ORIGINAL ARTICLE Impacts of CO 2 -induced seawater acidification on coastal Mediterranean bivalves and interactions with other climatic stressors P. Range • M. A. Chı ´charo • R. Ben-Hamadou • D. Pilo ´ • M. J. Fernandez-Reiriz • U. Labarta • M. G. Marin • M. Bressan • V. Matozzo • A. Chinellato • M. Munari • N. T. El Menif • M. Dellali • L. Chı ´charo Received: 5 March 2012 / Accepted: 14 May 2013 Ó Springer-Verlag Berlin Heidelberg 2013 Abstract The effects of seawater acidification caused by increasing concentrations of atmospheric carbon dioxide (CO 2 ), combined with other climatic stressors, were stud- ied on 3 coastal Mediterranean bivalve species: the mussel Mytilus galloprovincialis and the clams Chamelea gallina and Ruditapes decussatus. CO 2 perturbation experiments produced contrasting responses on growth and calcification of juvenile shells, according to species and location. In the Northern Adriatic (Italy), long-term exposure to reduced pH severely damaged the shells of M. galloprovincialis and C. gallina and reduced growth for the latter species. Sea- water in the Ria Formosa lagoon (Portugal) was consis- tently saturated in carbonates, which buffered the impacts on calcification and growth. After 80 days, no shell damage was observed in Portugal, but mussels in the acidified treatments were less calcified. Reduced clearance, ingestion and respiration rates and increased ammonia excretion were observed for R. decussatus under reduced pH. Clearance rates of juvenile mussels were significantly reduced by acidification in Italy, but not in Portugal. Both locations showed a consistent trend for increased ammonia excretion with decreasing pH, suggesting increased protein catabolism. Respiratory rates were generally not affected. Short-term factorial experiments done in Italy revealed that acidification caused alterations in immunological parame- ters of adult bivalves, particularly at temperature and salinity values far from the optimal for the species in the Mediterranean. Overall, our results showed large variations in the sensitivities of bivalves to climatic changes, among different species and between local populations of the same species. Expectations of impacts, mitigation and adaptation strategies have to consider such local variability. Keywords Carbon dioxide Á Ocean acidification Á Mollusks Á Coastal waters Á Gulf of Cadiz Á Lagoon of Venice Introduction The combustion of fossil fuels by human populations is increasing atmospheric concentrations of carbon dioxide (CO 2 ) at an unprecedented rate. It is now unequivocally accepted that this is causing global climatic changes, with noticeable increases in global temperature, sea level rise and changes to marine carbon chemistry (Meehl et al. 2007). Global average surface air temperature has increased by about 0.7–0.8 °C during the last century (Hansen et al. 2006) and further warming, ranging from 1.8 P. Range (&) Á M. A. Chı ´charo Á R. Ben-Hamadou Á D. Pilo ´ Á L. Chı ´charo CCMAR, Universidade do Algarve, Faro, Portugal e-mail: prange@ualg.pt Present Address: R. Ben-Hamadou Department of Biological and Environmental Sciences, College of Arts and Sciences, Qatar University, Doha, Qatar M. J. Fernandez-Reiriz Á U. Labarta CSIC, Instituto de Investigaciones Marinas, Vigo, Spain M. G. Marin Á M. Bressan Á V. Matozzo Á A. Chinellato Á M. Munari Department of Biology, University of Padova, Padova, Italy N. T. El Menif Á M. Dellali Department of Biology, University of Carthage, Carthage, Tunisia Present Address: L. Chı ´charo CIMA, Universidade do Algarve, Faro, Portugal 123 Reg Environ Change DOI 10.1007/s10113-013-0478-7