amerianna cumingi, Hydra viridissima, Moinodaphnia macleayi and Mogurnda mogurnda) were exposed to 4, 8 & 24-h Mg pulses in natural creek water. Mg toxicity to all species increased with exposure duration, however, the extent of increase and the nature of the relationship differed greatly between species. Based on IC50s, and comparing to continuous exposure data from a previous study, the increase in toxicity with increasing exposure duration from 4-h to continuous (72 h to 144 h) ranged from ∼two-fold for Chlorella sp. and H. viridissima to >40-fold for A. cumingi. Moreover, the form of the relationship between Mg toxicity and duration ranged from linear or near-linear to exponential for different species. The life-stage at which M. macleayi was exposed was important with cladocerans pulsed at the onset of reproductive maturity being ∼4 × more sensitive (based on IC50s) than <6 h old neonates. Species sensitivity distributions were constructed for the 4, 8 and 24-h pulse durations, from which 99% species protection guideline values (95% CLs) of 94 (6.4–1360) mg/L, 14 (0.5–384) mg/L and 8.0 (0.5–144) mg/L Mg, respectively, were derived. These values were plotted against exposure duration (h) and polynomial interpolation used to derive a guideline value for any pulse duration within the range assessed. Environ. Toxicol. Chem. © 2013 SETAC

Bisphenol A (BPA) and nonylphenol (NP) are well-known endocrine-disrupting chemicals (EDCs) ubiquitous in the aquatic environment, and present an ecotoxicological risk for the health of aquatic organisms. Limited attention has been given to the immunotoxicity of these chemicals. The present study revealed a concentration-dependent increase of reactive oxygen species content and an induced expression of redox-sensitive transcription factors in zebrafish embryos after exposure to various concentrations of BPA, NP and BPA/NP mixture for 4 to 168 hours post fertilization. Transcription of genes related to immune response, including IFNγ, IL1β, IL10, Mx, TNFα, CC-chemokine and CXCL-clc, were significantly up-regulated upon exposure to EDCs. A significant induction of concentrations of proinflammatory mediator, nitric oxide, accompanied by an increase in the activity of nitric oxide synthase (NOS) and an upregulation of inducible NOS gene expression, was detected in zebrafish embryos upon exposures to EDCs. To elucidate the potential mechanisms by which BPA and NP activate the innate immune response, expression profiles of genes related to the Toll-like receptors (TLRs) signaling pathway were examined. Expressions of TLR3, TRIF, MyD88, SARM, IRAK4 and TRAF6 were altered upon exposure to EDCs. Our results demonstrated that exposure to BPA and NP significantly affected the expression of genes related to immune response in zebrafish embryos following oxidative stress. Environ. Toxicol. Chem. © 2013 SETAC

The Fish Embryo Test (FET) is a potential animal alternative for the acute fish toxicity (AFT) test. A comprehensive validation program assessed 20 different chemicals to understand intra- and inter-laboratory variability for the FET. The FET had sufficient reproducibility across a range of potencies and modes of action. Here the suitability of the FET as an alternative model is subsequently reviewed by relating FET and acute fish toxicity. A total of 985 FET studies and 1531 AFT studies were summarized. FET-AFT regressions were performed to understand potential relationships based on physical-chemical properties, species choices, duration of exposure, chemical classes, chemical functional uses, and modes of action. The FET-AFT relationships are very robust (slopes near 1.0, intercepts near 0) across 9 orders of magnitude in potency. A recommendation for the predictive regression relationship is based on 96 hr FET and AFT data:

log FET LC₅₀ = (0.989*log Fish LC₅₀) −0.195, n = 72 chemicals, r = 0.95, p < 0.001 (LC₅₀ in mg/L)

A similar, not statistically different, regression was developed for the entire data set (n = 144 chemicals, unreliable studies deleted). FET-AFT regressions were robust for major chemical classes with suitably large data sets. Furthermore, regressions were similar to that above for large groups of functional chemical categories such as pesticides, surfactants, and industrial organics. Pharmaceutical regressions (n = 8 studies only) were directionally correct. FET-AFT relationships were not quantitatively different from acute fish-acute fish toxicity relationships with the following species: fathead minnow, rainbow trout, bluegill sunfish, Japanese medaka, zebrafish. The Fish Embryo Test is scientifically supportable as a rational animal alternative model for ecotoxicological testing of acute toxicity of chemicals to fish. Environ. Toxicol. Chem. © 2013 SETAC

The present study aimed to quantify the components of a biotic ligand model (BLM) for the effects of Cd on Folsomia candida (Collembola). Assuming that soil pore water is the main route of exposure and to exclude the effects of soil particles on metal availability, animals were exposed for seven days to different Cd concentrations between 0.1 and 100 mM in simplified soil solutions at different Ca concentrations (0.2, 0.8, 3.2, and 12.8 mM) or at different pH (5.0, 6.0, and 7.0). Higher Ca concentrations decreased the toxicity of Cd (adult survival) in test solutions, while toxicity was slightly lower at pH 7 and 6 than at pH 5, suggesting a mitigating effect of Ca and to a lesser extent pH on Cd toxicity to F. candida. Internal Cd concentrations in the animals increased with increasing exposure level but were significantly reduced by increasing Ca concentrations and not significantly affected by pH. Using Langmuir isotherms, binding constants for Cd, Ca, and protons and the fraction of binding sites occupied by Cd were calculated and used to predict effects of Cd on survival. Predicted toxicity showed a good agreement with measured responses when Ca and pH were used as separate factors or combined together. The present study shows indications of protective effects of Ca but less of protons on the toxicity and uptake of Cd in F. candida upon exposure to simplified soil solutions, which can be described using the principles of a biotic ligand model. Environ. Toxicol. Chem. © 2013 SETAC

Many Arctic animals carry high body burdens of organochlorine contaminants (OCs) due to long-range transport of persistent pollutants. It has been shown that seasonal mobilization of body fat in these species results in increased blood concentration of OCs. We investigated OC assimilation, tissue distribution and biotransformation in farmed Arctic fox (Vulpes lagopus) continuously fed a diet containing contaminated minke whale blubber or lard (control) from eight weeks of age in August 2003 until sampling when they were at their fattest (in November 2004) and leanest (in June 2005). Markedly higher tissue (liver, adrenals, brain and blood) OC levels were found in June than in November, despite low exposure to OCs during emaciation, suggesting that OCs had been redistributed from adipose tissues to vital organs. There were no differences in the activities of hepatic biotransforming enzymes between exposed fat and control fat foxes, except for 16α-hydroxylation that was higher in exposed fat foxes. In emaciated foxes, ethoxyresorufin activity was higher in exposed than in control foxes, indicating an enhanced potential for toxicity of OCs with emaciation. Lower activities of 6β- and 2β- hydroxylation were found in lean than in fat foxes, irrespective of OC treatment. The results show that emaciation increase the toxic potential of accumulated OCs and emphasize that body adiposity need to be considered when time-trend analyses, risk assessments and effect studies are designed. Environ. Toxicol. Chem. © 2013 SETAC

Soil leaching has been proposed as a way to reduce soil-spiking artefacts (i.e., increased acidity, metal solubility) that occur in soils amended with trace metal salts. Leaching metal-spiked samples prior to ecotoxicity testing is therefore expected to reduce toxicity, however, leaching not only removes excess amounts of the trace metal being tested, but also reduces the concentrations of cations that could decrease the toxic effects of the metal of interest. To clarify these conflicting processes, the effects of leaching on toxicity and bioaccumulation of Cu, Ca and Al, were investigated using 14-d plant assays conducted on leached and non-leached, Cu-spiked soils. The median inhibitive concentration (EC50) to root elongation ranged from 78 to 589 µg/g. Leaching was found to reduce toxicity by 1.2- to 2.1-fold. The Cu²⁺ activity predicted toxicity better than root or shoot Cu concentrations which were generally not affected by leaching. Plant uptake of Ca increased with increasing Cu dose in non-leached samples, which likely contributed to the hormesis-like response observed in these samples, whereas Ca uptake in the leached samples was more consistent with that of the control except at the largest Cu doses for which Ca uptake decreased. Surprisingly, Al uptake in the most acidic soil was greater in leached than non-leached samples, which may have contributed to the greater toxicity exhibited in this soil than was predicted by Cu²⁺ activity. These findings have implications for predicting trace metal toxicity in nutrient-stressed, acidic soils. Environ. Toxicol. Chem. © 2013 SETAC

In ecotoxicity assessment, the ambient exposure concentration is typically applied to quantify the toxic potential of xenobiotic substances. However, exposure and organism-related differences in bioconcentration often cause a considerable variability of toxicity data. This can be minimized by using the internal organism concentration, because toxicokinetic modifying factors are considered implicitly. In this study, the relationship between ambient and internal concentration-time profiles was investigated for zebrafish (Danio rerio) embryos. The aim was to gain a better understanding and interpretation of exposure based-methods using this model organism. For this purpose, a simple and effective approach to determine the internal concentration was developed. Embryos were exposed to a series of four neutral organic substances (naphthalene, fluorene, fluoranthene, benz[a]anthracene) of different hydrophobicity for 72 hours. The internal and ambient concentrations were measured at eight to nine time points. Kinetics of uptake and elimination were modeled using a first-order one-compartment model. Biotransformation processes appeared to influence the internal concentrations of fluoranthene and benz[a]anthracene after 48 hours. The bioconcentration factors (BCF) obtained are in excellent agreement with those determined in previous studies using radiolabelled substances. The method demonstrated here is a further step towards a refined ecotoxicity assessment using fish embryos, which links toxicity to the chemical concentration within the organism. This system may also be considered as an alternative to animal testing for BCF determination. Environ. Toxicol. Chem. © 2013 SETAC

The occurrence of pharmaceuticals in the environment presents a challenge of growing concern. In contrast to many industrial compounds, pharmaceuticals undergo extensive testing prior to their introduction to the environment. In principal, therefore, it may be possible to employ existing pharmacological safety data using biological “read-across” methods to support screening-level bioaccumulation environmental risk assessment. However, few approaches and robust empirical datasets exist, particularly for comparative pharmacokinetic applications. For many pharmaceuticals, the primary cytochrome P450 (CYP) enzymes responsible for their metabolism have been identified in humans. The purpose of this study was to employ a comparative approach to determine whether rainbow trout biotransform pharmaceuticals known to be substrates for specific human CYPs. Seven compounds were selected based on their primary metabolism in humans by CYP3A4, CYP2D6, or CYP2C9. Five additional test compounds are known to be substrates for multiple CYPs. Metabolism by rainbow trout liver S9 fractions was evaluated using a substrate depletion approach, which provided an estimate of intrinsic hepatic clearance (CL_{IN VITRO,INT}). An isotope dilution liquid chromatography tandem mass spectrometry (LC-MS/MS) method was employed for quantitation of parent chemical concentrations. Only two general CYP substrates demonstrated measureable levels of substrate depletion. No significant biotranformation was observed for known substrates of human CYP2D6, CYP2C9, or CYP3A4. The results of this study provide novel information for therapeutics that fish models are likely to metabolize based on existing mammalian data. Further, these results suggest that pharmaceuticals may possess a greater tendency to bioaccumulate in fish than previously anticipated. Environ. Toxicol. Chem. © 2013 SETAC

