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Coral Reefs are the oldest, most complex ecosystems on earth. They are home to more kinds of life than any other ocean environment and rival the tropical rainforests on land. They have existed for well over 200 million of years and achieved their current level of biologic diversity 50 million years ago. These majestic underwater worlds are home to some of the world’s most colorful and diverse life forms including fish, hard and soft corals, sponges, jellyfish, anemones, snails, rays, crabs, moray eels, lobsters, sea turtles, dolphins, and seabirds. However, most coral reefs are now threatened with extinction due to a combination of impacts that are particular to each reef, depending upon the use and upland activities affecting it. Here are some of the leading threats to coral reefs:

Threats

Water Quality Decline: Corals require clear, clean, nutrient-free waters to thrive. Algal blooms caused by excess nutrients in the water column out-compete slow growing corals for habitat and reduce oxygen levels, decreasing visibility, increasing chlorophyll levels, and inhibiting photosynthesis dependent on sunlight. The kinds and extent of diseases attacking corals have increased in recent years and have reduced coral coverage. As oxygen levels are reduced, fish and other sealife cannot survive at the reef.

Pollution: Coral reefs are impacted by multiple stressors including agricultural runoff from pesticides and fertilizers, inadequate sewage and stormwater treatment, siltation from coastal development and beach renourishment projects, contamination from petroleum products, and sewage, oil and toxic discharges from boats, including antifouling paint applied to boat bottoms.

Overharvesting: As fish and other wildlife populations decline, the delicate predator-prey balance of life on the reef is upset. Experts warn that fish populations are at risk because maximum sustainable yields for many species around the world, including some that are endangered, have been exceeded. Destructive fishing techniques such as the use of cyanide and trawling gear damage reef habitat. The outright depletion caused by the harvest of coral and live rock for construction and the aquarium/curio trade has destroyed many reefs around the world.

Physical Damage: Anchors dropped on reefs, as well as accidental boat groundings and propellor dredging can crush and scar coralheads, destroying years of growth. Diver/snorkeler impacts from fins, hands, equipment or standing on corals can crush the fragile living coral polyps. Marine debris, especially plastics and monofilament line, can smother or abrade corals and is deadly for birds, fish and turtles that become entangled in it or mistake it for food and ingest it. Storms and hurricanes wreak extensive damage on coral reefs, which serve as a barrier to adjacent lands.

Global Climate Change: Rising sea temperatures cause coral bleaching, stressing corals that expel their symbiotic algae, lose their color, and lose their vitality. Corals are the canaries in the coal mine for our planet’s health.

Click here to read more about reef threats in the Florida Keys.