|Basic Concepts in Environment, Agriculture and Natural Resources Management: An Information Kit (IIRR, 1993, 151 p.)|
|Freshwater and marine ecosystems|
Coral reef ecosystems
Coral reefs shallow-water, tropical marine ecosystems characterized by a tremendous variety of plants end animals and high primary productivity. Coral reefs are massive deposits of calcium carbonate that have been produced by corals with major additions from calcareous algae and other organisms that secrete calcium carbonate.
Common fauna found in coral reef ecosystems are cnidarians such as jellyfishes, hydroids, soft and hard corals, sea anemones; fishes (including aquarium fishes); fishes); mollusks such as clams, top shells and oysters; echinoderms such es sea cucumbers, sea urchins, brittle stars end starfishes; sponges; reptiles such as sea snakes; and, other miscellaneous invertebrates.
· Coral reefs are the most biologically productive of all natural communities. In fact, a single reef alone may support as many as 3,000 species of corals, fish and shelfish.
· Coral reefs provide an area for recreation and tourism due to its aesthetic appeal, biological richness, clear waters and relative accessibility.
· Coral reefs protect coastal villages by protecting the shoreline and acting as a self-repairing breakwater.
· Coral reefs provide an important source of animal protein. About 30t/km²/year of fish can be harvested in some island fisheries in the Philippines.
Factors favoring reef growth
· Water temperature above 18°C
· Water depth shallower than 50 m
· Constant salinity greater than 30 but less than 36 parts per thousand
· Low sedimentation rates
· Sufficient circulation of pollution-free water
· Pre-existing hard substrate.
Coral reefs are being degraded and destroyed at unprecedented rates, throughout the Philippines. In the 1982 survey, it was found that of the 632 reefs sampled, nearly 70% were found to be in poor to fair condition - having less than 50% live coral cover. As of 1987, more then half of the reefs in the Philippines are in advanced states of destruction, with only about 25 % of live coral cover in good condition and only 5 % in excellent condition.
Cause of destruction
· Increasing population pressure which leads to overexploitation of the resources;
· Sedimentation resulting from human terrestrial activities (unsound agricultural and forestry practices, mismanagement of watersheds, exploitation of mangroves, earth-moving for construction and the dumping of terrestrial and marine mine tailings and effluents);
· Destructive fishing practices (dynamite fishing, muro-ami, dragging nets over reefs, use of small mesh nets and traps, traditional spearing and spearing using scuba);
· Anchor damage by boats caused by inshore fishermen and tourists,
· Pollution due to nearby populated areas;
· Outbreak of crown-of-thorns starfish population which eats stony corals and devastates large areas of reef.
Heavily damaged coral reef