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Keywords:

  • Baltic Sea;
  • Cladophora glomerata ;
  • community production;
  • Fucus vesiculosus ;
  • individual production;
  • photosynthesis;
  • primary production

Abstract

  1. Top of page
  2. Abstract
  3. Introduction
  4. Study Area
  5. Material and Methods
  6. Results
  7. Discussion
  8. Acknowledgements
  9. References

Primary production is of special importance in ecology, since it fuels other trophic levels with energy and biomass. In aquatic ecosystems, almost all primary production is performed by algae. The primary production of aquatic macrophytes has been mainly quantified using detached phyto-elements (fronds and algal thalli) or whole plants, whereas the community level is usually ignored. In a field experiment we evaluated macroalgal photosynthesis at individual and community levels. We used natural communities dominated by the ephemeral green alga Cladophora glomerata (L.) Kützing and the perennial brown alga Fucus vesiculosus L. Fucus vesiculosus had temporally stable and C. glomerata highly variable photosynthetic production. On a biomass basis, net and gross photosynthetic production was always higher at the individual level than at the community level. The ratio of individual photosynthetic production to community photosynthetic production increased with light intensities. The observed relationships give clear evidence that in shallow water, where light is supposedly plentiful, macroalgae are nevertheless strongly light-limited. Although photosynthetic production estimates at individual levels are traditionally extrapolated to the community level, such estimates largely overestimate reality and give a false impression of the potential photosynthetic production of macroalgae.


Introduction

  1. Top of page
  2. Abstract
  3. Introduction
  4. Study Area
  5. Material and Methods
  6. Results
  7. Discussion
  8. Acknowledgements
  9. References

Primary production in the sea is the major process that supplies energy and matter to marine organisms. In coastal ecosystems, macroalgae constitute the most productive habitats and virtually all primary production is performed by them (Field et al. 1998; Mann 2000). Primary production is limited by abiotic and biotic factors (Field et al. 1998; Hauxwell et al. 2003), with abiotic constraints being the most important in natural ecosystems (Hill et al. 1995).

The availability of light is known to play a crucial role in regulating primary production of macroalgae (e.g. Pregnall & Rudy 1985; Field et al. 1998; Hauxwell et al. 1998; Duffy & Hay 2000; Binzer et al. 2006). The hyperbolic tangent function has been traditionally used to describe the relationship between light and photosynthetic production (Jassby & Platt 1976) as it can easily represent the transition from one state (light limitation) to another (light saturation). Light limitation may arise from the amount of irradiance arriving at the sea surface but more likely from self-shading. Thus, in addition to the light environment above the algal canopy, macroalgal density and structure determine overall community photosynthetic production. Therefore, it is not only the total light availability but also the distribution of light photons between different parts of the algal thalli that largely determine the community photosynthetic production (Binzer & Sand-Jensen 2002). Often the light is unevenly distributed and most of the photons are absorbed in the upper layers of photosynthetic tissue. Even though algal photosynthesis will be saturated locally with increasing irradiance, community photosynthesis will not become saturated because the lower photosynthetic tissue in the community will have an unused photosynthetic potential (Binzer & Middelboe 2005). In general, light availability is inversely related to algal densities, is highest in tips and decreases with distance from the tip along the thallus. Shaded algal parts are subject to less seasonal variation in irradiance (Stengel & Dring 1998; Binzer & Sand-Jensen 2002) and, due to photoacclimation, their photosynthetic performance may differ from of that of the upper thallus (Middelboe & Binzer 2004; Binzer & Middelboe 2005; Binzer et al. 2006).

The shape of irradiance–production curves may vary among macroalgae. Measurements of individual photosynthetic production have shown that thin, sheet-like and filamentous algae are capable of fast growth, which is coupled to high photosynthetic rates per unit biomass (Johansson & Snoeijs 2002). On the other hand, perennial bush-like macroalgae grow slowly and have low photosynthetic rates per unit biomass (King & Schramm 1976; Wallentinus 1984; Middelboe & Binzer 2004; Sand-Jensen et al. 2007). Moreover, the relationship and variability between irradiance and photosynthetic production may change with seasonal variations in thallus photosynthesis (King & Schramm 1976; Wallentinus 1978; Stengel & Dring 1998; Middelboe et al. 2006).

