Dr S.W. Jeffrey has achieved international eminence in marine science for her detailed and innovative studies of the photosynthetic pigments of plants, especially the planktonic micro-algae. Of particular significance are her discoveries of the chlorophyll c family of pigments, which have major implications, not only for photobiology, but for classifying and defining evolutionary relationships among plants. Her classic work on plant chlorophylls resulted in standard equations widely used for estimating ocean productivity. Her development of novel chromatographic techniques and algal culturing allows new insights into marine productivity. Her pioneering research in mariculture and toxic phytoplankton blooms are of great practical significance for Australia.