A publication in next week’s edition of PNAS magazine elaborates on the effects of continued acidification of ocean waters on shellfish. Larvae of two species of shellfish commonly found along the American East Coast (Northern quahog and Atlantic bay scallop) were shown to form calcium carbonates (CaCO3) much faster in water with artificial pre-industrial CO2 levels (260 ppm) than at the present rate, which is around 390 ppm.

Moreover, by increasing CO2 concentration of the water to values over 400 ppm (expected to be reached within 5 years) malformation grew worse – with the larvae developing thinner and eroded shells.

The authors, Stephanie Talmage and Christopher Gobler of New York’s Stony Brook University, point to the possibility of ecological implications of continued rise of CO2 concentrations, like a decline in shellfish populations.

However, as CaCO3 forming marine life also plays a role in slow carbon cycles – especially were ocean floor sedimentation is likely – such ecological declines (when net concentrations of CaCO3 biomass are affected) may also hamper natural carbon sequestration, effectively serving as a positive feedback to further rises in CO2 concentrations. Damage of ocean acidification should also be linked to the geoengineering debate, as the theoretically most potent of such measures (like stratospheric distribution of sulphur aerosols) focus on albedo only – perhaps compensating a rise in temperature, but leaving the CO2 curve untouched.

(c) Rolf Schuttenhelm | www.bitsofscience.org