Acidification – Marine life takes a bad trip
6 October 2008, CIESM News

Owing to the increasing amounts of carbon dioxide being released to the atmosphere “ocean acidification may soon threaten unique ecosystems in the Mediterranean Sea”, concluded an international group of 15 leading scientists who just met in Menton, France, at the invitation of the Mediterranean Science Commission (CIESM). This International Commission federates over 4000 researchers distributed around the Mediterranean Basin and keeps a scientific watch over the rapid changes in marine biodiversity, warming trends, emerging contaminants, tsunami risks, etc, that are closely intertwined in the region. Acidification is climbing fast on the agenda of CIESM since increased seawater temperatures due to global warming enhance the capture of carbon dioxide1 by the world ocean, leading to a gradual increase in acidity in recent years2.

According to Prof Frederic Briand, CIESM Director General, who attended the meeting, “While the time has not come to send catastrophic alarmist signals in the way Captain Jacques-Yves Cousteau did when he naively declared some forty years ago that the Mediterranean Sea would be dead by 1987 (!) ... there are serious causes for concern regarding the potential effects of acidification in the world ocean, because carbonate ions are the basic building blocks of skeletons and shells for a large number of marine organisms. Acidification is particularly worrisome in the Mediterranean Sea that harbors vulnerable marine habitats and hundreds of species that are found nowhere else”.

The CIESM Expert Group on Mediterranean/ Black Sea Acidification, composed of researchers from various disciplines led by Profs Aysen Yilmaz (Turkey) and Gert de Lange (Netherlands), concluded its analysis of the available information gathered from field observations and laboratory experiments in various countries with a stern catalogue of potential risks and with a list of defined priorities for research.

The group of scientists highlighted the fact that the effects of marine acidification on sensitive Mediterranean ecosystems, already threatened by massive anthropogenic activities and over-exploitation, will be likely accelerated by global warming. For example, unique habitats such as biologically constructed reefs may be severely altered if their constitutive organisms are restricted in their ability to form calcium carbonate skeletons under acidic conditions. While rates of change in marine acidity are still unclear, the CIESM Workshop stressed the need to promote ocean acidification and global warming-related studies in the Mediterranean region in order to better understand these processes and predict consequences.

photo: Sam Dupont, Dept of Marine Ecology, Göteborg University, Sweden

Example of abnormal larvae of Ophiothrix fragilis raised at low pH [polarized light is used to highlight skeletal malformations].
An adult Ophiothrix fragilis.

To quote Frederic Briand, “marine life is booked on a bad trip with acid”. He adds, “this is not a bad joke, one of our major concerns indeed is the risk of approaching in the space of a few decades an unknown ‘tipping point’ from which acidification might lead to the eradication of many marine species of major importance to man, such as mussels or corals. This would turn the Mediterranean into a sea filled mostly with jelly fish, sea anemones, tunicates or non calcareous algae. Not very exciting …”

The CIESM expert group recognized, among species appearing particularly at risk, corals, sea urchins, mollusks; their calcareous skeleton or shell will end up in time dissolved by a more and more acidic sea. “Obviously, says Briand, the response of these species and of other possible vulnerable targets - such as fish larvae - to acidification is in need of a major, well funded research initiative at the international scale.”

A White Report is in preparation by CIESM. Its recommendations and conclusions will soon be available to the scientific community and to relevant national and international agencies, beginning with the European Commission. In the meanwhile the findings of the CIESM Expert Group on the Mediterranean Sea will find a large echo in the Global Symposium dedicated to Acidification, which begins today in Monaco.


1  The CO2 released in the atmosphere by industrial and agricultural activities is absorbed by the oceans. The concentration of CO2 in the atmosphere has been increased since the industrial revolution by 30%.
2  When carbon dioxide (CO2) is absorbed by seawater, chemical changes occur that reduce seawater pH and the concentration of carbonate ions in a process commonly referred to as ocean acidification.

Further info: Dr Alessia Rodriguez y Baena