Researchers at UC San Diego’s Scripps Institution of Oceanography have released findings indicating that aquatic deoxygenation—a decrease in dissolved oxygen across oceans, coastal waters, rivers, lakes and streams—is accelerating and poses a significant threat to global stability. The team examined how this phenomenon intersects with established planetary boundaries, which are critical environmental thresholds identified in the Planetary Boundaries framework originally developed in 2009.
The Planetary Boundaries framework tracks nine major Earth system processes essential for maintaining a stable planet and monitors how human activities are pushing them beyond safe limits. These include climate change, ocean acidification, biodiversity loss, atmospheric aerosol loading, stratospheric ozone depletion, freshwater change, land-use change, chemical pollution and biogeochemical flows. The research team argues that dissolved oxygen levels in aquatic systems should be formally recognized as a tenth planetary boundary.
The primary drivers of aquatic deoxygenation are human-caused warming, excessive nutrient pollution and alterations in water movement and ventilation patterns in deeper zones. As oxygen concentrations decline, the disruption extends beyond individual organisms to affect biological and chemical processes that regulate Earth’s climate. The consequences ripple through aquatic food webs, impacting microscopic life, fish, sharks and marine mammals that depend on these ecosystems for food and habitat.
The review was motivated by discussions at the 2019 United Nations Climate Change Conference in Madrid. The authors emphasize that aquatic deoxygenation should be examined in connection with other planetary pressures rather than as an isolated issue. Adding this concern to the Planetary Boundaries framework could provide a more comprehensive understanding of threats to Earth system stability and inform strategies for preserving biodiversity and climate stability.
The study was published in Limnology and Oceanography and involved collaborators from multiple institutions including UCLA, the Institut de Physique du Globe de Paris and Rensselaer Polytechnic Institute.
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