Interannual chlorophyll variability in South Africa’s Saldanha Bay system, 1974–1979

Abstract

With data obtained in the course of a pollution monitoring programme in Saldanha Bay between 1974 and 1979, it is shown how chlorophyll is affected by interannual variability in the characteristics of coastal water. Inflow of warm, oligotrophic oceanic water into the inshore zone in December 1974 and 1976 caused a marked depression in the nitrate concentrations and in the expected chlorophyll concentrations at the time of the summer blooms. The timing of these inflows appears to influence the biosphere response, suggesting that annually or monthly averaged time-series may not always be appropriate for demonstrating links between biological variability and physical forcing. A finer resolution may be required. The impact of diurnal heating on sea surface temperatures may mask important source characteristics of the surface water. Salinity was found to be a more conservative property and its behaviour was therefore more useful in interpreting variability. © 1990 Taylor and Francis Group, LLC.