MECCA · Mediterranean Coral Calcification in response to global change

Mediterranean coral calcification in response to global change

Final report on the Marie-Curie project MECCA (1.4.2008-31.3.2010) The project on 'Mediterranean coral calcification as response to global change' (MECCA) had four principal objectives with: 1) the determination of calcification rates in response to increasing pCO2 and temperature; 2) to study the response of coral-associated prokaryotes; 3) to study the role of coral-associated prokaryotes in coral calcification and 4) to determine if there is a species-specific response to global change. These objectives were addressed by sampling live corals during several research cruises, by analyses and experiments in the laboratory at LOV and directly aboard during cruises. Laboratory experiments: A first phase was the set-up of four aquaria for coral maintenance under two pCO2 and two temperature treatments. The first corals were provided by colleagues from Barcelona (CSIC-ICM) in September 2007, and another opportunity to initiate the study on cold-water corals was the collection of cold-water corals during a campaign in collaboration to the Gulf Lacaze-Duthiers. These freshly collected corals were sub-divided to more than 60 small branches, weighted and distributed into the four aquaria. Unfortunately, the corals got infested by a parasitic foraminifer that spread very fast and a break down of the climate room killed most of the corals. To solve the problem of disease spreading between corals, but also to avoid 'pseudo-replication' by maintaining the replicate individuals in the same treatment tanks, individual vials had to designed to maintain the corals during and between experiments. These vials had to fulfil certain requirements with respect to size: they had to be small enough to allow for sufficient replication without taking too much space, but also they had to be big enough to provide an appropriate 'environment' to maintain the small coral branches in sufficient seawater. Also they needed to be relatively high to be able to generate water flow by bubbling air in a small plastic tube within the vial, but also to provide enough head-space when carrying out incubations. Finally, vials with an inner diameter of 4.5 cm and 25 cm high were built and 15 of these vials were used in each of the 4 treatments. Additionally, six bigger glass jars per treatment to allow the maintenance of several bigger branches of corals were also placed in the treatment aquaria. This way each treatment contained 15-16 corals and 5-6 blanks. The vials were supplied with flowing seawater and air bubbling with small tubings of 0.5 and 1 mm inner diameter. Three species of corals, Lophelia pertusa, Madrepora oculata and Desmophyllum sp. were studied using this set-up. Also, a more sophisticated system to provide different levels of pCO2 was designed and installed. This system contains four pairs of gas flow controllers mounted on a panel. This system can provide six different CO2-air mixtures with ambient air and CO2-stripped air and the air/CO2 mixtures generated with the gas flow controllers.

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