some coral species display vivid colors to try to reattract algae they cant live without trilobitesunder stress certain coral species put on displays to try to reattract symbiotic algae they need to survivecreditthe ocean agencyxl catlin seaview surveymay 22 2020breaking up is hard to do and the measures some take to get their partners back can be colorful at times coral reefs are that way too but for them its a matter of life and deathwhen certain species of coral flash a shimmering palette of vibrant pinks reds blues purples and yellows they arent simply showing off this coral is attempting to recover the algae they cannot live without according to a study published thursday in the journal current biologycoral depends on a remarkable symbiotic relationship with algae which lives inside the organisms tissue when the algaecoral partnership is thriving many coral display a healthy brown huesometimes after environmental stress such as a spike in seawater temperature the algae dies or the coral expels it without that brownish internal photosynthetic factory pumping out meals for the coral the underlying skeleton shines through the translucent coral flesh as bleach white and the coral is at risk of starving to deathbut the scientists found that in order to get the algae back some species envelop themselves in bright sometimes fluorescent colors which mitigate intense light reflections through the coral and create conditions for the lightsensitive algae to returnthey produce their own sunscreen these colorful pigments said jrg wiedenmann professor of biological oceanography at southampton university in england who led the study they do it on a regular basis as a survival techniqueas the centerpieces of vast marine ecosystems coral reefs are a critical component of life on earth they are said to account for one third of all biodiversity in the sea and are the source of food and income for an estimated halfbillion peoplebut over the last few decades and particularly the last several years scientists say global warming has threatened the reefs existence through widespread bleachingimagecreditryan goehrunguniversity of washingtonif the stress is not too severe or prolonged the technicolor display known as color bleaching can save some coral dr wiedenmanns team determinedsome healthy corals display vivid colors and many experts wondered if the color bleaching process was just a matter of visibility perhaps the brownish algae masked other corals pigments or perhaps the coral and the algae were competing over blue light rays and once the algae were gone the coral flexed its fluorescent muscles under all the extra blue lightbut dr wiedenmann said their study determined that the process is actually an optical feedback loop that helps to restore the symbiotic relationshipin the first stage of this loop the algae are lost and the coral turns bleach white that causes more light to reach and bounce off the reflective coral skeletonwithin two or three weeks of the original stress incident a heat wave or some shock to the nutrients available to the coral the extra light triggers genes in