SETTLEMENT AND TRANSPORT OF BENTHIC INVERTEBRATES IN AN INTERMITTENT UPWELLING REGION

We monitored settlement of sea urchins (Strongylocentrotus spp.) and c rabs (primarily Cancer spp.) and concurrent physical variables at Bode ga Marine Laboratory (BML) and Salt Point (northern California) from A pril through August 1992. Upwelling favorable winds led to lower tempe ratures, higher salinities, and lower subsurface pressures at BML, whi le periods of relaxation from upwelling typically caused a lagged reve rsal of each of these trends. This response to relaxation was due to a combination of alongshore and onshore flow of near-surface water at t his site. Crab settlement was significantly correlated with the rate o f temperature increase, corresponding to relaxation events. In contras t, sea urchins settled primarily during an unusual relaxation event wh ich possibly involved remote forcing. Sea urchin and crab settlement w ere negatively correlated. Possible reasons include residence in diffe rent water masses, different biomechanical characteristics, and predat ion by crab larvae on sea urchin larvae. The time-course of settlement at Salt Point was similar to that at BML for both species groups.