MEPS 179:13-25 (1999)  -  doi:10.3354/meps179013

Seasonal variation in nutrients, pelagic primary production and grazing in a high-Arctic coastal marine ecosystem, Young Sound, Northeast Greenland

Søren Rysgaard1,*, Torkel Gissel Nielsen2, Benni Winding Hansen3

1National Environmental Research Institute, Deptartment of Lake and Estuarine Ecology, Vejlsøvej 25, DK-8600 Silkeborg, Denmark
2National Environmental Research Institute, Deptartment of Marine Ecology and Microbiology, Frederiksborgvej 399, DK-4000 Roskilde, Denmark
3Roskilde University, Deptartment of Life Sciences and Chemistry, DK-4000 Roskilde, Denmark

ABSTRACT: The Young Sound estuary was covered by sea ice for approximately 10 mo during 1996. Investigations of pelagic primary production and estimated grazing were performed during the summer thaw (20 June to 25 August) and in the winter month of February. The phytoplankton community was dominated by diatoms in the surface samples, as well as in the subsurface bloom succeeding the spring bloom. Pelagic primary production was limited by light during sea ice cover. After break-up of the sea ice, silicate initially limited primary production in the surface water due to a well-established pycnocline, and maximum photosynthesis occurred in a subsurface layer at 15 to 20 m depth. In August, production sank to deeper water layers presumably due to nitrogen limitation. The carbon budget describing the fate of the annual pelagic primary production in Young Sound reveals that the pelagic production of ~10 g C m-2 yr-1 was tightly coupled to the grazer community, since total consumption by the grazer community amounted to 10-12 g C m-2 yr-1. The classical food web dominated this northeastern Greenlandic fjord, and it was estimated that copepods account for >80% of the grazing pressure upon phytoplankton. Based on this study and other values of annual pelagic primary production and sea ice cover found in the literature, we suggest that annual pelagic primary production in the Arctic can be described as proportional to the length of the open water light period. We propose that annual pelagic primary production, and hence secondary production, in a wide range of Arctic marine areas may increase in the future as a consequence of reduction and thinning of sea ice cover due to global warming.

KEY WORDS: Primary production · Zooplankton · Grazing · Nutrients · Global change · Arctic

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