Mortality of zooplankton in lake ecosystems and its contribution to vertical carbon fluxes (ZooFlux)

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The objective of the proposed study is to quantifying the role of dead zooplankton (carcasses) in the carbon cycle of aquatic ecosystems. Thereby, we will test the hypothesis that microbial degradation of carcasses during their sinking facilitates (primes) the degradation of more refractory organic matter. The project is part of the joint effort of a research team from Germany and Russia. In order to estimate the contribution of zooplankton carcasses to the carbon cycle, we combine field observations, mesocosm and laboratory experiments as well as modeling. In situ estimations of the zooplankton mortality and sinking rates by sediment traps in the lakes will be accompanied by measurements of turbulent mixing conditions across the stratified water column using modern hydrodynamic field techniques. Laboratory experiments will quantify microbial colonization and degradation rates of zooplankton carcasses. Both field and laboratory data will be used for an advanced model predicting retention time of carcasses in the water column and their contribution to the carbon cycle. Various model scenarios will focus on the role of environmental factors for settling and degradation of dead zooplankton and on potential changes due to climate-driven hypolimnion warming in lakes.