Plankton community structure and role of Oithona similis on the western coast of Greenland during the winter-spring transition

18 pages, 9 figures, 4 tables

The cyclopoid copepod Oithona similis is one of the most abundant copepods in the oceans and has a potentially important role in pelagic food webs. However, there is a lack of knowledge on aspects of its biology and function in planktonic communities. In the present study, we aimed to assess and compare the species’ trophic role in Greenlandic coastal waters during the winter-spring transition, with a focus on its winter behaviour, when large calanoids are not present in the surface layer. Two locations were studied: waters offshore from Godthåbsfjord (Nuuk) in winter, and Qeqertarsuaq (Disko Bay) in spring (bloom and post-bloom period). The potential prey of adult females of O. similis was quantified, and grazing experiments were conducted to determine the feeding rates of adult females on phytoplankton and protozooplankton >10 µm. The abundance, stage composition, and egg production of O. similis was also investigated. Ciliates were the preferred prey for O. similis, which confirms its importance as a link between the microbial food web and higher trophic levels. We observed high egg production rates and efficiencies of O. similis in winter, confirming that it is active and successfully reproductive in food-limited winter conditions. Our results stress that O. similis is a key component of Arctic and subarctic marine communities throughout the year

We thank the Greenland Institute of Natural Resources in Nuuk for excellent laboratory facilities, K. Arendt for helping with laboratory logistics, and F. Heinrich for helping on board the boat ‘Erisaalik’ during the samplings in Godthåbsfjord. We also thank the Arctic station in Qeqertarsuaq (University of Copenhagen) for providing an excellent working platform and ship time, and the crew of the RV ‘Porsild’ for enthusiastic help during sampling. We also thank N. Lundholm for her advice on diatom and protozooplankton identification. This research was funded by the Greenland Climate Research Centre through the project 6505 to T.G.N. and the European Commission FP7 EURO-BASIN (grant agreement: 264 933). The Spanish Ministry of Economy and Competitiveness supported this work through the projects CTM2007-60052, CTM2010-10036-E, and CTM2011-23480 to E.S. (2009SGR-1283) and a PhD fellowship (BES-2008-004231) and mobility grant to S.Z.T. We thank J. Turner for English editing and 2 anonymous reviewers for their positive comments on the manuscript

Peer reviewed