Short-term changes in the biology of a Gulf Stream warm-core ring: phytoplankton biomass and productivity.

Temporal changes in chloropyll a and primary production were followed in a Gulf Stream warm-core ring as it underwent an interaction with the Gulf Stream and a subsequent wind event. As the physical events altered the structure of the mixed layer, Chl a within the euphotic zone increased from approx 10 to 42mg m^-2 while productivity rates increased from 140 to >2400mg C m^-2d^-1. Carbon-specific growth rates in Ring 81-D derived from ATP-C biomass and ¹⁴C productivity rates increased 5-fold. Nanoplankton (<20mu m) initially accounted for nearly 90% of the total Chl a biomass in ring surface waters, although there was a subsurface maximum of Chl a was uniformly distributed throughout the mixed layer and net plankton accounted for an increased proportion of total Chl a standing stock and productivity. In the peripheral high velocity region and the surrounding Slope Water, phytoplankton standing stocks and productivity rates were less than the maximum values found at ring center.-from Authors