We believe that two mechanisms are important in regulating primary production and hence the abundance of phytoplankton in warm core rings. The first mechanism, anticyclogenesis, is associated with the rotary motion of rings since the resultant geostrophic forces are believed to be the basis for nutrient enrichment in the high velocity region. Phyoplankton populations in this peripheral region experience a near steady state growth closely coupled with the rotational velocity of the ring. The second mechanism is that phytoplankton populations in the ring center rely on seasonal changes in the depth of the mixed layer due to convection and stabilization. This process regulates both the mean light energy reaching phytoplankton and equalizes the nutrient distribution over a water column. Growth in populations at ring center occurs as pulses, responding to changes in the depth of the mixed layer.