In addition to global warming, carbon emissions are causing another problem just as serious and worrying:  acidification of the oceans. Researchers at the Villefranche Oceanography Laboratory (LOV) have shown that the key marine organisms will be deeply affected by this phenomenon in the years to come.

Since 1800, One third of CO2 emissions from human activities has been absorbed by the oceans, which is equivalent to 1 tonne of CO2 per person per year. This massive absorption reduced climate change and causes a disruption of the chemistry of seawater. The absorbed CO2 in effect causes acidification of the oceans and at the rate of current emissions, it is estimated that the pH will decrease by 0.4 units by 2100. This corresponds to a tripling of the average ocean acidity, which is a first for the past 20 million years.

The LOV team led by Jean-Pierre Gattuso has studied the impact of such a decrease in pH on various organisms calcification: The pteropods (marine snails swimmers) and cold-water corals live in areas that will be among the first to be affected by ocean acidification, although their role within their ecosystem is essential.

The pteropod Limacina helicina plays an important role in the food chain and the functioning of the Arctic marine ecosystem. Its limestone shell is a vital protection. However, the study shows that the LOV snail builds its shell at a speed 30% lower when kept in seawater with the features expected in 2100. An even stronger decrease (50%) was measured in the cold-water coral Lophelia pertusa. While the tropical coral reefs are formed by a large number of species, communities of cold-water coral are developed by one or two species of corals and are home for many other species. A decrease in the growth of coral manufacturers due to ocean acidification may therefore threaten the very existence.

The first published results raise serious concerns about the future of pteropods, corals and deep bodies that depend on them for nutrition or their habitat.

Ocean acidification can be controlled by limiting the future concentrations of CO2 in the atmosphere. Negotiations aimed at reducing emissions of greenhouse gases (COP 15) are underway and should be finalized in Copenhagen next December. Hopefully they will not forget to take into account the acidifying nature of CO2, once absorbed into the ocean, will have dramatic impact on many marine organisms and ecosystems.