Enrichment of CO2 in marine ecosystem: effects on marine bivalve Chamelea gallina

Oceans absorb 30% of the anthropogenic CO2 release in the atmosphere (IPCC 2014). With climate change, marine ecosystems are mainly exposed to rising temperature and ocean acidification. The principal consequences of adding CO2 to seawater is to decrease the concentration of carbonate ion and lower pH. These impacts can affect marine calcifying organisms such as bivalves to produce their CaCO3 shell or compromise their fitness. The IPCC proposes Carbon dioxide Capture and Storage (CCS) in the context of a measure for mitigating climate change consequences, however a leakage of CO2 could have negative environmental implications. The research work presented investigates the possible pH effects on marine bivalve C. gallina induced by acidification with a specific aim of assessing how benthic calcifying organisms react to a CO2 leakage or more generally to the coming changes in climate. Potential CO2 leakage could re-suspend high quantities of sediments and contaminants associated with negative effects for marine biota. Therefore, a secondary purpose is to investigate the effects on clams produced by interaction among acidification and an emerging contaminant such as microplastics. Three types of analysis were performed in the study: (1) survival rate of the clam under stressful conditions; (2) physical-chemical analysis of the principal components of shell calcification; (3) histopathological analysis in gills tissues to quantify the induced lesions. The data obtained revealed a significant low survival rate of clam C. gallina in relation to a pH reduction, with a limited ability to form calcified structures and disturbed metabolic activities. The study suggests that acidification induced by CO2 leakage can damage the gills of clams, instead it showed a non significant interaction with microplastics. Future research is needed to understand and predict the biological effects and economic implications for marine ecosystem resulting from CO2 leakage.