This leads us to the conclusion that the maximum chlorophyll a concentration can be partly ascribed to lower grazing pressure of the mesozooplankton on the microzooplankton, whose biomass is in equilibrium with its prey on a diel time scale, as it is in the equatorial region (e.g., Le Borgne and Landry, 2003). We now turn to reasons for the zooplankton minimum in winter and early spring.