ACTIVITY AND BIOMASS OF THE SMALL BENTHIC BIOTA UNDER PERMANENT ICE-COVERAGE IN THE CENTRAL ARCTIC-OCEAN

Sediment samples collected during the expedition ''Arctic Ocean '96'' with the Swedish ice-breaker ODEN were investigated to estimate for th e first time heterotrophic activity and total microbial biomass (size range from bacteria to small metazoans) from the perennially ice-cover ed central Arctic Ocean. Benthic activities and biomass were evaluated analysing a series of biogenic sediment compounds (i.e. bacterial exo enzymes, total adenylates, DNA, phospholipids, particulate proteins). In contrast to the very time-consuming sorting, enumeration and weight determination, analyses of biochemical sediment parameters may repres ent a useful method for obtaining rapid information on the ecological situation in a given benthic system. Bacterial cell numbers and biomas s were estimated for comparison with biochemically determined biomass data, to evaluate the contribution of the bacterial biomass to the tot al microbial biomass. It appeared that bacterial biomass made up only 8-31% (average of all stations = 20%) of the total microbial biomass. suggesting a large fraction of other small infaunal organisms within t he sediment samples (most probably fungi, yeasts, protozoans such as f lagellates, ciliates or amoebae, as well as a fraction of small metazo ans). Activity and biomass values determined within this study were ge nerally extremely low, and often even slightly lower than those given for other deep oceanic regions, thus characterizing the seafloor of th e central Arctic Ocean as a ''benthic desert''. Nevertheless, some cle ar trends in the data could be found, e.g. generally sharply decreasin g values within the sediment column, a vague tendency for declining va lues with increasing water depth of sampling stations, and also differ ences between various Arctic deep-sea regions.