Research Department

Ignored habitats of the sea: Seagrass Meadows

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Unlike coral reefs, seagrass meadows don’t get much attention from tourism or the general public. These “fields of the sea” support economically important fishes and invertebrates.

By Gregorio E. de la Rosa, Jr.

Do you know what seagrasses are? Why are they important to marine animals and beneficial to humans? They are the most overlooked of the coastal ecosystem. From the perspective of people who can afford to snorkel and dive, they cannot compare to the smattering of colors and the irresistible pull of coral reefs. They are not ‘iconic’ enough for most people to merit a mere glance to beachgoers.

Seagrasses are flowering plants that are adapted to seawater, much like mangroves. The only difference is that they live fully submerged in seawater and are exposed to direct sunlight only during low tides. They come from three families, Family Hydrocharitaceae, Family Zosteraceae and Family Cymodoceaceae. Globally, there are over 67 species of seagrasses.

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A sparse Halophila ovalis meadow next to a reef in Canlangi, Tubigon, Bohol. Photo by Ditto de la Rosa.

The Philippines has 18 seagrass species, found all over the Philippines. Some of the extensive seagrass beds include the Caluya in Antique, Northern Palawan, the Polillo Islands in Quezon, Hinatuan and Cortes in Surigao del Sur, Cateel Bay in Davao Oriental and others. They can live as deep as 15 meters (or 50 feet) like those found in the coast of Baler, Aurora and Polillo Island. They reproduce like grasses on land (hence their moniker), by duplicating (or cloning) themselves. By that characteristic, they (and the grasses) are called colonial organisms.

Have you ever seen a dugong (Dugong dugon)? I did, back in my university days when we spent three weeks during a summer course in Calauit Island in Busuanga. They’re big and brown and… deceptively fast. Dugongs eat seagrass. They selectively feed on some species which have richer nutrients than others like the Halodule sp. and Halophila species. If you see patches of white sand in a seagrass meadow with stubby seagrass, chances are they are dugongs grazing on them.

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The Dugong (Dugong dugon) is listed as a Vulnerable species under the IUCN Red List. Photo by Julien Willem, Creative Commons.

The main threat to seagrasses is reclamation. Because they are often perceive as having no direct benefit to humans, they are either gouged or covered up to allow industrial and tourism infrastructures such as resorts, ports or piers, expansion of runways, etc. They are also victims of improper mangrove reforestation and restoration.

Without proper guidance and information, mangrove reforestation projects plant directly and encroach on seagrass beds. This should never be done, not by you or anyone you know. The planted mangrove seedlings may either die from space and nutrient competition or kill and reduce the seagrass beds. If you see mangrove reforestation projects doing this, report them to the nearest DENR, BFAR or local government unit.

Of course there is the mega fauna like the dugong and the sea turtle seen around seagrass beds. But if you look closer, you can see exciting (to both novice and professional photographers alike) finds. If you ever have a chance, try doing a night dive. You might be lucky to find ghost pipefishes, frogfishes, nudibranches, seamoths, stargazers and other mind-boggling animals.

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Reported locations of seagrass meadows in the Philippines (Fortes 2013).

Haribon, through the Strengthening the Marine Protected Areas (MPA) to Protect the Marine Key Biodiversity Areas in the Philippines (MKBA) Project in Lanuza Bay, Surigao del Sur is assisting LGUs to properly manage seagrass meadows. Through the support of the Global Environment Facility, United Nations Development Programme, the Department of Environment and Natural Resources-Biodiversity Management Bureau, Haribon and its local partner, the Lanuza Bay Development Alliance, will assist the local government units and communities by establishing and strengthening MPAs and MPA network in Lanuza Bay in the next four years.

So, next time you go out on a beach or do diving, have a look at the seagrass. You might be surprised!

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