How do nutrient conditions and species identity influence the impact of mesograzers in eelgrass-epiphyte systems?
- 251 Downloads
Coastal eutrophication is thought to cause excessive growth of epiphytes in eelgrass beds, threatening the health and survival of these ecologically and economically valuable ecosystems worldwide. Mesograzers, small crustacean and gastropod grazers, have the potential to prevent seagrass loss by grazing preferentially and efficiently on epiphytes. We tested the impact of three mesograzers on epiphyte biomass and eelgrass productivity under threefold enriched nutrient concentrations in experimental indoor mesocosm systems under summer conditions. We compared the results with earlier identical experiments that were performed under ambient nutrient supply. The isopod Idotea baltica, the periwinkle Littorina littorea, and the small gastropod Rissoa membranacea significantly reduced epiphyte load under high nutrient supply with Rissoa being the most efficient grazer, but only high densities of Littorina and Rissoa had a significant positive effect on eelgrass productivity. Although all mesograzers increased epiphyte ingestion with higher nutrient load, most likely as a functional response to the quantitatively and qualitatively better food supply, the promotion of eelgrass growth by Idotea and Rissoa was diminished compared to the study performed under ambient nutrient supply. Littorina maintained the level of its positive impact on eelgrass productivity regardless of nutrient concentrations.
KeywordsFilamentous Alga Ambient Nutrient High Nutrient Supply Kiel Fjord Diatom Chain
We are grateful to S. Flöder for critical reading of the MS and helpful comments. Financial support was provided by the German Research Foundation (So 145/20).
- Beck MW, Heck JKL, Able KW, Childers DL, Eggleston DB, Gillanders BM, Halpern BS, Hays CG, Hoshino K, Minello TJ, Orth RJ, Sheridan PF, Weinstein MP (2001) The identification, conservation, and management of estuarine and marine nurseries for fish and invertebrates. Bioscience 51:633–641CrossRefGoogle Scholar
- Edgar GJ, Aoki M (1993) Resource limitation and fish predation: their importance to mobile epifauna associated with Japanese Sargassum. Oecologia 95:122–133Google Scholar
- Gurevitch J, Hedges LV (1993) Meta-analysis: combining the results of independent experiments. In: Scheiner SM, Gurevitch J (eds) Design and analysis of ecological experiments. Chapman and Hall, London, pp 378–398Google Scholar
- Hauxwell J, Cebrián J, Furlong C, Valiela I (2001) Macroalgal canopies contribute to eelgrass (Zostera marina) decline in temperate estuarine ecosystems. Ecology 82:1007–1022Google Scholar
- Hillebrand H (2002) Top-down versus bottom-up control of autotrophic biomass—a meta-analysis on experiments with periphyton. J North Am Benthol Soc 21:349–369Google Scholar
- Howarth RW, Anderson D, Cloern J, Elfring C, Hopkinson C, Lapointe B, Malone T, Marcus N, McGlathery K, Sharpley A, Walker D (2000) Nutrient pollution of coastal rivers, bays, and seas. Issues Ecol 7:1–15Google Scholar
- Jaschinski S, Flöder S, Sommer U (2010) Consumer identity, abundance, and nutrient concentration affect epiphyte diversity in an experimental eelgrass system. Oikos. doi: 10.1111/j.1600-0706.2010.18377.x
- Jernakoff P, Brearley A, Nielsen J (1996) Factors affecting grazer-epiphyte interactions in temperate seagrass meadows. Oceanogr Mar Biol Ann Rev 34:109–162Google Scholar
- Kemp WM, Boyton WR, Adolf JE, Boesch DF, Boicourt WC, Brush G, Cornwell JC, Fisher TR, Glibert PM, Hagy JD, Harding LW, Houde ED, Kimmel DG, Miller WD, Newell RIE, Roman MR, Smith EM, Stevenson JC (2005) Eutrophication of the Chesapeake Bay: historical trends and ecological interactions. Mar Ecol Prog Ser 303:1–29Google Scholar
- Lamberti GA (1996) The role of periphyton in benthic food webs. In: Stevenson RJ, Bothwell ML, Lowe RL (eds) Algal ecology: freshwater benthic ecosystems. Academic Press, San Diego, pp 533–572Google Scholar
- Lorenzen OJ (1967) Determination of chlorophyll and phaeopigments: spectrophotometric equations. Limnol Oceanogr 12:343–346Google Scholar
- Penhale P (1977) Macrophyte-epiphyte biomass and productivity in an eelgrass (Zostera marina L.) community. J Exp Mar Biol Ecol 26:211–224 Google Scholar
- Short FT, Coles RG, Short CA (2001) Global seagrass research methods. Elsevier, Amsterdam, pp 467Google Scholar
- Waycott M, Duarte CM, Carruthers TJB, Orth RJ, Dennison WC, Olyarnik S, Calladine A, Fourqurean JW, Heck KL Jr, Hughes AR, Kendrick GA, Kenworthy WJ, Short FT, Williams SL (2009) Accelerating loss of seagrasses across the globe threatens coastal ecosystems. PNAS 106:12377–12381CrossRefGoogle Scholar