talking points for nature guides
brown seaweeds text index | photo index
Seaweeds in general
Brown seaweeds
Division Phaeophyta
updated Aug 08

if you learn only three things about them ...
Large brown seaweeds are more common on our Southern than Northern shores.
Lots of little animals often hide in large brown seaweeds. Look for them!
Extracts of brown seaweeds are used extensively in our processed food.

Where seen?
Large brown seaweeds like sargassum are more common on our Southern shores, but other brown seaweeds are also seen on our Northern shores. Like other seaweeds, brown seaweeds appear to be seasonal. At certain times, for example, the Southern shores are blanketed under a thick golden carpet of sargassum.

Features: Brown seaweeds have green chlorophyll but this is masked by other pigments, in particular fucoxanthin, an orange carotenid pigment that gives their distinctive brown colour. Brown seaweeds may come in shades of brown, from light to yellowish, golden to dark brown.

Brown seaweeds are only found in the sea and are not found in freshwater.

Role in the habitat: Brown seaweeds provide shelter and food for small animals. The large sargassum seaweeds in particular may shelter tiny octopuses, shrimps and fishes. The Crosslandia slug (Crosslandia sp.) looks exactly like a sargassum blade!

Human uses:
Unlike red seaweeds and green seaweeds, few brown seaweeds are eaten directly by people. There are records that in the Philippines, Sargassum is widely used in the Ilocos region to enhance the taste of boiled rice or stewed fish. Some species of Sargassum and probably Turbinaria and Hormophysa are used as feritilisers and additives in poultry and cattle feed. Sargassum is also used as fish bait in basket traps and insect repellent. Various species of brown seaweed are also used as medicine for ailments ranging from children's fever, cholesterol problems, cleansing the blood, skin ailments.

Extracts of brown seaweeds, however, are used extensively in our food. Brown seaweeds are a source of alginates used to make water-based products thicker, creamier and more stable.

For example, alginates make smoother ice cream, dripless paint and cosmetics. The alginic acid in the extract absorbs large quantities of water and thus has an emulsifying effect.

Alginates are extracted from larger brown seaweeds which are more numerous in colder waters thus the major producers are in countries bordering colder waters such as the US, France, Norway, UK and Japan. Kelp is an important source of this product. Annual world production of alginates is estimated at 27,000 tonnes from 500,000 tonnes of raw material, valued at around US$230million (as at 2000).

Various brown seaweeds
Sentosa, Apr 04

The Crosslandia nudibranch looks
just like sargassum!

St. John's Island, Jan 06

Division Phaeophyta on Singapore shores
text index and photo index of brown seaweeds on this site

Links References
  • 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].
  • A. C. Lee, Lawrence M. Liao and K. S. Tan. New records of marine algae on artificial structures and intertidal flats in coastal waters of Singapore. Pp. 5-40. in the Raffles Bulletin of Zoology.
  • 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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