Coral Reefs

Coral is alive. It’s not a fancy, colorful type of rock. It’s also not a pretty plant. It is an animal, or often, a lot of animals living in a community. The large, hard structures that make up hard corals are home to a number of individual organisms called polyps.

A coral polyp is shaped like a cylinder with a mouth surrounded by tentacles at one end. The bodies of the polyp are usually clear although they often appear to be brightly colored. These colors come from a type of algae (zooxanthellae) that live within the tissue of the polyp. The coral and the zooxanthellae have a symbiotic relationship; the waste of the coral is used by the algae for photosynthesis, and the byproducts from that process feed the coral.

Together these colonies of coral polyps create coral reefs. The structure of coral reefs comes from the hard skeletons of the coral polyps which are created from calcium carbonate. Although coral reefs look like solid structures, between 40-70% of the reef is open space between corals. These open spaces provide habitat for huge numbers of fish, invertebrates, plants, and other organisms.

Corals have been around for over 400 million years. There are around 6000 species of coral today in many colors, shapes and sizes. There are soft corals as well as hard corals and although most coral lives symbiotically with zooxanthellae, not all species do.

Coral reefs are often referred to as the “rainforests of the sea” because of the incredible amount of biodiversity they host. These complex ecosystems make up less than 1% of the sea floor but are home to nearly a third of all known fish species. It is estimated that nearly a million different species live on coral reefs around the world.

Roughly 8% of the world’s coral reefs are found in the Atlantic Ocean, home to about 70 coral species. The Indo-Pacific (Indian and Pacific Oceans) house the remaining 92% with around 700 different species of coral.

In addition to being biodiversity hotspots, corals have a number of other benefits for the ocean, the coast, and humans.

  • Coastal Protection: coral reefs act as barriers protecting coasts from waves, storms, and erosion. Coral reefs can absorb up to 90% of the energy from waves, lessening their impact on shores.
  • Food Source: Coral reefs are vital for fisheries. Coral reefs provide 10% of the fish caught worldwide (25% in developing countries and over 70% in Southeast Asia). Reefs are nursery grounds for 25% of fish species, many of which do not live on the reef as adults. This nursery area protects the juvenile fish until they are large and strong enough to venture out.
  • Tourism: Coastal communities rely on coral reefs for tourism and recreation. Over 100 countries benefit from reef-related tourism. It generates over 30% of export earnings in over 20 nations. Tourism sustains 10% of all jobs worldwide generating nearly 10 billion USD per year.
  • Habitat Formation: Parrotfish graze on coral reefs, digesting the organic matter and releasing the calcium carbonate skeletons in the form of sand. Parrotfish waste is responsible for over 80% of the white sand in tropical areas. They form the shallows, and in some cases, even small islands.

Watch this video for more information about coral and its importance.

Although the hard structure of coral reefs may make them appear strong, coral reefs can be fragile. There are many threats to coral reef ecosystems. In hundreds of millions of years, coral has become very good at adaptation. However, with so many stresses at the same time and with changes happening quickly, corals are struggling to survive.

Half of the world’s reefs have already been lost or severely damaged. We cannot allow coral reefs to be the first ecosystem on Earth to disappear.

The excess CO2 in the atmosphere (primarily from the burning of fossil fuels) is being absorbed by the ocean and causing the pH to become more acidic. This excess carbon decreases the number of calcium carbonate ions in the water that are available for corals to build and repair their skeletons. This weakens the reefs and reduces their reproductive abilities.

Coastal Development
Deforestation, mining, land clearing for agriculture, and urbanization all cause erosion and release sediment into coastal waters. Sediment can settle on top of corals, blocking the sun needed for the zooxanthellae to photosynthesize and produce food for the coral polyps

Destructive Fishing Practices
Many destructive fishing practices are incredibly harmful to reefs. Although these practices aren’t targeting coral, reefs become collateral damage. Dynamite fishing reduces thousand-year-old reefs to rubble instantly. Cyanide fishing kills all surrounding reef in order to remove one aquarium fish. Bottom trawling can tear up large sections of reef at a time.

Global Warming
Corals are adapted to very specific temperature ranges. Different corals have different ranges, as they are found in regions all over the world. But specific corals do not easily adapt to drastic changes. With sea temperatures increasing at unprecedented rates, corals are suffering. When corals get too warm and become stressed, they expel the zooxanthellae (this causes them to lose their color and “bleach”). Without their algae partner, they lose an important food source and can die if conditions don’t change quickly. Additionally, global warming is causing more extreme weather and sea level rise, both of which can have physical impacts on coral reef ecosystems.

Irresponsible Tourism
When not properly managed, the increased activity and pollution from tourism can have a negative effect on coral reef ecosystems. More directly, touching, kicking, or walking on coral causes breaks and destruction. Dropping anchors, propellers or grounding boats can destroy large sections of reef. Sunscreen and other personal products containing harmful chemicals can kill or sterilize the coral reefs.

Marine Wildlife Trade
The worldwide aquarium trade is estimated to include up to 30 million fish and 1.5 million coral colonies each year. While some of the coral used is farmed, some isn’t. The vast majority of fish for the aquarium trade are wild caught; often in ways that damage the coral either physically or chemically. Coral is also often collected to create souvenirs such as jewelry and picture frames.

