Aquatic Sciences Meeting, Albuquerque 2001

PC07 Spatial and Temporal Connections

Date: Wednesday, February 14, 2001

Location: Southwest Hall

Currie, W, J, University of Connecticut, Groton, USA, wcurrie@uoguelph.ca

Lovejoy, S, , McGill University, Montreal, Canada, lovejoy@physics.mcgill.ca

Schertzer, D, , U. Pierre et Marie-Curie, Paris, France, dschertz@math.clemson.edu

Claereboudt, M, R, Sultan Qaboos University, Al-Khod, Oman, Michelc@squ.edu.om

Bourget, E, , Universite Laval, Quebec, Canada, edwin.bourget@fsq.ulaval.ca

Roff, J, C, University of Guelph, Guelph, Canada, jroff@uoguelph.ca

MULTIFRACTAL ZOOPLANKTON: MODELING GRAZING AND GROWTH IN THE PLANKTON

The pelagic research of CHASE investigates the scaling relationships (m-km) of horizontal plankton distributions from transects collected in-situ using CTD and Optical Plankton Counter. Consistent with turbulent dynamics, passive scaling behaviour is seen for the temperature spectra down to the smallest scales. However, fluorescence (phytoplankton) series showed breaks in scaling with large-scale (>100m) turbulence-growth dominated regime with structure function exponent ~1/8, and a rougher small-scale regime with exponent -1/3. Zooplankton spectra have similar discontinuities, separated by a planktoscale, below which they are no longer prisoners of turbulence. We propose a simple model involving both growth and turbulence to account for the large scale, and diffusive grazing and turbulence (predator-prey interactions) to account for the small scale. Depending on a dimensionless grazing constant Gr, zooplankton diffusion, phytoplankton growth, and turbulent energy flux, small scales are dominated either by turbulent grazing (Gr > 1) or passive scalar turbulence (Gr < 1). In the grazing regime, we theoretically predict the observed density fluctuation exponent -1/3 which quantifies the tendency of the zooplankton to uniformize the phytoplankton distributions by preferentially grazing high concentration patches.

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Aquatic Sciences Meeting, Albuquerque 2001

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