MESOSCALE CIRCULATION AND THE SURFACE DISTRIBUTION OF COPEPODS NEAR THE SOUTH FLORIDA KEYS

摘要

Near-surface zooplankton samples were collected during an interdisciplinary study of biological responses to oceanographic circulation south of Looe Reef in the southern Straits of Florida (SSF) in late May 1994. Surface currents in the sampling region were monitored during the study with the University of Miami's high frequency (HF) Ocean Surface Current Radar (OSCR). HF-radar was highly effective in resolving submesoscale (<30 km) circulation patterns that would have been difficult to discern using conventional current meters and shipboard surveys, particularly in this coastal region where local circulation patterns undergo rapid temporal transitions. The present study focused on the surface abundance and distribution of copepod nauplii and copepodites. These groups generally remain in the near-surface layer, tend to behave as passive drifting particles and in the case of nauplii, are good indicators of recent egg production. Copepod nauplii and juveniles were found to be most abundant in cyclonic submesoscale eddies (SMEs; 10-12 km) that traversed the frontal-mixing zone between the Florida Current and nearshore coastal water during the field study. The region of greatest zooplankton abundance was also associated with elevated pigment fluorescence. These data suggest that the SMEs in the SSF may enhance biological productivity, probably through a combination of accumulation and retention of zooplankton and upwelling of nutrients. General distribution patterns of numerically dominant copepod taxa were determined and linked with water of Florida Current origin or nearshore coastal water.