Tropical phytoplankton species and pigments of continental shelf waters of North and North-West Australia

Abstract

The phytoplankton of the shelf waters of the Gulf of Carpentaria, Arafura Sea, Timor Sea and North-West Australia is basically a diatom flora, distinctly different from the oceanic, predominantly dinoflagellate flora of the Coral Sea and Indian Ocean. Large morphologically elaborate tropical diatoms and dinoflagellates of this shelf region show great species diversity (more than 200 spp, identified) and a variety of symbiotic associations (28 species-pairs recognised). In contrast, the tropical nanoplankton (2 to 20 µm; mainly small diatoms, pryrnnesiophytes and dinoflagellates; 70 spp.) are remarkably similar in species composition to those of subtropical and temperate Australian waters. Water-column chlorophyll values in both North-West Shelf and Gulf waters ranged from 10 to 55 mg m-2. Nanoplankton accounts for 70 to 97 % of total phytoplankton chlorophyll, except in local diatom or Trichodesrniurn blooms (30 to 60%).