A study of zooplankton of the estuary of river Potengi in Natal, Brazil was carried out from April 1979 to March 1980 to find out the seasonal change in the composition of zooplankton in relation to physicochemical parameters of the estuary. In September, a more intensive sampling was done to elucidate the diurnal variation of zooplankton.

Copepods, appendicularians and cirriped nauplii formed the major component of the zooplankton in the study area during low tide, particularly during night. Zoeae of Brachyura also formed an important component and they were conspicuous during low tide, day and night. Maximum number of chaetognaths was collected during high tide.