Diel vertical migration of meso-and macrozooplankton in a small Antarctic cove during summer: role of abiotic conditions and trophic interactions

SCHLOSS I.R.; HOFFMEYER M.; GARCIA M.

Berguen

Congreso; 6th Zooplankton Production Symposium; 2016

ICES

Zooplankton diel vertical migration (DVM) is a common process in the ocean, descending at dawn and coming up again in late afternoon and evening. In order to investigate meso-and macrozooplankton DVM in Potter Cove (62° 14'S, 58° 38'W), sampling was conducted on 4 dates in summer 2013, at two different times (day and night) and two layers of the water column (surface=0-5 m and depth=10-30 m; N=16). Hydrographic variables were measured using a CTD, while sea water samples for quantitative analyses of chlorophyll-a (Chl-a) and microzooplankton were taken with a Niskin bottle. Meso-and macrozooplankton samples were collected by horizontal tows using a 80 µm mesh net. Preliminary results of this study come from data analysis through uni- and multivariate statistical tests. During the day, high biomass of phytoplankton, aloricate ciliates and dinoflagellates was evident in surface waters. Contrastingly, phytoplankton abundance was lower at depth, where high abundance of copepods and pteropods was evident. During the night, copepods and euphausiids were not only present but intensely grazed on phyto- and microzooplankton in surface waters. At depth, the highest relative zooplankton abundance at night was due to nauplius larvae, amphipods and meroplankton. Our results show that even in this shallow ecosystem DVM of zooplankton can be evidenced. Moreover, it plays an important role controlling phytoplankton abundance.