What caused this red tide? A possible doubt rises to the ocean current, which will bring nutrients from the depths of the ocean to the surface of the ocean, thus providing a material basis for the occurrence of red tides. Upwelling may indeed lead to red tides. However, when the research team drilled coral reef samples, they found that in the past 7000 years, there was a larger upwelling, but there was no corresponding mass death of coral reefs. This shows that upwelling may not be the cause of red tide. 2, the city gate is smoking and catching fire, and fish are raised in the pool. This fire not only released a lot of carbon dioxide (an estimate published in Nature last year showed that the carbon dioxide produced by this fire was equivalent to about 1/5 of the total carbon dioxide produced by human activities in that year), but also released about 1. 1.000 tons of iron and other nutrients, which are the delicious food that algae like. Fires release nutrients from plants and soil into the atmosphere in the form of smoke and dust. When the dust settles, it will enrich the surrounding environment. "Studies have found that nutrients produced by fires in tropical areas can produce red tides that are enough to kill all coral reefs and fish within hundreds of kilometers. The research team's paper was published in the August 15 issue of Science. " This study shows for the first time that nutrients will have an impact on the ocean and bring serious problems to coral reefs and other coastal marine ecosystems. "The decline of coral reefs is a microcosm of the global coral reef extinction. Two years ago, scientists found that overfishing is the main reason for the decline of global coastal ecosystems, including coral reef ecosystems. Since then, the same group of scientists who conducted this research have paid special attention to coral reefs. This time, they found that the decline of coral reefs did not begin in recent decades, but began thousands of years ago when humans learned to fish. Scientists have studied 14 coral reefs in the Pacific Ocean, the Atlantic Ocean and the Red Sea. It is found that coral diseases, bleaching caused by rising water temperature and global warming are only factors that have aggravated the decline of coral reefs since this century, and have begun to decrease before that. Scientists have found that in every study area, human activities in history have led to the decline and decline of coral reefs to varying degrees. This decline follows the same route without exception: first, large herbivores and carnivores are preyed by humans, then smaller fish, and finally algae and living corals on coral reefs. " The downward trend is universal, which left a deep impression on us. "Before the invention of diving masks at the beginning of this century, about 80% of the coral reefs in the world have embarked on the road of slow death. Even those coral reefs that seem to be well preserved are not immune. For example, the Great Barrier Reef, a famous tourist resort on the east coast of Australia. Benjedale said: "Sometimes people say that the Great Barrier Reef is largely in a primitive state, but in fact,13 coral reefs are going extinct. "Pollution, overfishing and climate change are the main reasons for the decline of coral reefs. It is more difficult for scientists to eliminate the crisis facing coral reefs than to find them. Even if people can stop coral diseases and bleaching immediately, coral reefs are still in a long-term crisis. " If we can go back to the past and implement strong management, then we can restore the ecosystem. But it depends on political will, funds and many other unpredictable influences. "Benjedel admits that this is indeed a problem. Under the current circumstances-funds and policies for coral reef research and management have not changed-the prospects are indeed very bleak. We watched the large coral reefs die, and they still existed 500 years ago. "