SS1.04 Small-scale Biophysical Coupling in Plankton Ecology
Date: Thursday, June 13, 2002
Time: 3:00:00 PM
Location: Esquimalt
 
Menden-Deuer S, University of Washington - School of Oceanography, Seattle, USA, smenden@ocean.washington.edu
Grünbaum, D, , University of Washington - School of Oceanography, Seattle, USA, grunbaum@ocean.washington.edu
 
QUANTIFYING PROTOZOOPLANKTON FORAGING BEHAVIOR IN PATCHY/ HETEROGENEOUS PHYTOPLANKTON DISTRIBUTIONS
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Virtually all estimates of grazing and productivity rates in marine communities assume uniform prey availability at average prey concentrations. However, real phytoplankton distributions are non-uniform and patchy, resulting in fluctuating prey availability to predators/consumers. Fluctuating prey availability may have important ramifications for trophic interactions, population demographics and productivity of marine microbial food-webs. How effectively predators navigate within heterogeneous prey environments dictates whether they experience significantly higher (within patches) or lower (between patches) prey concentrations. We hypothesize that predators can modulate their swimming behavior (e.g. speed, turning rate) to increase time in high-prey areas and thus increase grazing rates. We obtained quantitative observations of swimming behavior of important phytoplankton predators (ciliates, heterotrophic dinoflagellates) in gradients of prey concentrations in the laboratory. We used these data to simulate the movements of predators in individual based models, and quantify rates of aggregation to phytoplankton patches. These individual-level, quantitative behavioral models, based on empirical swimming statistics, yield specific predictions of when trophic rates of predators in spatially and temporally varying environments differ significantly from estimates of trophic rates based on uniform "averaged" phytoplankton densities.