Aquatic Oxygen Depletion Poses Growing Planetary Threat

Scientists Raise Alarm Over Declining Oxygen in Global WatersResearchers from the Scripps Institution of Oceanography at UC San Diego have issued a strong warning that oxygen levels are declining at an alarming rate in both marine and freshwater environments worldwide. This rapid loss could push Ear

Scientists Raise Alarm Over Declining Oxygen in Global Waters

Researchers from the Scripps Institution of Oceanography at UC San Diego have issued a strong warning that oxygen levels are declining at an alarming rate in both marine and freshwater environments worldwide. This rapid loss could push Earth's systems into a dangerous and unstable state. Many of the resulting environmental shifts may last for hundreds of years and cannot be reversed during a single human generation.

The comprehensive review focuses on aquatic deoxygenation, a process involving falling concentrations of dissolved oxygen in oceans, coastal zones, rivers, lakes, and streams. Experts evaluated how this accelerating issue connects with the nine critical Earth system processes outlined in the Planetary Boundaries framework, which was first proposed in 2009 to identify essential environmental processes required for planetary stability and to monitor human impacts that exceed safe thresholds.

The Planetary Boundaries and the Need for Oxygen Monitoring

The established nine planetary boundaries encompass climate change, ocean acidification, loss of biodiversity, atmospheric aerosol loading, depletion of stratospheric ozone, shifts in freshwater availability, alterations in land use, chemical pollution, and disruptions to biogeochemical flows such as the nitrogen cycle. The study authors strongly advocate for adding dissolved oxygen levels as an official tenth boundary because of its fundamental role in maintaining ecosystem health.

Lead author Erica Ferrer, a Scripps alumna now serving as a postdoctoral scholar at UC Santa Barbara, emphasized that planetary health relies directly on the vitality of aquatic ecosystems, which require adequate oxygen to operate properly. The research aims to highlight aquatic deoxygenation as a serious global concern that does not occur independently from other environmental pressures.

Primary Drivers of Oxygen Loss in Aquatic Systems

The main contributors to this oxygen depletion include human-induced climate warming, excessive nutrient runoff from pollution sources, and modifications in water circulation patterns that affect ventilation of deeper layers. As oxygen concentrations drop, they interfere with vital biological and chemical cycles that help stabilize Earth's climate system. This decline endangers species throughout aquatic food chains, ranging from tiny plankton and microbes to larger fish populations and apex predators such as sharks.

Even air-breathing marine mammals face indirect consequences because reduced oxygen can displace or diminish their food sources, destroy essential habitats, and reshape the interconnected food webs upon which they depend for survival. These cascading effects demonstrate how deoxygenation ripples through entire ecosystems rather than remaining isolated to specific water layers.

Linking Deoxygenation With Broader Environmental Challenges

The concept for this review emerged after Ferrer and senior author Lisa Levin attended the 2019 United Nations Climate Change Conference known as COP25 in Madrid. The researchers hope their findings will prompt scientists and decision-makers to consider oxygen loss in aquatic environments alongside issues like climate change, pollution, and biodiversity decline instead of addressing each challenge separately.

Ferrer noted that formally incorporating aquatic deoxygenation into the Planetary Boundaries framework would improve understanding of its effects on overall Earth system stability. She stressed that reducing the impacts of oxygen loss forms an essential part of efforts to preserve biodiversity and regulate climate patterns effectively over the long term.

Research Background and Publication Details

Ferrer conducted the review as part of her doctoral studies at Scripps, with funding provided by the National Science Foundation Graduate Research Fellowship Program along with additional graduate support from Scripps and UC San Diego. Postdoctoral funding came from UC Santa Cruz and UC Santa Barbara. The complete study appeared in the journal Limnology and Oceanography on June 30, 2026. Additional contributors included former Scripps doctoral students Shailja Gangrade, Lillian McCormick, Ariel Pezner, and Yassir Eddebbar, who now works as a climate scientist at Scripps, along with De'Marcus Robinson from UCLA, Véronique Carcon from the Institut de Physique du Globe de Paris, and Kevin Rose from Rensselaer Polytechnic Institute.