Sclerochronological Analysis of Two Contemporary Continental Shelf Bivalves and its Paleoceanographic Significance

Undergraduate: Ricardo Garcia

Faculty Advisor: Joel Hudley
Department: Computer Science

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Bivalve shells contain a record of their ontogeny (growth history), in the form of internal growth lines observed microscopically in sectioned shells (analogous to tree-rings). The analysis of these repeating shell structures (sclerochronology) has been shown to have considerable potential for recording environmental changes, (e.g. seasonal seawater temperature changes, storms, and disturbance) as well as anthropogenic perturbations (e.g. trawling activities). Recent temperature variations in the western Atlantic have impacted the biogeographic ranges of benthic, infaunal organisms and evidence of this thermal shift is likely encoded in the shells of long-lived organisms. The bivalves Arctica islandica, the ocean quahog, and Hemimactra (Spisula) solidissima, the Atlantic surf clam, are long-lived species often reaching ages of 20-200 years. Surveys conducted by the National Ocean and Atmospheric Administration Northeast Fisheries Science Center (NOAA-NEFSC) obtained live samples from across the Middle Atlantic Bight (MAB) during the summers of 1994 and 1997 and previous aging and growth studies have revealed maximum ages of 203 y for A. islandica and 26 y for S. solidissima. This work focuses on achieving cross-matching growth records from across the MAB for both archetypical bivalve proxies. By producing and then comparing these two separate bivalve chronologies, we may be able determine what local and regional environmental variabilities influence the species¿¿¿ shell inc