Seasonal patterns of water column particulate organic carbon and fluxes inthe Ross Sea, Antarctica

The standing stock of particulate organic carbon (POC) was determined durin g five cruises in the Ross Sea in 1996 and 1997 and compared with primary p roduction of carbon measured in short-term C-14-incubations and the flux of organic carbon collected in moored sediment traps. POC concentrations were estimated from transmissometer profiles that were calibrated with discrete POC bottle samples from each cruise. The mean standing stock of POC integr ated to a depth of 100 m and averaged along a 330 km transect at 76.5 degre esS in mid-October (early spring) was only 240 mmol C m(-2), but more than doubled to 560 mmol C m(-2) 10 days later. By mid-January (summer) the stan ding stock had increased by an order of magnitude to similar to 5300 mmol C m(-2), but dropped to 3500 mmol C m(-2) one week later. By late April (aut umn), the standing stock was only 200 mmol C m(-2). The following spring th e standing stock increased from 700 mmol C m(-2) in late November to 2200 m mol C m(-2) in early December. Despite the high standing stock in the photi c zone in summer, 1997, little POC was collected in the moored sediment tra ps until late summer (February-March) when the traps showed an increase in POC and silica flux. A three-fold increase in POC flux occurred in autumn ( March-April) dominated by pteropods, but the standing stock of POC in the p hotic zone at that time was very low. Light-scattering sensor data suggest that, although present in all seasons, aggregates were most abundant in aut umn and were distributed throughout the water column. These aggregates may have temporarily stored POC and provided food support for a pteropod popula tion that died and settled into the traps in March-April. Still, the trap P OC flux was only 5% of the peak standing stock. Resuspension and lateral ad vection of recently settled organic matter from a nearby topographic high m ay explain the larger flux measured in the deep sediment traps, a flux that continued into winter. (C) 2000 Elsevier Science Ltd. All rights reserved.