Zooplankton distribution and feeding in the Arctic Ocean during a Phaeocystis pouchetii bloom

17 pages, 14 figures, 5 tablesIn early summer 2007 we determined the vertical distribution of mesozooplankton (>200 μm) and assessed the copepod feeding rates in 19 stations distributed along the East Greenland Current and the Fram Strait. The study coincided with a bloom of the haptophyte Phaeocystis pouchetii in the colonial form. Copepods dominated the zooplankton community numerically, and were mainly distributed within the upper 150 m (except for Metridia longa and Oithona spp., that inhabited deeper waters), without showing a clear avoidance of the P. pouchetii layer. Copepod diet was diverse, ciliates having a relevant share (40% of the diet). Copepods also displayed active grazing upon the colonies of P. pouchetii. In general, feeding rates were low (on average, daily ration was 1.6% of body carbon), likely due to the scarcity of nano and microplankton during the study (<100 μg C L−1). Consequently, the trophic impacts on both the nano- and microplankton standing stocks and on primary production were negligible. These results suggest that during the period of study the transfer of carbon and energy from lower trophic levels towards copepods was lowWe thank Carlos Duarte for his task as cruise leader. We also thank the crew of the R/V Hespérides and all the UTM technicians for their help. Projects ATOS(POL200600550/CTM) and PERFIL (CTM 2006-12344-C02-01)funded this research. We thank Jordi Felipe and Alejandro Alonso for technical assistance. Dr.Maximino Delgado conducted the microscopic count sofphyto- and proto- zooplankton. We acknowledge the Zoo/PhytoImage development team for providing Zoo Image. We especially thank José Antonio Fernandes for answering our questions on Zoo Image, and for writing the code for manual classification. Torkel G. Nielsen kindly commented and suggested improvements on a draft version of the manuscriptPeer reviewe