Measuring dissolved concentrations of emerging contaminants, such as polybrominated diphenyl ethers (PBDEs) and triclosan, can be challenging due to their physicochemical properties resulting in low aqueous solubilities and association with particles. Passive sampling methods have been applied to assess dissolved concentrations in water and sediments primarily for legacy contaminants. Although the technology is applicable to some emerging contaminants, the use of passive samplers with emerging contaminants is limited. In the present study, the performance of three common passive samplers was evaluated for sampling PBDEs and triclosan. Passive sampling polymers included low density polyethylene (PE) and polyoxymethylene (POM) sheets, and polydimethylsiloxane (PDMS) coated solid phase microextraction (SPME) fibers. Dissolved concentrations were calculated using measured sampler concentrations and laboratory derived partition coefficients. Dissolved tri-, tetra-, and pentabrominated PBDE congeners were detected at several of the study sites at very low pg/L concentrations using PE and POM. Calculated dissolved water concentrations of triclosan ranged from 1.7 to 18 ng/L for POM and 8.8 to 13 ng/L for PE using performance reference compound (PRC) equilibrium adjustments. Concentrations in SPME were not reported due to lack of detectable chemical in the PDMS polymer deployed. Although both PE and POM were found to effectively accumulate emerging contaminants from the water column, further research is needed to determine their utility as passive sampling devices for emerging contaminants. Environ. Toxicol. Chem. © 2013 SETAC

A new toxicity test medium for C. elegans is presented. The test solution is designed so that it provides a better representation of natural soil pore water conditions than currently available test media. The medium has a composition that can readily be modified to allow for studies of the influences of a range of environmentally relevant parameters on nematode biology and toxicology. Tests conducted in the new medium confirmed that nematodes reproduction was possible at a range of solution pHs, offering the potential to conduct toxicity studies under a range of conditions. A test to establish silver nanoparticle and dissolved silver nitrate toxicity, a study type not feasible in M9 or agar media due to precipitation and nanoparticle agglomeration, indicated lower silver nanoparticle (EC₅₀ 6.5 mg Ag/L) than silver nitrate (EC₅₀ 0.28 mg Ag/L) toxicity. Characterisation identified stable nanoparticle behaviour in the new test medium. Environ. Toxicol. Chem. © 2013 SETAC

Nano-CeO₂, when combusted as an additive to diesel fuel, was transformed from 6-14 nm sizes into particles near 43 nm with no obvious change in the unit cell dimensions or crystalline form. Cerium sulfate, if formed during combustion, was below detection limits. Ceria nanoparticles were agglomerated within the soot matrix, with a mean aerodynamic diameter near 100 nm.

The dissolution of cerium from the dried ceria catalyst in synthetic soft water was extremely small (<0.0006% or <0.2 µg Ce/L), with particles being highly agglomerated (<450 nm). Agglomeration was reduced in the presence of humic acid. In the combusted samples, soot was dominant and the solubility of cerium in soft water showed an almost 100-fold increase in the <1 nm fraction over that before combustion. It appeared that the nano-CeO₂ remained agglomerated within the soot matrix and would not be present as dispersed nanoparticles in aquatic or soil environments.

Despite the increased dissolution, the solubility was not sufficient for the combusted ceria to represent a risk in aquatic ecosystems. The predicted environmental concentrations were still orders of magnitude below the predicted no effects concentration of near 1 mg/L. In the soil environment, any cerium released from soot materials would interact with natural colloids decreasing cerium concentrations in soil solutions and further minimising the potential risk to soil organisms. Environ. Toxicol. Chem. © 2013 SETAC

Previous studies showed that caffeine, diphenhydramine, and carbamazepine were bioconcentrated by mosquito fish (Gambusia holbrooki) from the freshwater bodies directly affected by reclaimed water. In order to understand the uptake and depuration as well as bioconcentration factors (BCFs) under the worst-case conditions, 84 mosquito fish were exposed to reclaimed water under static-renewal for 7 days, followed by a 14-day depuration phase in clean water. Characterization of the exposure media revealed the presence of 26 pharmaceuticals while only 5 pharmaceuticals including caffeine, diphenhydramine, diltiazem, carbamazepine, and ibuprofen were present in the organisms after only 5 h of the start of exposure. Caffeine, diltiazem, and carbamazepine were quickly uptaken by mosquito fish following a similar uptake curve. Diphenhydramine and ibuprofen, on the other hand, were more gradually uptaken by mosquito fish but were also eliminated fairly quickly, resulting in the two shortest depuration half-lives at 34 h and 32 h, respectively. For comparison, BCFs based on rate constants (BCF_b), steady-state (BCF_a), and saturation-state (BCF_c) concentrations were calculated. BCF_b ranged from 0.23 to 29 and increased in the order of caffeine < carbamazepine < diltiazem < diphenhydramine < Ibuprofen. BCF_a and BCF_c ranged from 2.0 to 28, and increased in the order of carbamazepine < caffeine < diltiazem < diphenhydramine < Ibuprofen. This is the first study using a non-artificial exposure treated wastewater matrix to generate pharmacokinetic data for pharmaceutical mixtures in aquatic organisms. Environ. Toxicol. Chem. © 2013 SETAC

Some submersed macrophyte species rapidly sorb some insecticides from the water, potentially reducing exposure for aquatic species. However, the rates at which macrophytes remove insecticides can differ widely between plant species. Further, few studies have examined how much macrophytes actually influence insecticide toxicity to sensitive animals. We quantified the ability of several macrophyte species to mitigate insecticide toxicity by comparing survival of the aquatic herbivore, Daphnia magna, following exposure to a factorial combination of three malathion concentrations (0, 3, and 24 µg/L) and seven macrophyte treatments (no macrophytes, four different macrophyte monocultures, and two inert substrates: plastic plants and polypropylene rope). We also quantified the rate that different macrophytes reduced malathion's toxicity by exposing D. magna to water samples collected from each treatment after 2, 8, and 48 h of exposure. We discovered that while 3 and 24 µg/L of malathion decimated D. magna in the no-macrophyte, plastic plant and rope treatments, all four macrophyte species strongly mitigated these effects. When we compared the rate at which malathion's toxicity decreased, we found that all macrophytes negated malathion's toxicity within 2 h, while it took more than 8 h in the absence of macrophytes or in the presence of inert substrates. These results demonstrate that numerous macrophyte species can equally and strongly mitigate insecticide toxicity while inert substrates cannot. © 2013 SETAC

Endocrine disruptors are known to alter endogenous free and/or esterified levels of androgenic and estrogenic steroid hormones in aquatic molluscs. However, there is still a controversy on the origin of steroids in these animals. In this study, free and esterified testosterone concentrations were measured in the hermaphroditic aquatic gastropod Lymnaea stagnalis exposed to molecules known for their androgenic (testosterone and tributyltin), anti-androgenic (cyproterone-acetate) and estrogenic (chlordecone) properties by reference to their mode of action in vertebrates. In parallel, snail oviposition and fecundity were followed over the 21-day exposure period. Testosterone exposure resulted in increased esterified testosterone levels whereas free testosterone concentrations remained stable. In contrast, cyproterone-acetate increased significantly the free form of testosterone with no changes in the esterified form whereas chlordecone showed a tendency to reduce, though not significantly, esterified testosterone concentrations without changes in free testosterone levels. Finally, tributyltin did not alter testosterone homeostasis. The production of egg-clutches and eggs was significantly reduced only in the snails exposed to the highest concentrations of chlordecone (19.6 µg/L) and tributyltin (94.2 ng Sn/L). Overall, this study demonstrates that uptake of testosterone from the exposure medium occurs in L. stagnalis. Moreover, it shows that cyproterone-acetate and, to a lesser extent, chlordecone can alter endogenous testosterone levels in this freshwater snail. However, relationship between hormonal changes and snail reproduction has not been established. © 2013 SETAC

Cadmium (Cd) is one of the most toxic elements. The ideal vegetal cover should be ensured by the selection of appropriate plant species for successful phytoremediation. In the present study, ecotoxicological effects of Cd to three ornamental herbs: Italian ryegrass (Lolium multiflorum Lam.), white clover (Trifolium repens L.) and alfalfa (Medicago sativa L.) were investigated. Based on the inhibition rate of seed germination, root and shoot elongation, early seedling growth, the values of the median inhibition concentration (IC50) and the index of tolerance (IT), ecotoxicological indicators were determined. The results showed that 10–50 µM Cd had little effect on seed germination, root and shoot elongation of the three ornamental herbs (p>0.01). With the increase of Cd concentrations, alfalfa (M. sativa) was the most sensitive to Cd toxicity in terms of seed germination and root elongation. Based on IC50 of root elongation, Italian ryegrass (L. multiflorum) was the least sensitive to Cd. Based on IC50 of seed germination and shoot elongation, white clover had the least sensitivity to Cd. Among the three ornamental herbs, based on IC50 of seed germination, and root and shoot elongation, alfalfa (M. sativa) was all the most sensitive plant. According to the index of tolerance (IT), Italian ryegrass (L. multiflorum) was the most tolerant plant. © 2013 SETAC

Chronic toxicity tests of mixtures of nine metals and one metalloid (As, Cd, Co, Cr, Cu, Mn, Ni, Pb, Tl, and Zn) at equi-toxic concentrations over an increasing concentration range were conducted with the epi-benthic, freshwater amphipod Hyalella azteca. Tests were conducted in 28 day, water-only tests. The bioaccumulation trends changed for eight of the elements in exposures to mixtures of the metals compared to individual metal exposures. The bioaccumulation of Co and Tl were affected the most. These changes may be due to interactions between all the metals as well as interactions with water borne ligands. A metal effects addition model (MEAM) is proposed as a more accurate method to assess the impact of mixtures of metals and to predict chronic mortality. The MEAM uses background corrected body concentration to predict toxicity. This is important since the chemical characteristics of different waters can greatly alter the bioavailability and bioaccumulation of metals. As well, interactions among metals for binding at the site of action within the organism can also affect body concentration. The MEAM accurately predicted toxicity in exposures to mixtures of metals and predicted results were within a factor of 1.1 of the observed data, using 24 h depurated body concentrations. The traditional concentration addition model over estimated toxicity by a factor of 2.7. © 2013 SETAC

One of the main objectives of ecological risk assessment is to evaluate the effects of toxicants on ecologically relevant biological systems such as populations or communities. However, the effects of toxicants are commonly measured on selected sub-individual or individual endpoints due to their specificity against chemical stressors. Introducing these effects into population models is a promising way to predict impacts on populations. Yet currently employed models are very simplistic and their environmental relevance needs to be improved to establish the ecological relevance of hazard assessment. This study with the gastropod Potamopyrgus antipodarum combines a field experimental approach with a modelling framework. It clarifies the role played by seasonal variability of life-history traits in the population's vulnerability to the alteration of individual performance, potentially caused by toxic stress. The study comprised three steps: (i) characterization of the seasonal variability of the life-history traits of a local population over 1 year with in situ experiments on caged snails, coupled with a demographic follow-up, (ii) development of a periodic matrix population model which visualizes the monthly variability of population dynamics, and (iii) simulation of the demographic consequences of an alteration of life-history traits (i.e., fertility, juvenile and adult survival). The results revealed that demographic impacts strongly depend on the season when alterations of individual performance occur. Model analysis showed that this seasonal variability of population vulnerability is strongly related to the phenology of the population. We underline that improving the realism of population models is a major objective for ecological risk assessment, and that taking into account species phenology in modelling approaches should be a priority. © 2013 SETAC

