AME 16:205-216 (1999)  -  doi:10.3354/ame016205

Plankton community structure and carbon cycling on the western coast of Greenland during the stratified summer situation. I. Hydrography, phytoplankton and bacterioplankton

Torkel Gissel Nielsen1,*, Benni Winding Hansen2

1National Environmental Research Institute, Department of Marine Ecology and Microbiology, Frederiksborgvej 399, PO Box 358, DK-4000 Roskilde, Denmark
2Roskilde University, Department of Life Sciences and Chemistry, PO Box 260, DK-4000 Roskilde, Denmark

ABSTRACT: Plankton community structure in Disko Bay, West Greenland, was examined during late summer 1994. Sampling with high temporal and vertical resolution was conducted at a 250 m deep station from mid-July to mid-September. The water column was strongly stratified and the phytoplankton community in the surface layer was nitrate and silicate depleted. A prominent feature was the occurrence of enhanced phytoplankton biomass in association with the pycnocline where nitrate became detectable. Three distinct blooms (chl a > 8 μg l-1) were observed in the pycnocline, the first dominated by haptophyte flagellates and subsequently by diatoms. Bacterial biomass mirrored the vertical and temporal distribution pattern of the phytoplankton. Comparison between primary production and bacterial production showed that pelagic bacterioplankton were important in this high latitude ecosystem, as documented for low latitude ecosystems. The most important bacterivores, the heterotrophic nanoflagellates, had the potential of clearing the daily bacterial production. It is concluded that future studies of Arctic pelagic ecology should consider the plankton community in the subsurface layer if carbon flow in the pelagic food web is to be fully understood.

KEY WORDS: Arctic pelagic food web · Nutrient dynamics · Phytoplankton · Bacterioplankton · Subsurface blooms

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