SCHNEIDER, KR*; HELMUTH, BST; University of South Carolina; University of South Carolina: The effect of intertidal thermal environments on survival and growth: a comparison between an invasive and native mussel species

The harsh and dynamic conditions of the rocky intertidal zone present an excellent system to examine how physiological constraints may contribute to species distribution patterns. Here, we use two mussel species, Mytilus galloprovincialis and M. trossulus , to address the role that both aerial and emersion temperature plays in such patterns. On the west coast of the United States, M. galloprovincialis was introduced ~100 years ago into Southern California replacing the endemic mussel, M. trossulus , they currently overlap in distribution in Central California. Laboratory experiments were completed under simulated intertidal conditions in both 18�C and 12�C water. Within each water temperature regime, four aerial exposure treatments were constructed including hot, warm, cool and no aerial (i.e. subtidal) exposure. In 18�C water survival was low for M. trossulus and high for M. galloprovincialis regardless of aerial exposure treatment. In contrast, aerial exposure affected survival of both species in 12�C water, although survival rates were lower for M. trossulus than M. galloprovincialis . This effect was only seen in mussels collected during the winter and was not observed in summer collected mussels. Additionally, growth was negatively affected by aerial exposure in both mussel species. Growth was higher in M. galloprovincialis than M. trossulus. Data indicate that M. galloprovincialis survival and growth are higher in all conditions tested when compared to M. trossulus . This may be a significant explanation for why this species has successfully invaded several locations around the world.