Elevated CO2 Levels do not Affect the Shell Structure of the Bivalve Arctica islandica from the Western Baltic

Shells of the bivalve Arctica islandica are used to reconstruct paleo-environmental conditions (e. g. temperature) via biogeochemical proxies, i.e. biogenic components that are related closely to environmental parameters at the time of shell formation. Several studies have shown that proxies like element and isotope-ratios can be affected by shell growth and microstructure. Thus it is essential to evaluate the impact of changing environmental parameters such as high pCO(2) and consequent changes in carbonate chemistry on shell properties to validate these biogeochemical proxies for a wider range of environmental conditions. Growth experiments with Arctica islandica from the Western Baltic Sea kept under different pCO(2) levels (from 380 to 1120 mu atm) indicate no affect of elevated pCO(2) on shell growth or crystal microstructure, indicating that A. islandica shows an adaptation to a wider range of pCO(2) levels than reported for other species. Accordingly, proxy information derived from A. islandica shells of this region contains no pCO(2) related bias.