Aquatic Sciences Meeting, Albuquerque 2001

PC12 Trophic Dynamic Studies

Date: Thursday, February 15, 2001

Location: Southwest Hall

Menden-Deuer, S, , University of Washington, School of Oceanography, Seattle, USA, smenden@ocean.washington.edu

Lessard, E, J, University of Washington, School of Oceanography, Seattle, USA, elessard@u.washington.edu

Satterberg, J, , University of Washington, School of Oceanography, Seattle, USA, jsatterb@u.washington.edu

GROWTH DYNAMICS OF THECATE HETEROTROPHIC DINOFLAGELLATES (PROTOPERIDINIUM): IMPLICATIONS FOR THE ABUNDANCE OF THEIR DIATOM PREY

Thecate dinoflagellates of the genus Protoperidinium can be important predators of diatoms. Growth dynamics of three Protoperdinium species (P. conicum, P. depressum, P. excentricum) in batch culture at six different diatom (Ditylum brightwellii) concentrations were examined daily for several weeks. Intermittent rather than constant exponential growth periods were observed. Growth rates based on intervals of exponential growth were generally higher than those estimated from one to three day incubations using initial and end-point measurements. Therefore, using end-point measurements to estimate growth rates may underestimate the growth potential of these predators. All species survived for several months at extremely low prey concentrations (0.6ugC l-1). Above threshold concentrations, all species achieved growth rates in excess of one doubling per day over short time intervals. Intermediate (50-150ugC l-1), but not high prey concentrations (>300ugC l-1), were rapidly grazed to threshold levels. These results suggest that at typical natural abundance, Protoperidinium grazing could delay or prevent the build-up of a diatom bloom. Furthermore, Protoperidinium grazing could accelerate the decline of a diatom bloom but might not initiate the decline itself.

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Aquatic Sciences Meeting, Albuquerque 2001

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