However, measurements of community photosynthetic production have shown a much more stable photosynthetic production than predicted from their individual photosynthetic production (Middelboe et al. 2006). Thus, macroalgae seem not to realize their individual potential at community level due to impoverishment in the light environment within the algal canopy. This allows us to conclude that a three-dimensional structure of communities and high species-richness can make community photosynthetic production more stable and predictable because different parts of the algal canopy and different species complement each other in utilizing all of the available light (Middelboe & Binzer 2004; Middelboe et al. 2006).

In a factorial field experiment, we evaluated the photosynthetic production of different species at individual and community levels in the Northern Baltic Sea in May, June and August 2008. The experiment involved shallow-water communities dominated either by the ephemeral green alga Cladophora glomerata (L.) Kützing or the perennial brown alga Fucus vesiculosus L. Our hypotheses were as follows: (i) per unit biomass photosynthetic production is higher at an individual level than at community level; (ii) elevated algal biomasses increase light limitation, as shown by larger differences in individual and community level photosynthetic production; (iii) due to higher structural and species diversity, the F. vesiculosus community has a more stable community photosynthetic production than the C. glomerata community. To date, most of the studies on macroalgal photosynthesis have been conducted under fully marine conditions (e.g. Middelboe & Binzer 2004; Binzer & Middelboe 2005; Middelboe et al. 2006). The current study reports the photosynthetic production of macroalgae at a reduced salinity.

Study Area

  1. Top of page
  2. Abstract
  3. Introduction
  4. Study Area
  5. Material and Methods
  6. Results
  7. Discussion
  8. Acknowledgements
  9. References

The study was conducted in the shallow semi-enclosed Kõiguste Bay, Gulf of Riga, Northern Baltic Sea (58°22.10′N, 22°58.69′E). In general, the bottom relief of the area is quite flat, gently sloping towards deeper areas. The prevailing substrate types of the bay are sandy clay mixed with pebbles, gravel or boulders, at between 1 and 4 m. The Gulf of Riga receives fresh water from a huge drainage area and therefore Kõiguste Bay has a reduced and stable salinity of 4.0–6.5 psu and elevated nutrient levels (Kotta et al. 2008). The benthic vegetation is well developed (Kersen et al. 2011) and an extensive proliferation of ephemeral macroalgae has been reported from the area in the recent years (Lauringson & Kotta 2006).

Material and Methods

  1. Top of page
  2. Abstract
  3. Introduction
  4. Study Area
  5. Material and Methods
  6. Results
  7. Discussion
  8. Acknowledgements
  9. References

In situ experiments were performed adjacent to Kõiguste Marine Biological Laboratory in May, June and August 2008. During the course of the experiment the macroalgal community had 50–70% algal coverage and consisted mainly of Cladophora glomerata, Pilayella littoralis and Fucus vesiculosus.

Stones with growing macroalgae were collected from a shallow (1 m) area and were placed in experimental mesocosms, with replicates in separate chambers. Experimental treatments consisted of communities dominated either by F. vesiculosus or C. glomerata. Both macroalgae had small amounts of epiphytes, mainly P. littoralis, Ceramium tenuicorne and Ulva intestinalis.

Algal photosynthetic production was estimated each month at individual and community levels over 4 days. On each day, three replicates were made for each combination of treatments. The individual-level photosynthetic production was measured in transparent and dark incubation bottles. About 0.5 g (dry weight) of algal material was incubated in 600-ml transparent and dark glass bottles, filled with the unfiltered seawater and incubated horizontally on special trays at 0.5 m depth. Bottles without algae served as the controls. The community-level production was measured in transparent and dark chambers holding 29 l of water. The surface area of the chamber was 0.08 m2. Macroalgal communities were placed in the chamber at coverage relevant to field conditions. The chambers were deployed on the sea floor at 1 m depth, i.e. close to the site of individual-level photosynthetic production estimates.

Oxygen concentration in the incubation bottles and chambers was measured using a calibrated Optode type oxygen sensor (Aanderaa Instruments) connected to a data logger (Compact-Optode data recorder by Alec Electronics). Changes in dissolved oxygen per g dry weight of algal tissue were used as a proxy of photosynthetic production and respiration. Rates of change in the light (includes both primary production and community respiration) indicated community net photosynthesis and rates of change in the dark represented community respiration. Community gross photosynthesis was a sum of community net photosynthesis and respiration. Production experiments lasted 40 min and dark respiration experiments 20 min, respectively. During deployment, the irradiance above the canopy was measured every second using a calibrated spherical quantum sensor connected to a data logger (ultra-miniature logger for light intensity by Alec Electronics).