The Dinghushan Biosphere Reserve (DBR) is a global preserve and site for study of tropical/subtropical forest ecosystems. Rapid industrialization and intensive electronic waste recycling activities around the DBR have resulted in elevated levels of industrial organic contaminants in the local environment that may cause adverse effects on wildlife that inhabits this area. In the present study, polychlorinated biphenyls (PCBs), polybrominated diphenyl ethers (PBDEs), and two alternative brominated flame retardants, namely, decabromodiphenyl ethane (DBDPE) and 1,2-bis(2,4,6-tribromophenoxy) ethane (BTBPE), were investigated in the DBR and a reference site by using the kingfisher (Alcedo atthis) as a bioindicator. Residue concentrations in kingfishers from the DBR ranged from 490–3000, 51–420, 0.44–90, and 0.04–0.87 ng/g lipid weight for ∑PCBs, ∑PBDEs, DBDPE, and BTBPE, respectively. With the exception of the BTBPE, these levels were 2–5 times higher than those detected in kingfishers from the reference site. The contaminant patterns from the DBR were also different, with larger PCB contributions in comparison with the reference site. The estimated predator/prey biomagnification factors (BMFs) showed that most of the PCB and PBDE congeners and BTBPE were biomagnified in kingfishers from the DBR. The calculated toxic equivalent quantity (TEQ) concentrations of major coplanar PCB congeners in kingfishers from the DBR ranged from 18 to 66 pg/g wet weight, some of which have reached or exceeded the levels known to impair bird reproduction and survival. Environ Toxicol Chem © 2013 SETAC

Null hypothesis significance testing is one of the most widely used forms of statistical testing in environmental toxicology. In this short communication we show that the reporting of statistical information when using null hypothesis significance testing is frequently inadequate in environmental toxicology research. We demonstrate this by analyzing the statistical information reported for papers employing t-tests or ANOVA in the Environmental Toxicology section of Environmental Toxicology and Chemistry in 2010, which comprised 68% of papers published by this journal in that year. Of these papers, 60% fail to report exact p-values, 85% fail to provide degrees of freedom and 90% of papers fail to report critical effect sizes. Statistical power was only reported in <2% of the published papers. The insufficient provision of statistical information makes interpretation of study results by reviewers and readers difficult. Consistently reporting exact p-values with degrees of freedom, considering and explicitly stating biologically relevant critical effect sizes and reporting statistical power associated with non-significant results would be easy to implement and would promote scientific progress in environmental toxicology through increased statistical transparency. Environ Toxicol Chem © 2013 SETAC

The objectives of the present study were to determine 1) if temporal variability influenced the toxicity of Elkhorn River water and 2) if the toxic effect was consistent between two sentinel organisms, the fathead minnow (Pimephales promelas) and the northern leopard frog (Rana pipiens). During spring 2012, atrazine indicator strips were used to document the occurrence of agrichemical pulses in the Elkhorn River. Polar organic chemical integrative samplers (POCIS) were deployed for 14 d during both a pulse and post-pulse period as indicated by the atrazine strips. Pesticide concentrations detected in the POCIS extracts ranged from 1.6 to 281 fold higher during the pulse period compared to the post-pulse period. Fish and frog bioassays were conducted for 7 d, and hepatic mRNA expression of vitellogenin (Vtg) and estrogen receptor-α (ERα) was determined by quantitative real-time PCR (RT-qPCR). Compared to lab water controls, fish exposed to water collected during an agrichemical pulse experienced significant reductions in Vtg and ERα, whereas exposed female frogs did not. Male leopard frogs, in contrast experienced significant increases in the expression of ERα, whereas pulse exposed male minnows did not. The significant effects observed following agrichemical pulse exposure demonstrate 1) that episodic agrichemical runoff adversely impacts sentinel organisms, and 2) that the adverse impacts observed depends upon the sex and species of the sentinel organism. Environ. Toxicol. Chem. © 2013 SETAC

Models were developed to predict the bioconcentration of well-metabolized chemicals by rainbow trout. The models employ intrinsic clearance data from in vitro studies with liver S9 fractions or isolated hepatocytes to estimate a liver clearance rate which is extrapolated to a whole-body biotransformation rate constant (k_MET). Estimated k_MET values are then used as inputs to a mass-balance bioconcentration prediction model. An updated algorithm based on measured binding values in trout is used to predict unbound chemical fractions in blood, while other model parameters are designed to be representative of small fish typically used in whole-animal bioconcentration testing efforts. Overall model behavior was shown to be strongly dependent on the relative hydrophobicity of the test compound and assumed rate of in vitro activity. The results of a restricted sensitivity analysis highlight critical research needs and provide guidance on the use of in vitro biotransformation data in a tiered approach to bioaccumulation assessment. Environ. Toxicol. Chem. © 2013 SETAC

The assessment of chemicals as bioaccumulative in the regulatory process makes use of the bioconcentration factor as a metric. However, this metric does not account for the dietary uptake route and therefore cannot be applied to terrestrial food chains. In recent years, the biomagnification factor (BMF) and the trophic magnification factor (TMF) have been suggested as standard metrics for bioaccumulation. For regulatory purposes, though, the BMF and the TMF also suffer from a number of shortcomings. They are not applicable to assess uptake routes other than the diet (e.g., dermal uptake, as is important for personal care products). When measured in the field, they depend largely on biological and ecological factors and less so on the chemical's properties, and they are difficult to normalize and standardize. In the present study, the authors suggest the elimination half-life (EL_0.5) of a chemical as an alternative metric for bioaccumulation. The EL_0.5 is equivalent to the depuration rate constant (k₂) that is measured in various bioaccumulation and bioconcentration tests. This metric can be applied to air- and water-breathing animals, and it is valuable for all uptake routes. It has a number of practical advantages over the BMF and the TMF. In combination with a standard uptake scenario, the EL_0.5 can also be linked directly to a BMF threshold of unity. Thus, the EL_0.5 as a bioaccumulation metric overcomes the shortcomings of the BMF and the TMF while still conserving the advantages of the latter metrics. Environ Toxicol Chem 2013;32:xxx–xxx. © 2013 SETAC

Fungicide application rates on row crop agriculture have increased across the United States, and subsequently, contamination of adjacent wetlands can occur through spray drift or field runoff. To investigate fungicide toxicity, Hyalella azteca amphipods were exposed to 2 fungicide formulations, Headline and Stratego, and their active strobilurin ingredients, pyraclostrobin and trifloxystrobin. Water-only exposures resulted in similar median lethal concentration (LC50; 20–25 µg/L) values for formulations and strobilurin ingredients, suggesting that toxicity is due to strobilurin ingredients. These values were below concentrations that could occur following spray drift over embedded cropland wetlands. When fungicides were added to overlying water of sediment-water microcosms, toxicity was reduced by 500% for Headline and 160% for Stratego, compared with water-only exposures, based on the total amount of fungicide added to the systems. In addition, when fungicides were added to sediment prior to the addition of water, the reduction in toxicity was even greater, with no toxicity occurring at environmentally relevant levels. Differences in toxicity among exposure groups were explained by dissipation from water as toxicity values based on measured water concentrations were within 20% between all systems. The present study reinforces previous studies that Headline and Stratego are toxic to nontarget aquatic organisms. However, the presence of sediment is likely to ameliorate some toxicity of fungicide formulations, especially if spraying occurs prior to wetland inundation. Environ Toxicol Chem 2013;32:xx–xx. © 2013 SETAC

Concentrations of copper (Cu), zinc (Zn), cadmium (Cd), lead (Pb), mercury (Hg), and selenium (Se) were determined in blood and feathers of spectacled (Procellaria conspicillata) and white-chinned (Procellaria aequinoctialis) petrels, species that are phylogenetically related, but with distinct ecological niches. In winter, they feed on similar foods, indicated by an overlapping range of whole-blood stable isotopes values (δ¹⁵N; δ¹³C). No relation was found between blood metal concentration and stable isotope values. In spectacled petrels, metal concentrations appeared lower in blood (Cu = 0.79–20.77 µg/g; Zn = 10.95–28.02 µg/g; Cd = 1.73–10.11 µg/g; Pb = 5.02–26.03 µg/g; Hg = 0.84–9.86 µg/g) than in feathers (Cu = 1.05–21.57 µg/g; Zn = 45.30–81.49 µg/g; Cd = 3.76–10.44 µg/g; Pb = 16.53–59.00 µg/g; Hg = 4.24–24.03 µg/g). In white-chinned petrels, metal concentrations also appeared lower in blood (Cu = 0.62–10.4 µg/g; Zn = 10.73–24.69 µg/g; Cd = 2.00–6.31 µg/g; Pb = 5.72–24.03 µg/g) than in feathers (Cu = 2.68–23.92 µg/g; Zn = 48.96–93.54 µg/g; Cd = 5.72–24.03 µg/g; Pb = 18.62–55.51 µg/g), except for Hg (blood = 0.20–15.82 µg/g; feathers = 0.19–8.91 µg/g). Selenium (0.24–14.18 µg/g) and Hg (0.22–1.44 µg/g) concentrations showed a positive correlation in growing feathers of spectacled petrels. Blood and feather Hg levels were higher in spectacled petrels while feathers Cu and Zn concentrations were greater in white-chinned petrels. Juvenile white-chinned petrels exhibited greater blood Hg concentrations than adults. In the south Atlantic Ocean, discards from commercial fishing operations consumed by spectacled petrels year-round and by white-chinned petrels during the wintering period have elevated Hg concentrations. Because Hg toxicity is associated with behavioral and reproductive changes in birds, it could potentially have impacts on breeding of these seabirds, as both species are listed as threatened by extinction. Environ Toxicol Chem 2013;32:XX–XX. © 2013 SETAC

Polybrominated diphenyl ethers (PBDEs), a class of flame retardants, are bioaccumulative toxins that can biomagnify in food webs. However, little is known about the toxicokinetics of total and congener-specific BDEs in lower vertebrates. The authors exposed northern leopard frog (Lithobates (Rana) pipiens) tadpoles to diets containing DE-71 (a pentabromodiphenyl ether mixture (0 ng/g as control, 71.4 ng/g, and 634 DE-71 ng/g wet mass)) for 50 d, followed by a period of depuration during which they were fed only undosed (control) food. After 28 d, tadpoles eliminated over 94% of the ΣPBDEs from their tissues (t_½ = 5.9 ± 1.9 d) with no significant differences in elimination rates for the predominant congeners. Elimination of BDE-99 was independent of dose, indicating first-order kinetics. It did not fit a biexponential model significantly better than a monoexponential model, indicating single-compartment elimination. To compare developmental life-stage kinetics following larval exposure, the authors collected individuals at the beginning and end of metamorphosis and at 70 d postmetamorphosis. During metamorphosis, total-body residues per individual did not significantly change, implying little to no elimination. After 70 d, juvenile frogs eliminated 89.7% of the ΣPBDEs from their tissues, and BDE-47 was eliminated at a faster rate (t_½= 17.3 d) than BDE-99 and BDE-100 (t_½ = 63.0 d and 69.3 d, respectively). Because the kinetics of PBDEs in L. pipiens differed among life stages, developmental life stage—especially for species that undergo metamorphosis—should be considered when determining the toxicity of persistent organic pollutants. Environ Toxicol Chem 2013;9999:XX–XX. © 2013 SETAC

