Title Inhibitory effects of wave action on destructive grazing by sea urchins:a review
Authers Shigeru KAWAMATA
Keywords barrens, grazing, kelp, sea urchin, waves
Citation Bull. Fish. Res. Agen. No.32, 95-102, 2010
Wave-induced water motion is one of the key determinant factors protecting kelp assemblages from destructive grazing by sea urchins; however few studies have quantitatively evaluated the hydrodynamic effect on rocky subtidal community ecology due to the complex nature of the water motion. Our quantitative understanding of the effects of waves on urchin foraging behavior has increased substantially over the past 15 years, primarily due to flow tank experiments on the sea urchin Strongylocentrotus nudus, which have formed extensive urchin barrens in northern Japan. This review evaluates the mechanism and extent that the oscillatory water flow influences the behaviors of sea urchins. The dislodgement velocity for stationary sea urchins, which has been determined in various studies based on the hydrodynamic theory, is discussed. Previously predicted dislodgement velocities for sea urchins are extremely high ( > ca. 5m/s) while the velocity limit for urchin movement on a smooth and flat substratum is much lower than 1m/s. The importance of attachment by spines to urchin movement in moving water is discussed. Dense cover of turf algae prevents the effective attachment of the distal suckers of tube feet and thus substantially reduces the critical velocity for urchin movement. Urchin climbing of upright thin objects, such as anchor ropes of buoyed systems for kelp cultivation, to which little attention has been paid, is discussed in relation to oscillatory water motion. Finally, the effect of oscillatory flow on urchin feeding is discussed.
URI http://www.fra.affrc.go.jp/bulletin/bull/bull32/95-102.pdf