A ‘clam-ring’ master-chronology constructed from a short-lived bivalve mollusc from the northern Gulf of California, USA

Abstract

Age-detrended and standardized annual growth increment width time series of 67 live-collected intertidal bivalve molluscs of the species Chione cortezi, C. fluctifraga and C. californiensis from the northern Gulf of California were strung together to form a master-chronology that covers the period from ad 1982 to 1999. A high positive correlation was found between standardized annual growth rates and summer sea-surface temperatures and river flow volume in the period 1988–99; and 63–76% of the variation in mean relative annual growth rates of Chione spp. is explained by temperature and river flow. Seven dead-collected specimens were cross-dated with the master-chronology permitting the reconstruction of the year of hatching and death for these shells. The incorporation of dead-collected specimens in the master-chronology improved the corre lation statistics slightly. Species-related growth differences were not significant, but geographic differences in growth rates occur: individuals at the Colorado River mouth grew more slowly when large amounts of fresh water reached the Gulf. This study demonstrates that even short-lived molluscs (average 6–10 years old) can be used to build a master-chronology of environmental and climatic history.