PHYTOPLANKTON BIOMASS AND PRODUCTION IN THE SOUTHERN NORTH-SEA

Surface chlorophyll concentrations in the southern North Sea have been contoured for a 15 mo period, from 4 August 1988 to 3 October 1989. S easonal changes in chlorophyll concentration show low phytoplankton bi omass in the western and central regions and highlight the high phytop lankton biomass which develops in the spring and early summer in the S outhern and German Bights. C-14 measurements made on each of the surve y cruises have been used to estimate primary production for the whole of the southern North Sea. These data also highlight very high daily r ates of primary production in phytoplankton blooms in the eastern Nort h Sea. Regional estimates, based on the ICES subdivisions of the North Sea, are 79 g C m-2 yr-1 for Region 3'', 199 g C m-2 yr-1 for Region 4, 261 g C m-2 Yr-1 for Region 5, and 119 g C m-2 yr-1 for Region 7''. In winter and early spring, the euphotic depth in the region off the Belgian and Dutch coast is as great as the water column depth and ligh t will reach the bottom sediments; this may be a factor in the early d evelopment of Phaeocystis blooms in these regions.