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

• Published in: Aquatic Microbial Ecology
• Main Authors: Seuthe, L., Töpper, B., Reigstad, Marit, Thyrhaug, R., Vaquer-Sunyer, Raquel
• Format: Article in Journal/Newspaper
• Language: English
• Published: Inter Research 2011
• Subjects: Arctic; Fram Strait; Phytoplankton
• Online Access: http://hdl.handle.net/10261/58688; https://doi.org/10.3354/ame01525

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. © Inter-Research 2011. Peer Reviewed