Composition and community structure of zooplankton in the sea ice-covered western Weddell Sea in spring 2004—with emphasis on calanoid copepods

• Published in: Deep Sea Research Part II: Topical Studies in Oceanography
• Main Authors: Schnack-Schiel, S. B., Michels, Jan, Mizdalski, Elke, Schodlok, M. P., Schröder, M.
• Format: Article in Journal/Newspaper
• Language: English
• Published: Elsevier 2008
• Subjects: Weddell; Weddell Sea; Sea ice; Copepods
• Online Access: https://oceanrep.geomar.de/id/eprint/27086/; https://oceanrep.geomar.de/id/eprint/27086/1/Deep_sea_research.pdf; https://doi.org/10.1016/j.dsr2.2007.12.013

The mesozooplankton community, with special emphasis on calanoid copepods, was studied with respect to its species composition, abundance, vertical distribution and developmental structure during the “Ice Station POLarstern” (ISPOL) expedition to the ice-covered western Weddell Sea. Stratified zooplankton tows were carried out nine times between 1 December 2004 and 2 January 2005 with a multiple opening–closing net between 0 and 1000 m depth. Copepods were by far the most abundant taxon, contributing more than 94% of the total mesozooplankton. Numerical dominants were cyclopoid copepods, mostly Oncaea spp. A total of 66 calanoid copepod species were identified, but the calanoid copepod community was characterised by the dominance of only a few species. The most numerous species was Microcalanus pygmaeus, which comprised on average 70% of all calanoids. Calanoides acutus and Metridia gerlachei represented other abundant calanoid species contributing an average of 8% and 7%, respectively. All other species comprised less than 3%. The temporal changes in the abundance and population structure of M. pygmaeus and M. gerlachei were small while a shift in the stage frequency distribution of C. acutus was observed during the study: copepodite stage IV (C IV) dominated the C. acutus population with 48–50% during the first week of December, while C V comprised 48% in late December. C I and C II of C. acutus were absent in the samples, and males occurred only in very low numbers in greater depths. In M. gerlachei, C I was not found, whereas all developmental stages of M. pygmaeus occurred throughout the study. All three species showed migratory behaviour, and they occurred in upper water layers towards the end of the investigation. This vertical ascent was most pronounced in C. acutus and relatively weak in the other two species. In M. pygmaeus and M. gerlachei, copepodids were responsible for the upward migration in late December, while the vertical distribution of adults did not change. In C. acutus, all abundant ...