Amendment of activated carbon to sediments has been shown to effectively reduce the bioavailability of hydrophobic organic contaminants, but concerns have been raised about the potential toxicological impacts of administering a strong sorbent into sediments. The present study provides a summary of several investigations carried out as part of a pilot-scale study in a river to understand the secondary effects of activated carbon added to reduce the bioavailability of sediment-associated polychlorinated biphenyls. While some previous laboratory amendment studies have found reduced lipid content in freshwater worms exposed to activated carbon-treated sediments, the authors did not observe an impact with fine-granular activated carbon-amended sediments aged in the field. Benthic community studies did not find differences between control and activated carbon-treated field sites over 3 yr of postapplication monitoring. Laboratory studies with submerged aquatic plants indicated reduced growth in sediments amended with ≥5% activated carbon, which was attributed to volume dilution of nutritional sediment or bulk density changes and was also observed when the sediment was amended with biochar and inert perlite. Since in situ sorbent amendment is likely to be implemented in depositional sediment environments, potential negative impacts will likely be short-term if the treated site is slowly covered with new sediment over time. Overall suitability of activated carbon amendment for a site will depend on balancing ecosystem and human health benefits from contaminant bioavailability reduction with any potential negative impacts expected under field conditions. Environ Toxicol Chem 2013;32:XX–XX. © 2013 SETAC

The widespread use of silver nanoparticles (AgNPs) raises the potential for environmental releases that could impact microbial ecosystem services. In the present study, the authors address how the AgNPs and Ag⁺ that they release may impact nitrogen-cycling bacteria. The authors studied the cellular and transcriptional response of the denitrifier Pseudomonas stutzeri, the nitrogen fixer Azotobacter vinelandii, and the nitrifier Nitrosomonas europaea exposed to 35 nm (carbon-coated) AgNPs or to Ag⁺ (added as AgNO₃). Based on minimum inhibitory concentrations (MICs), Ag⁺ was 20 times to 48 times more toxic to the tested strains than AgNPs (including Ag⁺ released during exposure). Exposure to sublethal concentrations of AgNPs or Ag⁺ (representing 10% of the respective MIC for AgNO₃) resulted in no significant effect on the expression of the denitrifying genes narG, napB, nirH, and norB in P. stutzeri or the nitrogen-fixing genes nifD, nifH, vnfD, and anfD in A. vinelandii, whereas nitrifying genes (amoA1 and amoC2) in N. europaea were upregulated (2.1- to 3.3-fold). This stimulatory effect disappeared at higher silver concentrations (60% of the Ag⁺ MIC), and toxicity was exerted at concentrations higher than 60% of the Ag⁺ MIC. The MIC for N. europaea was 8 times to 24 times lower than for the other strains, indicating higher susceptibility to AgNPs. This was corroborated by the lower half-lethal concentration for N. europaea (87 µg/L) compared with P. stutzeri (124 µg/L) and A. vinelandii (>250 µg/L) when cells were exposed with Ag⁺ for 24 h in 1 mM bicarbonate buffer. This suggests that ammonia oxidation would be the most vulnerable nitrogen-cycling process in wastewater treatment plants receiving AgNPs and in agricultural soils amended with biosolids that concentrate them. Environ Toxicol Chem 2013;9999:32–XX. © 2013 SETAC

The present study examined the relative importance of copper (aqueous Cu and CuO particles of different sizes) added to sediment to determine the bioaccumulation, toxicokinetics, and effects in the deposit feeder Potamopyrgus antipodarum. In experiment 1, the bioaccumulation of Cu (240 µg Cu/g dry wt of sediment) added as aqueous Cu (CuCl₂), nano- (6 nm, 100 nm), or micro- (<5 µm) CuO particles in adult snails was measured. In experiment 2, a more comprehensive analysis of the toxicokinetics of Cu (aqueous Cu, 6 nm, or 100 nm) was conducted. In experiment 3, the effects of Cu form (aqueous Cu and 6 nm CuO) on juvenile growth and survival at 0, 30, 60, 120, and 240 µg Cu/g dry weight sediment were assessed. Snails took up less of the 5-µm CuO particles than nano-CuO or aqueous Cu. A substantial fraction of Cu taken up was associated with shell, and this was rapidly lost when snails were transferred to clean sediment. Net uptake rates from sediment amended with 6 nm CuO and aqueous Cu were significantly higher (∼40–50%) than from sediment amended with 100 nm CuO. During 2 wk of depuration, there were no significant differences in depuration rates (k_d) among forms (aqueous Cu: k_d = −0.12 wk⁻¹; 6 nm CuO: k_d = −0.22 wk⁻¹; 100 nm CuO: k_d = −0.2 wk⁻¹). Average juvenile growth was reduced by 0.11 mm (41%) at measured exposure concentrations of 127.2 µg Cu/g dry weight sediment for aqueous Cu and 71.9 µg Cu/g dry weight sediment for 6 nm CuO compared with control; however, differences between forms were not statistically significant. Juvenile snails in the highest exposure concentrations (aqueous Cu and 6-nm CuO groups pooled) reduced their growth by 0.18 mm on average (67%) compared with the control group. Although we observed minor differences in toxicity among Cu forms, effects on juvenile snail growth occurred at bulk sediment concentrations lower than those in the Canadian interim sediment quality guidelines. Characterization of the CuO particles showed that particle size distributions of commercially prepared particles deviated substantially from the manufacturers' specifications and highlighted the importance of fully characterizing particles when using them in toxicity tests. Environ Toxicol Chem 2013;32:XX–XX. © 2013 SETAC

Phenanthrenes (Phs) substituted with alkyl groups are a class of compound present in the environment, and they appear to be toxic to developing fish. The present study aimed to investigate the effect of waterborne exposure to two monomethyl derivatives of phenanthrene, 1-methylphenanthrene (1M-Ph) and 4-methylphenanthrene (4M-Ph), on cytochrome P450 1A (CYP1A) gene expression in fish gills and liver. Juvenile common roaches (Rutilus rutilus) were exposed to water with dimethyl sulfoxide (DMSO) solutions of 1M-Ph, 4M-Ph, benzo[a]pyrene (BaP; positive control), each at a dose of 100 µg/L, or to water with DMSO alone (negative control group) for 2 d and 7 d. Significant CYP1A responses with regard to treatment and exposure duration were noted (2-way analysis of variance [ANOVA]) in gills (p = 0.013 and p = 0.003, respectively) and liver (p < 0.001). The 2 monomethyl Phs did not induce consistent gene expression changes, except for 4-MPh, which elevated the CYP1A messenger ribonucleic acid (mRNA) level in the liver at the end of the treatment (almost 4-fold; p < 0.05; 7 d). As was expected, exposure to BaP resulted in elevation of CYP1A mRNA expression in treated fish compared with the control group. Expressions after 2 d and 7 d were approximately 220- and 180-fold higher in liver and 8- and 6-fold higher in gills respectively. The CYP1A protein levels remained stable in both tissues, with one notable exception in roach liver treated for 2 d with BaP (∼ 6-fold increase; p < 0.05). The different effects of the 1- and 4-methylphenanthrenes on CYP1A gene expression in roach liver suggest a relationship between chemical or 3-D structure of the differentially substituted monomethyl Phs and their biological activity. Environ Toxicol Chem 2013;32:XX–XX. © 2013 SETAC

Credible ecological risk assessments often need to include analysis of population-level impacts. In the present study, a predictive model was developed to investigate population dynamics for white sucker (Catostomus commersoni) exposed to pulp mill effluent at a well-studied site in Jackfish Bay, Lake Superior, Canada. The model uniquely combines a Leslie population projection matrix and the logistic equation to translate changes in the fecundity and the age structure of a breeding population of white sucker exposed to pulp mill effluent to alterations in population growth rate. Application of this density-dependent population projection model requires construction of a life table for the organism of interest, a measure of carrying capacity, and an estimation of the effect of stressors on vital rates. A white sucker population existing at carrying capacity and subsequently exposed to pulp mill effluent equivalent to a documented exposure experienced during the period 1988 to 1994 in Jackfish Bay would be expected to exhibit a 34% to 51% annual decrease in recruitment during the first 5 yr of exposure and approach a population size of 71% of carrying capacity. The Jackfish Bay study site contains monitoring data for biochemical endpoints in white sucker, including circulating sex steroid concentrations, that could be combined with population modeling to utilize the model demonstrated at the Jackfish Bay study site for investigation of other white sucker populations at sites that are less data-rich. Environ Toxicol Chem 2013;32:xx–xx. © 2013 SETAC

Five widely used metrics of bioaccumulation in fish are defined and discussed, namely the octanol–water partition coefficient (K_OW), bioconcentration factor (BCF), bioaccumulation factor (BAF), biomagnification factor (BMF), and trophic magnification factor (TMF). Algebraic relationships between these metrics are developed and discussed using conventional expressions for chemical uptake from water and food and first-order losses by respiration, egestion, biotransformation, and growth dilution. Two BCFs may be defined, namely as an equilibrium partition coefficient K_FW or as a nonequilibrium BCF_K in which egestion losses are included. Bioaccumulation factors are shown to be the product of the BCF_K and a novel equilibrium multiplier M containing 2 ratios, namely, the diet-to-water concentration ratio and the ratio of uptake rate constants for respiration and dietary uptake. Biomagnification factors are shown to be proportional to the lipid-normalized ratio of the predator/prey values of BCF_K and the ratio of the equilibrium multipliers. Relationships with TMFs are also discussed. The effects of chemical hydrophobicity, biotransformation, and growth are evaluated by applying the relationships to a range of illustrative chemicals of varying K_OW in a linear 4-trophic-level food web with typical values for uptake and loss rate constants. The roles of respiratory and dietary intakes are demonstrated, and even slow rates of biotransformation and growth can significantly affect bioaccumulation. The BCF_Ks and the values of M can be regarded as the fundamental determinants of bioaccumulation and biomagnification in aquatic food webs. Analyzing data from food webs can be enhanced by plotting logarithmic lipid-normalized concentrations or fugacities as a linear function of trophic level to deduce TMFs. Implications for determining bioaccumulation by laboratory tests for regulatory purposes are discussed. Environ Toxicol Chem 2013;32:XX–XX. © 2013 SETAC

