Season fluctuation in zooplankton abundance are described from six 24 hour series taken from the Likoni Ferry, using Clarke Bumpus net of 180 um mesh size. Two samples every 2 hours were taken at 2 months intervals from April 1985, to February 1986 inclusive.
Salinities were consistently above 30%o and surface water temperature varied between 24.0 and 28.9°C. Fifty-one taxa of zooplanktonic organisms were recorded in the samples. The mean total zooplankton abundance was 236m-3. The density of zooplankton was highest during the 24 hour series of the North-East monsoon season.
Actual mean abundance of plankton was relatively low during the 24 hour seires taken in South-East monsoon in April, June, August and October.
Holoplanktonic forms dominated the fauna, averaging 71% of the total plankton, copepods numbered 69% of the total fauna. The most numerous taxa amongst holoplanktonic forms were (in order of abundance): copepods, chaetognaths and appendicularia.
The most numerous amongst meroplanktonic forms were: molluscan larvae, fish eggs and brachyuran zoeae. The total zooplankton density for the night-time samples was higher than the day-time ones.
KEYWORDS: zooplankton, tropical creek, Port Reitz, occurrence, season, day, night, Kenya.
