Ocean oxygen levels have been declining for 50 years.

The International Union for Conservation of Nature and Natural Resources (IUCN) is an organization made up of 1,200 countries or government and non-governmental organizations for the purpose of protecting nature. The report reported that between 1960 and 2010, the amount of oxygen dissolved in the ocean decreased by 2% as the water temperature increased. In addition, it is predicted that if each country continues its activities without sufficient measures against climate change, the amount of oxygen will decrease by 3-4% by 2100.

If you say 2%, you can think that there will be no big problems, but for large fish that require a lot of energy, such as marlin, shark, and tuna, even a slight deterioration of coral can be a serious problem. When wastewater containing nitrogen and phosphorus from industries such as agriculture or industry enters the ocean, it causes eutrophication, leading to a decrease in the amount of oxygen contained in the seawater. However, there is growing concern that heat is absorbed by the sea and dissolved in the ocean to reduce the amount of oxygen due to the greenhouse effect caused by climate change.

Although the direct link between ocean oxygenation and climate change is unknown, IUCN says the rate of oxygen decline has increased fourfold over the past 50 years, and that ocean oxygen levels continue to decline in any best-case scenario.

This problem is said to be starting to move to a shallow layer with a lot of oxygen because it is a life and death task for a creature with a lot of momentum. It means that it is more likely to be found on the female ship, and of course, it can accelerate the reduction of the population due to overfishing. In addition, it is pointed out that species that cannot respond to changes in the habitat environment can disappear, gradually losing biodiversity and gradually leaving only strong microorganisms and creatures such as jellyfish in a hypoxic environment.

The IUCN report can be said to be a prediction that the worst future will come if climate change measures are not properly formulated. Even if you are not very interested in sea level rise and the problems that occur on land, it can be a serious thing that tuna and sharks are reduced and the ecosystem balance is disrupted, resulting in a sea with only jellyfish and plankton. When there are fewer fish, seabirds disappear, nutrient circulation problems, and terrestrial ecosystems can also be affected. Related information can be found here .