- Mesozooplankton structure and functioning during the onset of the Kerguelen spring bloom: first results of the KEOPS2 survey hal link

Auteur(s): Carlotti F., Nowaczyk A., Jouandet M.-P., Lefevre D., Harmelin M.

Conference: ASLO 2013 Aquatic Sciences Meeting (, US, 2013-02-21)

Ref HAL: hal-00808280_v1
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During the KEOPS II survey in spring (Oct-Nov 2011), the northeast and southeast region Kerguelen Island (between 46°59S and 50°37 S and 69°50E and 74°59E) were intensively studied to understand the physical and biogeochemical processes governing the onset of the Kerguelen spring bloom. Mesozooplankton community spatial distribution, taxonomy structure, size structure and biomass were studied from 41 zooplankton net tow samples -(0-250m vertical net tows) analyzed both with a ZOOSCAN and a binocular. 13C and 15N content between distinct size fractions, pigment gut contents and respiration rates of of dominant species were measured as well. Here we report on first results obtained along two transects (East-West and North South) and along a lagrangian sampling in the central part of the region during the bloom development. Biomass, abundance and size structures show temporal and spatial differences linked to the different water masses and trophic conditions. Day-night sampling revealed strong variations in abundance and biomass during the bloom phase due to large organisms, mainly euphausiids. Different spatial patterns of zooplankton size spectra were found with the highest slope values on the shelf area showing a large ratio of small organisms and the lowest within the central part of the region.