Variability of phytoplankton and mesozooplankton biomass in the subtropical and tropical Atlantic Ocean

Data from over 40 yr (1950-1992) of expeditions to the Atlantic Ocean are summarised in the form of macroscale contour maps between 40degreesN and 40degreesS. The chl a concentrations from the surface and mesozooplankton in the upper layer (0 to 100 m) were analysed from 3992 casts and 1124 hauls respectively. General agreement between chlorophyll concentrations and mesozooplankton biomass distributions was noted on an ocean basin scale. There were non-linear relationships between mean chlorophyll concentration within the 0 to 10 m layer and mesozooplankton biomass within the 0 to 100 m layer for summed data between December to May and June to November. A comparison of the total biomass of mesozooplankton und phytoplankton, in carbon units, indicated that this ratio varied from 0.15 to 1 in the 0 to 100 m layer and, on average, the phytoplankton biomass exceeded twice that of mesozooplankton. The seasonal cycles of phyto- and zooplankton biomass for 6 provinces of the tropical zone were qualitatively comparable. Quantitative differences were found in the seasonal amplitudes, which were greater for the regions with nutrient enrichment of the upper layer. Relationships were established between phytoplankton and mesozooplankton biomass for 8 provinces.