AME 64:253-266 (2011)  -  doi:10.3354/ame01525

Microbial communities and processes in ice-covered Arctic waters of the northwestern Fram Strait (75 to 80°N) during the vernal pre-bloom phase

Lena Seuthe1,*, Birte Töpper2, Marit Reigstad1, Runar Thyrhaug, Raquel Vaquer-Sunyer3

1University of Tromsø, Department of Arctic and Marine Biology, 9037 Tromsø, Norway
2University of Bergen, Department of Biology, Box 7800, 5020 Bergen, Norway
3Department of Global Change Research, IMEDEA (CSIC-UIB), Institut Mediterrani d’Estudis Avançats, C/Miguel Marqués 21, 07190 Esporles, Mallorca, Spain
*Email: ‑†Deceased 

ABSTRACT: Marine microbial communities have been little studied in Arctic waters, especially ­during the winter–spring transition before the development of extensive phytoplankton blooms. This study investigated microbial plankton in the ice-covered polar surface waters of the northwestern Fram Strait (75 to 80°N) at the onset of the 24 h light period in spring (April to May). The system we encountered was characterised by low concentrations of chlorophyll a (<0.2 µg l−1) and a low abundance of both bacteria (1.4 to 2.5 × 108 cells l−1) and protists (1 to 1.7 × 105 cells l−1). Bacterial production was very low (≤0.63 µg C l−1 d−1), despite the dominance of nucleic-acid-rich bacteria (58 ± 6% of total bacterial abundance). Small (2 to 5 µm) phototrophs dominated the eukaryotic assemblage in the surface and most probably had profound effects on the composition and metabolic balance of the microbial community as a whole. Most stations appeared to have been net-autotrophic, and calculations of phagotrophy indicated a balanced carbon budget for the microbial community. Mixotrophy was seen in a large part of the ciliate assemblage and may have contributed to the productivity and stability of the pre-bloom system that we encountered.


KEY WORDS: Flow cytometry · Bacteria · Microzooplankton · Mixotrophy · Planktonic metabolism


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Cite this article as: Seuthe L, Töpper B, Reigstad M, Thyrhaug R, Vaquer-Sunyer R (2011) Microbial communities and processes in ice-covered Arctic waters of the northwestern Fram Strait (75 to 80°N) during the vernal pre-bloom phase. Aquat Microb Ecol 64:253-266

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