A modeling study was conducted to examine the question, Is the high phytoplankton biomass which often developes in warm-core rings of the Gulf Stream a consequence of the circulation associated with the frictional decay of the ring? A time-dependent, two-dimensional (r,z, t) model of plankton dynamics in a hypothetical ring similar in features to warm-core ring 82B generates a lens of high phytoplankton biomass at ring center. Phytoplankton grow on nutrients advected into the euphotic zone as the depressed warm water in the ring's core rebounds and spreads out at the surface. This vertical motion induced as the ring's rate of rotation slows may be an important process maintaining the high production in warm-core rings.