After the experiment, all algae were stored in a deep-freezer at −20°C and subsequent sorting, counting and determination of algal species were performed in the laboratory using a stereomicroscope. All species were determined to species level. The dry weight (dw) of species was obtained after drying the individuals at 60°C for 2 weeks.

Repeated measures anova was used to compare total macroalgal biomass, community species number and light intensities among macrophyte communities (levels: Cladophora glomerata, Fucus vesiculosus community) and months (levels: May, June, August). Repeated measures ancova was used to compare the effect of organizational level (levels: individual, community) and macroalgal community (levels: Cladophora glomerata, Fucus vesiculosus community) on the photosynthetic production of macroalgal communities among months (levels: May, June, August). In the ancova models, light and temperature were included into analysis as time-varying covariates. Post-hoc Bonferroni tests were used to analyse which treatment levels were statistically different from each other. Multiple regression analysis was used to learn more about the relationship between light, total macroalgal biomass and the ratio of individual net photosynthetic production to community net photosynthetic production.

Results

  1. Top of page
  2. Abstract
  3. Introduction
  4. Study Area
  5. Material and Methods
  6. Results
  7. Discussion
  8. Acknowledgements
  9. References

On a sample basis the Fucus vesiculosus community had on average about fivefold higher biomasses (Fig. 1, repeated measures anova, post-hoc Bonferroni test P < 0.001) and higher number of macrophyte species compared to the Cladophora glomerata communities (Fig. 2, repeated measures anova, post-hoc Bonferroni test P < 0.001). However, due to more equal spread of biomasses among species, the Shannon diversity values were higher in the C. glomerata community than in the F. vesiculosus community (Fig. 3, repeated measures anova, post-hoc Bonferroni test P < 0.01). When all samples were pooled together, the number of species within the studied macroalgal communities was almost equal (Table 1).

Table 1. Average biomasses of macrophyte species calculated from monthly pooled samples (means ± SE) (g dw m−2) in the Fucus vesiculosus- and Cladophora glomerata-dominated communities
SpeciesTaxonomic groupFucus vesiculosus communityCladophora glomerata community
MayJuneAugustMayJuneAugust
  1. The code of plant taxonomic groups is as follows: R = Rhodophyta; P = Phaeophyceae; C = Chlorophyta; A = Angiospermae.

Total biomass 215.333 ± 19.834172.499 ± 12.439159.726 ± 12.42159.493 ± 3.51841.311 ± 4.21012.782 ± 1.090
Fucus vesiculosus P202.305 ± 20.021163.737 ± 11.485154.272 ± 12.6765.902 ± 2.2340.005 ± 0.0030
Cladophora glomerata C2.953 ± 0.2773.328 ± 0.7260.997 ± 0.12330.396 ± 2.60217.712 ± 1.24012.475 ± 1.110
Pilayella littoralis P7.022 ± 1.0473.738 ± 0.7403.117 ± 0.6885.141 ± 0.50910.299 ± 1.2030.148 ± 0.081
Ceramium tenuicorne R1.813 ± 0.2670.699 ± 0.0800.238 ± 0.0350.341 ± 0.0629.994 ± 2.3420.034 ± 0.012
Sphacelaria arctica P0.183 ± 0.1020.033 ± 0.011000.273 ± 0.1150
Ruppia maritima A00.022 ± 0.00800.042 ± 0.0210.024 ± 0.0070
Ulva intestinalis C000.015 ± 0.0030.063 ± 0.01500.089 ± 0.020
Dictyosiphon foeniculaceus P00.01 ± 0.0050.06 ± 0.02100.001 ± 0.0000
Elachista fucicola P0.277 ± 0.1350.576 ± 0.1431.005 ± 0.163000
Polysiphonia fucoides R0.005 ± 0.00300.001 ± 0.0010.004 ± 0.00200
Polysiphonia fibrillosa R000.006 ± 0.003000
Potamogeton pectinatus A0.016 ± 0.0090.068 ± 0.02400.021 ± 0.0070.136 ± 0.0320.036 ± 0.012
Furcellaria lumbricalis R00.003 ± 0.0020.014 ± 0.0060.003 ± 0.0020.006 ± 0.0030
Myriophyllum spicatum A00000.003 ± 0.0020
Zannichellia palustris A0000.001 ± 0.00000
Chorda filum P00.001 ± 0.0000000
image

Figure 1. Average biomasses of the Fucus vesiculosus- (F) and Cladophora glomerata- (C) dominated communities (means ± SE) (g·dw·m²) in different months calculated on a sample basis.

