Urgent Message from Coral Reefs: The Ocean Has an Acid Problem

Our oceans can take up a lot of greenhouse gas; but it's nearly at capacity, and it's throwing the sea water's pH out of whack in many places.

WEDNESDAY, SEPTEMBER 4, 2019: Good evening from Crossville, Tennessee, folks! I'm here visiting my Mom and her two goofy cats for a couple of weeks, mostly for my birthday (two days ago), just as I did last year. Not long after I arrived, we happened to watch a NOVA program on the local PBS channel entitled "The Lethal Seas." This important program has its own page on the PBS website; and the entire 2015 NOVA episode can be seen on YouTube. I encourage everyone here to check it out, and share it widely, as it conveys a critically important message: the ocean can absorb and neutralize a lot of carbon dioxide and other greenhouse gases; but in many parts of the world, its capacity for CO2 uptake has nearly maxed out, and this is having a significant impact on the natural pH of sea water. In effect, it's raising the ocean's acidity to concerning levels, and the coral reefs and other marine life are feeling its effects.

Like Harry Potter, Potions--excuse me, Chemistry--has never been my top subject; and I'm hardly qualified to call myself a marine biologist. But hopefully I'm educated enough by now to understand and parrot back how ocean acidification occurs, and why it's a topic of concern for, basically, everyone. In a nutshell, ocean water has long been taking up excess atmospheric and exhaled carbon dioxide as a way to keep the atmosphere from warming too rapidly. When carbon dioxide (CO2) and water (H2O) interact, they form a weak and very unstable molecule called carbonic acid (H2CO3), from which the hydrogen ions (hydrogen atoms minus their single electron) keep dropping off, raising the acidity levels of the surrounding water. They also have an annoying habit of bonding with carbonate molecules to form bicarbonate molecules (HCO3–), which renders the carbonate molecule unavailable to bond with calcium salts to form Calcium Carbonate, the all-important building block of shells and coral structure (in fact, limestone, which is primarily calcium carbonate, dissolves in the presence of carbonic acid). Also, this happens more frequently, the more water temperature rises, which begins to make sea water bear a startling resemblance to soda. Yeah, that kind of carbonation.

Why is this a problem? Well, under normal, healthy conditions, ocean water has an average pH of 8.06-8.2 (fresh water, if you recall from high school chemistry, has an average pH of around 7.0, which is billed as the midpoint of pH balance), putting it in the Basic or Alkaline area of the pH spectrum. This allows for a healthy abundance of calcium carbonate molecules in the sea water for the purposes of shell-building by corals and crustaceans of all ages. But in the past two centuries, since the beginning of the western Industrial Revolution, the ocean has taken up enough carbon dioxide to move the global ocean pH down by 0.1 units on the pH scale--which doesn't sound too bad, until you read that this translates into a roughly 30 percent increase in natural ocean acidity worldwide. For an even scarier forecast, let's quote directly from the good folks at Yale Climate Connections: "Under the Intergovernmental Panel on Climate Change (IPCC) emission scenarios, [ocean] pH by the year 2100 will decline 0.3-0.4 units from the pre-industrial values, reaching a pH in the range of 7.76-7.86." In other words, not only are the oceans increasing in acidity, the rate of increase is expected to rise four to six times over the rate of the previous two centuries, c. 1800-2000. Yikes.

Still with me, folks? No worries; I'm still reading up on this as I go along. Now, ocean life doesn't just sit there and take rising acidification lying down. Many species of sea plants, algae and phytoplankton require healthy amounts of carbon dioxide to survive, after all; and they do their part, via photosynthesis, to try and maintain equilibrium in ocean water pH. Still, the interference of excess carbon dioxide in the production of calcium carbonate is a huge survival issue for any marine species that requires calcium carbonate to build and maintain shell or coral skeleton structure, including shellfish, pteropods, sea urchins and zooplankton. Hence, the entire oceanic food web is being affected by the increased rate of ocean acidification. The mortality rates of shellfish, plankton and their larvae are rising in regions where there is insufficient calcium carbonate in sea water solution, as these creatures must begin building and maintaining shells from the very beginning of their existence. As both water temperature and carbonic acid levels rise, shell structure begins dissolving or corroding in all species that require calcium carbonate shells to survive; those that don't die quickly must expend much more energy in maintaining shell structure in an environment where calcium carbonate molecules are in increasingly short supply. And as their survival rates are affected, the lives of all sea creatures that depend on smaller shelled species for food are similarly impacted; and so on it goes. Even human societies are beginning to feel the effects of this trend, including people who raise or harvest shellfish for a living.

Marine and climate scientists are in an ongoing quest to find real or potential solutions to the problem of ocean acidification, which last reached current levels some 20 million years ago. It is important to spread the word on these real, observable effects of excess greenhouse gases; coral reefs and oyster larvae don't lie or exaggerate, nor do they have any political agendas. We can best assist our neighbor species of the oceans by doing our part in significantly reducing excess carbon dioxide and methane in the atmosphere before they reach the ocean, not to mention bodies of fresh water. Are there ways that we can help ocean water limit acidification? Are there ways in which we can supplement the ocean's supply of calcium carbonate (I can just picture a new industry dedicated to producing quick-dissolving lime powder, or a similar carbonate material, to be fed into the ocean via special stations). My reading and study continue; meanwhile, let's have everyone reading this begin brainstorming ways to keep sea water at a basic pH level of 8.06, more or less. I await your laboratory results.