What new science and T.S. Eliot teach us about ocean acidification

The idea that ocean acidification might be a severe problem for the world’s coral reefs is already quite talked about. But studying that link has proved tricky, until now. A new study on the Australia’s Great Barrier Reef is one of the first to expose the effect that ocean acidification is already having on coral reefs.

Ocean acidification is simultaneously one of the most subtle and the most disquieting changes we can expect from our assault on the Earth’s atmosphere.

With climate change we pick up the drama in many ways — a storm here, a drought there, a flood, a heatwave. Sea levels are rising and long term shifts in weather patterns and temperatures are also now clearly felt — by farmers, by indigenous and traditional peoples. Thousands of species are already adjusting their habits, flowering times, movements and homes to accommodate the changing temperatures. This drama has goaded what is now a clear majority of the world’s people towards caring and even action.

But what you may not realize is that quietly, invisibly, the ocean is taking on a huge burden that we were slower to predict and even slower to understand. The sea has already absorbed a quarter of carbon dioxide coming out of our power-stations and cars. No storms, no drama, just a steady, gentle diffusion. The change in the oceans that follows is hard to trace: The water becomes a little more acidic, or technically a little less alkaline, but perhaps that’s splitting hairs.

The change is slow but constant — every minute, every hour, every day, the chemistry of our oceans is shifting. Tick, tock, tick, tock.

The scientists studying this change have mostly resorted to drama, acidifying aquaria to look at what happens. The results are deeply disturbing. Saltwater isn’t just water with a bit of salt — it is a complex cocktail of compounds and minerals, some dissolved, some still in mineral form. But as the water pH changes, more and more of these minerals dissolve and become inaccessible to the millions of organisms that need them to grow.

Scientists are predicting dire consequences for marine life. First reduced growth rates, then the actual dissolving of the skeletons of organisms critical to ocean environments — from plankton to corals to molluscs and crustaceans.

But this new study flipped this approach on its head. Instead of pumping acid into a lab aquarium, the researchers put things back to how they used to be in the ocean itself. They returned the water to pre-industrial levels of alkalinity in a series of remarkable field experiments on a lagoon in the Great Barrier Reef.

Out on the shallow reef flat of One Tree Island, they allowed a slow, continuous release of alkali and non-toxic dye to subtly alter the local pH over a series of experiments. Fine sensors recorded carbonates and calcification rates, not as physiological changes from individual corals in the lab, but of an entire ecosystem.

And lo and behold, when ocean acidity was reduced to pre-industrial levels, net community calcification, or the extraction of carbonates from ocean water and the building of skeletons, sped right up. Controls verified it was the pH that was the driver. A host of different corals and coralline algae, all working together, most likely produced this enhanced activity. In this one little place, the Great Barrier Reef was growing measurably faster than it had been for decades.

Some earlier big-picture studies have shown decadal declines in coral growth and calcification, but these have had too many confounding variables — it has been hard to make the case. This new study corroborates their observations. Corals and other organisms that build coral reefs aren’t growing like they used to.

This leaves us yet more certain of the need for action. Every now and again a big storm can flatten everything on a reef. In the interim, a host of strange animals on coral reefs act as bioeroders — constantly wearing down the reef — from the vicious biting and scraping of coral by parrotfish to the myriad holes bored right through the corals by strange bivalves and beautiful worms.

Without the surging, pulsing growth of corals and coralline algae to keep up, the balance is tipped and reefs lose their height and their complexity. Without their height they allow more waves to past — hitting our coasts and threatening towns and villages. Without their complexity they become less productive, leaving fewer fish for the millions who rely on the reefs for sustenance or income. While it would be tragic for the world’s most diverse ecosystem, the human tragedies of reef loss may be greater still. (…)

Mark Spalding, Cool Green Science, 2 March 2016. Article.

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OA-ICC HIGHLIGHTS

Ocean acidification in the IPCC AR5 WG II

OUP book