It has long been known that the world's oceans are actively heating and oxidizing. But according to the results of a recent study, it turned out that by the end of the century, it can also lose up to 7% oxygen.
In 50-100 years, chemical and biological changes can lead to the complete disappearance of coral reefs. Marine ecosystems will be destroyed by toxic algal blooms and an increase in the number of jellyfish.
These are the results of a study carried out several years ago by the International Ocean Science Program (IPSO). Since then, the situation has continued to deteriorate. According to Alex Rogers of the University of Oxford in the UK, IPSO's scientific director, the rate of deterioration in the well-being of the ocean has exceeded all forecasts, organisms have to face unpredictable and intolerable evolutionary pressures.
According to the scientist, there are three deadly threats. First of all, global warming - the heating rate of the world ocean surface is comparable to the heating of the atmosphere. The second threat is acidification - more carbon dioxide gets into the water than in the past. The third horseman of the apocalypse was the loss of oxygen.
It is worth noting that acidification can pose a real threat. For example, last year, scientists found that it causes the shells of sea snails that live in the waters of the Southern Ocean to dissolve. But, according to John Spicer of the University of Plymouth, an even greater threat could be low oxygen levels, as evidenced by laboratory experiments.
In part, there is less oxygen in the oceans due to the low oxygen content in warm water. In addition, water warms up most of all on the surface of the ocean, this upper layer becomes more buoyant, mixing less with the lower, colder layers. As a result, there is less and less oxygen at depth, so organisms begin to suffocate.
In some places near the coast, Rogers said these low-oxygen water layers could be re-surfaced by updrafts, killing shallow life. In particular, according to experts, such a situation has developed near the coast of North America in the area of the California Current. There was no hypoxia here until 2000, but over the past ten years, marine organisms are dying at a tremendous rate.
Another problem was the disappearance of large fish in the waters of tropical oceans, for example, members of the marlin family, whose fast metabolism requires a large amount of oxygen.
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If we believe the models of Ralph Keeling from the Scripps Institute of Oceanography in the United States, then during the current century the oceans will be deprived of up to 7% of all oxygen. Low oxygen levels coincide with periods of mass extinctions, Rogers said, so we are now seeing a return to those times.
According to Callum Roberts of the University of York, if CO2 emissions are not reduced over several decades, the entire biological productivity of the oceans will be at risk.