What are the other threats to corals?

In addition to the impacts of climate change such as bleaching and ocean acidification, pollution, diseases, and unsustainable fishing practices, coral reefs are routinely threatened by marine debris, vessel groundings, natural disasters, and thoughtless human activities on and around reef ecosystems.

Marine debris

Fishing nets and lines wash up onto beaches or get tangled on coral reefs. Learn more and view a larger image.

Marine debris is any form of human-made solid waste, materials, or litter that ends up in the ocean or other bodies of water. Marine debris originates from land-based sources, such as coastal areas and rivers, as well as maritime activities such as shipping, fishing, and oil rigs. Marine debris can smother or become entangled in coral, reducing their growth, breaking them apart, or killing them. Marine debris has been found in all parts of the ocean, even the bottom of the Mariana Trench at a depth of 36,000 feet! It is still unknown how marine debris may impact fragile deep ocean corals and their ecosystems.

Vessel groundings and hurricanes

Vessel groundings occur when a boat or ship runs into a coral reef and gets stuck. This can happen during a storm or if a boat sinks unexpectedly. When a vessel runs aground on a coral reef, the force of the impact can crush and destroy coral colonies, leading to irreversible damage. If a vessel becomes grounded near a coral reef it may displace sediments and kick up debris, which can settle on the corals, smothering and killing them.

Hurricanes can cause physical damage to coral reefs, toppling corals or breaking them apart. The loose coral pieces can damage adjacent corals as they are tossed around in the currents and violent waves produced by the storm.

A variety of vessels can become stuck on shallow coral reefs. Learn more and view a larger image.

Blue-green marks visible on these broken corals are from boat paint after a boat has run aground and been lifted off the coral. View a larger image.

Human interactions

Other human interactions with reefs, such as anchoring a boat or standing on the coral while snorkeling or SCUBA diving, damages coral reefs. These activities cause physical damage, like breaking the corals apart or killing individual coral polyps. Using mooring buoys for anchoring and not touching corals protects them. Most sunscreens have chemicals that interfere with coral growth and reproduction. Physical sunscreens, such as zinc oxide or titanium oxide, are better for corals and all marine life.

Never stand on or walk through a coral reef area. Make sure you can float above the corals while snorkeling. Learn more and view a larger image.

Scientists have discovered that chemicals found in some sunscreens and other personal health products threaten the health of coral reefs.Learn more and view a larger image.