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image

Figure 2. Average number of species in the Fucus vesiculosus and Cladophora glomerata dominated communities (means ± SE) in different months calculated on a sample basis.

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image

Figure 3. Shannon diversity index on a log-base-10 scale in the Fucus vesiculosus and Cladophora glomerata dominated communities in different months calculated on a sample basis.

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In terms of dominant species the F. vesiculosus and C. glomerata communities did not differ largely among months. Thus, seasonal differences were mostly due to the sporadic occurrence or absence of rare species (Table 1). On a sample basis, both studied communities had higher biomasses in May than in August (post-hoc Bonferroni test P < 0.001) (Fig. 1). Similarly, the C. glomerata community had a higher number of macrophyte species in May and June than in August, whereas the F. vesiculosus community had a lower number of macrophyte species in May than in June and August (Fig. 2; repeated measures anova, post-hoc Bonferroni tests P < 0.001). The Shannon diversity of the C. glomerata community was highest in June, intermediate in May and lowest in August. The Shannon diversity value in the F. vesiculosus community was opposed to the seasonal patterns of species number (Fig. 3; repeated measures anova, post-hoc Bonferroni tests P < 0.001). In May the studied communities had a similar number of macroalgal species, whereas in June and August the species number of the F. vesiculosus community exceeded the values in the C. glomerata community (Fig. 2). In May and August there was no difference in the Shannon diversity of the studied communities. In June, however, the C. glomerata community had higher Shannon diversity values compared with the F. vesiculosus community (Fig. 3; repeated measures anova, post-hoc Bonferroni tests P < 0.001).

During the measurements of photosynthetic production, light levels within benthic chambers were between 273 and 1929 μmol m−2 s−1. Light levels did not differ statistically among macrophyte communities and months (Fig. 4; Table 2; repeated measures anova, post-hoc Bonferroni test P > 0.05).

Table 2. RM factorial anova analysis on the separate and combined effects of the studied factors and interactions on net photosynthesis
SourceNumerator dfDenominator dfFSignificance
  1. Factors and levels were as follows: months (levels: May, June, August), organizational level (levels: individual, community), community (levels: Fucus vesiculosus, Cladophora glomerata). Covariates: (light, temperature).

Intercept186.68213.6<0.001
1: Community138.38155.8<0.001
2: Organization159.75434<0.001
3: Month2114.26617.6<0.001
1 × 2138.68612.70.001
1 × 3281.95224.3<0.001
2 × 3298.7846.370.003
1 × 2 × 3283.12950.009
4: Light1110.033.750.055
5: Temperature186.318.280.005
4 × 5195.2453.690.058
image

Figure 4. The variation of light intensity (μmol m−2 s−1) during photosynthetic production measurements of Cladophora glomerata and Fucus vesiculosus in May, June and August.

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The net photosynthetic production of macrophytes (NPP) was significantly affected by almost all studied factors and interactions. The NPP was mostly higher at the individual level than at the community level (Table 2; repeated measures ancova, post-hoc Bonferroni test P < 0.05), estimated at 0.017–0.048 and 0.004–0.037 mg O2 min−1 g−1 dw for F. vesiculosus, and at 0.011–0.400 and 0.005–0.309 mg O2 min−1 g−1 dw for C. glomerata, respectively (Fig. 5).

image

Figure 5. The net photosynthetic production of macroalgae at individual and community levels in different months (means ± SE). F = Fucus community; C = Cladophora community.

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There were clear differences in the NPP between macroalgal species level, with C. glomerata having significantly higher NPP compared with F. vesiculosus (post-hoc Bonferroni test: C. glomerata vs. F. vesiculosus P < 0.001). At the individual level C. glomerata had higher photosynthetic production than F. vesiculosus in all the months studied (post-hoc Bonferroni tests: P < 0.001), whereas at the community level the difference was statistically important only in August (post-hoc Bonferroni tests: P < 0.05). The individual NPP of C. glomerata was in the range 0.025–0.059, 0.011–0.098 and 0.082–0.400 mg O2 min−1 g−1 dw in May, June and August, respectively. The individual NPP values for F. vesiculosus were 0.015–0.034 mg O2 min−1 g−1 dw in May, 0.021–0.053 mg O2 min−1 g−1 dw in June and 0.022–0.048 mg O2 min−1 g−1 dw in August (Fig. 5). The community NPP of C. glomerata was in the range 0–0.023, 0–0.095 and 0.006–0.309 mg O2 min−1 g−1 dw in May, June and August, respectively. The community NPP of F. vesiculosus was 0.001–0.037 O2 min−1 g−1 dw in May, 0.001–0.028 O2 min−1 g−1 dw in June and 0.0002–0.012 O2 min−1 g−1 dw in August.

