Aquatic Sciences Meeting, Albuquerque 2001

SS13 Mixotrophic Plankton - Combining Phototrophic and Heterotrophic Nutrition

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

Location: Acoma/Zuni/Tesuque

Legrand, C, , Mar. Sciences, Inst. Biol. & Environ. Sc., Univ. Kalmar, Kalmar, Sweden, catherine.legrand@hik.se

Granéli, E, , Mar. Sciences, Inst. Biol. & Environ. Sc., Univ. Kalmar, Kalmar, Sweden, edna.graneli@hik.se

BENEFITS OF MIXOTROPHIC NUTRITION IN TWO MARINE HAPTOPHYTES

Previous studies report how abiotic (light or nutrients, organic substances) and biotic (prey density, physiological status of the mixotroph) factors, often examined separately, regulate the capabilities of marine mixotrophic haptophytes (e.g. Chrysochromulina spp., Prymnesium spp.) to switch between phototrophy and heterotrophy. We aim to present an integrated view of the combined effect of these environmental factors on mixotrophic nutrition in these species.Our cultures and field experiments have shown that phagotrophic nutrition was enhanced under nutrient (mostly P) limitation in C. polylepis and P. patelliferum. In these conditions, bacterial P and N contributed up to 100 and 80 % to mixotrophic growth respectively, thus reducing cellular N or P deficiency. High bacterivory also occurred when nitrate and organic N (humic substances, polyamines) were available. Organic substances promote bacterial growth, and bacterivory was possibly chosen over nitrate utilization as a consequence of increasing food supply for the mixotrophs. Under light limitation (and no nutrient limitation), bacterivory was not only providing an alternative source of carbon but possibly essential elements since bacterivory was inversely related to cellular chlorophyll a quota.

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Aquatic Sciences Meeting, Albuquerque 2001

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