Coral reefs why are they endangered

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Under the Endangered Species Act, 22 coral species are listed as threatened, and three are listed as endangered. The primary threats to coral reefs are climate change, pollution, and impacts from unsustainable fishing. About 25 percent of all marine species are found in, on, and around coral reefs, rivaling the biodiversity of tropical rainforests. Bleaching also occurred in much of the western Indian Ocean, including 69 percent to 99 percent of corals bleached and 50 percent dead in the Seychelles.

Carbon dioxide entering seawater reacts to form carbonic acid, causing an increase in acidity. Each year, the ocean absorbs about one-quarter of the carbon dioxide emitted from the burning of fossil fuels oil, coal, and natural gas. Increases in ocean acidity measured by lower pH values reduce the availability of dissolved salts and ions needed by corals to form the calcium carbonate structure.

Consequently, coral growth and reef growth can be slowed, with some species affected more than others. If acidification becomes severe, coral skeletons can actually dissolve. On a local level, nutrient enrichment due to run-off from human activities on land can also cause increased acidity in coastal waters, exacerbating the effects of ocean acidification.

Skip to main content. Contact Us. Local Threats to Coral Reefs Most coral reefs occur in shallow water near shore. Coral reefs face many threats from local sources, including: Physical damage or destruction from coastal development, dredging, quarrying, destructive fishing practices and gear, boat anchors and groundings, and recreational misuse touching or removing corals. Pollution that originates on land but finds its way into coastal waters.

There are many types and sources of pollution from land-based activities, for example: Sedimentation from coastal development, urban stormwater runoff, forestry, and agriculture Sedimentation has been identified as a primary stressor for the existence and recovery of coral species and their habitats.

Sediment deposited onto reefs can smother corals and interfere with their ability to feed, grow, and reproduce. Nutrients nitrogen and phosphorous from agricultural and residential fertilizer use, sewage discharges including wastewater treatment plants and septic systems , and animal waste Nutrients are generally recognized as beneficial for marine ecosystems; however, coral reefs are adapted to low nutrient levels; so an excess of nutrients can lead to the growth of algae that blocks sunlight and consumes oxygen corals need for respiration.

This often results in an imbalance affecting the entire ecosystem. Excess nutrients can also support growth of microorganisms, like bacteria and fungi, that can be pathogenic to corals.