About one third of the CO2 released into the atmosphere is absorbed by the sea. Finding out what the changes in the chemical composition of sea water means for marine life is a task being tackled by European researchers.
The CO2 being absorbed in the ocean leads to the forming of carbonic acid. According to Jean-Pierre Gattuso of the Villefranche-sur-Mer Oceanological Observatory, the acidity of the ocean has increased 30% since 1750. The pH level of the naturally alkaline waters is decreasing, causing great concern for marine biologists.
Up until now there has been limited research dealing with this problem, meaning that the collecting of experimental data is the first step. Ornella Passafiume, a research engineer at the Villefranche-sur-Mer Oceanological Observatory, takes weekly samples and probe measurements off the coast of Villefranche-sur-Mer near Nice. The sea water samples are taken from depths up to 75 metres. The dissolved inorganic carbon of the sample is measured and thus the pH level. But the analysis of the water has to be done before any chemical changes take place. Back on land a toxic substance is added to preserve the samples and the water must be kept in a fridge until it is analysed.
Experiments at the Villefranche-sur-Mer Oceanological Observatory are also investigating the affects of acidity on corals. Increased acidification leads to a decrease of carbonate ions in the water. At risk are all organisms, such as coral, that use the carbonate in the water to build a shell or a skeleton.
This work is conducted as part of the first international study into ocean acidification - the European project EPOCA. Jean-Pierre Gattuso, the project leader, has the wish to discover how rapidly the ocean acidification is taking place and how this will affect the marine life. 27 partners in 9 European countries are involved in EPOCA.
In the British port of Plymouth, the marine biologist Jason Hall-Spencer is studying sea water that has been naturally acidified by volcanic activity. He has been able to observe that the corals start to dissolve; however, they do not dissolve completely. The living component of the coral seem to survive, suggesting that the coral could also survive as naked polyps. This could prove to be valuable insight into what could occur with coral reefs in the tropics, which play an important role in protecting low-lying islands.
Participants of the EPOCA project at the Plymouth Marine Laboratory are investigating how acidification could affect fish, sea snails and molluscs. Environmental Toxicologist David Lowe and his team focus their work on the reproductive and digestive systems of such marine life. They have discovered that at the pH level of 7.6 the secretory cells begin dividing at an abnormal rate, meaning the digestive system seems to be struggling. A total breakdown of the digestive system seems to occur at a pH level of 6.
The results of increased CO2 in the atmosphere is well documented, but the impact of the same CO2 on the ocean is still unclear. Clear is that the ocean acidification is a direct result of man-made CO2 emissions. This rapidly evolving global issue is not likely to improve any time soon.