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Aquatic Microbial Ecology

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AME 30:57-68 (2002)  -  doi:10.3354/ame030057

Significance of sedimentation and grazing by ice micro- and meiofauna for carbon cycling in annual sea ice (northern Baffin Bay)

Christine Michel1,*, Torkel Gissel Nielsen2, Christian Nozais3, Michel Gosselin3

1Freshwater Institute, Fisheries and Oceans Canada, 501 University Crescent, Winnipeg, Manitoba R3T 2N6, Canada
2National Environmental Research Institute, Department of Marine Ecology, Frederiksborgvej 399, PO Box 358, 4000 Roskilde, Denmark
3Institut des sciences de la mer de Rimouski (ISMER), Université du Québec à Rimouski, 310 allée des Ursulines, Rimouski, Québec G5L 3A1, Canada

ABSTRACT: The fate of first-year ice algae production was assessed from April to June 1998, in the North Water Polynya. A landfast ice station was regularly visited and sampled for biomass, composition, and production of bottom ice algae, composition and grazing of the bottom ice meiofauna, and under-ice sedimentation. The latter was assessed using particle interceptor traps, which were installed at 1 m underneath the ice. The composition, carbon biomass and grazing of the bottom ice microfauna were also assessed at various stations within the polynya. A carbon budget for ice production and export, including meio- and microfauna grazing and sedimentation, was calculated based on 2 independent estimates. At the landfast ice station, the ice algae community was strongly dominated by pennate diatoms, with Nitzschia frigida averaging 85% of total cell numbers. The biomass of microheterotrophs and microautotrophs was less than 1% of total bottom ice carbon at the stations visited. Heterotrophic dinoflagellates and ciliates dominated the bottom ice microfauna community. Size-frequency distributions for the dominant ciliates (Strombidium spp. and hypotrichs) and dinoflagellates suggest that only the latter were able to utilise ice diatoms as a food resource. There was good agreement between carbon budget estimates and results showed that very little ice algal production was channelled through the meio- and microfauna within the ice. The bulk of the bottom ice carbon biomass was readily exported to the water column through direct sinking (75% of ice export). These results stress that the main flow of organic carbon at the ice-water interface was through sedimentation of ice algae and suggest that food-web interactions within the ice do not influence the availability of ice algae to pelagic grazers, in seasonally ice covered areas.

KEY WORDS: Protists · Dinoflagellates · Ciliates · Sedimentation · Carbon cycling · Sea ice · Ice algae

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