Winter-Spring Development of the Zooplankton Community Below Sea Ice in the Arctic Ocean

The impact of the rapidly changing Arctic on zooplankton community structure and seasonal behaviour is not yet understood. Here we examine 6 months under-ice observations from N-ICE2015 expedition (January to June 2015) in Nansen Basin Yermak Plateau north Svalbard. Stratified sampling water column was done with MultiNet during entire expedition, upper 5 m below sea ice performed April-May by divers using a hand-held net. Hydrographic conditions were dominated northward-flowing warm saline Atlantic Water at intermediate depth, southward-flowing cold Polar Surface 100 m. mesozooplankton copepods. Most numerous small ubiquitous Oithona similis 200 m, Microcalanus spp. Triconia borealis further down column. Calanus finmarchicus among species while Metridia longa also numerous. most abundant deep-water copepods Paraeuchaeta Spinocalanus Arrow worms (Chaetognatha) comb jellies (Ctenophora) non-copepods. more dependent surrounding mass characteristics, such as salinity than geographical location. Algal food availability, which closely linked seasonality, explained changes seen surface waters May due ascent recruitment. Seasonal winter spring mostly involved an increase herbivorous C. its nauplii coinciding peak phytoplankton bloom late May. adjacent characterised oceanic North species, many are deep specialists. Despite onset consolidated ice, both successfully reproduced study area. This explains species-rich this region opposed less productive central Ocean. Future prospects earlier will likely be positive for overall secondary production boreal region.