Waves with near-inertial frequencies were observed along a front associated with a large mesoscale feature in the Sargasso Sea during the late summer of 1987. High subsurface chlorophyll concentrations occurred on the edge of this front, coincident with the wave packets. The amplitude of the waves increased with time, and kinetic energy propagated downward, reducing 20-m Richardson numbers in the thermocline to 1 or less. Chlorophyll levels were episodic, showing no periodicity coincident with wave dynamics. However, on two occasions, chlorophyll concentration increased from 1 mg Chl m-3, several hours after the waves penetrated the thermocline. It was hypothesized that mixing associated with shear instabilities stimulated new production. A diffusivity model combined with nutrient data produced a phytoplankton bloom that accounted for only one of the maxima. The other increase in chlorophyll may have been the result of horizontal advection of the wave packets near the front. ¿ American Geophysical Union 1995.