Meeting Abstract
The sessile intertidal mussel Mytilus californianus is a sentinel of Global climate change because its distribution, abundance and growth are ultimately set by environmental constraints on resource acquisition, allocation and thermal stress. Mussels residing highest (vertically) on the shore live at the fringes of their bioenergetic capacity because of limited access to food and subjection to higher temperatures. While thermal stress has been studied comprehensively in these organisms, investigations of resource acquisition and digestive physiology are lacking. To assess digestive physiology in mussels, we measured the activity of several digestive enzymes that digest proteins and carbohydrates, metabolic rate, clearance rate, and digestive efficiency in individuals subjected to low, medium and high food rations under controlled conditions. We used these parameters to estimate scope for growth for each feeding condition. The stress imposed by feeding level was further expanded upon from environmental and biological data collected in the field. As expected, digestive enzyme activity and scope for growth increased with rising food ration under controlled conditions. Furthermore, field measurements revealed that populations in wave-protected, high-intertidal areas where temperatures are high and food availability low are bioenergetically challenged more than those in other spatially separated microhabitats (including wave-exposed, high-intertidal areas). This investigation will help to identify, more precisely, populations under environmental stress within a shore and predict their vulnerability to the negative impacts of Global Climate Change.
