David Ramjohn, June 5th 2019
Published June 4th in the Fayette County Record
How long can you hold your breath for? While we can go for days without food or water most of us won’t last more than five minutes without air. Of all the natural resources we consume on a daily basis, we use air, and more specifically oxygen, more than any other natural resource. What are the factors that affect the quality of the air that we breathe? Certainly important are the pollutants that affect human health, e.g. the “criteria pollutants” as established by the Clean Air Act of 1970, which are: carbon monoxide, lead, nitrogen dioxide, ozone (photochemical oxidants), particulate matter, and sulfur dioxide. However, while we must address the concerns of air pollutants and their impact on human health, it we must recognize the importance of maintaining the right concentration of oxygen in our atmosphere.
The United States Environmental Protection Agency (USEPA) provides Federal oversight of laws, regulations, policies and programs for air pollution control, yet does not contemplate oxygen concentration in air as a measure of air quality. The Occupational Safety and Health Administration (OSHA) Respiratory Protection Standard considers any atmosphere (indoors) with an oxygen level below 19.5 percent to be oxygen-deficient and immediately dangerous to life or health. All organisms that use oxygen for respiration will suffer as the percentage of oxygen in our atmosphere decreases but a decrease in atmospheric oxygen will also affect aquatic aerobic organisms. Henry’s law is a gas law that states that the amount of dissolved gas in a liquid is proportional to its partial pressure above the liquid; as the partial pressure of oxygen in the air declines, the oxygen dissolved in the waters will escape, causing deoxygenation of the waters resulting in stress or fatality for aquatic aerobic organisms. We must ensure that atmospheric concentration of oxygen remains at about 21% for aerobic life to survive.
But what controls the levels of oxygen in the air? Simply put, production and consumption of oxygen must balance. The major producer of oxygen is oxygenic photosynthesis, think plants, and the major contributor to photosynthetic oxygen production are microalgae, which are aquatic plants. In fact, estimates of oxygen output from microalgae in the oceans are between 50 and 85% of the total oxygen produced on the planet. Microalgae, not trees, are the real lungs of the planet. Main users of oxygen are aerobic respiration and combustion. Of course, there are other contributors and users of oxygen, but these mentioned here are the major players.
Any change in variables that affect either the production or consumption of oxygen will alter the balance and have significant effects on our quality of life, or ability to survive. For example, heating of the oceans causes the loss of oxygen in the water, which in turn leads to death of aerobic aquatic organisms, which when they decompose in the water use up even more oxygen. It’s a compounding cascading effect. Warming of oceans also affects the rate of photosynthetic activity, if oxygen production rates fluctuate significantly then the system dynamics change abruptly resulting in oxygen depletion and microalgae extinction. We lose the oxygen output from marine microalgae; we die.
Global deoxygenation—fact or fiction? Some will say we are Chicken Little and there is no evidence to show that we can use up our oxygen supply faster than microalgae can replace it. Some models show that at current population levels, if we shut down oxygen production completely there would still be enough oxygen to last thousands, if not hundreds of thousands of years. These models fail to account for several facts: not humans alone use oxygen; it won’t take a total depletion of oxygen to cause
human extinction; deoxygenation rates are not linear, meaning deoxygenation will accelerate exponentially. A more likely scenario is that we would be gone within two generations if we lost the oxygen production from microalgae. According to Martin et al1, “It is not possible to predict with certainty the threshold value at which mass extinction becomes inevitable, but we have no evidence that humans can persist for more than a generation in an atmosphere containing half the amount of oxygen currently available at sea level.”
The theme for World Environment Day, June 5, 2019 is “Beating Air Pollution.” I believe that we need to consider overall air quality, not just pollutants, but also the ecosystem’s ability to keep producing oxygen. If we lose marine microalgae, not only will the entire ocean ecosystem collapse followed swiftly by planetary ecosystem collapse, but I’m fairly certain that we will suffocate before we starve.
1 Martin, Daniel et al. “The human physiological impact of global deoxygenation.” The journal of physiological sciences : JPS vol. 67,1 (2017)] < https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5138252/#CR13> Accessed May 30, 2019.