Dissolved oxygen is vanishing from oceans, lakes, rivers and coastal waters worldwide, according to a new study led by Erica Ferrer of UC Santa Barbara's National Center for Ecological Analysis and Synthesis with Scripps Institution of Oceanography biological oceanographer Lisa Levin. The researchers argue the trend is severe enough that aquatic deoxygenation should be added as a tenth entry to the Planetary Boundaries framework, the set of thresholds scientists use to track how far humanity is pushing Earth's life-support systems.
The global ocean has lost roughly 2% of its average oxygen content over the past 50 years, while rivers are losing oxygen at a rate of about 1-1.5% per decade. The primary drivers are human-caused warming (warmer water holds less dissolved oxygen), excess nutrient pollution from agriculture and wastewater, and disrupted ventilation of deep and interior waters. Some of the resulting damage to aquatic ecosystems could persist for centuries and may not be reversible on human timescales.
"The health and stability of our planet depends on the health and stability of aquatic ecosystems, which need oxygen to function normally," said Ferrer, the study's lead author. The paper was published June 30, 2026, in the journal Limnology and Oceanography.