Oxygen is declining across oceans, coastal waters, rivers, lakes and streams, threatening the organisms and chemical processes that depend on it. A review led by researchers at UC San Diego’s Scripps Institution of Oceanography warns that this widespread deoxygenation is moving Earth toward an “unsafe space,” with some effects potentially lasting beyond human timescales.

The researchers examined how aquatic deoxygenation, meaning the loss of dissolved oxygen from marine and freshwater environments, interacts with the nine processes included in the Planetary Boundaries framework. Introduced in 2009, the framework identifies major Earth systems and evaluates how human activity is pushing them beyond the conditions that support a stable and resilient planet.

Those nine boundaries cover climate change, ocean acidification, biodiversity loss, atmospheric aerosol loading, stratospheric ozone depletion, freshwater change, land use change, chemical pollution and biogeochemical flows (including the nitrogen cycle). The authors argue that dissolved oxygen should also be included.

Oxygen loss threatens planetary stability
“The health and stability of our planet depends on the health and stability of aquatic ecosystems, which need oxygen to function normally,” said lead author Erica Ferrer, a Scripps Oceanography alumna and current postdoctoral scholar at UC Santa Barbara’s National Center for Ecological Analysis and Synthesis. “This study is designed to elevate the profile of aquatic deoxygenation as a global threat and show that it does not operate in isolation.”