MOESER, G.M.*; CARRINGTON, E.; University of Rhode Island: Causes of seasonal variation in mussel attachment: Byssal thread production and decay

The blue mussel, Mytilus edulis, maintains a strong attachment to the substrate in high energy environments by producing byssal threads. On Rhode Island shores, mussels increase attachment strength two-fold in winter in comparison to summer. While many factors could influence attachment strength (temperature, food supply, predator cues, etc.) it has been proposed that this variation is the result of increased thread production during winter months due to increased wave action. However, it remains unclear which specific aspects of wave action could potentially influence thread production. Mussels may respond not only to unidirectional flow, but also to acceleration (flow-induced vibrations of the body) or byssal loading (tension transferred from the threads to the byssal retractor muscles). This full factorial study evaluates the potential influence of these three factors on M. edulis thread production seasonally. Mussels were exposed to flow, acceleration, and byssal loading stimuli in the laboratory and the subsequent number of byssal threads produced was monitored. Results indicate that not only do all of these factors influence thread production, but contrary to our original hypothesis, thread production increases during summer. Therefore, we cannot explain the seasonal variation in attachment with varying rates of thread production due to increased wave action during winter. Instead, we present preliminary evidence that seasonal variation in attachment may be better explained by increased thread decay in summer.