Abstract
Surface maps of selected taxa of zooplankton were made off Pt. Conception, California, during three contrasting upwelling situations: moderate upwelling, strong upwelling, and downwelling. Number of taxa and number of individuals decreased with increasing upwelling intensity, indicating replacement of richer surface waters by relatively impoverished subsurface waters. The exception to this pattern was in copepodid stage V of Calanus pacificus which increased in numbers nearshore as upwelling strength increased. Since copepodid V is the deep-living, diapausing stage of this copepod, its increase in numbers is consistent with the upward movement of deep water and the life cycle of C. pacificus. Frontal zones always had more individuals than non-frontal zones, and these were primarily copepod nauplii. Estimated ingestion by copepod nauplii and Calanus pacificus in frontal zones during upwelling was twice the ingestion by these taxa outside the frontal zones, suggesting that the frontal zones associated with upwelling off Pt. Conception are sites of enhanced secondary production.