Review of data from several contaminated sediment sites suggested that biota-sediment accumulation factors (BSAFs) declined with increasing contaminant concentrations in the sediment. To evaluate the consistency and possible causes of this behavior, polychlorinated biphenyl (PCB)–contaminated sediment samples from the Hudson, Grasse, and Fox River Superfund sites were used in sediment bioaccumulation tests with the freshwater oligochaete, Lumbriculus variegatus, with PCB concentrations in interstitial water (IW) quantified using polyoxymethylene passive samplers. Measured BSAFs tended to decrease with increasing PCB concentration in sediment, especially for the more highly chlorinated congeners. Measures of partitioning between sediment, IW, and oligochaetes showed that measured sediment–IW partition coefficients (K_TOC) tended to increase slightly with increasing sediment contamination, whereas the ratio of tissue PCB to IW PCB tended to decrease with increasing concentration in IW. Variation in accumulation among sediments was clearly influenced by bioavailability, as reflected by IW measurements, although the specific cause of varying K_TOC was not clear. Calculated partitioning between IW and organism lipid (K_lipid) indicated that accumulation was generally 5 to 10-fold higher than would be predicted if K_lipid was approximately equal to the n-octanol–water partition coefficient (K_OW). While affirming previous observations of decreasing BSAFs with increasing PCB contamination, the relatively shallow slope of the observed relationship in the current data may suggest that this concentration dependence is not a major uncertainty in sediment risk assessment, particularly if measurements of PCBs in IW are incorporated. Environ Toxicol Chem 2013;32:XX–XX. © 2013 SETAC

Natural organic matter (NOM) is implicated in the binding of antibiotics by particles in soils and waters. The authors' previous computational study revealed structural rearrangement of both hydrophilic and hydrophobic moieties of NOM to favor H-bonding and other intermolecular interactions, as well as both competition with ion-exchange reactions and bridging interactions by NOM-bound divalent cations. The importance of these interactions was investigated using fluorescence-quenching spectroscopy to study the adsorption of ciprofloxacin (Cipro), a fluoroquinolone antibiotic, on 4 reference humic substances (HSs): Elliott soil humic acid (HA), Pahokee peat HA, and Suwannee river HA and fulvic acid. A simple affinity spectrum HS model was developed to characterize the cation-exchange capacity and the amount of H-bond donor moieties as a function of pH. The adsorption results stress the influence of both pH conditions and the type of HS: both soil HA and peat HA exhibited up to 3 times higher sorption capacity than the aquatic HS at pH ≥ 6, normalizing to the aromatic C content accounted for the differences among the terrestrial HS, and increasing the concentration of divalent cations led to a decrease in adsorption on aquatic HA but not on soil HA. In addition, the pH-dependent speciation models of the Cipro–HS complexes illustrate an increase in complexation due to an increase in deprotonation of HS ligands with increasing pH and, at circumneutral and alkaline pH, enhanced complexation of zwitterionic Cipro only in the presence of soil HA and peat HA. The findings of the present study imply that, in addition to electrostatic interactions, van der Waals interactions as facilitated by aromatic structures and H-bond donating moieties in terrestrial HS may facilitate a favorable binding environment. Environ Toxicol Chem 2013;32:XX–XX. © 2013 SETAC

Mercury (Hg) is a widespread environmental contaminant known for the neurotoxicity of its methylated forms, especially monomethylmercury, which bioaccumulates and biomagnifies in aquatic food webs. Mercury bioaccumulation and biomagnification rates are known to vary among species utilizing different food webs (benthic vs limnetic) within and between systems. The authors assessed whether carbon and nitrogen stable isotope values and total Hg (THg) concentrations differed between sympatric benthic and limnetic ecotypes and sexes of threespine stickleback fish (Gasterosteus aculeatus) from Benka Lake, Alaska, USA. The mean THg concentration in the limnetic ecotype was significantly higher (difference between benthic and limnetic means equals 26 mg/kg dry wt or 16.1%) than that of the benthic ecotype. Trophic position and benthic carbon percentage utilized were both important determinants of THg concentration; however, the 2 variables were of approximately equal importance in females, whereas trophic position clearly explained more of the variance than benthic carbon percentage in males. Additionally, strong sex effects (mean difference between females and males equals 45 mg/kg dry wt or 29.4%) were observed in both ecotypes, with female fish having lower THg concentrations than males. These results indicate that trophic ecology and sex are both important determinants of Hg contamination even within a single species and lake and likely play a role in governing Hg concentrations in higher trophic levels. Environ Toxicol Chem 2013;9999:XX–XX. © 2013 SETAC

Stimulating microbial growth through the use of acetate injection wells at the former uranium mill site in Rifle, Colorado, USA, has been shown to decrease dissolved uranium (VI) concentrations through bacterial reduction to immobile uranium (IV). Bioreduction also changed the redox chemistry of site groundwater, altering the mobility of several other redox-sensitive elements present in the subsurface, including iron, sulfur, and arsenic. Following acetate amendment at the site, elevated concentrations of arsenic in the groundwater were observed. Ion chromatography-inductively coupled plasma–mass spectrometry was used to determine the aqueous arsenic speciation. Upgradient samples, unexposed to acetate, showed low levels of arsenic (≈1 μM), with greater than 90% as arsenate (As[V]) and a small amount of arsenite (As[III]). Downgradient acetate-stimulated water samples had much higher levels of arsenic (up to 8 μM), and 4 additional thioarsenic species were present under sulfate-reducing conditions. These thioarsenic species demonstrate a strong correlation between arsenic release and sulfide concentrations in groundwater, and their formation may explain the elevated total arsenic concentrations. An alternative remediation approach, enhanced flushing of uranium, was accomplished by addition of bicarbonate and did not result in highly elevated arsenic concentrations. Environ Toxicol Chem 2013;32:1216–1223. © 2013 SETAC

Increasing usage of fullerenes (C₆₀) increases their opportunities to be released into the environment. For risk assessment, it is important to understand the environmental fate and ecotoxicological effects of C₆₀. In the present study, fullerene settling was measured during a 1-yr period with 4 different lake waters and an artificial freshwater, and Daphnia magna immobilization and fullerene accumulation was also measured in each of the lake waters. Depending on the characteristics of the lake waters, fullerenes either exhibited extended water stability or settled rapidly; in all waters, there was a fraction that remained stable after 1 yr. Water stability was affected by the quality and molecular size distribution of dissolved natural organic matter (DNOM). Increasing DNOM molecular sizes with high aromatic content enhanced water stability. Immobilization of D. magna was generally quite low (under 20%) and highly variable after 24 h and 48 h at initial fullerene concentrations up to 10 mg/L. Substantial settling occurred during the time period for acute toxicity assays (i.e., 48 h), which should be anticipated when conducting toxicity assays. There were no significant differences in the quantity of accumulated fullerenes among the different lake waters at fullerene concentrations of 0.5 mg/L, but there were differences at 2 mg/L. Environ Toxicol Chem 2013;32:1224-1232. © 2013 SETAC

The authors compared benthic wetland invertebrate matrix separation techniques (handpicking vs saltwater flotation) to test for effects on invertebrate mercury concentrations. Neither total mercury nor methylmercury concentrations differed significantly between techniques across 8 taxa. Matrix separation by the flotation technique took significantly less time and resulted in significantly greater abundance recovery in some taxa. The authors conclude that the saltwater-based flotation technique does not lead to mercury contamination or analytical interference issues. Environ Toxicol Chem 2013;32:1233–1236. © 2013 SETAC

Knowledge of Hg speciation in tissue is valuable for assessing potential toxicological effects in fish. Direct Hg analyzers, which use thermal decomposition and atomic absorption spectrometry, have recently gained popularity for determining organic Hg after procedural solvent extraction from some environmental media, although quantitative recovery from lipid-rich materials, such as fish liver, has been problematic. The authors developed a new method by which organic Hg in fish liver and muscle is estimated by the difference between direct measurements of inorganic Hg in an acid extract and total Hg in whole tissue. The method was validated by analysis of a certified reference material (DOLT-4 dogfish liver) and naturally contaminated fish tissues with comparison to an established Hg speciation method (gas chromatography cold vapor atomic fluorescence spectrometry). Recovery of organic Hg from DOLT-4, estimated by difference, averaged 99 ± 5% of the mean certified value for methylmercury. In most liver samples and all muscle samples, estimates of organic Hg from the proposed method were indiscernible from direct speciation measurements of methylmercury (99% ± 6%). Estimation of organic Hg by the difference between total Hg and inorganic Hg was less accurate in liver samples with a high percentage of inorganic Hg (90%). This was because of the increased uncertainty that results from estimating a third value (i.e., organic Hg) by using the difference between two large concentrations (inorganic and total Hg). The proposed method is a useful tool for examining the speciation of Hg in fish muscle and liver, and by extension, potentially other tissues and environmental media. Environ Toxicol Chem 2013;32:1237–1241. © 2013 SETAC

The south coast of Laizhou Bay, in northeastern China, is a production area for halogenated flame retardants (HFR). In 2007, the authors measured serum concentrations of polybrominated diphenyl ethers (PBDEs) in Laizhou Bay residents. To assess the PBDE concentration trend, and determine the concentrations of the emerging flame retardants Dechlorane Plus (DP) and bis(2-ethylhexyl)-3,4,5,6-tetrabromophthalate (TBPH), the authors measured the concentrations of 8 PBDE congeners, 2 DP isomers, and TBPH in 10 composite samples, which were pooled from the serum collected from 305 Laizhou Bay residents in October 2011. The average concentration of the total PBDE (∑₈PBDE) concentration in all serum pools was 240 ng/g lipid weight, and the highest serum pool concentration (in the 30- to 39-yr-old male group) was 780 ng/g lipid weight. Brominated diphenyl ether-209 was the dominant congener, accounting for 87% of ∑₈PBDE. Compared with a previous study, ∑₈PBDE serum concentrations in the present study showed no change in order of magnitude, but the relative contribution of BDE-209 to ∑₈PBDE was higher. The average concentration of ∑DP in all serum pools was 3.6 ng/g lipid weight, ranging from 1.4 ng/g lipid weight (in the 50- to 59-yr-old male group) to 11 ng/g lipid weight (in the 20- to 29-yr-old male group). The concentration of DP was lower than in other reported studies. The study also detected TBPH in the 30- to 39-yr-old female group, suggesting that TBPH, as an emerging HFR, requires further monitoring. Environ Toxicol Chem 2013;32:1242–1247. © 2013 SETAC

Brominated flame retardants (BFRs) in eucalyptus leaves and pine needles from a rural site in southern China were measured to investigate the air–plant exchange. Mean concentrations of BFRs were higher in pine needles (79.8 ng/g dry wt) than in eucalyptus leaves (74.5 ng/g), whereas an inverse result was found for the leaf surface particles, with mean concentrations of 3490 ng/g and 5718 ng/g, respectively. For most of the BFRs, the correlations between their concentrations in plants and those in the vapor phase, atmospheric particles, leaf surface particles, and the environmental variables (temperature, wind speed, and relative humidity) at this site were in contrast to the results the authors observed at an electronic waste site previously, indicating that ambient air level plays a vital role in the relationships. The interspecies difference in the BFR profiles and the correlations above implied that pine needles likely have more advantages for uptake of BFRs from gaseous deposition than eucalyptus leaves, for which particle-bound deposition is more important. Like the electronic waste site, the leaf scavenging ratios of BFRs were also controlled by their octanol–air partition coefficient. It was estimated that approximately 154 kg of BFRs in the atmosphere are scavenged annually by forest in this region, which was 1.7 times larger than that via atmospheric deposition to nonforest ground. Environ Toxicol Chem 2013;32:1248–1253. © 2013 SETAC

