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Marine Ecology Progress Series

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MEPS 390:97-104 (2009)  -  DOI:

Hydrostatic pressure affects physiology and community structure of marine bacteria during settling to 4000 m: an experimental approach

Hans-Peter Grossart1,*, Giselher Gust2

1Leibniz Institute of Freshwater Ecology and Inland Fisheries, Department of Limnology of Stratified Lakes, Alte Fischerhuette 2, 16775 Stechlin, Germany
2Hamburg University of Technology, Institute of Ocean Engineering, Schwarzenbergstrasse 95, 21073 Hamburg, Germany

ABSTRACT: The response of 5 strains of shallow-water microbes to changing hydrostatic pressure was explored in a pressurized microcosm setup, simulating a sinking at 1000 m d–1 from surface waters to 4000 m depth in an isothermal ocean. Technology and methods combined a new, computer-controlled pressure laboratory with classical and new genetic tools to evaluate pressure responses of selected bacterial strains. Size, number, growth and species composition were obtained in a time series pattern under regular, non-saturating feeding. Planned as an initial step in a quest for quantifying the role of hydrostatic pressure in observed oceanic microbial distributions, results from this study indicate that selected bacterial strains from the surface respond individually to pressure exposure. A strong physiological response led to reduced bacterial numbers of all strains at 4000 m depth, a result corroborated elsewhere in the literature. Unexpectedly, pressure changes (during sinking) generated depth-specific maxima and minima in number of the selected strains, not seen in the ambient pressure control. A reshuffling of species and changes in sizes of all strains tested occurred in the pressurized treatment. Therefore, time series experiments with non-intrusive sampling features rather than end-member experiments become mandatory to document physiological responses to pressure. Our results, together with recent findings on pressure-related effects on microbial growth and community structure in the deep-sea, indicate that estimates of microbial organic matter turnover in the deep-sea—not taking pressure-related effects into account—need to be revisited.

KEY WORDS: Hydrostatic pressure · Pressure laboratory · Bacteria · Aggregates · Growth · Species composition · CARD-FISH

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Cite this article as: Grossart HP, Gust G (2009) Hydrostatic pressure affects physiology and community structure of marine bacteria during settling to 4000 m: an experimental approach. Mar Ecol Prog Ser 390:97-104.

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