Aquatic Sciences Meeting, Albuquerque 2001

SS13 Mixotrophic Plankton - Combining Phototrophic and Heterotrophic Nutrition

Date: Friday, February 16, 2001, Time: 10:15:00 AM

Location: Acoma/Zuni/Tesuque

Sanders, R, W, Temple University, Philadelphia, USA, rsanders@nimbus.temple.edu

NUTRIENT ACQUISITION BY A MIXOTROPHIC OCHROMONAD IS MEDIATED BY PHAGOTROPHY

A strain of the freshwater mixotroph, Ochromonas sp., was grown in nutritionally different conditions that included both axenic and bacterized cultures in light and dark. The highest growth rates were observed in the presence of live bacteria; increases in Ochromonas abundance and grazing impacts on prey were similar in light and dark treatments with bacteria. However, algal cell size and total algal biovolume were consistently greater in the light with bacteria relative to dark incubations. This suggested that photosynthesis supplemented heterotrophic (phagotrophic) nutrition. In an inorganic nutrient medium, axenic populations of Ochromonas sp. did not grow in the dark and grew slowly in the light relative to treatments with bacteria. Addition of glucose to axenic cultures supported slow growth in the dark, but did not increase growth in the light. Axenic cultures supplemented with a more complex organic compound (MES) grew at similar rates in the light and dark. Ochromonas yield in the MES treatment was intermediate to bacterized treatments and axenic cultures with glucose added.

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Aquatic Sciences Meeting, Albuquerque 2001

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