Effects of temperature on the interaction between phytoplankton communities and benthic filter feeders
Hardenbicker, Paulin; Weitere, Markus; Fink, Patrick; Hillebrand, Helmut
published: Dec 1, 2015
ArtNo. ESP141018702000, Price: 29.00 €
We tested the effects of water temperature on bentho-pelagic coupling in a freshwater food web, particu- larly consumer effects on phytoplankton biomass and species composition as well as potential feedback effects of phytoplankton food quality on the consumer. We measured the filtration activities of two bivalve species (Dreissena polymorpha and Corbicula fluminea) in a water temperature gradient (15°C – 30°C) in two long-term (4 week) experiments with two different phytoplankton communities. High water temperatures generally decreased the food quality of the phytoplankton (amount of polyunsaturated fatty acids) and increased the dominance of cyanobacteria (both coccoid strain Synechocystis sp. and filamentous strain Cylindrospermum sp.) in consumer-free communities. The corresponding shifts in both size and composition of the phytoplankton in turn affected the filtration activity of the bivalves. The warming-induced cyanobacterial dominance was substantially suppressed by the presence of bivalves for the community with the coccoid strain, but not for the community with filamentous cyanobacteria. Thus, bivalves led to pronounced shifts in the phytoplankton community composition, which in turn depended on the initial phytoplankton community. Consumer effects on the different phytoplankton communities changed over time. In contrast to short-term and single-species feeding experiments, our results suggest that potentially strong interactions exist between direct temperature effects on mussels, and indirect effects mediated by temperature-related changes in phytoplankton species composition. Thus, filtration activity shows divergent responses to warming, which can affect ecosystem functions, given the importance of bentho-pelagic filtration as a key process in many aquatic ecosystems such as rivers, shallow lakes and littoral zones.