SEDIMENT COMMUNITY BIOMASS AND RESPIRATION IN THE NORTHEAST WATER POLYNYA, GREENLAND - A NUMERICAL-SIMULATION OF BENTHIC LANDER AND SPADE CORE DATA

Sediment community metabolism (oxygen demand) was measured in the Nort heast Water (NEW) polynya off Greenland employing two methods: in situ benthic chambers deployed with a benthic (GOMEX) lander and shipboard laboratory Batch Micro-Incubation Chambers (BMICs) utilizing 'cores' recovered from USNEL box cores. The mean benthic respiration rate meas ured with the lander was 0.057 mM O-2 m(-2) h(-1) (n = 5); whereas the mean measured with the BMICs was O.11 mM O-2 m(-2) h(-1) (n = 21; p < 0.01 that the means were the same), In terms of carbon fluxes (14 and 27 mg C m(-2) d(-1)), these respiration rates represent ca. 5-15% of the average net primary production measured in the euphotic zone in 19 92. The biomass of the bacteria, meiofauna and macrofauna were measure d at each location to quantify the relationship between total communit y respiration and total community biomass (mean 1.42 g C m(-2)). Avera ge carbon residence time in the biota, calculated by dividing the biom ass by the respiration, was on the order of 50-100 days, which is comp arable to relatively oligotrophic continental margins at temperate lat itudes. The biomass and respiration data for the aerobic heterotrophic bacteria, the infaunal invertebrates (meiofauna and macrofauna), and the epifaunal megabenthos (two species of brittle stars) are summarize d in a 'steady-state' solution of a sediment food chain model, in term s of carbon. This carbon budget illustrates the relative importance of the sediment-dwelling invertebrates in the benthic subsystem, compare d to the bacteria and the epibenthos, during the summer open-water per iod in mud-lined troughs at depths of about 300 m. The input needed to drive heterotrophic respiratory processes was within the range of the input of organic matter recorded in moored, time-sequencing sediment traps. A time-dependent numerical simulation of the model was run to i nvestigate the potential responses of the three size groups of benthos to abrupt seasonal pulses of particulate organic matter. The model su ggests that there is a time lag in the increase in bottom community bi omass and respiration following the POC pulse, and provides hypothetic al estimates for the potential carbon storage in the summer (open wate r), followed by catabolic losses during each ensuing winter (ice cover ed). This sequence of storage and respiration may contribute to the pr ocess of seasonal CO2 'rectification' (sensu Yager et al., 1995) in so me Arctic ecosystems.