BEIJING, July 27 — Oxygen minimum zones now cover approximately 10 million square kilometres of the tropical Pacific and Indian Oceans, up from roughly 6 million square kilometres in 1950, according to a study published in Science in 2025. That expansion carries direct market consequences: the World Bank estimated in 2019 that coastal dead zones—hypoxic areas where dissolved oxygen dips below 2 milligrams per litre—already cost global fisheries between $10 billion and $20 billion annually.
For supply-chain managers tracking protein sources from Southeast Asia to West Africa, these figures represent a tightening constraint on catch volumes and sourcing costs.
The Scale of Deoxygenation
The research draws on 20 different Earth system models from the Coupled Model Intercomparison Project Phase 6, or CMIP6. Those models show that global ocean oxygen content has fallen by about 1–2% since the 1950s (National Oceanic and Atmospheric Administration, 2020). The paper defines an “unsafe space” threshold—the point at which oxygen loss triggers irreversible changes to ecosystem structure and function.
That threshold is estimated at a 4% decline relative to pre-industrial levels. According to the study’s authors, the world has already crossed halfway toward that mark.
Coastal dead zones, a more localized manifestation of oxygen loss, now number over 500 globally, per the Global Environment Facility (2022). These zones often form in summer months when nutrient runoff fuels algal blooms that decay and consume oxygen. The resulting “hypoxic” conditions drive away or kill fish, shrimp, and crabs, forcing vessels to travel farther and burn more fuel to maintain their hauls.
Compounding Stressors
Ocean deoxygenation does not act alone. The frequency of marine heatwaves—events that can rapidly accelerate oxygen depletion—rose by 50% from 1925 to 2016, according to Hobday and colleagues (2018). Warmer water holds less dissolved oxygen, so each heatwave effectively shrinks the habitable volume of the water column.
Meanwhile, ocean acidification is advancing: surface pH has dropped from 8.2 to 8.1 since pre-industrial times, representing a 30% increase in hydrogen ion concentration (IPCC Sixth Assessment Report, 2021). The projected trajectory under the high-emissions scenario RCP8.5 adds a further 3–4% loss of total ocean oxygen by 2100, the IPCC Special Report on the Ocean and Cryosphere in a Changing Climate (2019) states.
That would push global oxygen decline well past the 4% “unsafe” line defined in the 2025 study, if current trends persist.
Industry Implications
For the seafood processing and aquaculture sectors, the expansion of oxygen minimum zones and coastal dead zones means that traditional fishing grounds may become unproductive for longer periods each year. The $10–20 billion annual loss estimate from the World Bank captures only the measurable economic damage today; the figure does not include indirect costs such as supply chain disruptions, price volatility, or the capital expenditure required to relocate fleets to healthier waters.
Companies that source raw material from tropical Pacific and Indian Ocean fisheries—tuna, skipjack, mackerel, shrimp—face particular exposure, as those basins host the world’s largest oxygen minimum zones. The 20-model ensemble used in the 2025 paper provides a basis for scenario planning, but the models themselves carry significant uncertainty at regional scales.
What is clear from the historical record, however, is the direction of travel. Since the mid-20th century, the ocean has been losing oxygen at a measurable rate, and the areas most affected—the tropical Pacific and Indian Oceans—are also home to some of the world’s most productive and fastest-growing fishing economies.
What to Watch
Market participants will be watching the next round of regional fisheries assessments, especially those from the Intergovernmental Oceanographic Commission and national oceanographic agencies in Southeast Asia and West Africa. If hypoxia expands into previously productive coastal waters, supply contracts for fishmeal, surimi, and canned tuna may come under renegotiation. The study’s threshold concept—4% oxygen loss relative to pre-industrial—offers a convenient benchmark: at current rates, that line could be crossed within decades, fundamentally altering the biological productivity of large swaths of the tropical ocean.
