OREANDA-NEWS Scientists have found that coral reefs bleach, not so much because of global warming, but because of the discharge of sewage and fertilizer into the sea. With waste water enters a large amount of nitrogen, which causes the rapid growth of phytoplankton and disrupts the symbiotic relationship between polyps and algae. This leads to the expulsion of old corals, and discoloration and death of new ones. 

Scientists from the United States summed up the study, which was conducted for about 30 years in the waters of the Florida Keys archipelago, and tested the hypothesis of coral death from pollution. They monitored the waters in which Florida corals live, from 1984 to 2014, studying the content of nitrogen, phosphorus, chlorophyll, and observing the state of coral reefs and water temperature. 

It turned out that despite the fact that the water was repeatedly heated above 30.5 C, the corals lost their color only when the water content of nitrogen increased and the ratio of nitrogen to phosphorus increased. 

The authors of the study believe that only well-cleaned waste with no nitrogen can be dumped into the sea. It is necessary to create new sewage treatment plants and control the discharge of water into the ocean.