Aquatic Sciences Meeting, Albuquerque 2001

PC12 Trophic Dynamic Studies

Date: Thursday, February 15, 2001

Location: Southwest Hall

Palsson, C, , Lund University, Dept. of Ecology/Limnology, Lund, Sweden, carina.palsson@limnol.lu.se

Granéli, W, , Lund University, Dept. of Ecology/Limnology, Lund, Sweden, wilhelm.graneli@limnol.lu.se

DIEL VARIATIONS IN INGESTION RATES OF BACTERIA BY MIXOTROPHIC AND HETEROTROPHIC FLAGELLATES: AN IN SITU STUDY IN TWO TEMPERATE LAKES DIFFERING IN HUMIC CONTENT.

Grazing rates on bacteria by mixotrophic and heteretrophic flagellates were measured in situ in a clear-water lake and a humic lake situated in south Sweden. The primary aim was to estimate diel variations in ingestion rates. Measurements were performed at 6-hour intervals during a twenty-four hours period at three depths distributed in the photic zones of the two lakes. To estimate bacterivory, carboxylate-modified FluoSpheres beads with a 1.0 micrometer diameter were added to a final concentration of 40% of natural bacterial densities. Ingestion rates were analyzed using an epifluorescence microscope. At each sampling occasion, samples for phytoplankton community composition, bacterial abundance and chlorophyll a were collected. At midday, primary and bacterial production were measured. The phytoplankton community in the high humic lake was dominated by small flagellates and blue green algae, whereas potential mixotrophs (Dinobryon sp., Uroglena sp.) were common in the clear-water lake. Preliminary results indicate low ingestion rates in both lakes.

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Aquatic Sciences Meeting, Albuquerque 2001

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