Dissolved oxygen supply in waters around the world Rapidly decliningScientists say this is one of the biggest risks to the Earth’s life support systems.
Just as oxygen in the atmosphere is essential to animals like us, dissolved oxygen (DO) in water is essential to healthy aquatic ecosystems, whether freshwater or saltwater. Billions of people Because we depend on marine and freshwater habitats for food and income, we are concerned by the significant and rapid decline in oxygen in these ecosystems.
A team of scientists describes the removal of oxygen from water asPlanetary Limits‘In its latest form, it describes nine areas in which it imposes thresholds.Humanity can continue to develop and prosper for future generations“
So far, the planet’s limits areLimiting change,Ocean acidification,Depletion of the stratospheric ozone layer,Interference with the global phosphorus and nitrogen cycles, rExtent of biodiversity loss, gWorld freshwater use, lAnd system changes,aerosol load, and cChemical contamination.
A team led by freshwater ecologist Kevin Rose of Rensselaer Polytechnic Institute in the US worries that the list misses one of the planet’s most important limits.
“The observed deoxygenation of Earth’s freshwater and marine ecosystems points to further processes at planetary boundaries,” the authors say. write“It is crucial to the health of Earth’s ecosystems and social systems, and it controls and responds to ongoing changes in other planetary boundary processes.”
“We are approaching a critical oxygen threshold at a rate comparable to other planetary boundary processes.”
There are several reasons why dissolved oxygen levels in water decline: as water gets warmer, it can no longer hold as much dissolved oxygen, and as air and water temperatures continue to rise above their long-term averages due to greenhouse gas emissions, surface waters will lose their ability to retain this important element.
Dissolved oxygen can also be depleted by aquatic organisms faster than it can be replenished by ecosystem producers. Algal blooms and bacterial proliferation Caused by organic matter and nutrients that enter the water in the form of agricultural and domestic fertilizers, sewage, and industrial waste, algae rapidly absorb available dissolved oxygen.
In the worst case scenario, oxygen will be depleted and microorganisms will suffocate and die. Take frequently big They and the tribe. Populations of oxygen-independent microbes thrive by feeding on a bounty of dead organic matter, growing to such densities that they reduce light and limit photosynthesis, trapping entire bodies of water in a vicious, suffocating cycle known as eutrophication.
Oxygen deficiency in water is also caused by an increasing density difference between layers in the water column, which causes surface waters to warm faster than deeper waters, melting ice and decreasing the ocean’s surface salinity.
The more clearly these layers are defined, the less movement between them in the water column on which the vertical strata of aquatic life depend. These density variations are the driving force behind the movement of oxygen-rich surface waters to greater depths, and without this temperature-driven transport ventilation of deeper aquatic environments would cease.
All this is taking a toll on aquatic ecosystems, with many of us humans struggling to find food, water, income and happiness.
The authors call for a coordinated global effort to monitor and study oxygen depletion in the “blue” parts of the planet, as well as policy efforts to prevent rapid oxygen depletion and the associated challenges we are already beginning to face.
“Deoxygenation could potentially be slowed or reversed by reducing greenhouse gas emissions, nutrient runoff, and organic carbon inputs (e.g., raw sewage loads),” they say. write.
“Expanding the planetary boundaries framework to include deoxygenation as a boundary” [will help] To focus those efforts.”
This paper is Natural Ecology and Evolution.
