Carbon’s Burden on the World’s Oceans

The burgeoning amount of carbon dioxide in oceans is affecting a lot more than coral reefs. It is also damaging marine life and, most ominously, threatening the future survival of marine populations.

When the annual meeting of the American Association for the Advancement of Science (AAAS) convened in Boston this year, a handful of marine biologists and physiologists exposed a whole new side of climate change. They offered no data about the atmosphere. Their focus was not on temperature. Their conversation referred to warming only as a secondary and confounding effect.

Instead, these scientists were talking about chemistry — not just of the ocean water but of ocean animals themselves: their cells, tissues, and body fluids. They were noting the increased costs of living that come as a result of elevated carbon dioxide inside the body and how this added cost stresses marine life and has led to massive extinctions in the past. They were issuing a warning about the potential for unabated elevated carbon dioxide to threaten directly the survival of all marine species.

The direct link between increased carbon dioxide concentrations in oceans and increased internal stress on marine creatures is largely absent from the “climate change” dialogue. It used to be enough to say “global warming” was the problem. But increasing concentrations of carbon dioxide in the atmosphere — and in oceans — have been causing more varied and faster effects than previously imagined. In fact, massive changes underway in the ocean are not captured with the word “climate.”

Certainly, warming itself is a colossal issue. Record world temperatures, melting sea ice, thermally expanding ocean waters, sea level rise, engorged rain clouds in some regions and droughts in others — “climate change” has been used to encapsulate all these effects.

Yet now, that term is beginning to hamper our understanding — and our conversation. Beyond the well-defined relationship between carbon dioxide and temperature lie various chemical reactions that have profound implications for life. These other issues are starving for attention, partly because they are not about warming, the atmosphere, or the climate. But they are about the same carbon dioxide.

Almost half of all the carbon dioxide emitted since industrialization has been absorbed by the ocean. When carbon dioxide reacts with water, it forms carbonic acid, and releases more hydrogen ions into the sea, lowering pH and causing “acidification” of the ocean. Further, these hydrogen ions quickly bind with carbonate ions. This deprives animals like hard corals and certain mollusks and plankton of the raw material for their calcium carbonate shells and skeletons. This may ultimately cause the world’s oceans to become corrosive to such animals, and coral reefs to dissolve.

Calcification rates (think of this as the rate at which a coral, say, can grow, based on its ability to construct its skeleton) decline in relation to carbonate concentrations. Models predict that coldwater corals may lose 70 percent of their habitat by 2100 with some waters becoming corrosive as early as 2020. Calcification rates in tropical waters have already declined by 6 to 11 percent and are expected to decline by as much as 17 to 35 percent by the end of the century. Some models predict concentrations of carbonate ions will be too low for reef growth by as early as 2065.

It turns out that carbon dioxide molecules not only penetrate the ocean; they also infiltrate the bodies of marine animals, permeating cell membranes and disrupting fundamental biological functions. Carbon dioxide is a small, uncharged gaseous molecule that in the ocean environment can rapidly cross cell membranes. Once inside the cell, the same acidification process that happens in ocean water occurs within the cell. Higher concentrations of CO2 alter the acid-base balance within cells and disrupt many cellular functions, from oxygen transport to protein synthesis. The more CO2 inside body tissues, the higher the cost of living for an organism. In its energy budget, the cost of dealing with CO2 comes directly out of energy that would otherwise have gone for other basic functions such as metabolism, growth, immune function, and making babies.

We call this cost “metabolic drag.” It has long-term consequences for survival because even if not acutely fatal, over time reduced growth, disease resistance, and reproductive output threaten the viability and resilience of populations. And they’re going to need resilience.

Too much carbon in the ocean particularly threatens creatures living in the deep sea. The depths of the ocean comprise one of Earth’s most stable environments. Its animals are adapted to that stability. They don’t handle change well. Scientists predict that the pH in the deep sea will be greater than for the ocean’s other regions.

Experiments show that elevated carbon dioxide affects various cellular and bodily functions, such as the ability to make proteins, transport oxygen through the body, or growth rates. But how will the ever-increasing CO2 affect individual animals, populations, and species in coming decades? No one knows. Significant harm appears possible, but evaluating long-term effects will require more work. Research is also critically needed to evaluate large-scale carbon disposal (sequestration) that would cause very high concentrations in deep ocean water (in some experiments, pH declined by more than 1 unit).

Consideration of these known and potential effects of elevated carbon dioxide levels has not been part of the “climate” debate, and it will be difficult to raise or understand these effects if people continue to believe that the problem only involves climate. The language lags behind the science, and needs to catch up.

No term in use captures the full array of issues from warming and climate to the chemistry changes throughout the ocean and inside every marine creature. Not “climate change,” certainly not the almost-quaintly catastrophic “global warming.” Those aren’t even the problem; they’re symptoms. Behind all these symptoms is the root of the problem. We call it “the carbon burden.”

So hear this: It is not just about climate. It is, and always has been, about the carbon. We need to place carbon back in the center of the equation. From atmosphere to ocean to cell, the carbon burden is the problem. It’s the heaviest load anyone’s ever placed on an unsuspecting planet, and the more we learn, the more its dimensions appear ever more staggering.