Phyto- and zooplankton community structure and production around South Georgia (Southern Ocean) during Summer 2001/02

Of the environmental variables measured in this study the proportion of microphytoplankton within samples, rather than for example, phytoplankton biomass, explained the greatest proportion of the variance associated with the carbon mass of individual copepod species stages, egg production rates and total zooplankton abundance. We conclude that stations in the western and eastern oceanic regions were dominated by bottom up controls, with physical forcing and adequate nutrient availability leading to bloom conditions of large diatoms in the west, whereas in the east, phytoplankton growth was lower (possibly due to micronutrient limitation) and zooplankton abundance was lower. Over the shelf we suggest that a higher average biomass of krill (∼80 g wet mass m−2) compared to offshelf (43 g wet mass m−2) may have exerted top down control and grazed out chl a and thus have been responsible for low mesozooplankton abundance.