Aquatic Sciences Meeting, Albuquerque 2001

PC01 Harmful Algal Blooms

Date: Tuesday, February 13, 2001

Location: Southwest Hall

Juhl, A, R, Scripps Institution of Oceanography, University of California, San Diego, La Jolla, CA, USA, ajuhl@ucsd.edu

MECHANISMS OF SHEAR-INDUCED MORTALITY OF A RED-TIDE DINOFLAGELLATE: INCREASED MORTALITY VS. REDUCED CELL DIVISION

Shear-induced inhibition of dinoflagellate net population growth may be due to reduced cell division or increased mortality. Experiments to determine the predominant mechanism for different shear stress levels used the red-tide dinoflagellate, Lingulodinium polyedrum, exposed to quantified laminar shear generated in Couette flow chambers at shear stresses of 0.004-0.019 N m^-2. The mechanism of growth inhibition varied depending on shear stress level and culture growth phase. During early exponential phase, the lowest shear stress level caused growth inhibition primarily through reduced cell division. By contrast, in experiments using higher shear stresses or late exponential phase cultures, mortality was largely responsible for the decline in net population growth. For realistic conditions of oceanic turbulence, when in situ physiological state resembles that of exponential culture growth, shear-induced inhibition of L. polyedrum growth may occur through reduced cell division. Mortality would not be expected unless shear stress levels were unusually high. However, shear-induced mortality could occur under less restrictive conditions if physiological state resembled late exponential/stationary phase cultures, as may be the case during later phases of in situ blooms.

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Aquatic Sciences Meeting, Albuquerque 2001

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