The Zooplankton of Mgazana, A Mangrove Estuary in Transkei, Southern Africa

Abstract

Mgazana, a mangrove estuary inTranskei, was investigated from May 1972 to March 1973 at six-week intervals. Salinities were consistently above 25 parts per thousand in the middle and lower estuary. In the upper estuary the salinity varied between 4 and 29 parts per thousand. Water temperatures varied between I5,5°C and 28°C. One hundred and fifteen taxa of zooplankton organisms were recorded in the samples. The copepods Acartia naialensis and Oithona brevicornis reached high population densities and numbers exceeding 100 000/m³ of water were recorded. Mysids were major contributors to zooplankton biomass. A maximum biomass of I 200 mg/m³ was recorded in February in the middle estuary and was attributed to the mysid Mesopodopsis africana. Species of mysids showed clear seasonal and spatial patterns of distribution in the estuary.