Aquatic Sciences Meeting, Albuquerque 2001

CS20 Microbial Dynamics

Date: Friday, February 16, 2001, Time: 11:15:00 AM

Location: Ruidoso/Pecos

Grossart, H, P, ICBM, University of Oldenburg, D-26111 Oldenburg, Germany, hgrossart@icbm.de

ROLE OF HETEROTROPHIC BACTERIA FOR THE RELEAS OF AMINO ACIDS AND CARBOHYDRATES BY MARINE DIATOMS

Bacterio-phytoplankton interactions in aquatic systems range from symbiosis to parasitism and are highly variable in space and time. Two marine diatoms were grown in axenic culture and incubated under controlled lab conditions. Natural seawater from the North Sea was added to the algae either during exponential or stationary. Release of dissolved amino acids and carbohydrates was highest during stationary growth and it was much higher when bacteria were absent. In contrast, release of dissolved amino acids and carbohydrates was relatively low during exponential growth of the algae when algal mortality was low. Concentrations of amino acids and carbohydrates strongly increased at the beginning of stationary growth but remained low when bacteria were present. In parallel to enhanced algal exsudation, bacterial number, production, and ectoenzyme activity strongly increased. Composition of dissolved amino acids and carbohydrates in axenic and non-axenic cultures were significantly different from eachother. Thus, bacteria influence the flux and cycling of carbon at both micro- and global scale.

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Aquatic Sciences Meeting, Albuquerque 2001

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