Deep planktonic filter-feeders found in the aphotic zone with the Cyana submersible in the Ligurian Sea (NW Mediterranean)

Abstract

Dives made during sprmg 1988 in the Ligunan Sea with the Cyana submersible uncovered a deep layer of active salps Salpa fusiforrnis and large appendiculanans (a new species of Oikopleura). These zooplanktomc organisms stayed at a depth of about 400 m, and did not perform vertical migrations There was a substantial amount of living micro-and nanoplankton, transported by the strong downwelling due to the Ligurian convergence, at the depth of the layer where the filterfeeders were. We believe that this circulation process occurs year-round and provides sufficient particulate matter to sustain midwater populations of salps and appendicularians.