Short-term changes in the biology of a warm-core ring: Zooplankton biomass and grazing’

Gale force winds in September 198 1 deepened the mixed layer and introduced nutrients to the surface waters of Gulf Stream warm-core ring 8 1 D. Phytoplankton nitrate uptake rates, primary productivity, and chlorophyll a in the mixed layer of ring 8 1 D increased after the mixing event. Microzooplankton biomass (64-333 pm) doubled after the storm, with the cyclopoid copepods having the largest numerical increase. Data on zooplankton biomass, numbers of naupliar and copepodite stages of copepods, zooplankton grazing rates inside the ring, and measurements of high egg production rates by ring copepod species uggest hat enhanced phytoplankton production and biomass in ring 8 1 D was utilized by the ring zooplankton. The data support the hypothesis that in situ processes dominate the biological dynamics of warm-core rings. Our findings also indicate that oceanic zooplankton respond to physical events on relatively brief time scales (< 10 d) and that such events may enhance secondary production. Gulf Stream warm-core rings (WCRs) are formed in the North Atlantic when north-ward meanders of the Gulf Stream separat