The study, published Monday in the journal Nature Climate Change, looked at the impact of marine heat waves on the diversity of life in the ocean. From coral reefs to kelp forests to sea grass beds, researchers found that these heat waves were destroying the framework of many ocean ecosystems.
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Between 1982 and 2016, the number of “marine heat waves” roughly doubled, and likely will become more common and intense as the planet warms, a study released Wednesday found. Prolonged periods of extreme heat in the oceans can damage kelp forests and coral reefs, and harm fish and other marine life.
Around the world, coral reefs are facing trouble. Coral bleaching, due in part to rising ocean temperatures, has stressed reefs, leaving them weakened and susceptible to disease. Now, in Florida, scientists are struggling to combat a mysterious disease that’s threatening the future of the world’s third largest coral reef.
Another reason global warming has not been too bad yet is because the ocean absorbs most of the earth’s excess heat. But oceans are warming due to greenhouse gas emissions. According to the National Oceanic and Atmospheric Administration, half of the increase in ocean heat content since 1865 has occurred over the past two decades. Warmer water holds less oxygen, but the respiration rate of animals (except for marine mammals) increases with temperature, so they need more oxygen at the same time that less is available. A warmer ocean has less turnover (vertical water movements), which normally brings nutrient-rich water up from deep water to the plankton that photosynthesize near the surface. With fewer nutrients, they photosynthesize less and animals can’t get enough food.
In the Florida Keys, the U.S. Virgin Islands and Maui, coral reef degradation has caused sea floor depths to increase as sand and other sea floor materials have eroded over the past few decades, the USGS study found. In the waters around Maui, the sea floor losses amounted to 81 million cubic meters of sand, rock and other material – about what it would take to fill up the Empire State Building 81 times, the researchers calculated.
We now have a 2017 event, which is not quite as bad as 2016, but certainly worse than the first two events that we studied [in 1998 and 2002]. That is significant because it postpones any hope of recovery. The current bleaching occupies a different geographical footprint from last year, which is bad news because it means between last year and this year a much greater extent of the Great Barrier Reef has now been damaged. In 2017, the hot water was in the middle of the Great Barrier Reef, the central section; last year it was in the north.