Primary production, nutrient dynamics and mineralisation in a northeastern Greenland fjord during the summer thaw

This investigation represents the first integrated study of primary production, nutrient dynamics and mineralisation in a northeastern fjord of Greenland. The data presented represent conditions and activities during the early summer thaw (first 2 weeks of July). Primary production (5.3 mmol C m(-2) d(-1)) and chlorophyll a (4.1 mu g l(-1)) values were found to be comparable with measurements from other Arctic regions. Water column N-fixation rates were low (<0.02 mu mol N m(-1) d(-1)), but comparable with other estuarine systems. Despite a constant low temperature in the bottom waters (-1.0 to -1.8 degrees C), a high sedimentary O-2 uptake (740 mu mol m(-2) h(-1)) was observed and was primarily caused by the presence of benthic infauna. Bioturbation by benthic infauna was reflected in both homogeneous Pb-210 and Cs-137 profiles in the upper 4 cm of the sediment. Permanent accumulation within Young Sound was measured to 0.12 cm/year corresponding to 153 mmol C m(-2) year(-1) and 15 mmol N m(-2) year(-1). Rates of nitrification (22 mu mol m(-2) h(-1)) and denitrification (9 mu mol m(-2) h(-1)) were comparable with rates reported for other sediments with much higher environmental temperatures. Suphate reduction rates integrated over the upper 12 cm of the sediment were calculated to be 44 mu mol m(-2) h(-1).