Fucus vesiculosus had quite stable NPP values, both at community and individual levels (post-hoc Bonferroni tests: difference among months P > 0.05). In contrast, C. glomerata had significantly higher production values at community and individual levels in August compared to May and June (post-hoc Bonferroni tests: August vs. May and June P < 0.001).

Gross photosynthetic production (GPP) showed similar responses to the studied factors, although the effects were more pronounced compared with NPP (Fig. 6, Table 3). The GPP was always higher at the individual than at the community level, estimated at 0.025–0.054 and 0.004–0.038 mg O2 min−1 g−1 dw for F. vesiculosus and at 0.035–0.416 and 0.006–0.333 mg O2 min−1 g−1 dw for C. glomerata, respectively.

Table 3. RM factorial anova analysis on the separate and combined effects of the studied factors and interactions on gross photosynthesis
SourceNumerator dfDenominator dfFSignificance
  1. Factors and levels were as follows: months (levels: May, June, August), organizational level (levels: individual, community), community (levels: Fucus vesiculosus, Cladophora glomerata). Covariates: (light, temperature).

Intercept171.4017.710.007
1: Community139.27895.28<0.001
2: Organization161.80135.35<0.001
3: Month2114.52212.16< 0.001
1 × 2139.71712.710.001
1 × 3283.39019.78<0.001
2 × 3299.5931.630.202
1 × 2 ×  3284.3911.150.322
4: Light1100.8572.310.132
5: Temperature171.0433.370.071
4 × 5182.9782.330.131
image

Figure 6. The gross photosynthetic production of macroalgae at individual and community levels in different months (means ± SE).

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The ratio of individual NPP to community NPP increased linearly with light intensities, whereas total macroalgal biomass had no separate and interactive effects on this ratio (Table 4). Nevertheless, the ratio varied more below 100 g m−2 of macroalgal biomass and levelled off at higher biomasses (Fig. 7). The GPP showed similar responses to increased light intensities as compared with the NPP.

Table 4. Summary table of the linear regression analysis on the separate and combined effects of macroalgal biomass and light on the ratio of individual photosynthetic production to community photosynthetic production (F3,36 = 3.66, P < 0.021, R² = 0.23)
 Regression coefficientsStandard error of coefficientstP
Intercept−1.0291.745−0.5900.559
1: Macroalgal biomass0.0290.0151.8950.066
2: Light0.0040.0012.9000.006
1 × 2<0.001<0.001−1.5740.124
image

Figure 7. Relationships between light, total macroalgal biomass and the ratio of individual photosynthetic production to community photosynthetic production.

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Discussion

  1. Top of page
  2. Abstract
  3. Introduction
  4. Study Area
  5. Material and Methods
  6. Results
  7. Discussion
  8. Acknowledgements
  9. References

We predicted that photosynthetic production is higher at the individual than the community level. The results of our experiment agreed with this hypothesis and showed significantly larger individual level photosynthetic production compared with community level photosynthetic production. Likewise, our results confirm that photosynthetic rates were much more variable for individual thalli than communities of the same algae (Binzer & Middelboe 2005; Middelboe et al. 2006; Sand-Jensen et al. 2007).

At low light intensities a large difference between individual and community photosynthetic production is not expected, as light is not sufficient to induce a positive net photosynthetic production. With increasing light intensities the difference in algal photosynthetic production between community and individual levels is expected to increase due to the greater effect of shading at the community level. The observed relationship was linear and the values of community photosynthetic production did not level off even at high light intensities around 2000 μmol m−2 s−1. This suggests that light saturation and light inhibition were never observed and the observed macroalgal communities were always light-limited.