The European Union's directive for sustainable use of pesticides requires implementing risk mitigation measures at streams threatened by pesticide entries. The need for mitigation measures was investigated at 10 stream sites within an intensively used arable region in central Germany by characterizing pesticide exposure following edge-of-field runoff and effects on the aquatic macroinvertebrates. Moreover, the influence of riparian buffer strip width (as a mitigation measure) at the sampling sites was considered. Generally, invertebrate fauna was dominated by pesticide-tolerant species, suggesting a high pesticide exposure at almost all sites. This result is also reflected by the elevated levels of suspended particle contamination in terms of toxic units (logTU_Max > −2), corresponding to one-hundredth of the median lethal concentration (LC50) to Daphnia magna. At two sites that received high aqueous-phase entries of the pyrethroid lambda-cyhalothrin (logTU_Max > −0.6), the abundance and number of sensitive species in terms of the species at risk index decreased during the pesticide application period. In contrast, no acute significant negative effects on macroinvertebrates were observed at sites characterised by low water-phase toxicity (logTU_Max < –3.5). An influence of riparian buffer strip width on pesticide exposure was not observed, supposedly because of the presence of erosion rills and ephemeral ditches. In conclusion, results show that mitigation measures (such as the improvement of currently present riparian buffer strips) are needed in the study area. Environ Toxicol Chem 2013;32:1254–1263. © 2013 SETAC

Zinc oxide (ZnO) nanoparticles are being increasingly utilized in a variety of products and applications and are therefore commonly discharged into aquatic environments, increasing exposure and potentially impacting aquatic organisms. Zinc oxide nanoparticles can depress growth of some marine phytoplankton, and several examples of nanoparticle trophic transfer have been documented, although not within planktonic communities. The authors test whether feeding on ZnO-exposed phytoplankton could cause toxic effects in a widespread and ecologically important marine grazer, the copepod Acartia tonsa. The authors exposed the diatom Thalassiosira weissflogii to ZnO nanoparticles for 7 d and measured growth, zinc accumulation, and zinc distribution within the algal cells to elucidate bioavailability to grazing copepods. Thalassiosira weissflogii cultured with nano-ZnO were continuously fed to A. tonsa for 7 d, and reproduction and survival were quantified. A dose-dependent growth reduction was observed in T. weissflogii exposed to nano-ZnO, with a 20% effective concentration (EC20) of 70 µg/L Zn and a lowest observed effect concentration (LOEC) of 99 µg/L Zn. Zinc accumulation in the algae occurred dose-dependently over time, with the majority of the zinc partitioning into the cell wall fraction. Feeding on ZnO-exposed diatoms led to a decrease in copepod survival and reproduction. The EC20s corresponding to the dissolved zinc concentration in the T. weissflogii exposure media were 112 µg/L (13 µg/g dry wt) and 143 µg/L (16 µg/g dry wt), and the LOECs were 168 µg/L (17 µg/g dry wt) and 263 µg/L (21 µg/g dry wt) for copepod survival and reproduction, respectively. These results provide evidence of trophic transfer of metal contaminants associated with metal oxide nanomaterials within a marine plankton community, leading to a reduction in individual demographic performance of an important coastal marine grazer. Environ Toxicol Chem 2013;32:1264–1269. © 2013 SETAC

As the use of single-walled carbon nanotubes (SWNTs) increases over time, so does the potential for environmental release. This research aimed to determine the toxicity, bioavailability, and bioaccumulation of SWNTs in marine benthic organisms at the base of the food chain. The toxicity of SWNTs was tested in a whole sediment exposure with the amphipod Ampelisca abdita and the mysid Americamysis bahia. In addition, SWNTs were amended to sediment and/or food matrices to determine their bioavailability and bioaccumulation through these routes in A. abdita, A. bahia, and the estuarine amphipod Leptocheirus plumulosus. No significant mortality to any species via sediment or food matrices was observed at concentrations up to 100 ppm. A novel near-infrared fluorescence spectroscopic method was utilized to measure and characterize the body burdens of pristine SWNTs in nondepurated and depurated organisms. We did not detect SWNTs in depurated organisms but quantified them in nondepurated A. abdita fed SWNT-amended algae. After a 28-d exposure to [¹⁴C]SWNT-amended sediment (100 µg/g) and algae (100 µg/g), [¹⁴C]SWNT was detected in depurated and nondepurated L. plumulosus amphipods at 0.50 µg/g and 5.38 µg/g, respectively. The results indicate that SWNTs are bioaccessible to marine benthic organisms but do not appear to accumulate or cause toxicity. Environ Toxicol Chem 2013;32:1270–1277. © 2013 SETAC

The production and use of engineered nanomaterials (ENMs) are increasing rapidly, and therefore, the need to assess their environmental exposure and associated risks has become increasingly important. Only a handful of studies have quantified the release and environmental concentrations of ENMs, but much work has been done to investigate the effects of these materials on organisms. The aim of the present study was to quantify probabilistically the environmental risks of ENMs, producing species sensitivity distributions that were then compared with probability distributions of predicted environmental concentrations. Five nanomaterials (nano-Ag, nano-TiO₂, nano-ZnO, carbon nanotubes [CNTs], and fullerenes) and 4 environmental compartments (surface water, sewage treatment plant effluents, soils, and sludge-treated soils) were considered. From 60 ecotoxicological studies, the authors extracted 112 single values to work with (25 values in 13 studies for nano-Ag, 17 values in 10 studies for CNTs, 7 values in 7 studies for fullerenes, 34 values in 23 studies for nano-TiO₂, and 29 values in 17 studies for nano-ZnO). The results indicate there is only a marginal risk for these metal-based nanomaterials in surface water (0.7% risk for nano-Ag and <0.1% for nano-TiO₂) and some risk in sewage treatment plant effluents (nano-Ag 39.7%, nano-TiO₂ 18.7%, and nano-ZnO 1.1%). Apart from a marginal value of <0.1% for nano-TiO₂ in sludge-treated soils, no risk from the other evaluated ENMs in terrestrial compartments is currently predicted. The discussion of the results considers the influence of the effects of different forms of 1 ENM (coating, agglomeration state, and mineralogy), the test conditions (dissolution and agglomeration), and transformation reactions. Environ Toxicol Chem 2013;32:1278–1287. © 2013 SETAC

The present study addresses the bioaccumulation behavior of cadmium selenide quantum dots by Eisenia andrei earthworms in a terrestrial environment. Earthworms were exposed to quantum dot-treated soil for up to 4 wk and analyzed for cadmium and selenium concentration using inductively coupled plasma mass spectrometry. Results were compared with those from earthworms exposed to cadmium nitrate and selenious acid, as positive controls, and those exposed in untreated soil (negative control). Earthworms exposed to quantum dots showed significant bioaccumulation of cadmium and selenium (5.3- and 1.5-fold higher concentration over negative controls, respectively) after 4 wk. Over the same 4 wk, positive control earthworms accumulated 9.2- and 2.2-fold higher cadmium and selenium, respectively, than negative controls for a much more substantial final body burden of the 2 elements. The concentrations also increased with exposure time; cadmium concentrations increased from 3600 ± 310 ng/g to 8080 ± 660 ng/g, from 1 to 4 wk, suggesting that further bioaccumulation may take place with even longer exposure time. The molar ratio of cadmium to selenium in the quantum dot-exposed worms (6.2) is closer to the ratios seen in positive control worms (7.2) than to the pure quantum dots (1.8), which implies that quantum dots are taken up predominantly in the degraded form. The results suggest that chemical modification of quantum dots to protect them from environmental degradation could potentially reduce bioaccumulation of the nanoparticles by earthworms. Environ Toxicol Chem 2013;32:1288–1294. © 2013 SETAC

Absorption, distribution, and biotransformation are 3 critical aspects affecting toxicant action in animals. In the present study, B6C3F1 mice (Mus musculus) were exposed for 28 d to contaminated feed that contained 1 of 5 different hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) concentrations: 0 mg/kg, 0.5 mg/kg, 5 mg/kg, 50 mg/kg, and 500 mg/kg. The authors quantified RDX and its reductive transformation products hexahydro-1-nitroso-3,5-dinitro-1,3,5-triazine (MNX), hexahydro-1,3-dinitroso-5-nitro-1,3,5-triazine (DNX), and hexahydro-1,3,5-trinitroso-1,3,5-triazine (TNX) in the stomach, intestine, plasma, liver, and brain of these mice. Average RDX concentrations followed a dose-dependent pattern for all matrices tested. No controls had concentrations above limits of detection. Average RDX concentrations in tissues of exposed mice ranged from 11.1 ng/mL to 182 ng/mL, 25.6 ng/g to 3319 ng/g, 123 ng/g to 233 ng/g, 144 ng/g to 35 900 ng/g, and 51.1 ng/g to 2697 ng/g in the plasma, brain, liver, stomach, and intestine, respectively. A considerable amount of RDX was present in the brain, especially in the highest-exposure group. This is consistent with the widely observed central nervous system effects caused by γ-aminobutyric acid inhibition associated with RDX exposure. N-nitroso metabolites of RDX were also present in tested tissues in a dose-dependent pattern. Average MNX concentrations in the stomachs of mice exposed to RDX ranged from nondetectable in control exposures to 490 ng/g in the highest-exposure groups. In the brain, MNX accumulated at a maximum average concentration of 165.1 ng/g, suggesting the potential formation of MNX from RDX within the brain. At higher exposures, DNX and TNX were present in the stomach, plasma, and brain of mice. The presence of RDX metabolites at notable amounts in different tissues suggests that RDX can transform into its N-nitroso metabolites in vivo by an undefined mechanism. Environ Toxicol Chem 2013;32:1295–1303. © 2013 SETAC

Concentrations of polychlorinated dibenzofurans (PCDFs) and polychlorinated dibenzo-p-dioxins (PCDDs) in Tittabawassee River floodplain soils and biota downstream of Midland, Michigan, USA, are greater than regional background concentrations. From 2005 to 2008, a multiple lines of evidence approach was utilized to evaluate the potential for effects of PCDD/DFs on American robins (Turdus migratorius) breeding in the floodplains. A dietary-based assessment indicated there was potential for adverse effects for American robins predicted to have the greatest exposures. Conversely, a tissue-based risk assessment based on site-specific PCDD/DF concentrations in American robin eggs indicated minimal potential for adverse effects. An assessment based on reproductive endpoints indicated that measures of hatch success in study areas were significantly less than those of reference areas. However, there was no dose-response relationship between that endpoint and concentrations of PCDD/DF. Although dietary-based exposure and reproductive endpoint assessments predicted potential for adverse effects to resident American robins, the tissue-based assessment indicates minimal to no potential for adverse effects, which is reinforced by the fact the response was not dose related. It is likely that the dietary assessment is overly conservative given the inherent uncertainties of estimating dietary exposure relative to direct tissue-based assessment measures. Based on the available data, it can be concluded that exposure to PCDD/DFs in the Tittabawassee River floodplain would not likely result in adverse population-level effects to American robins. Environ Toxicol Chem 2013;32:1304–1316. © 2013 SETAC

