Study confirms ‘high acidification vulnerability’ of the Mediterranean

For the first time an investigation led by the Higher Council for Scientific Research (CSIC) has thoroughly found pH decline in the water leaving the Mediterranean through the Strait of Gibraltar.

The research, published in the latest issue of the journal Scientific Reports, confirmed the “high” vulnerability of the Mediterranean Sea to the acidification process.

The absorption of man-made carbon dioxide by the oceans causes ocean acidification, responsible for lowering seawater pH.

“So, even though CO2 capture helps mitigate the climatic effects of this gas emissions, the resulting decrease in pH leads to adverse consequences for the marine ecosystems as it affects the biogeochemical cycles that are developed in them and almost all of the food chain,” explains CSIC researcher Emma Huertas at the Marine Science Institute of Andalusia.

The Mediterranean Sea is particularly sensitive to acidification because of its semi-closed nature, chemical properties and circulation mechanisms of its main water bodies as well as to the fact that it gets anthropogenic carbon from the North Atlantic through the Strait of Gibraltar.

“Our results confirm the high vulnerability of the Mediterranean to the CO2 increase in the atmosphere and in the ocean waters, caused by man-made emissions,” states Susana Flecha, co-author of the article and researcher of the Institute of Marine Sciences of Andalusia.

The pH decrease affects the oceanic plankton and corals as well as bivalves, which have their basic cellular mechanism functioning altered as well as the access to the carbonate, which is the cement from which marine calcareous structures are built.

According to Huertas, “in the Mediterranean iconic ecosystems that are particularly sensitive to changes in the water pH of the water have been identified, ranging from the extensive seagrass meadows to the coastal coral communities.”

And she adds: “It is essential, therefore, to precisely determine what exposure level to lower pH these Mediterranean habitats are experiencing.”

The researchers have determined the acidification rates through the measurements continuously made for three years with high precision autonomous sensors that all the time recorded both seawater pH as well as dissolved CO2 levels.

The management and maintenance of the bottom line containing the sensors has been carried out in collaboration with the Spanish Institute of Oceanography and the University of Malaga.

CSIC, via FIS, 27 November 2015. Press release.

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