Ecosystems are increasingly imperiled due to species loss, habitat alteration, and climate change. To predict how these factors may impact ecosystems in the future, we must understand how groups of interacting organisms (communities) process and assimilate energy and materials. An important question concerns whether ecosystem processes are influenced more by the combined effects of species in the community (biodiversity) or by the effects of a few abundant species (dominant species) best suited to local environmental conditions. Freshwater mussels are sediment-dwelling, filter-feeding, bivalve mollusks that live as dense, multi-species aggregations. Because they are thermo-conformers whose metabolic rate varies with temperature, they process materials differently in response to local temperature. They serve important roles in rivers and lakes by filtering organisms from the water and depositing nutrients to the bottom sediments. The relative importance of mussel communities to river function depends on river volume, flow and temperature. This study integrates physiology, community and ecosystem ecology to ask how variation in both community structure (mussel species dominance) and environment (temperature regime) affect ecosystem processes in rivers. Using laboratory stream mesocosms, species dominance will be manipulated to determine if dominant species contribute ecological services by providing the highest contribution of ecological processes at their preferential temperature or by facilitating other species in the community. Freshwater mussels are a highly imperiled group and results of this project will contribute to their conservation and management. In addition, this research will be used for teaching trophic ecology to undergraduate students.
