Feeding physiology of suspension-feeding bivalves: Inter- and intraspecific plasticity

Abstract

Suspension-feeding bivalves play important ecological roles in many marine environments, functioning as links between pelagic and benthic ecosystems, and providing habitat and food for invertebrates and juvenile fish. Through fisheries and aquaculture, bivalves also play important socio-economic roles in many coastal communities, providing jobs and a source of sustainable protein. One of the most well-studied characteristics of bivalves is their suspension-feeding mechanism, which allows them to filter plankton from water with high efficiencies and is one of the primary ways that they interact with their ecosystems. In light of the socio-ecological importance of suspension-feeding marine bivalves, the goal of this thesis is to contribute to the mechanistic understanding of how bivalves acquire energy through suspension feeding. First, an overview of processes that mediate energy acquisition and expenditure, and the extent to which they are subject to plasticity and adaptation is examined in suspension-feeding bivalves. Next, plasticity in feeding physiology is examined both interspecifically and intraspecifically, using a combination of field and laboratory experiments. The results of these experiments show both inter- and intraspecific variability in the feeding physiology of bivalves. Interspecifically, relationships between particle capture efficiency and pumping rate were observed to vary between species of bivalves from different families. Intraspecifically, in the blue mussel, Mytilus edulis, plasticity in feeding physiology was observed as mussels were transplanted along a fjord gradient, and high levels of variability in feeing physiology were observed both between and within individuals during 4-day experiments. Finally, recommendations are made for future experiments to observe suspension-feeding mechanisms in marine bivalves. Understanding the mechanisms of suspension-feeding in bivalves is a primary step in predicting how the ecological role of bivalves changes between species and environments.