Pelagic food webs and eutrophication of coastal waters: Impact of grazers on algal communities

This review considers theoretical and empirical aspects of the role of grazers in the pelagic food web. We discuss how grazers may affect eutrophication development in coastal waters both through the direct effects of differential prey selectivity on the composition of the algal community, and through the indirect effects of nutrient sequestration and regeneration on the pelagic nutrient regime. We identify dominance of oligotrich ciliates or calanoid copepods on the primary herbivore level as two major food web configurations with different overall impacts on both algal communities and pelagic nutrient retention. Literature data on numerical and functional responses are compiled to make a quantitative assessment of competitive and predatory interactions between ciliates and copepods.