Aquatic Sciences Meeting, Albuquerque 2001

SS13 Mixotrophic Plankton - Combining Phototrophic and Heterotrophic Nutrition

Date: Friday, February 16, 2001, Time: 9:00:00 AM

Location: Acoma/Zuni/Tesuque

Bergström, A, , Umeå University/Ecology and Environmental Science, Umeå, Sweden, ann-kristin.bergstrom@eg.umu.se

Isaksson, A, , Uppsala University/Department of Limnology, Uppsala, Sweden,

THE IMPORTANCE OF MIXOTROPHIC FLAGELLATES AS BACTERIAL GRAZERS IN A LARGE HUMIC LAKE - RESULTS FROM A THREE YEAR STUDY IN NORTHERN SWEDEN

The abundance and the importance of mixotrophic flagellates as bacterial grazers were investigated during June to August in 1995-1997 in the epilimnion of Lake Örträsket, northern Sweden. The mixotrophic flagellates, dominated by Ochromonas spp., were always the most abundant group among phytoplankton in early summer. High abundance of mixotrophic flagellates usually followed the bacterial production and biomass peak connected to the spring flood input of readily available DOC. The mixotrophic biomass was also positively related to the effective light climate in the lake. The clearance rates of mixotrophs were fairly constant throughout the investigated periods and ranged between 1-4 nl/flagellate/h. Mixotrophic clearance rates were similar to those of heterotrophs, but due to their high abundance, mixotrophs were more important as bacterial grazers in the lake. On average the mixotrophs were able to remove 128%, 41%, 26% of the bacterial production in 1995, 1996 and 1997, respectively. Mixotrophs must therefore be regarded as higly important bacterial garzers in this kind of lake, and probably uses the bacteria as an energy and nutrient source.

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Aquatic Sciences Meeting, Albuquerque 2001

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