Social justice and reduced calcification in planktonic foraminifera

So, you may be asking yourself, what does reduced calcification in modern Southern Ocean planktonic foraminifera have to with social justice? You can either read the study yourself (entitled "Reduced Calcification in Modern Southern Ocean Planktonic Foraminifera"), or read on in this post!

Excessive carbon dioxide in the atmosphere doesn't stay put, thankfully. Various processes in the earth's systems remove carbon from the atmosphere, and these mechanisms have kept atmospheric carbon dioxide levels pretty stable for a long period of time. Everyone knows by now that plants take up carbon dioxide. But oceans absorb a lot more, and there is new evidence that one of the biological pumps removing CO2 from the atmosphere is giving out.

There's been a growing awareness for the last five years that oceans are getting more acidic, not because of global warming but because of the indisputed rise in atmospheric carbon dioxide levels. That rise is due to humanity's use of fossil fuels, which is also undisputed. That extra carbon dioxide dissolves in the oceans and makes them more acidic (the same process makes rain slightly acidic).

Are acidifying oceans a problem? They are if you're a foraminiferan. These microscopic organisms have shells made of calcium carbonate–and calcium carbonate is dissolved by acid. The more acidic the oceans, the harder to create a shell. Oysters and coral create calcium carbonate structures too, but foraminifera create a lot more. A recent study shows that foraminifera create shells that are thinner and lighter, and contain a third less carbon in the form of calcium carbonate, than shells from the same creatures that lived before the industrial revolution.

What if you're not a foraminiferan? Are acidifying oceans still a problem? Turns out the answer to that is a resounding yes. Ocean organisms that form calcium carbonate shells are important consituents of a marine food chains, which ultimately provide food for people. And the collapse of coral reefs systems worldwide is at least partly due to more acid ocean waters (although there are are other factors, including warmer ocean waters, higher sea levels, and water pollution). Already-stressed marine ecosystems are further harmed by acidification.

According to the FAO, 43.5 million people worldwide depend directly on fishing to make a living, and most (86%) live in Asia. Including indirect employment, nearly half a billion people depend on the world's fisheries. Almost 3 billion people depend on fish for a large part of their daily protein intake, many of them in the developing world. Any disruption to the chemistry of the systems they manage has big social justice implications.

This chemistry problem would be troubling enough, even if there were no connection to global warming. But there is a link, and an important one.

The formation of calcium carbonate shells by marine organisms is an important mechanism that mitigates our carbon dioxide pollution. They take up carbon that has accumulated in the atmosphere, and when the organisms die the carbon-rich shells fall to the ocean floor and become incorporated in sediments (which can eventually form limestone deposits–the great pyramids of Egypt are made of limestone formed by foraminiferans). We get a discount on the impacts of our global warming pollution, because so much carbon is absorbed by ocean organisms like foraminiferans. Acidification of the oceans slows that process, and diminishes one of the main stabilizing mechanisms for the climate system.

This points to the need to get our carbon dioxide pollution under control, not just to mitigate global warming, but to maintain the ocean ecosystems we depend on for food and to preserve the amazing biodiversity of coral reef systems. Even if global warming weren't caused by humans, ocean acidification is, and it deserves our hand of stewardship.

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