Terrestrial Tour: Coral Reefs at Risk

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Corals are acutely sensitive to changes in their environment, which can cause them to expel their symbiotic algae. Without the algae, bleached corals often starve and die within a few weeks.

Produced by the Space Telescope Science Institute’s Office of Public Outreach in collaboration with the NASA Earth Observatory.

All images, illustrations, and videos courtesy of NASA except:
·       Great Barrier Reef underwater video footage courtesy of Andy Green at greenwaterproductions.net
·       Photo of reef fishers courtesy of Rebecca Weeks/Marine Photobank
·       Sea creature illustration copyright The National Library of Israel, Shapell Family Digitization Project _and The Hebrew University of Jerusalem, Department of Geography – Historic Cities Research Project
·       Photo of fish at a coral reef courtesy of Linda Wade/NOAA
·       Photo of a dead reef in American Samoa copyright Wolcott Henry 2005/Marine Photobank
·       Photo of a bleached reef courtesy of Armando Jenik 2009/Marine Photobank
·       Staghorn coral photo courtesy of William Harrigan/Florida Keys National Marine Sanctuary/NOAA
·       Photo of coral in Perhentian Islands, Malaysia, courtesy of Nazir Amin
·       Mediterranean red coral photo courtesy of Lorenzo Bramanti/Marine Photobank
·       Gorgonian coral photo courtesy of Mohammed Al Momany/NOAA
·       Acropora table coral photo copyright Pete Faulkner, Mission:awareness/Marine Photobank 
·       Sewage pipe photo courtesy of Steve Spring/Marine Photobank
·       Photo of coral with black band disease courtesy of Sven Zea, Universidad Nacional de Colombia/Marine Photobank
·       Blast-fishing photo courtesy of Benjamin De Ridder/Marine Photobank
·       Photo of coral with yellow band disease courtesy of Craig Quirolo, Reef Relief/Marine Photobank
·       Before-and-after photos of bleached coral courtesy of Craig Quirolo, Reef Relief/Marine Photobank
·       Photo of bleached coral in the Galapagos Islands courtesy of David Jacobsen-Fried/Marine Photobank
·       Photo of dead coral reef in Taiwan courtesy of Konstantin Tkachenko/Marine Photobank
·       Bleached coral video footage courtesy of National Oceanic and Atmospheric Administration (NOAA)
·       Thermometer and coral reef illustrations: Marc Lussier, STScI
Written by Vanessa Thomas
Designed by Marc Lussier 
Music courtesy of Associated Production Music

Text, Coral Reefs at Risk
Coral reefs are the rainforests of the sea.
Nowhere on Earth is there a wider variety of marine life than around coral reefs.
A group of yellow and blue fish
A shark swims along the seafloor.
Small fish swim in and around coral.
Text, but recently, many corals have been dying.
An ailment known as "bleaching" is affecting reefs in tropical waters around the world.
Corals are small, tentacled marine animals that usually live in colonies.
Most corals are transparent and have no color of their own.
Instead, the corals get their color from symbiotic algae that live inside them.
These algae help many corals build hard, protective structures.
Over thousands of years, coral colonies build up these structures into large coral reefs that can often be seen from space.
Corals are acutely sensitive to changes in their environment.
Destructive fishing practices
Ocean temperature change
These pressures can put corals under stress.
When corals are stressed, they often expel their algae.
Without algae, the transparent corals look pale or white, the color of their stony reef.
This is "coral bleaching."
Corals can use their tentacles to capture food, but reef-building corals usually get most of their energy from their symbiotic algae.
Without the algae, bleached corals often starve and die within a few weeks.
Corals that do survive are more susceptible to disease and other threats.
It can take decades for a reef to recover.
Typically, other sea creatures will abandon a dead or dying reef.
The ocean loses a once-thriving habitat, while people lose a source of food and income.
Increases in water temperature have caused most of the bleaching episodes in recent decades
Fortunately, some satellites are equipped to record and map the surface temperatures of the oceans.
These satellite maps help us identify where temperature changes could be causing corals to bleach and predict where reefs might be in danger of bleaching.
Satellites can also survey reefs in remote locations in a fraction of the time it takes from boats or airplanes.
In addition, they can observe reefs regularly to look for changes.
Marine scientists and volunteers are working to better understand the causes of coral bleaching to learn just how many reefs are dying and find ways to protect these natural treasures.
In these efforts, satellite observations are a valuable resource for monitoring and assessing the health of the "rainforests of the sea."