BEN G

1. Coral reefs are the most diverse and beautiful of all marine habitats. Large wave resistant
structures have accumulated from the slow growth of corals. The development of these
structures is aided by algae that are symbiotic with reef-building corals, known as
zooxanthellae. Coralline algae, sponges, and other organisms, combined with a number of
cementation processes also contribute to reef growth.
The dominant organisms are known as framework builders, because they provide the matrix
for the growing reef. Corals and coralline algae precipitate calcium carbonate, whereas the
framework- building sponges may also precipitate silica. Most of these organisms are colonial,
and the slow process of precipitation moves the living surface layer of the reef upward and
seaward.
The reef is topographically complex. Much like a rain forest, it has many strata and areas of
strong shade, cast by the overtowering coral colonies. Because of the complexity, thousands of
species of fish and invertebrates live in association with reefs, which are by far our richest
marine habitats. In Caribbean reefs, for example, several hundred species of colonial
invertebrates can be found living on the undersides of platy corals. It is not unusual for a reef
to have several hundred species of snails, sixty species of corals, and several hundred species
of fish. Of all ocean habitats, reefs seem to have the greatest development of complex
symbiotic associations.

2. CORAL REEF THREATS
Overfishing: This affects the ecological balance of coral reef communities, warping the
food chain and causing effects far beyond the directly overfished population.
Careless tourism: Careless boating, diving, snorkeling, and fishing happens around the
world, with people touching reefs, stirring up sediment, collecting coral, and dropping
anchors on reefs. Some tourist resorts and infrastructure have been built directly on top of
reefs, and some resorts empty their sewage or other wastes directly into water
surrounding coral reefs.
Pollution: Urban and industrial waste, sewage, agrochemicals, and oil pollution are
poisoning reefs. These toxins are dumped directly into the ocean or carried by river
systems from sources upstream. Some pollutants, such as sewage and runoff from farming,
increase the level of nitrogen in seawater, causing an overgrowth of algae, which
'smothers' reefs by cutting off their sunlight.

3. CORAL REEF’S GLOBAL ISSUES
Coral reefs cover an area of over 280,000 km2 and support thousands of species in
what many describe as the “rainforests of the seas”.
Coral reefs benefit the environment and people in numerous ways. For example,
they:
Protect shores from the impact of waves and from storms;
Provide benefits to humans in the form of food and medicine;
Provide economic benefits to local communities from tourism.