FLOW PATTERNS INDUCED BY SUBSTRATA AND BODY MORPHOLOGIES OF BENTHIC ORGANISMS, AND THEIR ROLES IN DETERMINING AVAILABILITY OF FOOD PARTICLES

A physical model, supported by field experiments, predicts that body and substratum morphology of benthic organisms can determine the particle composition encountered by the organisms. The model is based on the velocity gradient of boundary-layer flows, its resultant particle distribution, and the flow pattern induced by bluff bodies (benthic organisms and substrata). The various body morphologies of benthic organisms can be divided into two categories of slenderness ratio (SR-height to width ratio of the body plane normal to the flow) that induce two distinct ambient flow patterns. Ascending flow is induced by low-SR body morphologies and diverging flow by high-SR morphologies. The model predicts, based on the induced flow pattern, that high-SR bodies encounter higher fluxes of fine suspended particles, whereas low-SR bodies encounter higher fluxes of bedload particles. We suggest, therefore, that high-SR species are suspension feeders, and low-SR species are coarse particle or bedload feeders.