An initiative of Earthwatch Institute

  1. Img_3625-c_gillies Neptune's Necklace washed up on beach by Chris Gilles
  2. Img_3627_c_gillies Close up of Neptune's Necklace (fronds 10-30cm long, beads 0.5-1.5cm in diameter) by Chris Gilles
  3. Img_c_gillies Neptune's Necklace attached to hard substrate by Chris Gilles

Neptune's Necklace

Hormosira banksii


  • A small, brown seaweed (algae) which resembles a beaded necklace.
  • It has branches (thalli) which are made up of strings of hollow, water-filled, round or oval-shaped beads joined together by a short stalk. Each bead is covered in many pores, giving it a rough surface. It is attached to the substrate by a thin disc (holdfast).
  • Size: its fronds are 10 – 30 cm long, its beads are 5 – 15 mm in diameter, and its holdfast is 3 – 10 mm across.


What to Observe

Search area for 30 minutes and record under the following categories-

  • Abundant - found easily with little searching
  • Frequent - found with minimal searching
  • Rare - only 1 or 2 individuals found with intensive searching
  • Not found - not present during search

ClimateWatch Science Advisor

As a result of climate change, warm tropical ocean currents are expected to strengthen and persist for longer periods in southern coastal area normally dominated by cooler waters. The consequent increases in water temperature are likely to result in unfavourable growing conditions for cool water algae species casing seaweed loss in some areas.

When To Look

Throughout the year

Where To Look

  • In the intertidal zone, on rocky shores and in rock pools. It is usually attached to rocks and often occurs in vast colonies forming a thick cover.
  • From King George Sound in Western Australia, around southern Australia and Tasmania to Port Macquarie in New South Wales. It is also found at Lord Howe Island and Norfolk Island.
 Neptune's Necklace distribution map - GBIF

Neptune's Necklace distribution map - GBIF



Edgar GJ 1997. Australian Marine Life: the plants and animals of temperate waters. Reed Books, Kew.

Quinn GP, Wescott GC & Synnot RN 1992. Life on the Rocky Shores of South-Eastern Australia: an illustrated field guide. Victorian National Parks Association, Melbourne.

Underwood AJ & Chapman MG 1993. Seashores: a beachcomber's guide. New South Wales University Press, Sydney.

Womersley HBS 1967. A critical survey of the marine algae of southern Australia. II. Phaeophyta. Australian Journal of Botany 15, 189–270.

Womersley HBS 1987. The marine benthic flora of southern Australia. Part II. pp. 481, 169 figs, 1 table, 8 plates, 4 maps. Adelaide: South Australian Government Printing Division.



  1. Search Species

  1. What Else?

    Neptune's Necklace is a very distinctive seaweed which is hard to confuse with any other seaweeds which are often larger, brown in colour and have leaf-like rather than bead-like fronds.

  1. Did You Know?

    It is named after the English naturalist and botanist Sir Joseph Banks.

    It is eaten by sea urchins, crabs and fish.

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