I love Bali: The acidic truth

by Chris O’Connor on 2013-03-28

One of the lesser discussed but major environmental factors is the change underway in the oceans’ level of acidity, measured by pH. The stability in the oceans’ pH value has in no small way contributed to the massive diversity of animal and plant life tropical seas, such as those surrounding Bali, support.

Thirteen years ago, American marine biologists Joan Kleypas and Chris Langdon published the Overview of CO2-Induced Changes in Seawater Chemistry following extensive research in the waters around the island. They stated that geological records indicated carbon dioxide (CO2) levels and ocean pH were higher than any level in the past 24 million years and suggested that over the next 30 to 50 years the change would accelerate as humans pumped ever more CO2 into the atmosphere.

They predicted that all marine life would be exposed to significantly different ocean chemistry than had existed for millennia and short-term risk to reefs due to reduced calcification was enormous. The temperature-pH balance is important to shallow water reefs, like the many that surround Bali.

These delicate and complex ecosystems are extremely vulnerable to changes in water conditions and the slightest parameter change can have serious consequences. As predicted by Kleypas and Langdon, recent research is clearly illustrating that there is a global decline in surface pH values making the waters, especially in the tropics, more acidic.

The oceans and seas are particularly adept at absorbing CO2 and are estimated to have trapped about half of the devastating greenhouse gases we have produced in the last 200 years or so. In a dire warning, speaking to the BBC yesterday, Professor Sir John Beddington, the UK government’s chief scientist, said that even if effective action was taken now on global warming there would be significant climate change over the next 20 to 25 years resulting from past global emissions.

Reefs, because of their delicate balance and historically stable parameters, provide an early warning of changes in water chemistry. CO2 absorption results in the life cycles of many lower marine organisms being severely affected; ask any diver, snorkeler or fisherman.

The often devastating results we see today in terms of reef loss, bleaching and depleted fish stocks, are in part due to a change in acid values of only 0.1. Based on the current levels of CO2 absorption and projected emissions, by 2050 there will be a further 0.2 change, and a further 0.3 change by the end of the century. In value terms that will have taken the oceans from an average of 8.2 pH to an average of 7.7 pH.

As CO2 dissolves in the ocean, carbonic acid is formed by chemical reaction leading to higher acidity, mainly near the surface. In turn, this raises the hydrogen concentration, thus limiting access to the carbonate atoms required by many marine organisms, such as hard corals, to grow.

To add further fuel to this fire, as the world’s seas and oceans absorb more CO2, their capacity as a carbon sink will most likely reduce. The result is that even more of the greenhouse gas emissions man produces will stay in the atmosphere and further accelerate climate change.

Researchers and scientists are only now becoming aware of the rising risks from ocean acidification and its effects on marine ecosystems. It is increasingly clear that unless humans control, and ultimately eliminate, fossil fuel emissions, many sea creatures unable to adapt to the changing water chemistry will die, and with them the livelihood of many coastal-dwelling humans.

Talking about the Southeast Asian Coral Triangle, Jane Lubchenco, of the National Oceanic and Atmospheric Administration (NOAA), said at a news conference in Washington to launch the 2012 “Reefs at Risk Revisited” report, “Threats on land, along the coast and in the water are converging in a perfect storm of threats to reefs.”

For the island, the next decades might see not only a vital source of tourist income lost, but a major source of food. The acidification of the oceans can no longer be a peripheral climate issue. At current rates, it is predicted 90% of the world’s coral reefs will be affected by as early as 2030 and before the close of the century all reefs will have ceased to exist.

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