Examining the dynamics of storm disturbance on intertidal mussel beds through field studies and models Patti Halpin Arizona State University, Department of Biology Winter storms in the Pacific Northwest create disturbances in the large mussel beds of the rocky intertidal zone. The size and frequency of disturbance have significant impact on the diversity and community structure of the rocky shore. The formation and recovery of gaps are affected by factors such as bed topography, disturbance size, mussel recruitment rates, and mussel growth rates. Previous work has demonstrated that sites along the Oregon coast vary in the recruitment and growth of California mussel, M. californianus. We examined how these factors might affect the dynamics of mussel bed disturbance and recovery through observation of naturally occurring disturbances, the creation of artificial disturbances, and computer models.
Results indicate that recruitment and growth of mussels have significant impacts on recovery.
Gaps created in areas of low recruitment and growth may take over 4 years to recover from severe storm years, such as those associated with El Ni o and La Ni a, while gaps in high recruitment areas with favorable food conditions can recover in 1 year. Model results show that though storm activity, recruitment and food supply for mussels are all large scale processes, an adaptation of a forest fire model that implements these processes at a local scale can have significant explanatory power. Validation of proposed mechanisms for the formation of these features requires spatial mapping of turbulence in the bottom boundary layer over the banks. Spectra of velocity estimated from the ADV data are distorted due to the presence of the body, and the goal of this project is to find a way to recover information about the tidally-forced turbulence in the bottom boundary layer from these data. Although the net production of TKE at the ADV is small, it is concentrated at relatively small scales, and hence affects the velocity spectrum principally at high wavenumbers.