Although they cover less than 0.1% of the earth’s surface, coral reefs are the most biodiverse marine ecosystem in the world.
Coral reefs are home to:
Coral reefs are built by coral polyps as they secrete layers of calcium carbonate beneath their bodies.
The corals that build reefs are known as “hard” or “reef-building” corals. Soft corals, such as sea fans and sea whips, do not produce reefs. The calcium carbonate that is created by hard corals provides a foundation for baby corals to settle upon, and if the local threats to coral reefs are limited, then the corals will build up over time and create a healthy, vibrant coral reef.
Other types of animals and plants also contribute to the structure of coral reefs. Many types of algae, seaweed, sponges, sediment, and even mollusks like giant clams and oysters add to the architecture of coral reefs. When these organisms die, they also serve as foundations for new corals.
Because of the diversity of life found in the habitats created by corals, reefs are often called the "rainforests of the sea." About 25% of the ocean's fish depend on healthy coral reefs. Fishes and other organisms shelter, find food, reproduce, and rear their young in the many nooks and crannies formed by corals. The Northwest Hawaiian Island coral reefs, which are part of the Papahānaumokuākea National Marine Monument, provide an example of the diversity of life associated with shallow-water reef ecosystems. This area supports more than 7,000 species of fish, invertebrates, plants, sea turtles, birds, and marine mammals. Deepwater reefs or mounds are less well known, but they also support a wide array of sea life in a comparatively barren world.
Coral reefs protect coastlines from storms and erosion, provide jobs for local communities, and offer opportunities for recreation. They are also a source of food and new medicines. Over half a billion people depend on reefs for food, income, and protection. Fishing, diving, and snorkeling on and near reefs add hundreds of millions of dollars to local businesses. The net economic value of the world’s coral reefs is estimated to be nearly tens of billions offsite link of U.S. dollars per year. These ecosystems are culturally important to indigenous people around the world.
Information from The Coral Reef Alliance and The National Oceanic and Atmospheric Administration.
Coral reefs support over 500 million people around the world by providing food, income, coastal protection, and more. They provide over $375 billion per year in goods and services. And despite only covering 0.1% of the earth’s surface, they contain the highest number of species of any ecosystem besides rainforests.
They also play a vital role in medical research—scientists have developed treatments for cardiovascular diseases, ulcers, leukemia, lymphoma, and skin cancer all from chemicals in reef plants and animals. And more than half of all new cancer drug research focuses on marine organisms, many of which are found on coral reefs.
Biodiversity refers to the variety of living species that can be found in a particular place. Coral reefs are believed by many to have the highest biodiversity of any ecosystem on the planet—even more than a tropical rainforest. Occupying less than one percent of the ocean floor, coral reefs are home to more than 25% of all marine life.
Why is that important? A highly biodiverse ecosystem, one with many different species, is often more resilient to changing conditions and can better withstand significant disturbances.
If properly managed, coral reefs can yield an average of 15 tons of fish and other seafood per square kilometer (.4 square miles) per year. Coral reefs support 6 million fishers in nearly 100 countries. Reefs account for 10-12% of the fish caught in tropical countries and 20-25% of the fish caught in developing nations.
They are a primary source of food and protein for many coastal communities. In fact, 4.3 billion people around the world rely on fish for 15% of their animal protein intake.
Many organisms found on reefs produce chemical compounds that have been used in treatments for cardiovascular diseases, ulcers, leukemia, lymphoma, and skin cancer, and many more remain undiscovered. More than half of all new cancer drug research focuses on marine organisms, many of which can be found on coral reefs. -Coral Reef Alliance
You may have heard on the news in recent years bout coral bleaching and how harmful it has been. But what exactly is coral bleaching?
Bleaching is a stress response that results when the coral-algae symbiosis breaks down. The corals lose their algae, causing them to turn pale or completely white, which is referred to as bleaching.
Coral bleaching can be caused by a wide range of environmental stressors such as pollution, oil spills, increased sedimentation, extreme increases or decreases in ocean temperatures, fluctuations in salinity, low oxygen, disease, and predation.
Bleached corals are still living, and if the environmental conditions return to normal soon enough, the corals can regain or regrow their symbionts and survive the bleaching event. If the stressors are severe, repeated, or prolonged, however, bleaching can lead to the death of corals. Bleached corals are more susceptible to disease, predation, and death because they are without their primary energy source.
Unfortunately, coral reef ecosystems are severely threatened. Some threats are natural, such as diseases, predators, and storms. Other threats are caused by people, including pollution, sedimentation, unsustainable fishing practices, and climate change, which are raising ocean temperatures and causing ocean acidification. Many of these threats can stress corals, leading to coral bleaching and possible death, while others cause physical damage to these delicate ecosystems. During the 2014-2017 coral bleaching event, unusually warm waters (partially associated with a strong El Niño) affected 70% of coral reef ecosystems worldwide. Some areas were hit particularly hard, like the Great Barrier Reef in Australia, where hundreds of miles of coral were bleached.
Corals are able to recover from bleaching events if conditions improve before they die, though it can take many years for the ecosystems to fully heal. Scientists are also testing new ways to help coral reef ecosystems, such as growing coral in a nursery and then transplanting it to damaged areas.
Information from Florida's Coral Reef and The Coral Reef Alliance.
