Marine algae of southeastern Australia

A project undertaken by the Royal Botanic Gardens Sydney and supervised by AJK Millar

Certain stretches of the NSW seaboard remain unexplored as far as their marine life is concerned. This applies especially to the far southern section, yet information about that part of the coast is critical to delineating the boundaries of two major biogeographic provinces. Two prominent ocean currents (the East Australia Current which originates in the tropical Coral Sea and the Southern Ocean current which originates in the Antarctic and drains across Bass Strait) meet at this part of the coast and it was thought that the boundary of the Flindersian and Peronian marine biogeographic Provinces might occur here. The differences between the marine algal floras of the two provinces could be used as indicators of the boundary.

Until this project was undertaken, the marine algae along the NSW coast from Twofold Bay (Eden) to Montague Island (off Narooma) had not been studied.  Project results have now pinpointed Green Cape, south of the town of Eden, as the boundary between the Pacific and Southern Ocean.

A spectacular feature of this boundary and an important discovery due to this project was the presence of Durvillaea potatorum (Bull Kelp), a cold water species that occurs as far north as Tathra, some 50 kilometres past Green Cape. Critical surveillance of this stretch of coast has shown that the headland at Tathra is the absolute northern limit of Durvillaea, yet we know that in the early 1940s, Durvillaea was a common inhabitant of the rocks around the coast at Bermagui, some 35 kilometres further north. Thus, the possibility is raised that Durvillaea is retreating south as water temperatures rise.

Montague Island was an ideal place to study the biogeographic boundary of marine algae in the south-western Pacific Ocean. On the leeward sides of islands, the diversity of marine algae is often far higher than that on the seaward, exposed sides.  Montague thus offered the unique opportunity to study a western aspect coast on what is the eastern aspect seaboard of Australia.

Final results of this project have shown that Montague Island has approximately 250 species of marine algae, making it one of the richer areas along the eastern seaboard of Australia. Not only does Montague Island have a rich diversity, but it also hosts species not normally known from NSW shores.  The expeditions added 44 new records for the State, as well as discovering 14 new species and four new genera to science. While a large percentage of the new records were of species previously considered endemic to the southern Australian mainland coast, representatives from Tasmania, and as far east as New Zealand, were also documented.


Millar, AJK and Kraft GT (2001). Monograph of the green macroalgal genus Rhipilia (Udoteaceae, Halimedales), with a description of R. crassa sp. nov. from Australia and the Philippines. Phycologia 40: 21-34.

Millar, AJK (1998). Marine benthis algal biogeography of the south western Pacific. International Phycological Congress, Leiden, The Netherlands.

Millar, AJK (2003). The Peronian Marine Biogeographic Province. Australian Biological Resources Survey (in press).

Millar, AJK (2003). New records of marine benthic algae from New South Wales. Australian Systematic Botany.

Millar, AJK (2002). Ceramium juliae (Ceramiaceae, Ceramiales), a new red algal species with distinctive spines from eastern Australia. Australian Systematic Botany 15: 493-500.

Harvey, A, Woelkerling, Wm.J. and Millar, A.J.K. (2002). The Sporolithaceae (Corallinales, Rhodophyta) in south-eastern Australia: taxonomy and 18S rDNA phylogeny. Phycologia 41: 207-227.

Sydney Morning Herald article by James Woodford. “Where great oceans join, it’s a well-kelped secret. SMH, Monday 11 October 1999, page 5.


A deep water red alga, Asparagopsis taxiformis, found in 30 m depths on the northern side of Montague Island (photo: Alan Millar)

Dr Alan Millar collecting marine algae (seaweeds) along the north wall of the Trench at Montague Island. (photo: James Eu)