Editor’s Note: In this essay, Carl (one of our editors) describes the process of ocean acidification, and how it relates with other ecological crises.
First we need to know what an acid is. An acid is any substance (species) who’s molecules or ions are capable of donating a hydrogen ion proton (H+) to another substance in aqueous solution. The opposite of an acid is a base. Which is a substance who’s molecules or ions are able to accept a hydrogen ion from an acid. Acidic substances are usually identified by their sour taste while bases are bitter. The quantitative means to measure the degree to which a substance is acidic or basic is the detection of “potential of hydrogen” (pH) or “power of hydrogen”. This is expressed with a logarithmic scale 0 -14 that inversely indicates the activity of hydrogen ions in solution. The greater the amount of hydrogen ions which are measured below 7 the more acidic a substance is, going to 0. The less hydrogen ions are present which are measured above 7 the more basic a substance is, going to 14. So the pH values are inverse to number of hydrogen ions present. As the concentration of hydrogen ions increases the pH decreases (acidic). As the concentration of hydrogen ions decreases the pH increases (basic). With the value of 7 being neutral which is where pure distilled water falls on the scale. So acidification would be increasing hydrogen ions.
Basic (or alkaline) properties can be associated with the presence of hydroxide ions (OH−) in aqueous solution, and the neutralization of acids (H+) by bases can be explained in terms of the reaction of these two ions to give the neutral molecule water (H+ + OH− → H2O).
For millions of years the average pH of the ocean had maintained around 8.2, which is on the basic side of the scale. But since industrial development that number has dropped to slightly below 8.1. So not acidic but going in that direction. While this may not seem like a lot, remember the decrease is nonlinear and measures the amount of hydrogen ions present. A change in pH of 1 unit is equivalent to a tenfold change in the concentration of (H+) ions. So the drop of .11 units represents a 30% increase of (H+) ions than were present in the relative homeostasis state of preindustrial time. Ocean acidification is an increase in the dissolved hydrogen ions (H+) in the water.
What is causing this decrease in pH?
Oceans absorb carbon dioxide (CO2) from the atmosphere through wave action. Pre-industrialization there was a balance between the CO2 going into the water and coming out of the water. The pH was stable in this narrow range. Life in the oceans have evolved to survive in a balanced condition. Industrialization through the burning of fossil fuel has released increased amounts of CO2 into the atmosphere. This has caused the oceans to absorb more CO2. So here is where the chemistry comes into play. As CO2 dissolves in water (H2O) the two create Hydroxycarboxylic (Carbonic) Acid (H2CO3).
CO2 + H2O = H2CO3
This breaks down easily into Hydrogen Carbonate ions (HCO3) and H+ ions.
H2CO3 = HCO3 + H+
Hydrogen ions break off of the Carbonic Acid. So more CO2 means more H+ ions which means increased acidity.
And this is where the problem is. Shells are formed primarily of Calcium Carbonate (CaCO3). But Carbonate (CO3) binds more easily with H+ than with Calcium (Ca), CO3 + 2H+. This takes away Carbonate that would have bonded with the Calcium for shell production. Calcium is relatively constant, so it is the concentration of carbonate that determines formation of calcium carbonate. Less carbonate available makes it more difficult for corals, mollusks, echinoderms, calcareous algae and other shelled organisms to form Calcium Carbonate (CaCO3), their major mineral building block. Also, when Carbonate concentrations fall too low, already formed CaCO3 starts to dissolve. So, marine organisms have a harder time making new shells and maintaining the ones they’ve already got. This causes decreased calcification. In healthy humans, normal body pH average is 7.4. This is one of the main reasons why the pH in swimming pools should be maintained around 7.5.
The acid-base balance of the oceans has been critical in maintaining the Earth’s habitability and allowing the emergence of early life.
“Scientists have long known that tiny marine organisms—phytoplankton(microscopic aquatic plants)—are central to cooling the world by emitting an organic compound known as dimethylsulphide (DMS). Acidification affects phytoplankton in the laboratory by lowering the pH (i.e. acidifying) in plankton-filled water tanks and measuring DMS emissions. When they set the ocean acidification levels for what is expected by 2100 (under a moderate greenhouse gas scenario) they found that cooling DMS emissions fell.”
Given the importance of plankton, the fact that they are the life-support system for the planet and humanity cannot survive without them, the resulting effects will be disastrous. These organisms produce 50% of the world’s oxygen – every other breath animals take and are the basis for the food web. Covering more than 70 percent of the earth’s surface the oceans, the planets lungs, are in peril.
“Over the past 200 years, the oceans have absorbed approximately half of the carbon dioxide (CO2) emitted by human activities, providing long-term carbon storage. Without this sink, the greenhouse gas concentration in the atmosphere would be much higher, and the planet much warmer.”
But absorbing the CO2 causes changes in ocean chemistry, namely lowering pH and decreasing carbonate (CO3) concentrations.
