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Aquatic Microbial Ecology

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AME 20:107-118 (1999)  -  doi:10.3354/ame020107

Primary and bacterial production in sea ice in the northern Baltic Sea

Pia Haecky*, Agneta Andersson**

Department of Microbiology, Umeå University, 901 87 Umeå, Sweden
Present addresses:
*Marine Biological Laboratory (University of Copenhagen) Strandpromenaden 5, 3000 Helsingør, Denmark. E-mail:
**Marine Ecology, Department of Ecology and Environmen-tal Science, Umeå University, 901 87 Umeå, Sweden

ABSTRACT: The temporal variation of ice primary and bacterial production along with ice algal, bacterial and heterotrophic flagellate biomass were studied at a coastal station in the northern Baltic Sea throughout the ice-covered period of 1996 (January to April). Ice core samples were taken every week and analyzed for abundance and production of different microorganisms. In addition, physical and chemical parameters were measured. The ice algae were limited by light during the first 3 mo of the study. The algal production showed a peak in the middle of April, which coincided with a marked increase in light availability. Shortly after that, the system became phosphorus depleted and primary production decreased rapidly. Bacterial biomass and production rates were relatively low and stable before the ice algal bloom. After the ice algal bloom, bacterial production increased rapidly, while the biomass remained low. The growth rate of small heterotrophic flagellates (<10 μm), calculated from increase in biomass, was more than 1 order of magnitude higher than the bacterial production rate following the ice algal bloom. Thus, small heterotrophic flagellates were using food sources other than bacteria for growth after the ice algal bloom. On an annual basis, the ice algal and bacterial production accounted for <1% and <0.1% respectively of the total production (ice + pelagic) due to a short ice-covered season. During the ice-covered season, however, the ice algae accounted for 10% of the total algal production, while ice bacterial production was 0.2% of the total bacterial production.

KEY WORDS: Sea-ice · Primary production · Bacterial production · Heterotrophic flagellates · Nutrients · Light

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