Spatial-temporal changes in phytoplankton biomass and primary production in Chwaka Bay, Zanzibar

Abstract

Spatial-temporal variations in phytoplankton primary production (PP) and biomass (B) were studied for a period of about one year, from July 1999 to July 2000. In addition, changes in corresponding environmental variables were examined. Sampling took place at two stations in Chwaka Bay, one located in mangrove areas, Station I, and the other in an open area, Station II. Although there were changes both with location and time, there were no clear seasonal trends. Generally, the phytoplankton biomass and primary production (mg C m^-3 h^-1) were higher at Station I than at Station II. However, specific production, that is, primary production normalized to phytoplankton biomass, P^B (mg C (mg chl-a)^-1 h^-1) was higher at Station II than at Station I. No relationship could be found between phytoplankton biomass and the rate of primary production. These observations suggest that the presence of the mangrove ecosystem, and the processes therein, influenced the rate of phytoplankton primary production in the Mapopwe Creek, causing the differences between stations.