Science Gazette

The world’s fisheries are expected to be suffocating as a result of climate change

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According to a recent research, about 70% of the world’s seas might be suffocating from a lack of oxygen by 2080 as a consequence of climate change, possibly affecting marine ecosystems globally. The new models show that mid-ocean depths, which feed many fisheries throughout the globe, are already losing oxygen at unnaturally high rates and have already crossed a key oxygen loss barrier in 2021.

Oceans hold dissolved oxygen as a gas, and aquatic species, like terrestrial animals, need it to breathe. However, when the seas warm as a result of global warming, their water can store less oxygen. For years, scientists have been watching the seas’ inexorable loss of oxygen, but the latest research adds to the list of urgent reasons to be worried now rather than later.

The new research is the first to utilize climate models to estimate how and when deoxygenation, or the loss of dissolved oxygen in water, would occur in the world’s oceans outside of natural fluctuation.

It indicates that severe, perhaps permanent deoxygenation of the ocean’s intermediate depths, which sustain many of the world’s fished species, starts in 2021 and is anticipated to have an impact on global fisheries. Deoxygenation is anticipated to afflict all ocean zones by 2080, according to the latest models.

The findings were published in Geophysical Research Letters, an AGU publication that publishes high-impact, short-format research with direct ramifications across all Earth and space disciplines.

According to the new research, the ocean’s intermediate depths (between 200 and 1,000 meters deep), known as mesopelagic zones, would be the first to lose large levels of oxygen as a result of climate change. Many of the world’s commercially fished species live in the mesopelagic zone, making the latest discovery a possible portent of economic hardship, seafood shortages, and environmental damage.

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Warmer waters may store less dissolved oxygen, resulting in decreased circulation between the ocean’s layers as temperatures rise. Because it is not replenished with oxygen by the atmosphere and photosynthesis like the top layer, the intermediate layer of the ocean is especially sensitive to deoxygenation, and it is also where the greatest breakdown of algae — a process that consumes oxygen — happens.

“This zone is really quite significant to us because it contains a lot of commercial fish,” says Yuntao Zhou, principal research author and oceanographer at Shanghai Jiao Tong University. “Other marine resources are also affected by deoxygenation, but fisheries are perhaps the most closely linked to our everyday lives.”

According to Matthew Long, an oceanographer at NCAR who was not involved in the research, the new results are highly alarming and add to the need to act meaningfully in climate change mitigation.

“Humanity is actively altering the metabolic status of the planet’s greatest ecosystem, with unforeseeable ramifications for marine ecosystems,” he stated. “This might have a big influence on the ocean’s capacity to support critical fisheries.”

Vulnerability assessment

By predicting when the loss of oxygen from the water surpasses natural oscillations in oxygen levels, the researchers were able to pinpoint the start of the deoxygenation process in three ocean depth zones: shallow, medium, and deep. The research used data from two climate model simulations to forecast when deoxygenation will begin in global ocean basins: one reflecting a high emissions scenario and the other indicating a low emissions scenario.

Although the process began roughly 20 years later in the low emissions scenario, the mesopelagic zone lost oxygen at the highest pace and across the biggest area of the world seas in both scenarios. This suggests that reducing carbon dioxide and other greenhouse gas emissions might assist to prevent worldwide marine habitat damage.

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The researchers also discovered that seas closest to the poles, such as the west and north Pacific, as well as the southern oceans, are more susceptible to deoxygenation. They don’t know why, but it’s possible that faster warming is to blame. According to Zhou, areas in the tropics notorious for having low quantities of dissolved oxygen, known as oxygen minimum zones, are also expanding.

“The oxygen minimum zones are really extending north and south throughout high latitude locations. That is something to which we must pay greater attention “she explains. “Whether dissolved oxygen would return to pre-industrial levels is uncertain,” even if global warming were to reverse, enabling concentrations of dissolved oxygen to rise.

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