The longest-lasting coral bleaching event in the world has damaged reefs from the Caribbean to Australia to Southeast Asia, and according to the U.S. National Oceanic and Atmospheric Administration (NOAA), it’s not likely to stop anytime soon. The bleaching event began in June 2014 and continues today.
It’s caused extensive damage to coral reefs, ecosystems that support a wide variety of marine life around the world.
What are coral reefs?
Coral reefs are built by tiny marine invertebrates called corals. Certain species of corals use calcium carbonate found in ocean water to create a durable exoskeleton in order to protect themselves.
When a coral polyp — the name for an individual coral — dies, it leaves its exoskeleton behind, which forms coral reefs. New coral polyps living on that structure make calcium carbonate exoskeletons, and the structure slowly grows over time.
Some species of corals feed themselves by catching small plankton and fish with their tentacles. Most species, though, have a symbiotic relationship with a type of algae called zooxanthellae, which allows both species to survive.
The algae live inside the coral polyps and use photosynthesis to produce food for themselves and for the polyps. The polyps provide the zooxanthellae with carbon dioxide and a place to live. The algae are also the source of a coral reef’s vibrant colors.
What is coral bleaching?
When the ocean water around coral warms rapidly, even if it’s by a small amount, the zooxanthellae desert the corals. This means the corals lose their food source, as well as their color, and gradually turn white. If the water stays too warm for too long, the coral eventually dies.
Living corals usually clean off algae other than zooxanthellae. After corals die, algae can accumulate on the structure, making it nearly impossible for new coral polyps to grow, even if temperatures return to normal. Coral reefs may not recover from this, and even if they do, it takes decades.
Why coral reefs matter
Though coral reefs only make up less than 1 percent of the total marine environment, they’re home to 25 percent of all ocean life. Up to 2 million different marine species live in, on, or around them.
Around a quarter of the ocean’s fish also use coral reefs as nurseries for their eggs. Widespread loss of coral reefs results in the loss of habitat for all this varied marine life, and could even wipe certain species out.
The loss of some of this marine life could directly impact people, as well. Some of the species that rely on coral reefs are important sources of food and income. Coral reefs also create a thriving tourism industry for coastal communities. Additionally, reefs create barriers against the worst destruction caused by storms, typhoons and hurricanes.
How scientists study coral reefs
In order to help save the reefs, scientists are trying out new, innovative methods for studying the ecosystem. Some have begun using underwater drones to monitor ocean ecosystems. They also collect samples from particular regions.
Recent advances in sampling technologies have also been helpful. By testing sediment or water an organism has come into contact with, scientists can now detect its DNA, and determine what its habitat is like and whether it has migrated from a different area.
This could help tell researchers what species still live in the bleaching coral reefs, and which may have left their original homes due to the bleaching event.
Can the coral reefs be saved?
In order to save the Earth’s coral reefs, we need to take better care of the oceans, marine life, and our environment in general.
Overfishing harms underwater ecosystems, which can indirectly affect coral reefs. Some fishing methods, such as bottom trawling, can destroy coral reefs and their environment. Careless tourism can also sometimes damage reefs.
Toxins that enter the water through dumping, runoff, and accidental spills change the makeup of ocean water. Some pollutants increase nitrogen levels, which cause algae to grow at higher rates. This can suffocate reefs by blocking out their sunlight.
In order to protect the reefs, humans need to fish and vacation more responsibly, and pollute less. Better laws and regulations around fishing and pollution may help. Buying from environmentally conscious companies, conserving water, not using chemicals on your lawn, and using fewer fossil fuels are all ways everyday people can help.
While coral reefs cover only a small portion of the Earth, they play a crucial role in marine ecosystems, coastal economies, food security, biodiversity, and life on our planet.
This article was written by Megan Ray Nichols. If you enjoyed this article, please visit her page Schooled by Science.