Meeting Abstract

28.2  Monday, Jan. 5  Large scale shrinkage: climate change and distributional contractions of Mytilus JONES, S.J.*; WETHEY, D.S.; Univ. of S. Carolina, Columbia; Univ. of S. Carolina, Columbia sierra@biol.sc.edu

Intertidal ecosystems are physically rigorous habitats which may serve as models for the effects of climate on biogeography. Organisms residing in the intertidal zone are exposed to a suite of stressful abiotic factors, such as desiccation stress and variable salinity, and must be able to cope with both water and aerial conditions. Changes in the environment can occur rapidly, and extreme temperatures may be experienced. Most organisms have latitudinally discreet biogeographical distributions. While various factors may affect these distributions, the range limits are likely to be set primarily by environmental temperature. Thus, with changing climatic conditions, the biogeographic ranges of organisms are predicted to shift polewards. Historical records indicate that the southern limit of the arctic-boreal blue mussel, Mytilus edulis, is in the vicinity of Cape Hatteras, NC. This system has been investigated to determine if temperature is the limiting factor of distribution, and whether it is contracting in a manner predictive of a warming climate. Thermal tolerance experiments were conducted to establish survivorship for a range of temperatures in both air and water, and transplant experiments were carried out at a latitudinal scale in order to determine survival in the field. A survival model was developed and predicts, with reasonable accuracy, mortality events observed in the field. Results suggest that the southern limit of Mytilus edulis on the east coast of the United States is contracting polewards. Sea surface temperatures for field sites have increased by approximately 1C since 1960. Modeling survival in relation to water and air temperature profiles indicate that both water and air temperature limit survival at southern sites, while at more northern sites observed mortality is due to aerial exposure.