Oxygen is disappearing from the world's oceans, lakes, rivers, and coastal waters at an alarming rate — and scientists warn the consequences could reshape life on Earth for centuries.
A comprehensive new review led by UC San Diego's Scripps Institution of Oceanography, published in the journal Limnology and Oceanography, warns that aquatic deoxygenation is pushing the planet into an "unsafe space." Some of the resulting changes could persist for centuries and may not be reversible within human lifetimes.
"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 postdoctoral scholar at UC Santa Barbara. "This study is designed to elevate the profile of aquatic deoxygenation as a global threat and show that it does not operate in isolation."
The review examines how deoxygenation interacts with the nine major Earth system processes included in the Planetary Boundaries framework, originally introduced in 2009. The researchers argue that dissolved oxygen levels should be formally added as a tenth boundary.
The main drivers of deoxygenation are human-caused warming, excessive nutrient pollution from agriculture and industry, and changes in the movement and ventilation of deeper waters. As oxygen levels fall, they disrupt biological and chemical processes that help regulate Earth's climate. The decline threatens organisms across entire aquatic food webs — from microscopic plankton to fish, sharks, and marine mammals.
Even air-breathing marine mammals suffer, because oxygen loss reduces or relocates their prey, damages habitats, and alters the food webs they depend on.
Ferrer and senior author Lisa Levin developed the idea for the review after attending COP25, the 2019 UN Climate Change Conference in Madrid. They hope the findings will encourage researchers and policymakers to treat aquatic oxygen loss as interconnected with climate change, pollution, and biodiversity decline, rather than as a separate problem.
"Adding aquatic deoxygenation to the Planetary Boundaries framework will help us understand its impacts on Earth system stability," said Ferrer. "Mitigating its impacts represents a critical component of maintaining biodiversity and climate."
The study was published on June 30, 2026, and received support from the National Science Foundation's Graduate Research Fellowship Program, Scripps Oceanography, and UC San Diego.
