Ocean Acidification – The Other CO2 Problem

“The ocean is sick, and one of its problems is ocean acidification,” said James Orr, chairman of the symposium’s International Scientific Planning Committee.

The ocean has provided an important buffer to higher concentrations of CO2 in the atmosphere by soaking up 4 kg of the 11 kg of the greenhouse gas produced by the average person every day. But once it mixes with seawater, CO2 dissolves, making the oceans increasingly acidic. As CO2 emissions rise, so does the acidity of the ocean. The ocean acidity level has already increased by 30% since the onset of industrialisation, with half of that increase occurring in the last 30 years. The increased acidity is adversely affecting the capability of marine corals and shell-forming organisms to build their skeletal material. It also may be affecting the development lifecycles of marine life, reducing growth, production and life spans. This is bad news for fish stocks, which are already stressed by overfishing and warmer sea temperatures.

Research presented at the symposium underscores the notion that ocean acidification is happening now and is measurable. Evidence supporting this fact includes:

• shell weights of pteropods (small plankton that are food for fish) are decreasing;
• calcification rates for coral reefs are decreasing, and will not be able to make up for the erosion of reefs by a more acidic ocean;
• impacts of ocean acidification vary with species;
• ecosystems located near undersea volcanic CO2 vents—where high CO2 levels create a more acidic local environment—have experienced a total loss of some species and reduced biodiversity, providing a glimpse of what may happen on a much larger scale if the rate of ocean acidification continues at its current pace;
• controlled laboratory experiments on the effect of ocean acidification on certain calcifiers showed that the organisms could not adapt to a more acidic environment, even after 150 generations;
• ocean acidification could impact underwater sound by increasing noise levels particularly at a shallow depth where marine mammals migrate, which could cause higher stress for them.

A key message from the symposium is that ocean acidity is expected to increase to the point where marine corals and shell forming organisms will actually start to dissolve by the middle of the century. The only way to reduce or slow the trend of ocean acidification is substantial and urgent reductions in CO2 emissions, according to scientists attending the symposium.

Prince Albert II of Monaco, whose environmental foundation provided support for the symposium, attended a special session devoted to raising awareness of ocean acidification amongst policy makers and the general public. He re-affirmed his foundation’s commitment to supporting the scientific community’s research efforts. “Only by working together will we be able to move this important issue forward,” he said.