Ocean Dead Zones
Increased nutrient run-off from agriculture and other land-based sources can create harmful algal growth directly on coral which can smother the polyps or near the surface of the water which block the sun that reaches the reef. If the surface blooms get too large, when the algae dies, the oxygen needed for their decomposition can deprive the marine environment of enough oxygen to support some forms of life in the water.

Oil Pollution
Oil spills near reefs cause massive amounts of oil to enter the ocean. Even small amounts from increased urbanization near coasts increases the amount of oil and other chemicals that enter the water from roads, parking lots, and other sources. If oil comes in contact with coral, it can reduce reproductive rates, stunt growth and development and even cause death.

Overfishing of reef species can completely alter the balance of the ecosystem. For example, if too many herbivores are removed, algae grows out of control and smothers the coral. If apex predators, like sharks are removed, second level predators reproduce unchecked and overeat herbivores with the same result for coral reefs.

Plastic Pollution
Plastic in the ocean often gets trapped on corals. This can block both light and oxygen from reaching coral, both of which are essential to its survival. It can also break branches off of coral when it gets twisted or caught and pulled by the currents. Finally, new research has shown that the toxins from plastics in the ocean can increase the likelihood of disease in corals by over 80%.

Coral reef ecosystems are affected by so many of the threats to our ocean. Anything you do to reduce stress on the ocean, will help the coral. The suggestions below are a start but are by no means exhaustive. More than anything, please spread the word about the importance of coral reef ecosystems. Talk with others about the ocean and protection of aquatic wildlife. Let people know what they can do to protect ocean habitats. The more people know, the more they care. Together we can Protect the Living Reef.

Support Marine Protected Areas
Learn about and support local and national marine protected areas. Spend time there and consider volunteering; remember that local support is key to a successful MPA.
When you travel, visit marine protected areas to show your support. The MPA will likely have beautiful things to see; fully protected MPAs have more than twice the number of divers and snorkelers than unprotected coastal areas. Just be sure to take only pictures, and leave only footprints!

Support Coral Restoration Efforts
Some organizations are working on coral restoration in various parts of the world. Support these groups by donating and participating as a volunteer where you can. Consider an eco vacation to assist with coral restoration projects.

Help to Collect Coral Data
CoralWatch monitoring is a citizen science program through the University of Queensland in Australia. For the past 20 years, they have collected coral data worldwide, to help coral scientists to study the health of corals. It is a great way for anyone who is in the water with coral to assist with scientific research to protect coral.

Use Ocean Safe Personal Care Products
To limit your use of sunscreen, seek shade during the day whenever possible and wear clothing that covers your skin when in the sun. For the sunscreen you so use, purchase reef-safe sunscreen without chemicals that can harm marine life. The Protect Land + Sea Certification website lists ingredients and safe products.

Protect the Health of the Coasts

  • Help to keep beaches and coastal areas clean. Participate in (or organize) beach, creek, and wetland cleanups.
  • Volunteer to replant coastal vegetation.
  • When planning a vacation, research coastal hotels and restaurants. Ensure they are not negatively impacting the coastal ecosystem and are supporting conservation efforts. Use online resources, like TripAdvisor, to share why you are or are not supporting certain establishments.

Make Personal Changes for a Healthy Ocean

  • Don’t use single-use plastics (grocery bags, straws, take-away containers, bottles, etc.)
  • Reduce waste, use only what you need
  • Buy only sustainably fished seafood in restaurants and at supermarkets
  • Use organic foods that don’t use pesticides
  • Buy local to reduce the need for international shipping
  • Buy clothing made of natural fibers and, for synthetic materials, wash them in a washing bag to reduce microfibers entering the water
  • Reduce your carbon footprint: ride a bike, walk, use public transportation, attend virtual meetings and conferences, use renewable energy, reduce your meat consumption

Coral reefs have a lot of champions in the conservation world! Many people are working to protect them, spread awareness about how vital they are to the ocean (and the planet!), and to restore reefs in areas where they have been damaged. 

Please check out these (and others) and do what you can to lend them your support!

Coral Gardeners
Coral Watch
Gili Shark Conservation
Inland Ocean Coalition

Restoring Coral Reefs with Heat Resistant Corals, French Polynesia
Three years ago, on the island of Mo’orea, a group of local ocean lovers decided to help their local coral reef to combat rising ocean temperatures. After surviving bleaching incidents, they took note of which coral species were the most resistant to warmer temperatures. They are now taking fragments of these corals and transplanting them in damaged zones to help build the reef and encourage the return of marine life.

Community-Led Marine Protection, Apo Island, Philippines
After years of destructive fishing and damaging the surrounding coral reef, local fishermen, working with a marine scientist, decided to create a marine protected area near their village. They designated 10% of the reef as a no-take zone. Within a few years, the coral reef ecosystem was healthy and recovering. Fish in the no-take zone and the areas around the protected zone were also thriving with life. Community-led conservation has incredible success around the world!