Metabolism of deep-sea sponges in the Greenland-Norwegian Sea

During two cruises with RV ''Meteor'' in 1991 and 1992 to the Norwegian and Greenland Sea, sponges were collected by either box corer or Agassiz trawl at a depth of >2000m, in order to assess the role of deep-sea sponges for energy fluxes through the deep-sea benthic community. Heat production was measured via direct microcalorimetry and adenosine nucleotide levels were determined. Energy charge ranged between 0.5-0.8 for most individuals and was thus comparable to values for normally active shallow water organisms. Oxygen consumption calculated from heat production measurements was about 20 mu mol O-2 . h(-1) . g(-1) ash-free dry weight (AFDW) for all species studied. From the combination of body mass values with individual respiration rates, sponge community oxygen demand, ranging from 20-140 mu mol O-2 . m(-1) . h(-1), could be determined. A comparison with sediment oxygen demand (SOD) measurements (Graf et al., 1995) showed that sponges contribute up to 22% of SOD to benthic oxygen consumption and thus in the deep Greenland Sea belong to the primary organisms involved in the turnover of organic carbon at the deep-sea floor.