This hard coral reef is showing the effects of abnormally high water temperatures, evident by the bleached appearance of many coral colonies. This happens when stressed zooxanthellae, plant-like micro-organisms that normally live within coral tissues, abandon their hosts, typcally when water temps rise 1-2 degrees Celsius for 5-10 wks. or more. Corals are stressed by losing the extra energy normally provided by their photosynthesizing partners, which can account for up to 90%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% of their energy needs. Fortunately, if water temps return to normal within a month or two, chances are good that zoothanthellae will re-colonize, and coral colonies will return to good health. Koh Surin Marine National Park, Thailand, Andaman Sea

Credit to: Blue Planet Archive / Mark Strickland

Image dimensions: 3601x5400

URL for this image: https://pictures.blueplanetarchive.com/image/I0000ZKtlYTyS8ag