Science Alert reports:

Supplies of dissolved oxygen in bodies of water across the globe are dwindling rapidly, and scientists say it’s one of the greatest risks to Earth’s life support system.

Just as atmospheric oxygen is vital for animals like ourselves, dissolved oxygen (DO) in water is essential for healthy aquatic ecosystems, whether freshwater or marine. With billions of people relying on marine and freshwater habitats for food and income, it’s concerning these ecosystems’ oxygen has been substantially and rapidly declining.

A team of scientists is proposing that aquatic deoxygenation be added to the list of ‘planetary boundaries‘, which in its latest form describes nine domains that impose thresholds “within which humanity can continue to develop and thrive for generations to come.”

So far, the planetary boundaries are climate change, ocean acidification, stratospheric ozone depletion, interference with the global phosphorus and nitrogen cycles, rate of biodiversity loss, global freshwater use, land-system change, aerosol loading, and chemical pollution.

A team led by freshwater ecologist Kevin Rose from Rensselaer Polytechnic Institute in the US is concerned that this list overlooks one of the Earth’s most important limits.

“The observed deoxygenation of the Earth’s freshwater and marine ecosystems represents an additional planetary boundary process,” the authors write, “that is critical to the integrity of Earth’s ecological and social systems, and both regulates and responds to ongoing changes in other planetary boundary processes.

“Relevant, critical oxygen thresholds are being approached at rates comparable to other planetary boundary processes.” [Continue reading…]