Get access

Exploring Lemna gibba thresholds to nutrient and chemical stressors: Differential effects of triclosan on internal stoichiometry and nitrate uptake across a nitrogen:phosphorus gradient

Authors

  • Barry A. Fulton,

    1. Department of Environmental Science, Baylor University, Waco, Texas, USA
    2. Center for Reservoir and Aquatic Systems Research, Baylor University, Waco, Texas, USA
    Search for more papers by this author
  • Richard A. Brain,

    1. Department of Environmental Science, Baylor University, Waco, Texas, USA
    2. Center for Reservoir and Aquatic Systems Research, Baylor University, Waco, Texas, USA
    Search for more papers by this author
  • Sascha Usenko,

    1. Department of Environmental Science, Baylor University, Waco, Texas, USA
    2. Center for Reservoir and Aquatic Systems Research, Baylor University, Waco, Texas, USA
    Search for more papers by this author
  • Jeffrey A. Back,

    1. Center for Reservoir and Aquatic Systems Research, Baylor University, Waco, Texas, USA
    2. Department of Biology, Baylor University, Waco, Texas, USA
    Search for more papers by this author
  • Bryan W. Brooks

    Corresponding author
    1. Department of Environmental Science, Baylor University, Waco, Texas, USA
    2. Center for Reservoir and Aquatic Systems Research, Baylor University, Waco, Texas, USA
    • Department of Environmental Science, Baylor University, Waco, Texas, USA
    Search for more papers by this author

Abstract

Nutrient enrichment often co-occurs with chemical stressors in aquatic ecosystems, but the impacts of these multiple stressors across nutrient gradients is poorly understood and not typically addressed in ecotoxicity studies of lower trophic level models. Moreover, laboratory assays performed to determine threshold responses of aquatic macrophytes to contaminants typically use growth and morphometric endpoints to establish threshold effects and seldom report other important functional responses of lower trophic levels. Using the aquatic macrophyte Lemna gibba, we examined influences of varying nitrogen (N) and phosphorus (P) levels in combination with triclosan, a widely used antimicrobial agent in consumer care products, on internal carbon (C):N:P and NOmath image uptake kinetics. Triclosan modulated L. gibba tissue N and P content, and these stoichiometric responses for P-limited plants to triclosan exposure were more sensitive than growth endpoints employed in standardized phytotoxicity assays. Nitrate uptake capacities were also differentially inhibited by triclosan exposure according to external nutrient levels. Uptake rates for plants cultured and exposed under saturating N-levels were inhibited by more than threefold compared with N-limited plants. The results suggest that stoichiometric and nutrient uptake responses to chemical stressors provide useful information regarding adverse ecological thresholds not defined in standardized phytotoxicity assays with aquatic macrophytes. Our findings further indicate that site-specific impacts of chemicals associated with the wide ambient ranges of N and P typical of surface waters may be anticipated in lower trophic levels. Future studies should examine adverse effects of other stressors to these ecologically relevant endpoints, which may be useful in environmental assessment and management. Environ. Toxicol. Chem. 2010;29:2363–2370. © 2010 SETAC

Get access to the full text of this article

Ancillary