The annual organic carbon budget of Young Sound, NE Greenland

Abstract

On the basis of data presented in the previous chapters a carbon budget for the respective compartments of the outer region of Young Sound (76 km2) was established. The average and maximum water depth of the region was 76 m and 177 m, respectively. Primary production was mainly related to the activity of phytoplankton (65%), benthic macrophytes (21%) and benthic microphytes (13%), while the contribution sea-ice algae and corallines was negligible (<1%). The pelagic grazing community was completely dominated by copepods, which were capable of consuming 87% of the pelagic primary production.
 The benthic carbon demand was almost balanced by the measured sedimentation of POC and the benthic primary production. The organic carbon collected in the sediment traps was estimated to consist of 40% terrestrial carbon, 20% fecal pellets, while the rest was poorly defined marine detritus. The benthic sink for settling organic material was dominated by microbial respiration (59%) and only to a minor extent related to macrofauna respiration (15%) and carbon preservation (26%).
 The total primary production in the region (1119 t C yr-1) only sustained c. 40% the estimated organic carbon demand (2850 t C yr-1). Thus, the independently determined input of TOC (990 t C yr-1) imported to Region 1 from land via freshwater runoff and the TOC import of 1446 t C yr-1 from the Greenland Sea are required to balance the carbon sinks of the net heterotrophic region. A complete balance between the respective compartments cannot be expected, as the various components of the carbon budget are determined independently. The microbial and viral loops remain poorly constrained, as does the carbon demand of the top predators. Only the importance of walrus was quantitatively assessed.