Chicken (Gallus domesticus) embryonic exposure in ovo to a 58-congener polychlorinated biphenyl (PCB) mixture resulted in teratogenic heart defects in chick embryos at critical heart developmental stages Hamburger–Hamilton (HH) stages 10, 16, and 20. The 58-congener mixture contained relative proportions of primary congeners measured in belted sandpiper (Megaceryle alcyon) and spotted sandpiper (Actitis macularia) eggs collected along the upper Hudson River, New York, USA, and chicken doses were well below observed environmental exposure levels. Embryos were injected with 0.08 µg PCBs/g egg weight and 0.50 µg PCBs/g egg weight (0.01 and 0.064 ng toxic equivalent/g, respectively) at embryonic day 0, prior to incubation. Mortality of exposed embryos was increased at all developmental stages, with a marked rise in cardiomyopathies at HH16 and HH20 (p < 0.05). Heart abnormalities occurred across all treatments, including abnormal elongation and expansion of the heart tube at HH10, improper looping and orientation, indentations in the emerging ventricular wall (HH16 and HH20), and irregularities in overall heart shape (HH10, HH16, and HH20). Histology was conducted on 2 cardiac proteins critical to embryonic heart development, ventricular myosin heavy chain and titin, to investigate potential mechanistic effects of PCBs on heart development, but no difference was observed in spatiotemporal expression. Similarly, cellular apoptosis in the developing heart was not affected by exposure to the PCB mixture. Conversely, cardiomyocyte proliferation rates dramatically declined (p < 0.01) at HH16 and HH20 as PCB exposure concentrations increased. Early embryonic cardiomyocyte proliferation contributes to proper formation of the morphology and overall thickness of the ventricular wall. Therefore, in ovo exposure to this 58-congener PCB mixture at critical stages adversely affects embryonic heart development. Environ Toxicol Chem 2013;32:1317–1324. © 2013 SETAC

A 58-congener polychlorinated biphenyl (PCB) mixture based on contaminant analysis of spotted sandpiper eggs collected along the upper Hudson River, New York, USA, in 2004 was used to study in ovo PCB effects on cardiac development in the domestic chicken. Fertile eggs were injected prior to incubation with the following doses of the PCB mixture: untreated, sham, 0, 0.03, 0.08, 0.3, 0.5, 0.7, and 2.06 µg PCBs/g egg weight (toxic equivalent quotient [TEQ] range of 0.004–0.266 ng/g). In addition, there were untreated and sham-control groups. Embryonic development was monitored throughout incubation and chicks were necropsied at hatch. Hatchability followed a dose-dependent curve with significant (p < 0.05) mortality above the 0.5 µg PCBs/g egg weight treatment compared with controls. The median lethal dose (LD50) of this PCB mixture in hatchling chicks was estimated as 0.4 µg/g egg weight (0.052 ng TEQ/g egg wt) based on the lethality curve. Cardiac arrhythmia was observed at embryonic day 14 of development in embryos treated at concentrations of 0.5 µg/g egg weight and above. Histological analysis was utilized to characterize any cardiac abnormalities. Cardiomyopathies increased across treatments in a dose-dependent manner compared with control groups. Identified abnormalities included the absence of the trabeculated layer of the ventricular wall, ventricular dilation, thinning of the ventricular walls, malformation of the septal wall, and most commonly, absence of the compact layer of the ventricular wall. Chick heart width, depth, total area, compact layer depth, septal width, chamber area, and ventricular wall dimensions did not differ across treatments. The present study supports prior reports of adverse developmental effects of PCBs on cardiovascular systems in birds. Although the eggs hatched, measured cardiomyopathies suggest potential deleterious long-term impacts on individual health and fitness. Environ Toxicol Chem 2013;32:1325–1331. © 2013 SETAC

11-Oxoetiocholanolone and related substances are important metabolites of cortisol and are excreted via feces in ruminants. To investigate whether 11-ketotestosterone (11-KT) or its immunoreactive metabolites are formed and excreted in ruminant feces, an enzyme immunoassay (EIA) was developed and validated. The antibody was raised in rabbits against 11-KT-3-CMO:bovine serum albumin with biotinylated 11-KT as a label. The assay showed a sensitivity of 0.3 pg/well. To validate the assay biologically, 6 rams were injected with a synthetic analogue of the adrenocorticotropic hormone (Synacthen, 2 µg/kg body wt). An aliquot was collected of each fecal portion spontaneously defecated 8 h before Synacthen injection to 24 h after injection and stored at −20 °C until analysis. Samples (0.5 g) were extracted using 80% methanol and immunoreactive metabolites measured using the 11-KT EIA and an already established 11,17-dioxoandrostane (11,17-DOA) EIA. High-performance liquid chromatography separation revealed no peak in the same elution position as authentic 11-KT; therefore, reacting substances were referred to as 11-KT equivalents. In the case of 11-KT immunoreactive substances, the values increased from baseline (median, 136 ng/g feces) to a peak concentration (median, 424 ng/g) 10 to 14 h after Synacthen injection and declined afterwards. Concentrations of 11,17-DOA showed the same pattern, but the values were 2 to 4 times higher. From this data, the authors conclude that 11-KT-like substances, specifically C₁₉O₃-androgens with a 17ß-hydroxy group, were present in the feces. These substances originate from the adrenals and are most likely cortisol metabolites. Environ Toxicol Chem 2013;32:1332–1336. © 2013 SETAC

An emerging issue in environmental toxicology is in understanding how climate change will alter responses of organisms to chemical contaminants. The objective of the present study was to characterize the interactive effects of cadmium and elevated temperature on life-stage-specific responses in the freshwater snail Physa pomilia. We exposed developing eggs, juveniles, and adults to Cd (5 µg/L, 15 µg/L, and 25 µg/L for eggs, and 250 µg/L for juveniles and adults) and 2 temperatures of 25 °C (control) and 35 °C (upper range of tolerance). In the absence of Cd, time to hatch was shorter at 35 °C compared with 25 °C, demonstrating a stimulatory effect of the higher temperature. However, when egg masses were reared at 35 °C and exposed to Cd, hatching success was significantly lower, and time-to-hatching was significantly longer. The effects of the higher temperature and Cd on newly hatched neonate survival were additive, except at the highest Cd concentration, at which effects of the 2 stressors were greater than additive. Overall, within the combined stressor treatments, adult snails generally survived significantly longer than did juvenile snails, and both were more tolerant than developing snails. Many climate projection models predict future increases in global temperatures. The present study shows that combined stressors may produce greater-than-additive effects, challenging predictive power. More studies are needed to better characterize the interactive effects of chemical contaminants and stressors related to climate change. Environ Toxicol Chem 2013;32:1337–1343. © 2013 SETAC

Various aquatic bioassays using one of several fish species have been developed or are in the process of being developed by organizations like the US Environmental Protection Agency and the Office of Economic Cooperation and Development for testing potential endocrine-disrupting chemicals (EDCs). Often, these involve assessment of the gonad phenotype of individuals as a key endpoint that is inputted into a risk or hazard assessment. Typically, gonad phenotype is determined histologically, which involves specialized and time-consuming techniques. The methods detailed here utilize an entirely different methodology, reverse-transcription quantitative polymerase chain reaction, to determine the relative expression levels of 4 genes after exposure to either 17β-estradiol or 17β-trenbolone and, by extension, the effects of EDCs on the phenotypic status of the gonad. The 4 genes quantified, Sox9b, protamine, Fig1α, and ZPC1, are all involved in gonad development and maintenance in Japanese medaka (Oryzias latipes); these data were then inputted into a permutational multivariate analysis of variance to determine whether significant differences exist between treatment groups. This information in conjunction with the sexual genotype, which can be determined in medaka, can be used to determine adverse effects of exposure to EDCs in a similar fashion to the histologically determined gonad phenotype. Environ Toxicol Chem 2013;32:1344–1353. © 2013 SETAC

Nickel (Ni) is a common pollutant found in aquatic environments and may be harmful at elevated concentrations. Increasing salinity has been shown to decrease the bioavailability and toxicity of other metals to aquatic organisms. In the present study, acute Ni toxicity experiments (96-h) were conducted at various salinities (0–36 ppt) to determine the effects of salinity on Ni toxicity to 2 euryhaline fish species, Kryptolebias marmoratus and Fundulus heteroclitus. Nickel concentrations causing lethality to 50% of the fish ranged from 2 mg/L in moderately hard freshwater to 66.6 mg/L in 36 ppt saltwater. Nickel toxicity to F. heteroclitus decreased linearly with increasing salinity; however, Ni toxicity to K. marmoratus was only lowered by salinities above 6 ppt, demonstrating potential physiological differences between the 2 species when they are functioning as freshwater fish. Furthermore, the authors investigated the influence of Mg²⁺, Ca²⁺, Na⁺, and Cl^– on Ni toxicity to F. heteroclitus. Freshwater with up to 120 mg/L Ca²⁺ as CaSO₄, 250 mg/L Mg²⁺ as MgSO₄, or 250 mg/L Na⁺ as NaHCO₃ did not provide protection against Ni toxicity. Alternatively, 250 mg/L Na⁺, as NaCl, was protective against Ni toxicity; and the extent of protection was similar to that demonstrated from salt water with the same Cl^– concentration. These results suggest that Cl^– is the predominant ion responsible for reducing Ni toxicity to K. marmoratus and F. heteroclitus in higher salinity waters. Environ Toxicol Chem 2013;32:1354–1359. © 2013 SETAC

Species sensitivity distributions (SSDs) are cumulative distributions of measures of species sensitivity to a stressor or toxicant, and are used to estimate concentrations that will protect p% of a community (PC_p). There is conflict between the desire to use high-quality sensitivity data in SSDs, and to construct them with a large number of species forming a representative sample. Trade-offs between data quality and quantity were investigated using the effects of increasing salinity on the macroinvertebrate community from the Hunter River catchment, in eastern Australia. Five SSDs were constructed, representing five points along a continuum of data quality versus data quantity and representativeness. This continuum was achieved by the various inclusion/exclusion of censored data, nonmodeled data, and extrapolation from related species. Protective concentrations were estimated using the Burr type III distribution, Kaplan-Meier survival function, and two Bayesian statistical models. The dominant taxonomic group was the prime determinant of protective concentrations, with an increase in PC₉₅ values resulting from a decrease in the proportion of Ephemeropteran species included in the SSD. In addition, decreases in data quantity in a SSD decreased community representativeness. The authors suggest, at least for salinity, that the inclusion of right censored data provides a more representative sample of species that reflects the natural biotic assemblage of an area to be protected, and will therefore improve risk assessment. Environ Toxicol Chem 2013;32:1360–1369. © 2013 SETAC

