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Aquatic Microbial Ecology

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AME 54:305-318 (2009)  -  DOI:

Effects of rising temperature on the formation and microbial degradation of marine diatom aggregates

Judith Piontek1,*, Nicole Händel1, Gerald Langer1, Julia Wohlers2, Ulf Riebesell2, Anja Engel1

1Alfred Wegener Institute for Polar and Marine Research, Am Handelshafen 12, 27570 Bremerhaven, Germany
2IFM-Geomar, Leibniz Institute of Marine Science, Düsternbrooker Weg 20, 24105 Kiel, Germany

ABSTRACT: Effects of elevated temperature on the formation and subsequent degradation of diatom aggregates were studied in a laboratory experiment with a natural plankton community from the Kiel Fjord (Baltic Sea). Aggregates were derived from diatom blooms that developed in indoor mesocosms at 2.5 and 8.5°C, corresponding to the 1993 to 2002 mean winter in situ temperature of the Western Baltic Sea and the projected sea surface temperature during winter in 2100, respectively. Formation and degradation of diatom aggregates at these 2 temperatures in the dark were promoted with roller tanks over a period of 11 d. Comparison of the 2 temperature settings revealed an enhanced aggregation potential of diatom cells at elevated temperature, which was likely induced by an increased concentration of transparent exopolymer particles (TEP). The enhanced aggregation potential led to a significantly higher proportion of particulate organic matter in aggregates at 8.5°C. Moreover, the elevated temperature favoured the growth of bacteria, bacterial biomass production, and the activities of sugar- and protein-degrading extracellular enzymes in aggregates. Stimulating effects of rising temperature on growth and metabolism of the bacterial community resulted in an earlier onset of aggregate degradation and silica dissolution. Remineralization of carbon in aggregates at elevated temperature was partially compensated by the formation of carbon-rich TEP during dark incubation. Hence, our results suggest that increasing temperature will affect both formation and degradation of diatom aggregates. We conclude that the vertical export of organic matter through aggregates may change in the future, depending on the magnitude and vertical depth penetration of warming in the ocean. 

KEY WORDS: Diatom aggregates · Temperature · Degradation · Extracellular enzymes · Bacterial growth · Global warming

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Cite this article as: Piontek J, Händel N, Langer G, Wohlers J, Riebesell U, Engel A (2009) Effects of rising temperature on the formation and microbial degradation of marine diatom aggregates. Aquat Microb Ecol 54:305-318.

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