Meeting Abstract

66.3  Monday, Jan. 6 08:30  Thermal Stress and Energetics in the Ecological Dominant Marine Mussel Mytilus californianus along Within-Shore Environmental Gradients CONNOR, K.M.*; GERMAN, D.P.; GRACEY, A.Y.; Univ. of California, Irvine; Univ. of California, Irvine; Univ. of Southern California kconnor@uci.edu

The mussel Mytilus californianus aggregates to form beds that dominate the intertidal zone along the rocky coastlines of western North America. During low tide, mussels are exposed to the air and show marked resilience to solar heating, limited oxygen and lack of food. The chronic heat stress and lower feeding time of high shore mussels is reflected in slower growth rates and smaller terminal sizes. While the physiological responses of mussels along the tidal (vertical) gradient are well known, less is known about these responses along the wave exposure (horizontal) gradient: from wave-exposed to wave-sheltered microhabitats. In this study, we investigated mussel physiology in response to horizontal microhabitat variation by first developing markers of energy intake level including measurements of digestive enzyme activity and digestive enzyme gene expression in the digestive gland. Experimentally, we subjected mussels to low, mid and high food feeding treatments and measured enzyme activity and gene expression. We then collected mussels from wave exposed and wave sheltered sites during low tide and assayed the tissues for digestive enzyme activity and gene expression, and levels of heat shock protein. We predict that at a given shore level, variation in heat stress along the horizontal gradient will be greater than that of food intake, suggesting that temperature plays a significant role in reduced growth grates in wave sheltered microhabitats. These results will have marked implications for future predictions regarding the influence of Global Climate change on mussel populations, as it shows that the horizontal microhabitat gradient may be as important as the vertical one.