We also predicted that elevated algal biomasses increase light limitation as shown by larger differences in individual and community level photosynthetic production. The data did not fully agree with the hypothesis. Instead, the light limitation (i.e. assessed by a ratio of individual to community level photosynthetic production) seemed to be variable at low macroalgal biomasses and displayed uniformly high values at biomasses above 100 g m−2. This suggests that dense macroalgal communities are characterized by near-constant light limitation of photosynthesis regardless of light intensities. This lack of a continuous relationship with macroalgal biomass and light limitation may arise from the morphology of macroalgae. Macroalgae are generally able to become saturated at lower irradiances than terrestrial plants because their non-rigid structure can ensure an even distribution of light among the photosynthetic tissue (Sand-Jensen & Krause-Jensen 1997; Beyschlag & Ryel 1998; Binzer & Sand-Jensen 2002). As the algae are in continuous motion, small changes in biomass might not affect light limitation in the canopy (Hurd 2000). Besides, the different parts of macroalgal thalli have variable capabilities to utilize irradiance depending on their absorption abilities, potential to carry out photosynthesis and capacity to distribute irradiance (Binzer & Middelboe 2005).

Finally, we predicted that owing to higher structural and species diversity, the Fucus vesiculosus community would have a more stable community photosynthetic production than the Cladophora glomerata community. The results of our experiment agreed with this hypothesis. Within a diverse community of F. vesiculosus, different species complement each other spatially and temporally and thus such a functional redundancy in the community has a positive and stabilizing effect on production (Middelboe et al. 2006; Sand-Jensen et al. 2007). In fact variable or high abundance of species can ensure stable and predictable community metabolism, because different species complement one another in utilizing all of the available light (Middelboe et al. 2006). Moreover, as compared with the light environment above algae, the natural variability in light intensity within the algal canopy is not large and therefore low variability in community photosynthetic parameters and production capacity is expected (Sand-Jensen et al. 2007). In addition, the perennial F. vesiculosus plants are relatively resistant to physical disturbances, independent of the direct resource acquisition and therefore vary less in their occurrence and biomass seasonally, as compared with C. glomerata (Pedersen & Borum 1996; Kiirkki & Lehvo 1997). On the other hand, the filamentous C. glomerata may occasionally bloom and have a high productivity (Littler & Littler 1984) but even small physical disturbances may severely damage the photosynthetic tissues of the algae and result in a large decrease in the community photosynthetic production.

Reduced salinity is known to decrease the photosynthetic production of macrophytes (Pregnall & Rudy 1985; Koch & Lawrence 1987; Phooprong et al. 2007). As our measurements were conducted at a low salinity level (Kotta et al. 2008; Lauringson et al. 2009), the observed differences in the macroalgal photosynthetic production between individual and community levels are expected to be even larger in fully marine conditions. This is also confirmed when comparing our estimates with the published data on the macroalgal photosynthetic production. Although different studies report in different units, the photosynthetic production values are much lower in our study than those measured under fully marine conditions (Middelboe & Binzer 2004; Binzer & Middelboe 2005; Middelboe et al. 2006).

To conclude, the observed relationships give clear evidence that in shallow water, where light should be plentiful, macroalgal communities are nevertheless strongly light-limited. Although the photosynthetic production estimates at individual level are traditionally extrapolated to the community level, such estimates largely overestimate reality and give a false impression of potential photosynthetic production of macroalgae. In addition, this study adds to the knowledge of how the canopy-forming algae provide not only biodiversty (Kotta et al. 2000; Råberg & Kautsky 2007; Wikström & Kautsky 2007) but also stable photosynthetic production (i.e. food and habitat resource) through the large range of hydrographic conditions.

Acknowledgements

  1. Top of page
  2. Abstract
  3. Introduction
  4. Study Area
  5. Material and Methods
  6. Results
  7. Discussion
  8. Acknowledgements
  9. References

Funding for this research was provided by Institutional Research Funding IUT02-20 of the Estonian Research Council, the Estonian Science Foundation grants 7813 and 8254, the Central Baltic Interreg IVa Programme HISPARES, the projects ‘The status of marine biodiversity and its potential futures in the Estonian coastal sea’ no. 3.2.0801.11-0029 and ‘EstKliima’ no. 3.2.0802.11-0043 of the Environmental Protection and Technology Programme of the European Regional Fund and Archimedes Foundation (Estonia, DoRa programme 8).

References

  1. Top of page
  2. Abstract
  3. Introduction
  4. Study Area
  5. Material and Methods
  6. Results
  7. Discussion
  8. Acknowledgements
  9. References
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