BENTHIC MINERALIZATION AND EXCHANGE IN ARCTIC SEDIMENTS (SVALBARD, NORWAY)

By means of benthic landers, sediment core incubations and the whole c ore squeezing (WCS) technique, benthic exchange and mineralization rat es were investigated in 4 different fjords of Arctic Norway (Svalbard) . These coastal sediments experience constant low temperatures close t d 0 degrees C. The sediments were dominated by large densities of bioi rrigating macrofauna, which enhanced the benthic in situ Oz uptake by a factor of 1.8 to 2.9 over the diffusive mediated uptake. Recovered s ediment cores significantly underestimated the in situ solute exchange rate, presumably due to exclusion of fauna. Faunal activity in situ a dditionally resulted in a complex sediment structure, which created a smearing of chemical profiles when applying the WCS technique. The ben thic exchange rates of dissolved inorganic carbon determined in situ v aried between 9 and 20 mmol m(-2) d(-1) at the different stations. Den itrification was of minor importance for benthic mineralization, and t he C/N ratio of the effluxing inorganic solutes was close to 10, indic ating that relatively fresh organic material was mineralized. The sedi ment accumulation rate was estimated from Pb-210 profiles to be in the range of 1.3 to 5.9 mm yr(-1). Assuming that our estimated mineraliza tion rates approach the yearly average, it was calculated that 31 to 4 7 % of the organic carbon reaching the sediment surface was permanentl y buried. Benthic mineralization rates and carbon burial rates were si milar to those obtained in coastal sediments of temperate and tropical regions. This indicates that benthic communities in Arctic sediments rather than being limited by low temperatures are Limited by carbon av ailability.