Variability of chlorophyll profiles on the west coast of southern Africa in June/July 1999

The BENEFIT research training cruises on FRS Africana in June/July 1999 bet ween Cape Columbine and Walvis Bay, and Walvis Bay and Cape Frio, provided an opportunity to examine vertical and horizontal variability of phytoplank ton biomass in relation to the physical environment within four subprovince s of the Benguela upwelling system. Upwelling was evident inshore during th e cruise and the upper mixed layer was generally deep. The shape of chlorop hyll profiles generally changed from surface or nearsurface peaks inshore t o progressively weaker and deeper subsurface peaks offshore. Chlorophyll pr ofiles were analysed in terms of a shifted-Gaussian curve, yielding four pa rameters describing the depth and height of the chlorophyll peak, the sprea d of the peak and the background chlorophyll concentration. Using a small s et of data, this preliminary analysis provided chlorophyll profile shapes t ypical for shelf and slope waters of four Benguela subprovinces in winter, with the caveat that variability is high under upwelling conditions.