Hopkins Marine Station Student Paper

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(full paper is archived in the Miller Library)

Title: Surviving hydrodynamic forces in a wave swept environment: consequences of morphology in Egregia menziesii
Student Author(s): Friedland, Michelle
Faculty Advisor(s): Denny, Mark W.
Pages: 39
Location: Final Papers Biology 175H
Date: June 1993
Abstract: Organisms on rocky intertidal shores must withstand water velocities of 10-20 meters/second (Denny 1988, Carrington 1989, Jones and Demetropoulos 1968) and accompanying accelerations of 400 m/s^2 (Denny et al. 1985, Gaylord et al. in press). Because drag and accelerational forces increase with area and volume respectively, the bigger a species is, the larger the forces on it become. Egregia menziesii is an unusually large alga that lives in the intertidal region amid violent water motion. Here, I address how E. menziesii interacts with flow. A hydro-mechanical model is used to predict the magnitude of the the forces on E. menziesii in various conditions and for various plant sizes. Based on measurements of the strength of E. menziesii, an intact average-sized plant's survivorship in the range of predicted wave forces is found to be nearly 100%. However predation and entanglement with other plants can lower an individual's chace of surviving an severe storm to nearly 70%. E. menziesii's strap like shape is found to be necessary for accomodating the distribution of tensions along the plant's stipe and for reducing drag.