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Neptune's Necklace Hormosira banksii


Photo of Neptune's NecklaceNeptune's Necklace is a distinctive algae made up of strings of hollow, water-filled, round or oval-shaped beads joined together by a short stalk.

The fronds may be between 10 - 30 cm long, and the beads may be 15 mm in diameter.

Many pores cover the outside surface of each bead, forming a rough surface. Within these pores are the reproductive cells. Neptune's Necklace is sometimes called "sea grapes".


Dark brown, with some green in colour. When it is dried out and killed by the sun, it turns a quite yellowish-orange.




Decaisne, 1842




100 - 300 mm


Distribution map of Neptune's NecklaceFound from Port Macquarie, in northern New South Wales around southern Australia to King George Sound in Western Australia.


Often occurs in vast colonies forming a thick covering over most of the rock surface at mid-tide levels down to the Galeolaria zone on some rocky shores.


The dense colony of fronds can form a protective microhabitat where many molluscs, worms and small crustaceans shelter.

Although the algae may be exposed to the sun at low tide, underneath the dense mat of fronds remains moist and protected.

Hot summer days can actually damage and kill the algae fronds, so that they may turn a deep reddish brown in colour, which is not uncommon at the end of summer.

Other common names are Necklace Seaweed and Bubbleweed.


Bennett, I. (1987) W.J. Dakin's classic study: Australian Seashores. p132, Angus & Robertson, Sydney.

Davey, K. (1998) A Photographic Guide to Seashore Life of Australia. p.26, New Holland, Sydney.

Edgar, G.J. (1997) Australian Marine Life: the plants and animals of temperate waters. p.56, Reed Books, Kew.

Quinn, G.P., Wescott, G.C. & Synnot, R.N. (1992) Life on the Rocky Shores of South-Eastern Australia: an illustrated field guide. p.18, Victorian National Parks Association, Melbourne.

Underwood, A.J. & Chapman, M.G. (1993) Seashores: a beachcomber's guide. p49,New South Wales University Press, Sydney.

Womersley, H.B.S. (1987) The Marine Benthic Flora of Southern Australia. pt. 2, p.342, South Australian Government Printer, Adelaide.

Brown Algae

Sausage Weed
Doubling Weed
Globe Algae
Leather Kelp
Neptune's Necklace
Strap Weed

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photo of Keith DaveyLife on Australian Seashores
by Keith Davey (C) 2000

Learning Consultant - Media
The University of Newcastle

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Scientific Consultant: Phil Colman
site created 01.01.98 : updated 01.04.2000