CLIMATE RECORDS FROM SHELLS OF A LONG-LIVED BIVALVE MOLLUSK (ARCTICA ISLANDICA, NORTH ATLANTIC)

High-resolution, long-term and temporally equidistant data of environmental variables from marine settings of mid to high latitudes are extremely scarce. We utilize shells of the ocean quahog, Arctica islandica, as multi-proxy recorders of environmental variables over the past centuries. The ocean quahog is the longest-lived animal known as of yet that produces periodic and accretionary growth structures. Some individuals collected alive near Iceland in AD 1868 and 1986 reached ages of 221 to 376 years. Annual and daily growth increments add a calendar axis to the shell growth and geochemical records. Oxygen and carbon isotope ratios of shell carbonate can reconstruct past ocean temperatures and phytoplankton abundances. Water temperatures reconstructed from stable oxygen isotope ratios of the shells closely match ambient water temperatures during February through September. Ontogenetic trends do not occur in O- and C-isotopes. Similarly, changes in shell growth rates provide environmental proxy records. Up to 70% of the variability of annual shell growth is explained by ambient water temperature and food availability. In addition, shell growth reveals typical NAO-type periods of around seven to eight years. Faster growth rates occurred during positive stages of the North Atlantic Oscillation. Our results indicate that long-lived bivalve mollusk shells from the North Atlantic can reconstruct one of the most important circulation patterns in the Northern Hemisphere as well as water temperatures and phytoplankton concentration for periods prior to direct measurements. These findings can significantly improve Global Circulation Models and help to evaluate the human impact on climate.