On a human time scale these changes have been slow and steady relative to that baseline. But on a geological time scale this change is more rapid than any change documented over the last 300 million years. So organisms that have evolved tolerance to a certain range of conditions may encounter increasingly stressful or even lethal conditions in the coming decades.
We know this through carbon dating of ice cores which offer scientists’ the best source for historical climate data. Also deep-sea sediment cores from the ocean floor are used to detail the Earth’s history.
Estimates of future carbon dioxide levels, based on business-as-usual emission scenarios, indicate that by the end of this century the surface waters of the ocean could have a pH around 7.8 The last time the ocean pH was that low was during the middle Miocene, 14-17 million years ago. The Earth was several degrees warmer and a major extinction event was occurring. Animals take millions of years to evolve. They go extinct without an adequate timeframe to adapt to changes in habitat. Ocean acidification is currently affecting the entire ocean, including coastal estuaries and waterways. Billions of people worldwide rely on food from the ocean as their primary source of protein. Many jobs and economies in the U.S. and around the world depend on the fish and shellfish that live in the ocean.
By absorbing increased carbon dioxide from the atmosphere, the ocean reduces the warming impact of these emissions if they were to have remained in the atmosphere. Shockingly, though, only 1 percent of that heat has ended up in the atmosphere nearly 90 percent of it, is going into the ocean. There, it’s setting ocean heat records year after year and driving increasingly severe marine heat waves. As the ocean temperature has risen its ability to absorb CO2 has decreased. Colder ocean water dissolves more CO2, absorbing more from the atmosphere. But we have steadily increased carbon emissions. The percent of current emissions produced sequestered into the oceans is thirty.
It is unknown if this uptake can be sustained. What might happen to the Earth’s atmosphere if the ocean is unable to absorb continued increased carbon dioxide?
“If the seas are warmer than usual, you can expect higher air temperatures too, says Tim Lenton, professor of climate change at Exeter University. Most of the extra heat trapped by the build-up of greenhouse gases has gone into warming the surface ocean, he explains. That extra heat tends to get mixed downwards towards the deeper ocean, but movements in oceans currents – like El Niño – can bring it back to the surface.”
The ocean surface favors mineral formation, in deeper waters it dissolves.
We have enter a new Epoch, The Pyroscene
So it is obvious industrializing the oceans with offshore wind farms and deep sea mining, what capitalism calls the Blue Economy, will have the effect of continued acidification. But it will cause even more ramifications because it will have a direct impact on the species that live there and in the habitat where “raw” materials are extracted.
Regions of the ocean where the plankton communities are more efficiently utilizing organic matter, such as the deep sea, are places where the ocean has a naturally lower capacity to absorb some of the carbon dioxide produced by humans. “So understanding how zooplankton(small aquatic animals) communities process carbon, which, to them, represents food and energy, helps us to understand the role of the ocean in absorbing carbon dioxide in the atmosphere,” – Conner Shea doctoral student in the UH Mānoa School of Ocean and Earth Science and Technology (SOEST) Department of Oceanography.
We are headed for a Blue Ocean Event by 2030 – that is for the first time since ancient humans started roaming Earth several million years ago, an ice-free Arctic Ocean in the summer. The water instead of ice will be absorbing the suns heat rather than reflexing it back. Thus increasing sea temperature rise and disruption of the jet stream. This is basically what solar panels and wind turbines do. They make the earth hotter. Wind turbines extract the cooling breezes for their energy, the opposite of a fan. Miles and miles of solar panels destroy habitat and absorb the heat.
Continued industrialization will have the devastating effect of threats to food supplies, loss of coastal protection, diminished biodiversity and disruption of the carbon cycling – arising from these chemical reactions. This story involves a fundamental change within the largest living space on the planet, changes that are happening fast, and right now.
The oceans will find a new balance hundreds of thousands of years from now but between now and then marine organisms and environments will suffer.
What causes climate change?
The earth’s temperature cycles, glacial – interglacial, are primarily driven by periodic changes in the Earth’s orbit. Three distinct orbital cycles – called Milankovitch cycles. A Serbian scientist calculated that Ice Ages occur approximately every 41,000 years. Subsequent research confirms that they did occur at 41,000-year intervals between one and three million years ago. But about 800,000 years ago, the cycle of Ice Ages lengthened to 100,000 years, matching Earth’s deviation of orbit from circularity cycle. While various theories have been proposed to explain this transition, scientists do not yet have a clear answer. So CO2 historically has not caused climate change, it’s increased in the atmosphere during warmer temperatures and decreased during colder temperatures. Feedback loops have amplified changes initiated by orbital variations. But it is now humans that are currently increasing the amount of CO2 in the atmosphere by burning fossil fuels.
Strictly from an anthropocentric point of view, humanity could adapt to global warming and extreme weather changes. It will not survive the extinction of most marine plants and animals. The destruction of nature is more dangerous than climate change. It is sad that in the effort to save the climate and continuance of business as usual, we are destroying the environment. All of life came from the sea, it would be unwise to harm the birthplace of all species.