How much do you know about coral reefs?

Coral reefs are home to an abundance of sea food
Photo: Rich Carey/Shutterstock

These unusual creatures are stunningly beautiful and surprisingly important to life on Earth. Show us what you know!

Question 1 of 10

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Coral reefs support marine life
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Coral reefs are home to what percentage of all marine life on Earth?

Though they take up less than 1 percent of the marine environment, coral reefs are home to over 25 percent of all known fish species. Acting as both sanctuaries and nurseries for thousands of species, corals are critical to the survival of marine diversity across the planet.

Question 2 of 10

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Corals are animals
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Corals are plants.

As NOAA explains, "Corals are sessile, which means that they permanently attach themselves to the ocean floor, essentially 'taking root' like most plants do...Corals are animals, though, because they do not make their own food, as plants do. Corals have tiny, tentacle-like arms that they use to capture their food from the water and sweep into their inscrutable mouths."

Question 3 of 10

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Coral reefs are home to an abundance of sea food
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Where are coral reefs located?

Coral reefs grow best in warm, shallow water where plenty of sunlight filters down. This ensures that algae, which lives a symbiotic relationship with corals, get plenty of light to photosynthesize. However, coral species that do not rely on algae as part of their food source can be found in colder, deeper water. WWF writes, "Cold-water coral reefs are commonly found where current flow is accelerated. They are found on the continental shelf, and also in deep-sea areas with topographic highs, such as seamounts, mounds, ridges, and pinnacles."

Question 4 of 10

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Corals become white when faced with significant stress
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What causes coral bleaching?

When a coral undergoes stress, it will eject the symbiotic algae living inside its tissue. The algae is the source of color in corals, so the corals appear white. Sometimes corals can recover from a bleaching event; however, corals are particularly fragile at this point and sometimes bleaching events are fatal.

The sources of stress that cause a coral to eject algae and thus look "bleached" include a change in water temperature, pollution, chemical runoff from agriculture or industry, sedimentation from dredging, overexposure to sunlight or air or changes in salinity. When several of these factors combine, it may be too much for a reef to recover from.

Question 5 of 10

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Coral reefs are home to an abundance of sea food
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What is considered the maximum amount of seafood a single square kilometer of a properly managed coral reef yield each year?

Coral reefs are home to abundant life, and they are of vital importance as a food source for the world. The lives of hundreds of millions of people directly depend on the health of coral reefs, and the continued abundance and diversity of fish found within reefs. World Resources Institute reports, "A healthy, well-managed reef in the Indian or Pacific oceans can yield between 5 and 15 tons of seafood per square kilometer per year in perpetuity."

Question 6 of 10

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There are three types of coral reef
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What is a barrier reef?

Barrier reefs are one of several types of coral reef. Barrier reefs are reefs that run parallel to the shoreline and "they are separated from land by an expanse of water. This creates a lagoon of open, often deep water between the reef and the shore," states NOAA. This type of reef creates a protective border between the ocean and the shallow water near shore.

Question 7 of 10

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Corals are valuable to ecology and economy
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How much does the loss of just 1 kilometer (.62 mile) of coral reef cost the world economy?

According to WWF, "Counting only the economic value of fisheries, tourism, and shoreline protection, the costs of destroying 1km of coral reef ranges between $137,000-1,200,000 over a 25-year period." Coral reefs are clearly worth far more alive and thriving than damaged or dead, which is why protecting them is so important.

Question 8 of 10

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Coral with a ghost net
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What percentage of the world’s coral reefs are threatened by human activity?

According to a 2011 report by the World Resources Institute, "More than 60 percent of the world’s reefs are under immediate and direct threat from one or more local sources —such as overfishing and destructive fishing, coastal development, watershed-based pollution, or marine-based pollution and damage."

When factoring in the thermal stress of warming ocean temperatures, that number rises to 75 percent.

"By 2050, nearly all reefs will be affected by warming and acidification and almost all reefs will be classified as threatened, assuming there is no change in local pressure on reefs."

Question 9 of 10

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There is still much to learn about corals
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Coral reefs are important to the development of new medicines.

According to NOAA, "Coral reef plants and animals are important sources of new medicines being developed to treat cancer, arthritis, human bacterial infections, Alzheimer’s disease, heart disease, viruses, and other diseases."

Question 10 of 10

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Sewage spills into a coral reef
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What are the threats to survival of coral reefs?

There is a laundry list of threats to corals. This list includes overfishing, destructive fishing such as bottom trawling; pollution from urban and industrial waste including sewage, chemicals and oil; reckless tourism; sedimentation from coastal development, mining, the destruction of mangroves and farming; and of course, ocean acidification and warming waters due to global climate change.

Essentially, if it affects our oceans, it affects corals. Check out NOAA's 25 ways you can help coral reefs.

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Coral reefs are home to an abundance of sea food
Photo: Rich Carey/Shutterstock
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