HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Gaylord, B. Articles by Koehl, M. A. R. Search for Related Content PubMed PubMed Citation Articles by Gaylord, B. Articles by Koehl, M. A. R. Related Collections Algae Ecology Biomaterials Biomechanics

Flow Forces on Seaweeds: Field Evidence for Roles of Wave Impingement and Organism Inertia

¹ Bodega Marine Laboratory and Department of Evolution and Ecology, University of California at Davis, Bodega Bay, California 94923
² Department of Biological Sciences, Stanford University, Hopkins Marine Station, Pacific Grove, California 93950
³ Department of Integrative Biology, University of California at Berkeley, Berkeley, California 94720-3140

^* To whom correspondence should be addressed. E-mail: bpgaylord{at}ucdavis.edu

Hydrodynamic forces dislodge and kill large numbers of organisms in intertidal and subtidal habitats along rocky shores. Although this feature of wave-driven water motion is well recognized, the mechanics of force imposition on compliant organisms is incompletely understood. Here we undertake a field examination of two processes that are thought to impose many of the more dangerous forces that act on flexible benthic seaweeds: impingement of breaking waves directly on emergent organisms, and inertial effects tied to the rapid deceleration of mass that occurs when a passively moving but attached organism abruptly reaches the extent of its range of motion. We focus on two common and important seaweed species: one intertidal kelp (Egregia menziesii) and one subtidal kelp (Macrocystis pyrifera). Results support the concept that wave impingement and inertial effects produce intermittent force transients whose magnitudes commonly exceed values readily attributable to drag. Peak force transients are elevated by as much as a factor of 3 relative to drag in both small and large individuals, consistent with smaller seaweeds being more susceptible to brief impingement forces, and larger seaweeds being more vulnerable to inertial forces. Because both wave impingement and inertial effects vary with the size of an organism, they may have the potential to influence the demographics of physical disturbance in an array of flexible species.