Aquatic Sciences Meeting, Albuquerque 2001

SS13 Mixotrophic Plankton - Combining Phototrophic and Heterotrophic Nutrition

Date: Friday, February 16, 2001, Time: 10:30:00 AM

Location: Acoma/Zuni/Tesuque

Smalley, G, W, Smithsonian Environmental Research Center, Edgewater, Maryland, USA, smalley@serc.si.edu

Coats, D, W, Smithsonian Environmental Research Center, Edgewater, Maryland, USA, coats@serc.si.edu

Stoecker, D, K, Horn Point Laboratory, UMCES, Cambridge, Maryland, USA, stoecker@hpl.umces.edu

PHOSPHORUS LIMITATION INDUCES FEEDING IN LABORATORY CULTURES OF THE MIXOTROPHIC DINOFLAGELLATE CERATIUM FURCA

Previous field and laboratory experiments indicate that feeding in the mixotrophic dinoflagellate Ceratium furca is influenced by nutrient concentrations. To examine the effect of phosphorus levels on feeding rate, we grew phototrophic cultures of C. furca at five different inorganic P concentrations. Daily, 25% of the culture and/or medium were removed and replaced by fresh medium, maintaining cell density at 5000 ml-1 and ensuring relatively constant nutrient concentrations. Ingestion of ciliate prey in subsamples of the cultures was highest in the treatment where no P was added. Other parameters were also determined, including inorganic nutrient concentrations, cellular C, N, and P contents of C. furca, photosynthesis, and chl a content. In a second experiment, we added different concentrations of PO4 to P-depleted batch cultures of C. furca to investigate the effect of nutrient addition on feeding. Ingestion of ciliates in subsamples of the cultures decreased to almost zero within the first few hours of P-addition in all treatments, while remaining constant in controls. Subsequently, feeding increased in some of the treatments, presumably as P became depleted.

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Aquatic Sciences Meeting, Albuquerque 2001

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