In the intense political controversy over the effect of ever-growing levels of carbon dioxide in our atmosphere as it pertains to climate change, an important factor is left out: oxygen.
This is the really critical gas that all vertebrates including mankind need to stay alive. It takes just about five minutes without oxygen at normal body temperature to irreparably damage the human brain.
According to OSHA (The Occupational Safety and Health Administration), the safe range for the oxygen in the air we breathe, is between 19 and 24% at sea level. Below the 15% oxygen level we would turn blue, and become breathless and confused, before eventually dying. Above the 45% level, tissue damage occurs from “oxygen toxicity”. This occurs when there is too much oxygen in the body and results in oxygen-derived free radicals which damage cell membrane, as well as neutralizing the important signaling molecule nitric oxide. This causes chest pain as the lungs are the first major organs to get hit.
Between 24 and 45% the health risk is one of increasing fire hazard. The average person takes about 20,000 breaths a day to stay alive; so, with literally every breath we take, we should be grateful for the way the atmosphere is so accommodating.
Which brings us to the great mystery: where did all our oxygen come from? And more importantly, how long is it going to stay? It turns out that this as controversial as global warming and the politics of carbon dioxide emission. The fancy name for this science is “Paleoclimatology.” It is like the “Weather on the Ones” we see every 10 minutes on the Spectrum TV channel, only instead of being 10 minutes, it is the study of changes every 10,000,000 years! The first real atmosphere is believed to have consisted largely of nitrogen, carbon dioxide, and inert gases produced by volcanic activity and was probably also affected by the heavy bombardment of the Earth by asteroids.
About 3.9 billion years ago, after the Earth’s surface had cooled, enough water had accumulated to form the first seas, which in turn was probably followed by the carbon dioxide dissolving in this water to form carbonate sediment. This is based on the finding of ancient sediment dated to 3.8 billion years ago. As a result nitrogen was left as the major component of the then stable atmosphere. The reader will notice that no mention has been made as yet of any oxygen, and the Earth is already 800 million years old, and life forms have been dated to as early as 3.5 billion years ago, (when the Earth was 11 million years old). The main point about these early life forms is that functioned without any oxygen; in other words, they were anaerobic, and relied on sulfate for their energy needs. In addition, to support the concept of absence of any oxygen, elements like iron and uranium are found in their non-oxidized state in early rock formations.
Then about 3 billion years ago a change was noted, and compounds of oxygen and iron and uranium began to appear in the rocks. This marked the beginning of the Great Oxygen Event. As we shall see, it was by some measures a disaster!
It is currently believed that Cyanobacteria, which evolved 200 million years before the Great Oxygen Event, that would be 3.2 billion years ago, (when the Earth was 1.4 billion years old) were responsible for the production of all the oxygen. Any oxygen produced would have combined with “reservoirs”, metals particularly iron, or combined with hydrogen to make water.
Any oxygen left over, after these “reservoirs” had been filled was allowed to escape into the atmosphere where it promptly reacted with the methane gas. This resulted in a loss of the positive “greenhouse” effect which was keeping the Earth warm and as a result, the longest period of glaciation ensued as the extreme cold caused the Earth to turn into a gigantic snowball! What made things even worse was that the Sun’s energy output was less then than it is now.
This episode in the history of the Earth and its atmosphere is called the “Huronian glaciation” because the evidence for its occurrence was discovered near Lake Huron in Michigan. This all happened between 2.4 and 2.1 billion years ago. Not only that, but all the anaerobic life forms on Earth would die because oxygen was poisonous to them, and so we experienced a “mass extinction” as the oxygen also dissolved in the seas.
The net result of this experience was the atmosphere was thinner than it is now and mostly nitrogen with small amounts of oxygen. The real heroes that saved the day for future life to evolve were the Cyanobacteria that managed to stay alive despite the extreme cold. They emerged from the icy graves of their anaerobic cousins to proliferate and to continue the process of photosynthesis, which has been described by Dr. Dismukes in the following way: “The creation of a photosynthetic apparatus capable of splitting water was the pivotal innovation in the evolution of life on Earth.”
Even more remarkably, this photosynthesis biochemistry has not changed over the last 3 billion years; it is the same in cyanobacteria, algae and contemporary plant. The absence of evolutionary change is probably because the oxidation of water involves the most challenging multi-electron reaction as yet found in biology.
From this point on there was always some oxygen in the air, which we now call the second atmosphere. The amount of carbon dioxide is impacted by numerous events: for example plate tectonics, the study of the movement of the outer crust of the Earth’s structure and how continents drift apart, tells us that the movement of a continent can release huge amounts of carbon dioxide from the continental carbonate stores.
In this way the composition of the atmosphere varied depending on the relative amounts of oxygen and carbon dioxide present, but by the time of the Cambrian Period, 543 to 490 million years ago, oxygen had stabilized at about 15%.
