Occurrence and vertical flux of faecal pellets of probably protozoan origin in the southeastern Weddell Sea (Antarctica)

Abstract

Amount of faecal material in the water column and in sediment traps deployed at 7 different stations was investigated during a cruise of RV 'Polarstern' off Vestkapp (73 degree S, 19 degree W), Weddell Sea, Antarctica. Numerous small round, ellipsoidal or triangular pellets (30 to 150 mu-m) were identified in the water column and the traps. Most of the pellets contained intact, but empty, frustules of the abundant diatoms. We suggest that these small pellets were produced by protozoan grazers (ciliates, heterotrophic dinoflagellates, radiolarians and probably foraminifers). These pellets occurred in numbers up to 214 l-1 in the water column and contributed significantly (36% of total sedimented faeces volume in traps) to vertical particle transport of empty but intact diatom frustules from the euphotic zone to deeper water layers. The greatest part of the remaining faecal material in the sediment traps consisted of larger, nearly round faecal pellets (150 to 300 mu-m). These faecal pellets are of unknown origin, but could have been produced by small metazoans.