Zooplankton response to organic carbon content in a shallow lake covered by macrophytes

Abstract

ABSTRACTZooplankton are an important link between trophic levels in aquatic ecosystems, and their response to organic carbon is likely to have broad implications for lake food webs. The main objective of the research was to determine variations in zooplankton communities against the background of the structural heterogeneity of the lake and to link the observed patterns to the organic carbon content of the lake water. Spatial differences were noted in the organic carbon content of the lake water. Higher total organic carbon (TOC) and dissolved organic carbon (DOC) concentrations were recorded in the vegetated littoral area than in the lake pelagic zone. Zooplankton distribution and response to organic carbon content varied among habitats. At sites covered by plants, DOC and the bacterial sized fraction of particulate organic carbon were positively correlated with zooplankton biomass. In reeds, the grazing pressure by zooplankton on bacterial sized organic carbon was particularly strong. This implied that the microbial carbon link could be an important food web component providing carbon to higher trophic levels in areas covered by plants. This assumption corresponded well with the results of redundancy analysis (RDA).