The planet’s coral reefs have been taking a hammering lately. With the National Oceanic and Atmospheric Administration (NOAA) declaring only the third ever global coral bleaching event last year, what started around Hawaii and Florida has spread to all oceans, even causing devastating impacts on the Great Barrier Reef. But now scientists might have another tool in their box to help monitor the health of the reefs, from 780 kilometers (485 miles) up.
Going operational at the end of last year, the European Space Agency’s new Sentinel-2a satellite’s color camera has been taking incredible pictures of Earth’s surface. To be used by scientists to track everything from the yields of crops to the growth of cities, it seems that it might also be able to peer under the waves and assess the health and growth of coral reefs around the world. A new project, called Sen2Coral, is tracking one particular reef, and has already detected a lightening of the coral that's indicative of bleaching.
By selecting only the blue band of light from the camera, the satellite is able to see between 10 and 15 meters (33 and 50 feet) below the surface of the ocean. By doing this, features of the reef that you cannot see in the full color images jump out and become much more prominent. This could be a vital tool in assessing the health of reefs over a much larger area than is currently possible by boat or air-based surveys, and would also be much cheaper, giving scientists a precise picture of just what exactly is going on in the oceans.
Currently, as ocean surface temperatures rise, it causes coral around the world to bleach. This occurs when the stressed coral expel the algae that live in their tissues, turning them white. This in itself doesn’t kill the coral, but if the water temperatures stay warm for too long, it can eventually do so. The bleaching also makes the reefs more susceptible to disease.
Hopefully, if Sentinel-2a's techniques can be definitively validated, the satellite can become another useful tool to detect and track changes in coral reefs.
