Mesozooplankton biomass and epipelagic copepod assemblages in the Gerlache Strait (Antarctica) during the 2015 austral summer

Abstract

Mesozooplankton biomass and epipelagic copepod assemblage composition and distribution were studied in the Gerlache Strait from January 17 to 22, 2015, as part of the first Colombian oceanographic expedition to the Antarctic. Mesozooplankton-integrated biomass was generally low (< 5 mgdry weight/m−2) in the outer area of the northern section of the Gerlache Strait (between Crocker Passage and Hughes Bay) although there was a notable increase southward, with the highest value (1.02 g dry weight / m−2) at the entrance of Wilhelmina Bay in the central zone of the Strait. The epipelagic copepod assemblage comprised 17 species belonging to 4 orders and 13 families. The dominant species by number was Oithona similis, followed by O. frigida, Ctenocalanus citer, Drescheriella glacialis, and Calanoides acutus. Aetideus armatus is reported for the first time in the western sector of the Antarctic Peninsula. Differences in the assemblages of copepods between the northern and southern section of the Gerlache Strait were established. Considering the previous results reported about hydrography and phytoplankton composition in Gerlache Strait and our analysis of the copepod assemblage structure, a scenario is suggested in which, at less during January 2015, each section of the Strait exhibited a particular copepod assemblage structure: a northern section was dominated by small-sized copepods while the southern section was dominated by small-sized and large-sized copepods.