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Seaweeds > Division Chlorophyta
Coin green seaweeds
Halimeda sp.*
Family Halimedaceae
updated Jan 12
Where seen? These seaweeds are made up of small, hard segments that are joined together. They are commonly seen on many of our shores, usually growing on coral rubble or among living corals, as well as in sandy areas near reefs. Sometimes forming rather large 'thickets' covering an area of 40-50cm.

Features: An upright chain of joined up coin-like flattened segments. Each coin-like segment is hard as it is impregnated with calcium carbonate. These segments may be circular or other shapes, some are thick and flat, others thinner with crinkled or ruffled edges. The portions between the segments are not calcified, so the 'string' of coins is rather flexible.

A new segment develops from the top and can appear rapidly, within 1-2 days! In some species, the segments are anchored by one large long bulbous holdfast. In others by a small holdfast of matted filaments, and yet others in inconspicuous patches of root-like structures emerging from segments or nodes.

These seaweeds can relocate their chlorophyll (the green pigment used in photosynthesis). At night, chlorophyll might be concentrated in the centre of the segment. As a result, the seaweed may appear white.

In addition to calcium carbonate, they also have chemicals that protect them from herbivores. Despite this, some slugs like the Halimeda slug (Elysiella pusilla) actually eat the seaweed and incorporates these chemicals into their tissues to protect themselves!

The calcium carbonate released from dead Halimeda seaweeds are said to make major contributions to sand in some areas such as the Bahamas and the Great Barrier Reef.

According to AlgaeBase, there are 60 current Halimeda species.

Big and small coin green seaweed
next to one another
Kusu Island, May 05

A pair of Halimeda slugs on the seaweed.
Labrador, Mar 05
Human uses: Some species of Halimeda are used as fertilizers to recondition acidic soils. They are also used as animal feed and reportedly have anti-bacterial and anti-fungal properties.

*Species are difficult to positively identify without close examination of internal parts.
On this website, they are grouped by external features for convenience of display.

Halimeda species recorded for Singapore
Pham, M. N., H. T. W. Tan, S. Mitrovic & H. H. T. Yeo, 2011. A Checklist of the Algae of Singapore.

  Halimeda discoidea
Halimeda discoidea
cf. intermedia
Halimeda fragilis
Halimeda gracilis
Halimeda incrassata
Halimeda macroloba
Halimeda opuntia
Halimeda opuntia
var. minor
Halimeda papyracea
Halimeda tuna



  • Lee Ai Chin, Iris U. Baula, Lilibeth N. Miranda and Sin Tsai Min ; editors: Sin Tsai Min and Wang Luan Keng, A photographic guide to the marine algae of Singapore, 2015. Tropical Marine Science Institute, 201 pp.
  • Pham, M. N., H. T. W. Tan, S. Mitrovic & H. H. T. Yeo, 2011. A Checklist of the Algae of Singapore, 2nd Edition. Lee Kong Chian Natural History Museum, National University of Singapore, Singapore. 99 pp. Uploaded 1 October 2011. [PDF, 1.58 MB].
  • Lim, S., P. Ng, L. Tan, & W. Y. Chin, 1994. Rhythm of the Sea: The Life and Times of Labrador Beach. Division of Biology, School of Science, Nanyang Technological University & Department of Zoology, the National University of Singapore. 160 pp.
  • Chou, L. M., 1998. A Guide to the Coral Reef Life of Singapore. Singapore Science Centre. 128 pages.
  • Huisman, John M. 2000. Marine Plants of Australia University of Western Australia Press. 300pp.
  • Calumpong, H. P. & Menez, E. G., 1997.Field Guide to the Common Mangroves, Seagrasses and Algae of the Philippines. Bookmark, Inc., the Philippines. 197 pp.
  • Trono, Gavino. C. Jr., 1997. Field Guide and Atlas of the Seaweed Resources of the Philippines.. Bookmark, Inc., the Philippines. 306 pp.
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