Dr. Saltzman, and his team at the Ohio State University, have produced convincing evidence for a kind of reverse – greenhouse effect that was caused by upheavals in the Earth’s crust, around this time, that cooled the world’s oceans and allowed the phytoplankton to proliferate.
Rock cores from different parts of the world told the same story, of a so-called “SPICE event,” (technically the Steptoean Positive Carbon Isotope Excursion), occurring about 500 million years ago, which was followed by a surge of oxygen into the atmosphere with levels up to 28%, as a consequence of the recovering phytoplankton. Steptoe Butte in Whitman County, Washington, consists of rock over 400 million years old, and is probably the origin of the word “Steptoean.”
What we found to be really interesting is that this SPICE event occurred at the same time as the axis of rotation of Earth also changed, by some 75 degrees so that areas that had been tropical in nature relatively suddenly, became arctic, and vice versa. This seems to be too much of a coincidence, and makes us think that what biologists call the “Cambrian Explosion” when many new and diverse species suddenly appeared, is related to the Spice Event. Oxygen may prove to be the common denominator, as sudden surges in atmospheric oxygen seem to be followed by equally big increases in the number of new species. Ozone is produced when some di-oxygen (O2) absorb energy from the Sun’s ultraviolet rays and splits to form single oxygen atoms (O1).
These then combine with O2 to form O3 or Ozone. This thin layer of ozone is sufficient to protect the land below from deadly ultraviolet radiation, thus permitting life to develop and continue to flourish in a terrestrial environment.
Somehow despite all these calamities, photosynthesis persevered and to this day keeps us supplied with sufficient oxygen, roughly 85% from phytoplankton in the ocean, the remainder from other plant life, which makes the continued survival of these organisms so critically important.
Rather than typecasting them as irritating little critters as in the TV show “Spongebob Squarepants”, they deserve to be regarded at least on a par with the Centaur, the mythological Half Horse and Half Man, for this simple reason: no phytoplankton means no oxygen, which in turn means the mass extinction of man. We would be identified as a rather thin stratum in the geological records, noted for its plastic and radioactivity.
The complex interplay between life stimulating oxygen surges on the one hand, and the massive physical forces on the other that usually result in a diminution of oxygen, means that for the time being at least, we are in a positive balance.
Unfortunately we do not know how long it is going to stay this way, for a number of reasons; firstly contamination of the oceans by plastic waste which blocks the light preventing it from getting to the plankton. There is an astounding quarter of a million tons of such plastic in the oceans of the world, and the really bad part of this, is that it has broken up into over 5 trillion small pieces! The second big threat is global warming from climate change; the contribution of carbon dioxide to this problem is hotly debated in some circles, which means only one thing to us as physicians – we desperately need some reliable evidence.
What we do know for a certainty is that the sea is becoming more and more acid from the increasing amounts of carbon dioxide dissolving in it and in turn this reduces the amount of iron, an essential nutrient for phytoplankton growth. The fourth deadly threat is warming of the seas; this has already caused a staggering 40 % loss of plankton in just the last sixty years!
The oceans cover 72% of the Earth’s surface (140 million square miles), but in contradistinction to the volumes of laws governing the actions of man on land, there are only a few internationally accepted laws that apply to the seas and the oceans. The United Nations through its Regional Seas Program, acts to protect the environmentally safe use of marine resources, and regretfully this is one of the few laws of this type.
The International Maritime Organization is also helping by working to create an acceptable regulatory framework for the shipping industry.
Considering how important oxygen is to the survival of the human race, it is quite remarkable that our knowledge is so fragmented, particularly in regard to its arrival and its eventual departure. We have increasing information about how plate tectonics can influence the amount of oxygen indirectly by causing continental drift and volcanic activity, which in turn result in the release of hydrogen and carbon dioxide. Events on an astronomical scale such as asteroid hits and changes in the Earth’s axis of rotation have also been responsible for massive changes in our atmosphere.
Hitherto these potential disasters have usually been offset by resilience of phytoplankton, however the destructive ”ingenuity” of man may prove to be the end of the current era either by nuclear war or contamination of our environment.
What it comes down to as geophysicist Kasting of Pennsylvania State University admitted recently: “we don’t understand the modern oxygen control system that well.” This was an admission that we found to be rather perturbing. Of all the sciences, the study of the atmosphere and its interaction with the oceans, should be of the highest importance.
To this end we suggest that The US government should establish annual international awards, the equivalent of “Nobel Prizes”, with huge financial awards and enormous prestige; and encourage the teaching of basic environmental knowledge in high schools to stimulate more students to work in this important area.
The writing is on the wall. The world’s oxygen supply could develop a serious illness and would need environmental “physicians” associated with politicians of the highest caliber, to cure it.
