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seagrass lagoon

What are seagrasses?

Seagrasses are the only flowering plants that grow submerged in the sea. Seagrasses generally grow in intertidal areas to depths of 30m.

Seagrass parts: Like other 'normal' land plants, seagrasses have green leaves where photosynthesis takes place. These leaves have veins to transport water around (called a vascular system). Seagrass leaves emerge from rhizomes (underground stems). These rhizomes spread along the soft sediments. Roots anchor the plant. Thus seagrass form a firm mat over the sea bottom. Unlike land plants, seagrass absorb water and nutrients through all parts of the plant, not just the roots. Seagrasses also have air canals in their leaves and rhizomes so they can 'breathe' while underwater.

Seagrass flowers: Seagrass flowers are usually small and inconspicuous. They are pollinated mainly by water. The pollen are usually long and thread-like. Floating in the currents, with luck, they will get entangled in the female flower of the same species. Their seeds are also dispersed by water. In some species, the same plant produces male and female flowers. In others, male and female flowers are produced in separate plants. However, seagrasses seldom flower. They spread mainly through vegetative reproduction through their underground rhizomes. Thus seagrasses do not easily colonise new places.

Seagrasses need the sea: Seagrasses dry out easily because, unlike land plants, their leaves and stems lack a waxy covering. They can tolerate short periods out of water, but must be submerged most of the time. This is why you will find few seagrasses growing on the sand bar of Chek Jawa.

Keep off the grass! Seagrasses can rapidly regrow their leaves. However, if their underground stems are damaged, it takes them longer to recover. So please do not step on the seagrasses.

Seagrass are not grass: Seagrasses do not belong to the same family of plants as the land grasses (Family Graminae). Despite the name, the leaves of seagrasses are not always grass-like. Seagrasses in Singapore belong to either the Family Cymodoceaceae or Family Hydrocharitaceae. For more details on the classification of seagrasses, see the Western Australia Seagrass Web Page.

Seagrass
meadows

Halophila ovalis
Place your mouse
over the photo for the different parts of the seagrass

Halophila sp.
flower
Place your mouse
over the diagram
to see the male
and female flowers

Classification
Class Monocotyledoneae
Phylum Angiospermophyta

See also ...
Seagrass lagoon in general

Links
Survey of Seagrasses of Chek Jawa: preliminary findings.
Fruits of the Sea: Seeds of Coastal Seagrasses on the CRC Reef Research Centre website: brief introduction to the ways seagrasses reproduce and re-establish themselves if affected by natural disturbances.
Seed production and seed banks of coastal plants (PDF file) on Prediction of the Resilience and Recovery of Disturbed Coastal Communities in the Tropics (SE Asia) page on the University of the Balearic Islands website: includes a long discussion of the seed banks produced by seagrasses and their role in restoring seagrasses after a natural disturbance.
What is seagrass? on the Hervey Bay Dugong and Seagrass Monitoring Program (Australia) website: brief rather technical fact sheet on the structures and functions of different parts of seagrasses.
Seagrasses by Dr Laurence McCook on the Australian Institue of Marine Science website: lots of details for the layman on what seagrasses are, where they are found, their role, and threats to them.
Seagrasses on the CRC Reef Research Centre: brief introduction to seagrasses and links.
Seagrasses on the Florida Keys National Marine Sanctuary website: about the structure, role and threats to seagrasses.
Bugs, Beasts and Biodiversity on the Australian Association for Environmental Education website: a student's fact and work sheet on seagrasses.

Other references

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.
Hartog, C. Den. The Sea-grasses of the World, 1970. North-Holland Pub. Co., Amsterdam. 276 pp., 20 pp. of photos.
Tan, Leo W. H. & Ng, Peter K. L., 1988. A Guide to Seashore Life. The Singapore Science Centre, Singapore. 160 pp. online version
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.
Ong, Jin Eong & Gong, Wooi Khoon (eds.), 2001. The Encyclopedia of Malaysia (Vol. 6): The Seas. Didier Millet, Malaysia. 144 pp.

a companion website to the chek jawa guidebook website©ria tan 2003 www.wildsingapore.com

a companion website to the chek jawa guidebook
website©ria tan 2003 www.wildsingapore.com