Seasonal variation in remotely-sensed phytoplankton size structure around southern Africa

The three-component model of Brewin et al. (2010) computes fractional contributions of three phytoplankton size classes (micro- (>20μm), nano- (2–20μm), picophytoplankton (1mgm−3 was limited to shelf regions along the coasts of Southern Africa and Madagascar, while values 50% of the total Chla in these regions with little change throughout the year. The AR shelf differed, with picophytoplankton dominating in summer, and micro- and nanophytoplankton the rest of the year. In the open ocean domains of the NB, SB, and AB regions, nanophytoplankton dominated for most of the year, with picophytoplankton being more prevalent during summer and autumn. In contrast, in the AR open ocean, nanophytoplankton were dominant only during winter and early spring, whereas picophytoplankton dominated throughout the year in the MC open ocean. The refined model characterised previously unknown spatial and temporal changes in size structure in various ecosystems around Southern Africa. •PSC model characterised seasonal size structure variations around Southern Africa.•Micro-phytoplankton dominated in most shelf regions with little seasonal change.•Greater seasonality in nano- and pico-phytoplankton occurred in open ocean regions.