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Seminar Abstract

Are Strom - May 16, 2001

Environmental history from a geoduck's perspective

Geoducks are the largest burrowing clams in the world. They are native to coastal and estuarine waters ranging from California to Alaska, and are among the longest-lived bivalves known. Internal growth rings in geoduck shells are deposited annually, and shell accretion in samples obtained from several sites in the Straits of Juan de Fuca and SE Alaska appears to be limited by water temperatures. We are measuring growth increment widths present in thin-sections extracted from the hinge area of the shells. Images of the growth rings are being obtained using a combination of scanning electron and light microscopy. A growth chronology has been constructed for the Straits of Juan de Fuca sites spanning the last 160 years, and samples from both the Washington and SE Alaska sites indicate a strong relationship between geoduck growth and 20th century temperature records. While the present chronology is constructed entirely from the shells of recently living clams, much older shell material can be obtained from a variety of sources and could potentially be used to reconstruct ocean temperatures over several centuries. Such a reconstruction would be especially useful for exploring relationships between shifts in ocean temperature and historical changes in marine ecosystems.

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