Region: Philippines

Introduction
Between the reef and the shore there is often a broad, shallow seagrass bed. These areas are dense with the grass. Like land grasses, sea grass can spread by growing offshoot roots by sending out roots every which way but up. In fact, roots make up most of the plant. The dense root system holds the lagoon floor in place.

Where Do They Live
Throughout the warm waters of the tropics, seagrass beds can be found just beyond the shoreline. They need warm water (at least 75°F (24°C)) to survive. They are found just about anywhere a coral reef is found.

Important Functions
The neighboring habitats, mangroves and coral reefs, rely on seagrass beds for their health. Seagrass beds provide special services for these other areas.

Seagrass is an indicator of good water quality because it declines rapidly in the presence of pollutants and excess nutrients. As rivers empty into the sea, they carry fresh water, silt and chemicals—all of which can kill coral. Seagrass beds improve water quality by absorbing low levels of excess nutrients and mixing the fresh water with the salt water. The roots and blades of seagrass trap, filter, and recycle nutrients, such as phosphorus and nitrogen, and transform them into something that can be eaten by other organisms.

The seagrass slows down the water, cutting down on wave action and allowing dangerous elements to settle out. It reduces property damage in coastal areas by decreasing the wave action and water movement that can cause erosion. The dense roots of seagrass trap the sediment carried by the powerful waves and hold it in place. This action keeps the sediment and nutrients that might otherwise feed algae that can grow out of control and end up smothering corals on the reef. Cool, fresh river water also mixes with warm, salty seawater in the seagrass bed before reaching the reef.

Seagrass beds are a breeding ground and safe place for reef animals to leave their eggs. The waters are calm and filled with dense seagrass and algae. Many reef animals come to the seagrass bed to mate, hiding in the lush grasses, and then lay their eggs in these calm waters. Baby animals can nestle into the tangles of the blades or the maze of roots, taking cover from larger fish. Seagrass beds act as an important nursery area for many animals, including scallops, cod, winter flounder, and lobsters.

Eelgrass also provides food and shelter for other animals that don’t live under the water, like ducks and geese, whose migratory paths often include coastal areas with seagrass. Only a few animals, like dugongs, sea turtles, sea urchins and some fish, have the ability to digest the blades of seagrass. These animals are important to keep the seagrass beds from getting so large that they overgrow coral reefs.

Not all corals live on reefs. Some live in seagrass beds. These corals have adapted to conditions that are different from the reef. The water is warmer, mixed with fresh water, and because of the changing tides, they experience periodic exposure to the air.

Seagrasses are also home to a number of fish species valued by fishers, as catch or bait. They are also home to beautiful animals that are valued by home aquarium hobbyists.

Fishers can earn income by harvesting and selling sea grasses. Many common products, like toothpaste and ice cream, use ingredients extracted from seagrass. Seagrass is eaten in many Asian cultures.

Conservation Issues
The beds take a long time to recover from any serious damage because they don’t grow very fast—only about 10 inches a year. And sea grass can’t tolerate long exposure to excessive pollution, silt or destructive fishing practices.

Many invertebrates live in lagoons, feeding on seagrass. People walk through lagoons at low tide, looking for shells and other invertebrates. Some are food sources and the empty shells are used for crafts, which are sold for income. Demand for shellcraft leads to over-harvesting, which depletes populations and upsets ecological balance.

Urban, industrial and agricultural runoff can have detrimental effects on seagrasses and the communities they support. Sedimentation from development sites runs into the ocean, clouding the water and keeping the sun from reaching the seagrass. This prevents seagrass from making food from the energy it gets from sunlight.

Outboard motors and fishing gear can destroy seagrass. Boats can catch the blades of seagrass in the motor blades, ripping up rows and rows of the grass. Certain fishing methods can also destroy large fields of seagrass, and the fishing gear often gets ruined in the process.

Protection
Seagrass beds need clear water in order to make food from sunlight. Mangroves, which border the shoreline, trap sediments running off from the land. This prevents the sediments from smothering the seagrasses. Reefs, which are in the deeper waters heading out to the ocean, block powerful waves from crashing onto seagrass beds. Slowing down the waves keeps the waters in seagrass beds calm and keeps the sand and sediments from making the water too cloudy.

Many nations, like the Philippines, are beginning to recognize the benefits of seagrass beds. They are designating them as protected areas and limit the use of these grasses.

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References
Print Publications:
Calumpong, H. and Menez, E. 1997. Field Guide to Common Mangroves, Seagrasses and Algae of the Philippines. The Philippines: The Bookmark, Inc. 197 p. ISBN# 971-569-197-8.

Perrine, D. 1997. Mysteries of the Sea. Lincolnwood, Illinois: Publications International, Ltd. 312p. ISBN# 0-7853-2430-5.

Reader’s Digest. 1984. Reader’s Digest Book of the Great Barrier Reef. Sydney, Australia: Reader’s Digest Services Pty Limited. 384p. ISBN# 0-949819-41-7.

Veron, J. 2000. Corals of the World. Volume 1. Townsville, Australia: Australian Institute of Marine Science. 463p. ISBN# 0-642-32236-8.

Vocabulary Words

Seagrass bed – A shallow water marine habitat where there are dense thickets of seagrass. This area serves to trap sediments to stabilize the ocean floor, prevent sediments from settling and covering coral, and to serve as a nursery and mating ground for reef animals.

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