CURRENTS IN THE HIGH DRAG ENVIRONMENT OF A COASTAL KELP STAND OFF CALIFORNIA

The physical environment within a California kelp bed is modified from that of the region by the large drag of the massed plants. The change is greatest for longshore motions, where velocities diminish with dis tance upcoast of the leading edge of the bed in a manner consistent wi th the damping expected for coastally-trapped waves. Cross-shore veloc ity fluctuations are more important for the movement of material betwe en offshore waters and the kelp bed interior. Results suggest that pen etration of water for distances of 400 m into the kelp is common. The importance of water motions for ecological processes ranging from enha ncing boundary layer transport to kelp blades to moving planktonic lar vae implies that size of a kelp bed and position within it are importa nt for the kelp ecosystem. (C) 1998 Elsevier Science Ltd. All rights r eserved.