Aquatic Sciences Meeting, Albuquerque 2001

SS14 Microbial Diversity (Disciplinary Connections)

Date: Tuesday, February 13, 2001, Time: 2:30:00 PM

Location: Mesilla

Stoderegger, K, E, Netherlands Institute for Sea Research, Den Burg, Netherlands, karen@nioz.nl

Herndl, G, J, Netherlands Institute for Sea Research, Den Burg, Netherlands, herndl@nioz.nl

Distribution of capsulated bacterioplankton in the North Atlantic and North Sea

During two cruises, one to the North Atlantic the other one to the North Sea, we investigated the distribution and abundance of bacteria surrounded by a capsular layer. Capsulated bacteria were more abundant in eutrophic surface waters than in deeper or more oligotrophic regions. The percentage of capsulated bacteria correlated with bacterial production, bacterial abundance and chlorophyll a concentration. On average, about 20-30 % of the bacterioplankton in the surface water were capsulated while less than 5% were capsulated in the water layers > 500 m. The bioavailability of dissolved organic carbon (DOC) was estimated by the ratio between bacterial activity : DOC concentration which significantly correlated with the percentage of capsulated bacteria. Even in the shallow North Sea, a significant decrease from the surface (3m depth) to the bottom waters (25-35m) from 20 % to 14 % capsulated bacteria was detectable. In laboratory experiments, bacterioplankton were incubated under different nutrient conditions and the percentage of capsulated bacteria and of CTC (cyano-tetrazolium-chloride)-positive and therefore metabolically highly active bacteria was determined. It was found that more than 95 % of the CTC-positive bacteria exhibited also a capsule.

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Aquatic Sciences Meeting, Albuquerque 2001

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