Phytoplankton species successions and their hydrological environment at a coastal station off Sydney

Abstract

Phytoplankton species occurrence was studied during 1978-1981 at a coastal station off Sydney and succession patterns were sought using polythetic agglomerative classification analysis. Three major phytoplankton categories were distinguished: (1) a large group of species (including most nanoplankton), which were present throughout the year; (2) a group of diatom species, which bloomed following episodic nutrient enrichments in spring, early summer, autumn and winter; (3) a group of warm-water species (e.g. Trichodesmium), which were associated with admixture of tropical water masses. Gross features of the phytoplankton cycle in these waters are related to the erratic flow pattern of the East Australian Current. However, clear short-term (4-14 weeks) species successions were evident within the spring and summer diatom blooms. These began with small diatoms (Asterionella, Leptocylindrus, Skeletonema, Thalassiosira) followed first by large diatoms (Detonula, Rhizosolenia, Stephanopyxis) and then by large dinoflagellates (Ceratium, Protoperidinium). This sequence is identical to that observed in coastal waters of other parts of the world. A phytoplankton checklist (280 species) for Sydney coastal waters is included as an appendix.