The surface layer of the ocean is teeming with photosynthetic plankton. Though they're invisible to the naked eye, they produce more oxygen than the largest redwoods. Scientists estimate that roughly half of the oxygen production on Earth comes from the ocean, but can the oceans run out?
The air we breathe: the ocean produces over half of the world's oxygen and absorbs 50 times more carbon dioxide than our atmosphere. Climate regulation: covering 70% of the Earth's surface, the ocean transports heat from the equator to the poles, regulating our climate and weather patterns. You might already know that our oxygen from the sea comes from photosynthetic organisms like plants. But did you know that most of the oxygen you breathe comes from those organisms in the ocean? That's right—more than half of the oxygen you breathe comes from marine photosynthesizers , like phytoplankton and seaweed.
Low or depleted oxygen in a water body often leads to 'dead zones '— regions where life cannot be sustained. In ocean and freshwater environments, the term "hypoxia" refers to low or depleted oxygen in a water body. Because of climate change and the warming of Oceans there is increasing Hypoxia occurring globally and it is especially detrimental to our coral reefs that feed the primary oxygenating life of the Oceans. Ocean deoxygenation is already threatening marine ecosystems globally. However, the current and future oxygen concentrations and the occurrence of hypoxic events on coral reefs remain significantly underexplored for fear of panicking the populace. Researchers engaged in the studies on a small scale are using autonomous sensor data to explore oxygen variability and hypoxia exposure at 32 representative reef sites, recent results have revealed that hypoxia is already pervasive on many reefs. Eighty-four percent of reefs studied experienced weak to moderate hypoxia and 13% experienced severe hypoxia.
On December 11 2023 hypoxia in the seas near Japan killed conservatively over 1500 tons of fish which floated to the shores. Vast numbers of sardines and chub mackerels were discovered on the beaches of Northern Japan most prominently in areas near Hokkaido like Hakodate Beach. This latest fish death is similar to one that occurred in June in Texas. Thousands of fish washed ashore along the Texas Gulf Coast due to “a low dissolved oxygen event” in warm water, US officials have said. Quintana Beach County Park officials said the species most impacted by this fish kill was the Gulf menhaden, but this is not an issue of one or two events over the last year but dozens and it is continuing to rise in scale and number. Ocean areas without oxygen called dead anoxic are essentially dead or dying areas. The volume of anoxic ocean waters – areas completely depleted of oxygen – has quadrupled since the 1960s.
Oxygen in the oceans is being lost at an unprecedented rate, The Guardian Reports, with “dead zones” proliferating and hundreds more areas showing oxygen dangerously depleted, as a result of the climate emergency and intensive farming, experts have warned. Sharks, tuna, marlin and other large fish species were at particular risk, scientists said, with many vital ecosystems in danger of collapse. Dead zones – where oxygen is effectively absent – have quadrupled in extent in the last half-century, and there are also at least 700 areas where oxygen is at dangerously low levels, up from 45 when research was undertaken in the 1960s. The International Union for the Conservation of Nature presented the findings on Saturday at the UN climate conference in Madrid, where governments are halfway through tense negotiations aimed at tackling the climate crisis. The continued reliance on fossil fuels is actually turning the oceans into the primordial seas of antiquity not to mention increased acidification.
All fish need dissolved oxygen, but the biggest species are particularly vulnerable to depleted oxygen levels because they need much more to survive. Evidence shows that depleted levels are forcing them to move towards the surface and to shallow areas of sea, where they are more vulnerable to fishing. Some ocean areas are naturally lower in oxygen than others, but these are even more susceptible to damage when their oxygen levels are depleted further, the report’s authors said. Species that can more easily tolerate low oxygen levels, such as jellyfish, some squid and marine microbes, can flourish at the expense of fish, upsetting the balance of ecosystems. The natural oceanic cycles of phosphorus and nitrogen are also at risk. The question many ask is if the fish go will mankind be far behind?
Low oxygen levels are also associated with global heating, because the warmer water holds less oxygen and the heating causes stratification, so there is less of the vital mixing of oxygen-rich and oxygen-poor layers. Oceans are expected to lose about 3-4% of their oxygen by the end of this century if nations leave fossil fuels behind, if not we could see numbers as high as 20% loss of living oceans, but the impact will be much greater in the levels closest to the surface, where many species are concentrated, and in the mid to high latitudes. In terms of human survivability of a 50% loss of oxygen we must note that Generally speaking, humans would all die. Humans become very nauseous or unconscious when the oxygen level drops below 10% (normal is 20%), and it becomes difficult to think properly. Life would go on despite the mass extinctions; there are, no doubt, many organisms that don't need a lot of oxygen (such as insects), and, in fact, there are bacteria out there that were around billions of years living in an oxygen-free environment until the Oxygen Catastrophe killed most of them off.
Humans, however, if they became unconscious, would just die, along with most large mammals. Realistically, we would see this coming and some fraction of humans would start running around with an extra supply of O2 pulled from the atmosphere and a breathing mask. Earthship houses with algae tanks and green houses would be a necessity to survive.