Vertical distribution (0–1000 m) of gelatinous zooplankton and particulate matter (60ìm<<5mm) along the Mid Atlantic ridge in the North Atlantic. Potential impact of appendicularians on particle aggregation
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The vertical distribution (0-1000 m depth) of macrozooplankton along the northern portion of the Mid-Atlantic Ridge (59°58N, 25°53W to 41°29N, 28°19W) was investigated during the MARECO program (June and July 2004) using the Underwater Video Profiler (UVP). Twelve relatively large (> 1 cm) groups were selected from the recorded images: sarcodines (with two sub-groups), crustaceans (excluding copepods), chaetognaths, ctenophores (with two sub-groups cydippids and lobates), siphonophores, medusae (with three subgroups Aeginura grimaldii, Aglantha spp. and all other medusae), appendicularians, and thaliaceans. The numerically dominant groups over the whole area were crustaceans (26%), medusae (20%) and appendicularians (17%). The gelatinous fauna were consistently most numerous between 400-900 m. Appendicularians, ctenophores and A. grimaldii occurred mostly below 300 m (maximum concentrations of 75, 58, and 30 individuals 100m-3, respectively). The macrozooplankton community below 200 m varied with the spatial distribution of the four regions defined by the temperature and salinity profiles. The results suggest that the Sub-Polar Front restricts the mixing of macrozooplankton communities down to 1000 m depth. The observed relationship between appendicularians and biovolume and size of particles is investigated in the four oceanic regions. Keywords: Gelatinous zooplankton, mesopelagic zooplankton, Sub Polar Front, North Atlantic, Underwater Video Profiler, MARECO .