Scientists from UC San Diego’s Scripps Institution of Oceanography warn that declining oxygen levels in oceans and freshwater systems could push Earth beyond a safe ecological limit, with some impacts lasting centuries.
The review examines aquatic deoxygenation, the decline of oxygen in oceans and freshwater systems, and its effects on the nine Earth system processes that maintain planetary stability.
Created in 2009, the Planetary Boundaries framework highlights critical environmental processes that help keep Earth stable and resilient. It also measures how human activities are driving these systems beyond their safe operating limits.
Aquatic Oxygen Loss as a Planetary Boundary
The framework identifies nine planetary boundaries, including climate change, biodiversity loss, freshwater changes, pollution, ozone depletion, and biogeochemical disruptions. The researchers suggest that declining dissolved oxygen levels in aquatic environments should be added as an official planetary boundary.
Lead author Erica Ferrer said Earth’s stability depends on healthy, oxygen-rich aquatic ecosystems. The study highlights aquatic deoxygenation as a global threat linked to broader planetary challenges.
Human activities are the main drivers behind the decline of oxygen in aquatic environments, with climate warming, excessive nutrient runoff, and disruptions to the circulation and mixing of deep waters playing major roles.
As dissolved oxygen levels decrease, they can interfere with important biological and chemical processes that contribute to regulating Earth’s climate. Oxygen loss threatens aquatic ecosystems, affecting species from microbes to fish and sharks.
Deoxygenation Threatens Marine Mammal Survival
Even marine mammals that breathe air can be affected by deoxygenation. Low oxygen levels can alter prey availability, damage habitats, and disrupt food networks.
Ferrer and Lisa Levin, a Scripps biological oceanographer and the study’s senior author, developed the review after participating in COP25, the 2019 United Nations Climate Change Conference in Madrid.
They hope the research will motivate scientists and decision-makers to address the loss of oxygen in aquatic systems as part of the broader global environmental crisis, considering it alongside climate change, pollution, biodiversity loss, and other human-driven pressures instead of viewing it as an isolated issue.
Ferrer said adding aquatic deoxygenation to the Planetary Boundaries framework would clarify its impact on Earth’s stability. She emphasized that reducing its impacts is essential for protecting biodiversity and helping maintain a stable climate.
Read the original article on: sciencedaily