Occurrence and Retention of Plankton Within the Estuary

An estuary is a region of continually changing currents and tides. Certain estuaries maintain a plankton in spite of the outflowing current of river water, either by the plankton remaining in the salt water below or owing to a mechanism which consists of an inflowing bottom current of salt water combined with a diurnal vertical migration of the plankton. Other estuaries contain only a temporary plankton.