Plankton community structure and carbon cycling on the western coast of Greenland during and after the sedimentation of a diatom bloom

Abstract

Pelagic food web structure and carbon dynamics were studied in Disko Bay, western Greenland, following the breakup of the sea ice in June-July 1992. Disko Bay was influenced by melt water, and calm sunny weather heated the surface water from 0 to 6 degrees C. Initially a diatom bloom was present throughout the photic zone. Due to nutrient depletion, and deepening of the surface layer, the bloom left the photic zone. Active bacterioplankton was observed from the first sampling. Bacterial production increased from a few percent to one-third of the primary production after the sedimentation of the bloom. The grazing impact by the copepod community was assessed by 2 independent methods. The gut fluorescence method and the egg production method resulted in copepod grazing estimates of about 80 and 45 % of the primary production d(-1), respectively. Carbon budget considerations showed that the estimated protozooplankton grazing impact was comparable, or higher, than grazing by the Calanus spp. dominated copepod community. The observed importance of Arctic bacteria and protozooplankton stress that high latitude pelagic food webs potentially have the same trophic complexity as low latitude pelagic ecosystems.