Benthic oxygen uptake, hydrolytic potentials and microbial biomass at the Arctic continental slope

Oxygen (O(2)) uptake and microbial activity in sediments of the eastern Arctic continental slope were investigated in both ice-covered and ice-free areas of the Laptev Sea. Total O(2) flux (J) decreased markedly from 2 mmol m(-2) d(-1) at the shelf edge (50 m) to 0.07 mmol m(-2) d(-1) at the bottom of the slope (3500 m), matched by the more than tenfold decline in chlorophyll pigments (CPE), protein and dissolved amino acids (DFAA). Furthermore, concentrations of these labile organic compounds were strongly correlated with extracellular enzyme potentials (EEA) in the sediments as well as with microbial biomass. The concentrations of labile substances and total microbial biomass (TMB) as well as the rates of O(2) uptake and EEA were independent of the distribution of TOC, probably due to the dominance of nonlabile terrigenous compounds. Differences in O(2) uptake and microbial EEA between ice-covered and ice-free transects were relatively small. Values of O(2) uptake, CPE, EEA and TMB at the Laptev Sea slope were considerably lower than at temperate continental slopes but nevertheless higher than in the central Arctic deep-sea basin. Considering newly published data on primary productivity in the central Arctic, our results indicate that the benthic respiratory demand at the Laptev Sea slope and in the Arctic basin could be satisfied by the vertical flux of POC and does not necessarily depend on lateral advection of POC from the shelf seas as previously anticipated. (C) 1998 Elsevier Science Ltd. All rights reserved.