MECCA

Mediterranean Coral Calcification in response to global change

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 Obiettivo del progetto (Objective)

'Global environmental change and the rise of CO2 have been identified as a major threat to scleractinian corals and coral reefs. General predictions are that ocean acidification will be detrimental to reef growth and that 40 to > 80 % of present-day reefs will decline during the next 50 years. While the impact of global change on reef-building corals has been intensely studied, not much is known on the response of deep-sea, cold-water corals or azooxanthellate shallow water corals. Also, the role of coral-associated prokaryotes in coral calcification and the microbial response to variable pCO2 and temperature and its impact on host calcification needs to be addressed. To tackle these open questions experiments with Mediterranean deep and shallow water azooxanthellate corals under controlled lab conditions with varying pCO2 and temperature will be conducted. The choice to study corals from the Mediterranean has several reasons: 1) the Mediterranean is an enclosed system and can be regarded as a miniature ocean that is expected to react faster to global change than the open ocean; 2) in general all 'ecotypes' of corals ranging from zooxanthellate, shallow water corals that are also known from tropical reefs to azooxanthellate deep, cold-water corals are actually present in the Mediterranean; 3) some tropical and cold water coral species in the Mediterranean are at their biogeographic distribution limits confined by temperature constraints, and as such the study of Mediterranean corals and their response to global change will likely result in the identification of 'tipping points' in response to temperature and pH changes. A last point is that no model predictions exist on the carbonate chemistry of the Mediterranean, but data compilation is in progress (J. Orr, IAEA Monaco) and the study of Mediterranean corals can thus contribute to the modelling of Mediterranean response to anthropogenic CO2 and global warming.'

Introduzione (Teaser)

An EU-funded initiative has been studying the effect of changing carbon dioxide (CO2) levels on corals.

Descrizione progetto (Article)

Climate change and the increase of CO2 levels are now recognised as a serious threat to corals and coral reefs. Scientists believe that rising levels of CO2 will result in the acidification of the world's oceans and seriously affect the growth of coral reefs, resulting in their decline.

The 'Mediterranean coral calcification in response to global change' (MECCA) project has examined the effect of different CO2 levels on calcification rates, when coral tissues become hardened with deposits of calcium. Scientists have also investigated the role of coral-associated microorganisms in calcification and their response to changing conditions.

Project partners have examined samples of live Mediterranean corals in the laboratory. The Mediterranean is an enclosed system that can be regarded as a miniature ocean. This body of water is expected to react faster to global change than the open sea.

Coral samples were originally kept in aquaria, but they were found to be vulnerable to attack from parasites. As a result, the samples have been maintained in aerated vials and exposed to six different CO2/air mixtures including ambient air and air stripped of CO2.

Results from the MECCA project enable scientists to determine the effect of rising CO2 levels on the calcification of corals and coral reefs. The work will support environmental policy decision-makers to take mitigating action.