Our oceans are in trouble. Again. While plastic pollution threatens the diet of marine wildlife, another threat looms before fish have even taken their first bite. Oxygen-deprived oceans. For some time, scientists have been aware of ‘dead zones’ -- areas of the ocean especially impacted by deoxygenation. But awareness alone isn’t enough to face a reality that has unfolded into an alarming wake up call.
Fish depend on oxygen almost as much as humans do. When they are in waters that face a depletion, they either swim to more oxygen-rich areas or die as a result. What’s troubling about this situation is some fish are regionally-dependent. An area native to a specific species says a lot about a fish’s evolution; they may simply be unable to evolve elsewhere. Larger fish such as tuna, swordfish, and even sharks naturally require more oxygen due to their size. Forced relocation would almost certainly equate to major ecological behavioral changes. While migration and hunting patterns could adapt over time, genetic make-up could potentially be forever altered. And a lack of oxygen in some areas mean fish will travel near the surface, raising food competition and potentially disrupting the ocean’s food chain. If fish are forced to leave areas known to them due to the inability to thrive in their natural habitat, it raises the potential of endangerment or worse, extinction.
A recent study concluded that between 1960 and 2010, ocean oxygen content decreased by 2 percent. The primary factor for this decrease is climate change. Large areas of deoxygenation exist today mostly near equatorial waters and coastlines. The Pacific Ocean, the largest ocean on earth, encompasses most of the areas of deoxygenation and has suffered the greatest loss of oxygen. Other oceans are not immune, having witnessed sharp declines in their oxygen levels. With an overabundance of carbon dioxide creating a greenhouse effect on earth, temperatures are locked into our atmosphere, heating the oceans and finding solace in other oxygen sources such as trees and land dwelling plants. In 2017, we witnessed the devastation of warm ocean waters through a series of hurricanes and tropical storms throughout the Atlantic.
What Is Ocean Deoxygenation
Deoxygenation occurs when warm surface waters’ inability to dissolve oxygen results in stratification -- an increase in ocean layers. These layers essentially “block” the passage of oxygen into deeper waters -- also known as vertical mixing -- resulting in suffocation of marine life and plants that depend on oxygen for food and life. Stratification generally doesn’t happen in colder waters, instead its energy is derived from warm waters. Warm waters absorb less oxygen.
Water runoff from sources like agricultural fertilizers and wastewater significantly contribute to the problem. The runoff houses nutrients and oxygen, perfect for algae as they absorb much of it, yet harmful to other marine life that depend on those very same nutrients. Unlike what we see in the news media such as plastic filled beaches, the majority of ocean pollution begins before it reaches the water.
The livestock industry is notorious for producing high amounts of methane gases. The extensive land plowing of soil, which when eroded by weather becomes runoff and seeps into our water sources, adds unnecessary toxins to the ocean. This runoff devastates plant life that is responsible for producing oxygen. Much of the time, methane gas caused by livestock practices begin on a trajectory of air pollution and ends in our waterways where it is stored among marine plant life.
An Ocean Without Oxygen
An ocean without oxygen would make for a dire scene. Though trees get much of the street cred for providing us with oxygen, as much 70 percent of our breathable air comes directly from oceans which pales in comparison to trees’ 28 percent oxygen production rate. After studies concluded a measurable change attributed to global warming could be seen when examining ocean deoxygenation, both oceanographers and climate scientists kicked into high gear to raise public awareness.
Photosynthetic organisms, also known as ocean plants -- think phytoplankton, kelp, and algal plankton, many of which are invisible to the naked eye -- live on the surface of the ocean. As these microscopic plants drift along with the current, they take in carbon dioxide. When carbon dioxide mixes with water through the process of photosynthesis, oxygen is produced and distributed throughout the earth. And because oceans cover more than 70 percent of all earth, it proves as an integral source of oxygen for much of the planet’s life forms.
Imagine if you will, a society that took great pains to protect the ocean through conservation, recognizing its vitalness to life, both to those on land and those in the deep. Imagine a world that fully understood its responsibility in climate action and took necessary steps in daily life to mitigate these problems, overall reducing the effects of climate change on our oceans.
Now, let your imagination come to a halt and for just a moment, allow it to seize into action.