Zooplankton and Micronekton in Cyclones and Anticyclones in the Northeast Gulf of Mexico

Two cruises were made to the northeast Gulf of Mexico in October 1996 and August 1997. The main objectives of the cruises were to survey cetacean and seabird populations and describe their hydrographic and biological environments. An additional objective was to characterize cetacean and seabird habitats in terms of food resources. During both cruises a cyclone and an anticyclone were sampled as well as the confluence region between them. Zooplankton and micronekton were sampled both directly with nets and indirectly with a 153-kHz acoustic Doppler current profiler. Within cruises, zooplankton and micronekton biomass was higher in cyclones than in anticyclones. Biomass within the confluence was either highest or intermediate for both cruises. Between cruises, within features, August 1997 biomass was significantly higher than October 1996 biomass