Near-future levels of p CO 2 impact skeletal weights of coral primary polyps ( Acropora digitifera )

Ocean acidification poses a severe threat to corals; declines in carbonate ion concentrations caused by increasing atmospheric CO2 partial pressure (pCO2) can severely impact coral calcification. Thus, there is an urgent need to understand the impacts of near-future ocean acidification on corals. In this study, we compared the effects of seawater at present and near-future pCO2 (approximately +200 μatm) levels on skeletal weights of new coral recruits. Experiments were carried out using precisely pCO2-controlled aquaria supplying stable pCO2-controlled seawater in a flow-through system. Our results show that skeletal weights of new coral recruits decreased significantly at +200 μatm pCO2, which is expected to be reached within this century if ocean acidification continues at the present pace.