A LATE HOLOCENE SCLEROCHRONOLOGICAL ANALYSIS OF THE BIVALVE ARCTICA ISLANDICA FROM THE MID-ATLANTIC BIGHT

Recent temperature variations in the western Atlantic have impacted the biogeographic ranges of benthic, infaunal organisms Evidence of this thermal shift is likely encoded in the shells of long-lived organisms. Past marine climate variations were reconstructed using the annual growth patterns in the shells of Arctica islandica (Linnaeus, 1767) by previous workers. Many paleoclimate studies were completed in the intensively sampled regions around Iceland and the North Sea; however, no chronologies exist for the Mid-Atlantic Bight (MAB). The MAB is the most southern extent of A. islandica’s modern biogeographic range. The goal of this study is to reconstruct the climate of the MAB during the time of the lifespan of live collected bivalves. Surveys conducted by the National Ocean and Atmospheric Administration Northeast Fisheries Science Center (NOAA-NEFSC) obtained live samples from across the MAB during the summers of 1994 and 1997. Chronologies and growth indices were constructed to determine variations in environmental conditions during the years that the clams were alive. A total of 73 shells have been processed for sclerochronological analyses. 
 Analysis of the growth patterns revealed ontogenetic ages of up to 203 years for individual specimens. Growth increment width time-series were used to construct a composite chronology. Preliminary results indicate shell growth of contemporaneous specimens is related to SST. Ongoing analysis focuses on the interannual to multi-decadal variability of the shell increment width time series. Frequency variations in increment time series may be related to regional environmental variations from 1791-1997.