Zooplankton samples and hydrographic data were collected on two cruises to the area of the equatorial Atlantic that is influenced by the Amazon River outflow: one cruise during the dry season, October and November 1964, the other during the wet season that followed, May and June 1965. In the area where the cruise tracks overlapped, the average displacement volume of total zooplankton was almost three times higher during the wet season than during the dry season....