Growth and population dynamics of the Mediterranean endemic solitary coral Balanophyllia europaea living along a natural pCO2 gradient

ncreasing research effort on marine calcifying organisms is important and urgent, given the projected CO2-driven ocean acidification for the coming century. Here we assess the growth and population dynamics of the Mediterranean endemic zooxanthellate solitary coral Balanophyllia europaea at three sites along a natural pCO2 gradient of the volcanic vents off Panarea Island (Italy). B. europaea was the only scleractinian found along the gradient. The age-length relationships obtained for each site by dating corals by means of computerized tomography resulted homogeneous, then a general age-length relationship was calculated. Growth parameters (linear extension rate, bulk skeletal density, and net calcification rate) were obtained for each site. While linear extension rate did not vary with pCO2, bulk skeletal density and net calcification rate decreased with increasing pCO2. At each site, the age structure was obtained, and several observed and theoretical demographic parameters were derived (age structure stability, istantaneous rate of mortality, average age, % of immature individuals, age at maximum biomass, average age of biomass) and compared among sites. The results are discussed in relation to the envisaged ocean acidification scenarios