An international team of scientists from the US, Canada and Germany has warned of the rapid decline in dissolved oxygen levels in water bodies around the world and the risks associated with it. The research was published in the scientific journal magazine Nature Ecology and Evolution (NEE).
Just as atmospheric oxygen is essential for land organisms, dissolved oxygen is essential for aquatic life.
A team of experts led by freshwater ecologist Kevin Rose of Rensselaer Polytechnic Institute in the US concluded that until recently, deoxygenation (loss of oxygen) in Earth’s freshwater and marine ecosystems had not been taken into account when assessing the stability of planetary systems.
The concentration of dissolved oxygen in water decreases for a variety of reasons. For example, warmer waters cannot hold as much dissolved oxygen, and as greenhouse gas emissions continue to raise air and water temperatures above long-term averages, surface waters become less and less able to hold this vital element.
Dissolved oxygen can be depleted by aquatic life faster than it can be replenished by the ecosystem. Algal blooms and bacterial blooms resulting from runoff of organic matter and nutrients in the form of agricultural and household fertilizers, sewage, and industrial wastes rapidly deplete available dissolved oxygen.
In the worst cases, oxygen becomes so depleted that microbes suffocate and die, often taking larger species with them. Microbial populations that are not dependent on oxygen then feed on the abundance of organic material, reaching densities that reduce light and limit photosynthesis, trapping the entire water body in a suffocating cycle called eutrophication.
Aqueous deoxygenation also results from increased density differences between layers of the water column, which can be explained by the faster warming of surface waters than deep waters and the decrease in surface salinity in the oceans due to melting ice.
All of this has wreaked havoc on aquatic ecosystems, many of which depend on us for our food, water, income and well-being.
The authors of the paper called for a concerted global effort to monitor and study deoxygenation in our planet’s aquatic environments, as well as measures to prevent the rapid deoxygenation and related problems we are already beginning to face.
Previously scientists He warned of the risk of food shortages in the Atlantic due to the weakening of the Gulf Stream.