Summary:
Declining oxygen concentrations in oceans and inland waters may disrupt ecological functions essential to healthy aquatic ecosystems, according to a review published in Limnology and Oceanography.
Researchers led by the Scripps Institution of Oceanography at the University of California San Diego (UC San Diego) assessed aquatic deoxygenation in relation to the nine processes included in the Planetary Boundaries framework. Their analysis connects oxygen decline with climate change, excess nutrient inputs, biodiversity loss, ocean acidification and reduced ventilation of deeper waters.
Lower oxygen availability can alter habitats, food webs and the cycling of elements through aquatic ecosystems. These changes can affect organisms ranging from microorganisms to large predators, while also interfering with processes involved in climate regulation and placing pressure on human communities that depend on aquatic resources.
The authors propose including dissolved oxygen conditions in assessments of Earth system stability. They identify four indicators that could be used to evaluate aquatic deoxygenation and support the future development of a global boundary. Based on current rates of oxygen loss and its interactions with other environmental pressures, they conclude that aquatic deoxygenation is moving towards unsafe conditions, with some impacts potentially irreversible within human lifetimes.
Underwater oxygen loss threatens Earth’s stability, researchers warn
A new review paper led by scientists at UC San Diego’s Scripps Institution of Oceanography warns that the rapid loss of oxygen from the ocean and other aquatic ecosystems is pushing Earth toward an ‘unsafe space’, with consequences that could be irreversible on human timescales.
The study reviews the widespread interactions between aquatic deoxygenation – the decline of dissolved oxygen in the ocean (ocean deoxygenation), coastal waters, rivers, lakes and streams – and the nine processes outlined by the Planetary Boundaries framework. First introduced in 2009, the framework identifies critical Earth system processes and the ways human activities are pushing them beyond the conditions needed to keep the planet stable and resilient.
The nine planetary boundaries are 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 propose adding dissolved oxygen conditions to the framework.
“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.”
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Aquatic deoxygenation is driven primarily by human-caused warming, excess nutrient pollution and changes in the ventilation of interior waters. Oxygen loss disrupts the biological and chemical processes that help regulate Earth’s climate and it threatens aquatic life ranging from microscopic organisms to fish and sharks. Although marine mammals breathe air at the surface, they can still be affected as oxygen loss alters their prey, habitats and food webs.
Ferrer and Scripps biological oceanographer Lisa Levin, the study’s senior author, conceived the idea for the paper after attending COP25, the 2019 United Nations Climate Change Conference held in Madrid. They hope the review encourages scientists and policymakers to consider the drivers and impacts of aquatic deoxygenation in combination with other planetary stressors.
“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.”
Ferrer conducted this review as part of her doctoral research at Scripps, supported by the National Science Foundation’s Graduate Research Fellowship Program and graduate funds from Scripps and UC San Diego, followed by postdoctoral support from UC Santa Cruz and UC Santa Barbara.
The study was published in the journal Limnology and Oceanography. Additional authors include four former Scripps PhD students – Shailja Gangrade, Lillian McCormick, Ariel Pezner and Yassir Eddebbar, who is now a Scripps climate scientist – along with De’Marcus Robinson of UCLA, Véronique Carcon of the Institut de Physique du Globe de Paris and Kevin Rose of the Rensselaer Polytechnic Institute.
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Journal Reference:
Ferrer, E.M., Eddebbar, Y.A., Gangrade, S., McCormick, L.R., Pezner, A.K., Robinson, D., Garçon, V., Rose, K.C. and Levin, L.A., ‘Abundant interactions and feedbacks between aquatic deoxygenation and the other planetary boundaries suggest “unsafe” levels of oxygen loss with far-reaching impacts’, Limnology and Oceanography 71, 7: e70434 (2026). DOI: 10.1002/lno.70434
Article Source:
Press Release/Material by Brittany Hook | UC San Diego
Featured image credit: Max Gotts | Unsplash
