Biogeochemistry of platelet ice: its influence on particle flux under fastice in the Weddell Sea, Antarctica

An array of four sediment traps and one current meter was deployed under a well-developed platelet layer for 15 days in the Drescher Inlet in the Riis er Larsen ice shelf. in February 1998. Traps were deployed at 10 m (just un der the platelet layer), 112 rn (above the thermocline), 230 m (below therm ocline) and 360 rn (close to sea floor). There was a substantial flux of pa rticulate organic material out of the platelet layer, although higher amoun ts were collected in the traps either side of the thermocline. Material col lected was predominantly composed of faecal pellets containing diatom speci es growing within the platelet layer. The size classes of these pellets sug gest they derive from protists grazing rather than from larger metazoans. S ediment trap material was analysed for particulate organic carbon ' /nitrog en/phosphorus (POC/PON/POP) and delta C-13(POC) (carbon isotopic compositio n of POC). These were compared with organic matter in the overlying platele t layer and the water column. In turn. the biogeochemistry of the platelet layer and water column was investigated and the organic matter characterist ics related to inorganic nutrients (nitrate, nitrite, ammonium. silicate. p hosphate), dissolved organic carbon/nitrogen (DOC/DON), PH, dissolved inorg anic carbon (DIC), oxygen and delta C-13(DIC) (carbon isotopic composition dissolved inorganic carbon).