ANNUALLY RECURRENT DIATOM BLOOMS IN SPRING ALONG THE NEW-SOUTH-WALES COAST OF AUSTRALIA

Blooms of phytoplankton (100-280 mg chlorophyll a m-2) occur on the co ntinental shelf off Sydney in the spring of most years. These sudden c hlorophyll increases (more than 10 times the normal algal biomass) are due to short-lived diatom blooms that evolve in a predictable sequenc e from small chain-forming species (Nitzschia, Thalassiosira) to large centric species (Lauderia, Rhizosolenia) and eventually to large dino flagellates (Protoperidinium). Two research cruises (October 1981, Sep tember 1984) were conducted to define the longshore extent of this phe nomenon. Diatom blooms were widespread along the whole New South Wales coastline, occurring in the 700-km-long region from Cape Hawke in the north (32-degrees-S), where the East Australian Current separates fro m the coast, to Maria Island off Tasmania in the south (43-degrees-S). Hydrological mechanisms of these annually recurrent enrichments are r elated to the action of the East Australian Current and are unlike tho se triggering spring blooms in temperate European waters. Implications of these diatom blooms for coastal fisheries along the New South Wale s coast are briefly discussed.