| Summary: | participant Geochemical fluxes have received particular attention in marine ecosystems in the context of climate changes and potential CO2 sequestration by the oceans. In addition, areas where changes are expected to be the most important and the fastest are the polar ones and especially the Arctic Ocean. It is thus particularly important to better understand the role played by marine biological pump in regulating the essential elements, which are carbon, nitrogen but also phosphorous, in Arctic seas. Most of the regulation through the biological pump is realised by primary and secondary producers. In the arctic, few data are available on C, N and P elements and ratios of secondary producers. Those ratios can change according to several parameters including species, development stage, feeding mode, etc. Secondary producers are represented by zooplankton, of which 90% are copepods. One result of their feeding activities is the creation of faecal pellets, which can sink out of the euphotic zone and contribute to chemical fluxes. Faecal pellets produced by copepods in the first 50m depth are equivalent to 20% of the particulate carbon flux and 12% of the particulate nitrogen flux in the Arctic seas. Moreover copepods are known to ingest on average 45% of the primary production in Arctic water. It stress the point for an understanding of how stochiometric changes in C, N and P in food sources (primary producers) influence the contents and ratios of these elements in faecal pellets for future predictions of potential changes of the biochemical fluxes.
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