Meeting Abstract

36.1  Tuesday, Jan. 5  Mussels, models, and mortality: exploring the respective roles of air and seawater temperatures in the southern range limit contraction of Mytilus edulis JONES, S.J.*; WETHEY, D.S.; Univ. of South Carolina; Univ. of South Carolina sierra@biol.sc.edu

Poleward range expansions and contractions have been documented for aquatic and terrestrial organisms as a result of the recent climatic warming. Presented here is the first example of a contraction of the equatorward limit of an intertidal organism along the Atlantic coast of the United States. The blue mussel, Mytilus edulis, has a historical southern limit at Cape Hatteras, North Carolina. Field experiments coupled with modeling simulations indicate that along the southern portion of its range this species is experiencing catastrophic mortality directly associated with high summer temperatures. In accordance with previously measured upper thermal limits, high levels of mortality as well as expression of the inducible heat shock protein 70 are observed after multiple consecutive daily aerial exposures to temperatures of 32°C or greater, causing shifts of vertical distribution within the intertidal. While exposures to high temperatures during low tide will cause patchy intertidal distributions and change the vertical limit, considering that M. edulis may live subtidally, water temperatures in excess of thermal tolerance will have the potential to shift a geographic range. Seasonal air and sea surface temperatures were examined at six locations along the eastern seaboard and determined to have increased by an average of 0.78–1.65°C. South of Lewes, Delaware, summer sea surface temperature have now exceeded the tolerance of this species, and have caused a southern limit contractions of approximately 350 km over the past 50 years.