Benthic carbon mineralization in a high-Arctic sound (Young Sound, NE Greenland)

Benthic carbon mineralization was investigated along a depth transect across a sound in the high Arctic. Aerobic mineralization accounted for approximately 30% of the total degradation. Anaerobic degradation, responsible for the remaining 70%, was dominated by sulfate- and iron respiration, while denitrification and manganese respiration were of marginal importance. The total benthic degradation rate exhibited a rapidly attenuating exponential decline with increasing water depth. Permanent carbon burial accounted for approximately 50% of the total degradation rate, and was comparable to estimates from similar settings at lower latitudes. At the shallow stations, benthic infauna stimulated the benthic oxygen exchange by a factor of 1.5 to 3 relative to molecular diffusion. However, the estimated metabolic activity of the fauna itself accounted for <10% of total benthic degradation. From the rates of benthic degradation, permanent burial, pelagic primary production, and sedimentation of organic carbon, a budget for the pelagic-benthic coupling for outer Young Sound was established. Pelagic production accounted for only a minor fraction of the carbon required by the benthic community, and <delta>C-13 values suggested that terrestric carbon inputs were significant. However, the budget also indicated that additional sources of labile organic carbon (ice-algae, benthic microphytes and oceanic inputs) were important. During July, the time of the summer bloom, 36% of the sedimenting organic material was either degraded or buried. The remainder fueled the community respiration during the long, non-productive, winter.