In this study we used data from dietary metabarcoding studies of zooplankton to calculate prey selectivity indices and assess energy fluxes in a pelagic resource-consumer network. We show that food web dynamics are influenced by prey selectivity and temporal match-mismatch in growth cycles and that cyanobacteria are the main source of primary production in the investigated coastal pelagic food web. The latter challenges the common assumption that cyanobacteria are not supporting food web productivity, a result that is increasingly relevant as global warming promotes cyanobacteria dominance. While this study provides a method for how DNA metabarcoding can be used to quantify energy fluxes in a marine food web, the approach presented here can easily be extended to other ecosystems.
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Fig. 2. Consumer-resource network of the pelagic Baltic Sea. Link width is proportional to fluxes of energy (kJ/m2) between resources (phytoplankton, bottom) and consumers (zooplankton, top). The width of the nodes (taxa) corresponds to each population’s contribution to annual secondary production. The diameter of each plot is proportional to the square root of the total production.