New study on nutritional composition of zooplankton

Here we investigate the nutritional value of resources for pelagic fishes of the upper San Francisco Estuary to understand whether recent fish declines are liked to shifts in zooplankton nutritional conditions due to the establishment of invasive species. Using stable isotopes, elemental stoichiometry and fatty acid analyses for all dominant invasive and native zooplankton taxa and seston, we characterized the plankton community structure in the estuary and demonstrated taxon-specific differences in their nutritional value. We found temporal increase in the community-level DHA, n3 to n6 fatty acid ratio, decrease in the community-level EPA and PUFA in the brackish water region, but no change in the bulk PUFA proportions in the freshwater region of the estuary. These changes were caused mainly by declines of native cladocerans that are rich in EPA and by an increase in the dominance of invasive taxa with high DHA concentrations, similar to that of native taxa. Although we showed temporal shifts in individual fatty acid classes, the proportion of the essential fatty acids remained relatively high, suggesting that nutritional prey availability for fish remained unchanged with the shift in species composition. The study in published in:

Kratina P, Winder M (2015) Biotic invasions can alter nutritional composition of zooplankton communities. OIKOS. DOI: 10.1111/oik.02240

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