Polybrominated diphenyl ethers (PBDEs) cause neurobehavioral toxicity, but their effects on visual behavior remain unknown. In the present study, the impact of PBDEs on visual behavior was examined using optokinetic responses and phototaxis in zebrafish larvae. Zebrafish embryos were exposed to pentabrominated diphenyl ethers mixture (DE-71) at concentrations of 0, 0.32, 3.58, and 31.0 µg/L until 15 d postfertilization. The authors then assessed photoreceptor opsin expression, retinal histology, and visual behavior of the larvae. The results showed that the transcriptions of the opsin genes, zfrho and zfgr1, were significantly upregulated. Western blotting further demonstrated a significant increase in rhodopsin protein expression after exposure of the larvae to DE-71. Histological examination revealed the following morphological alterations in the retina: increased area of inner nuclear layer, decreased area of inner plexiform layer, and decreased density of ganglion cells. Tests of optokinetic and phototactic behavior showed hyperactive responses on exposure to DE-71, including increased saccadic eye movements and phototactic response. The present study is the first to demonstrate that the acute exposure of zebrafish larvae to DE-71 causes biochemical and structural changes in the eye that lead to behavioral alterations. Analysis of these visual behavioral paradigms may be useful in predicting the adverse effects of toxicants on visual function in fish. Environ Toxicol Chem 2013;32:1370–1375. © 2013 SETAC

Compounds related to the high-production-volume flame retardant Dechlorane Plus (DP) were measured in a Lake Ontario food web located downstream of a DP manufacturing plant. These compounds, 1,3- and 1,5-DP-monoadducts (DPMA), are positional isomers and are thought to arise from the incomplete reaction of DP or impurities in the DP starting material during its manufacture. The 1,3-DPMA isomer was measured (0.12–199 ng g⁻¹ lipid wt) in all trophic levels, whereas 1,5-DPMA was measured only sporadically in the food web and was not detectable in the apex predator, lake trout (Salvelinus namaycush). Concentrations of DPMA isomers when detected in Lake Ontario biota were greater than that of total DP for all trophic levels. The prevalence of 1,3-DPMA in the food web, and especially in lake trout, may be due to obstruction of the existing carbon double bond to enzyme attack, rendering it less readily metabolized. To examine this hypothesis, biotransformation kinetic experiments using in vitro lake trout liver microsomal exposures were performed. Zero-order depletion rate constants for 1,3- and 1,5-DPMA were 92.2 and 134.6 pmole h⁻¹, respectively, with corresponding half-lives of 2.03 ± 0.14 h (1,3-DPMA) and 1.39 ± 0.09 h (1,5-DPMA). Furthermore, the 1,5-isomer was depleted to a greater extent than 1,3-DPMA. Specific biotransformation products were not identified. These data support the hypothesis that 1,5-DPMA is more readily metabolized than 1,3-DPMA by lake trout. The present study also shows that the concentrations of these isomers, which the authors speculate might be unintended impurities or byproducts in some technical DP formulations, exceed that of the intended product in biota. Environ Toxicol Chem 2013;32:1376–1381. © 2013 SETAC

A tiered investigative approach was employed to characterize and identify substances responsible for the persistent toxicity of a primary-treated municipal effluent to gametes of the Hawaiian sea urchin, Tripneustes gratilla. Toxicity identification evaluation (TIE) procedures from the US Environmental Protection Agency were modified to account for the tolerance of T. gratilla gametes to various sample manipulations. Microtox rapid toxicity screening was applied in some aspects of the study after verifying a correlation between the pattern of toxic responses of T. gratilla gametes and that of the bioluminescent bacteria Vibrio fischeri. Toxicity identification evaluation phase I manipulations revealed a toxicity profile implicating surfactants as possible toxicants, and TIE phase II toxicity assessment of isolated fractions coupled with colorimetric surfactant analyses confirmed the possible role of surfactants in effluent toxicity. The toxic effects of standard reference surfactants on T. gratilla fertilization indicated a concordance with the effects of the more nonpolar effluent fractions. Treatability studies showed that biodegradation by activated sludge eliminated effluent toxicity to urchin gametes. Environ Toxicol Chem 2013;32:1382–1387. © 2013 SETAC

Paralytic shellfish toxins are secondary metabolites produced by several species of dinoflagellates and cyanobacteria. Known targets of these toxins, which typically occur at detrimental concentrations during harmful algal blooms, include voltage-gated ion channels in humans and other mammals. However, the effects of the toxins on the co-occurring phytoplankton community remain unknown. The present study examined the molecular mechanisms of the model photosynthetic alga Chlamydomonas reinhardtii in response to saxitoxin exposure as a means of gaining insight into the phytoplankton community response to a bloom. Previous work with yeast indicated that saxitoxin inhibited copper uptake, so experiments were designed to examine whether saxitoxin exhibited a similar mode of action in algae. Expression profiling following exposure to saxitoxin or a copper chelator produced similar profiles in copper homeostasis genes, notably induction of the cytochrome c₆ (CYC6) and copper transporter (COPT1, CTR1) genes. Cytochrome c₆ is used as an alternative to plastocyanin under conditions of copper deficiency, and immunofluorescence data showed this protein to be present in a significantly greater proportion of saxitoxin-exposed cells compared to controls. Live-cell imaging with a copper-sensor probe for intracellular labile Cu(I) confirmed that saxitoxin blocked copper uptake. Extrapolations of these data to phytoplankton metabolic processes along with the copper transporter as a molecular target of saxitoxin based on existing structural models are discussed. Environ Toxicol Chem 2013;32:1388–1395. © 2013 SETAC

Estimation of population-level benchmark concentrations for protecting aquatic organisms from chemicals is important for value-relevant ecological risk assessments. By employing a species sensitivity distribution (SSD) approach, the authors aimed to derive the population-level hazardous concentration for 5% of species (PHC5) for copper. Based on available information on copper toxicity and population models, the authors estimated population threshold concentrations at which the population size is stable (that is, 0 net population growth) for 13 freshwater species (3 algal, 6 invertebrate, and 4 fish species). The PHC5 for copper was then estimated (6.8 µg/L; 95% confidence interval [CI], 1.8–13.6 µg/L), by fitting a log-normal distribution to the population threshold concentrations obtained. The close overlap between the present study's estimate of the PHC5 and a field-derived threshold concentration suggests that the population-level SSD approach provides a reasonable level of protection for species richness in the natural environment. By contrast, and counterintuitively, the authors' estimate was comparable with the individual-level HC5 reported in the European Union risk assessment. Although the present study cannot determine the underlying reasons for the similar figures, the result provides an indication that the margin between individual-level and population-level benchmarks derived from SSD approaches can be very small. The results therefore suggest that attention is needed to achieve population-level protection using an individual-level SSD approach. Environ Toxicol Chem 2013;32:1396–1402. © 2013 SETAC

Compared with acute toxicity, chronic exposures to low levels of contaminants are more environmentally relevant, but fewer data are available. In the present study, sediment toxicity of the pyrethoid permethrin to Chironomus dilutus was determined. The whole-life-cycle toxicity testing was conducted with the endpoints covering survival, growth, emergence, and reproduction. Permethrin caused 50% lethality in C. dilutus at 1.83 ± 1.13 µg/g organic carbon (OC) and 1.20 ± 0.55 µg/g OC after exposures of 20 d (before pupation) and 58 d (the end of the testing), respectively. The 5% and median effect concentrations (EC5 and EC50) represented the marginal and toxic levels of the sublethal effects, respectively, and effect data were all normalized to the controls before Probit analysis. The EC5s for growth, emergence, and reproduction were 0.034 ± 0.006 µg/g OC, 0.016 ± 0.008 µg/g OC, and 0.009 ± 0.008 µg/g OC, respectively; the respective EC50s were 1.09 ± 0.56 µg/g OC, 0.838 ± 0.077 µg/g OC, and 0.039 ± 0.105 µg/g OC. In addition, a 24-h Tenax extraction was employed to better assess permethrin bioavailability. Ultimately, response spectra with a series of endpoints were developed for permethrin using either OC-normalized bulk sediment concentrations or bioavailability-based Tenax extractable concentrations as the dose metric. The development of bioavailability-based chronic toxicity endpoints for sediment-associated permethrin would provide valuable benchmarks for evaluating ecological risk of this contaminant and contributing to improve sediment management policies. Environ Toxicol Chem 2013;32:1403–1411. © 2013 SETAC

The influence of natural dissolved organic matter (DOM) on acute waterborne Cu toxicity was evaluated in the euryhaline copepod Acartia tonsa at 3 different water salinities. Three sources of freshwater DOM (extracted by reverse osmosis) and 2 sources of marine DOM (extracted using a solid-phase technique) were used. Artificial salt water was used to prepare the experimental media. Different combinations of Cu concentrations and DOM sources and concentrations were tested at salinities of 5, 15, and 30 ppt. Toxicity data (48-h median lethal concentration [LC50] values) were calculated based on dissolved Cu concentrations. In a broad view, data showed that increasing salinity was protective against the acute waterborne Cu toxicity. In general, Cu toxicity was also lower in the presence than in the absence of DOM. Toxicity (48-h LC50) values from all treatments at the same salinity showed a positive linear relationship with the dissolved organic carbon (DOC). Thus, the protective effect of DOM against the acute Cu toxicity seems to be dependent mainly on the DOM concentration. However, it seems also to be dependent to some extent on the source of DOM used. In summary, findings reported in the present study clearly indicate that both salinity and DOM (source and concentration) should be taken into account in the development of an estuarine version of the biotic ligand model. Environ Toxicol Chem 2013;32:1412–1419. © 2013 SETAC

The effect of sodium chloride (NaCl) on cadmium (Cd) uptake, translocation, and oxidative stress was investigated using 2 tobacco cultivars differing in Cd tolerance. The growth inhibition of the tobacco plants exposed to Cd toxicity was in part alleviated by moderate addition of NaCl in the culture solution. Cadmium concentration of shoots and roots in the 2 cultivars increased with increasing Cd levels in the solution and decreased with the addition of NaCl. The addition of NaCl could alleviate the oxidative stress caused by Cd toxicity, as reflected by reduced production of malondialdehyde and recovered or enhanced activities of antioxidative enzymes catalase and glutathione peroxidase. The results also showed that the enhancement of antioxidative enzyme activity by NaCl for the tobacco plants exposed to Cd stress is related to induced Ca signaling. Environ Toxicol Chem 2013;32:1420–1425. © 2013 SETAC

Nitrobenzene (NB) is an important organic compound intermediate that is used widely in industry. In the present study, to evaluate the phytotoxicity and genotoxicity of NB on plants, Vicia faba was exposed to increasing concentrations of NB (5 mg L⁻¹, 10 mg L⁻¹, 25 mg L⁻¹, 50 mg L⁻¹, and 100 mg L⁻¹). The data revealed that germination rate and radicle length of V. faba seedlings were promoted by low NB concentrations and short exposure periods, whereas these parameters were inhibited at greater NB concentrations and longer exposures. When assessed by mitotic index, micronucleus, and chromosomal aberration assays, NB showed dose-dependent genotoxicity at 0 mg L⁻¹ to 50 mg L⁻¹. Environ Toxicol Chem 2013;32:1426–1432. © 2013 SETAC