Department of Marine Science
Spatial Realism in the Mussel Bed Disturbance Paradigm
As part of a collaboration with California State University, Los Angeles and the University of California at Los Angeles our lab group is participating in a project to enhance our understanding of how disturbance structures natural communities.
Our understanding of how physical disturbance shapes the structure of populations and communities owes much to field studies of wave-generated gap formation in mussel beds. Prior studies depict mussel beds as a non-equilibrium system, in which disturbance is spatially unpredictable, generating a random patchwork of mussel cover and gaps. The proposed work would test assumptions and predictions of an alternative view – that disturbance shows predictable landscape patterns that depend not merely on spatial distribution of external forcing (wave stress) but also on biological processes determining the structure of the aggregation. Specifically, spatially varying mussel productivity (recruitment and growth), physiological stress, and predation interact to produce landscape patterns in the structure of the mussel cover. Certain regions of the mussel bed develop as mono-layers attached directly to the rock, resisting disturbance. Other regions develop in multi-layered configurations that when very deep force superficial mussels to attach solely to adjacent mussels instead of the rock surface, and cause interior mussels to only weakly attach to either rock or one another, favoring propagating disturbances. Therefore, spatial patterns of gap formation and recovery emerge from a unified landscape process.
Field work emphasizes construction of a detailed GIS database using geospatial sampling methods applied to mussel bed sites in Barkley Sound, British Columbia. GIS data layers for each site will include wave force, topography (tidal height, slope, and aspect), mussel size structure, mussel bed thickness, differentiation of layering, and size-specific attachment strengths stratified by layer. GIS interpolations and regression analyses will used to first examine assumptions of the hypothetical landscape process and then test specific predictions regarding spatial patterns in the occurrence of disturbance and recovery. Finally, controlled field experiments will test the key proposition that different mussel bed structures cause different resistance to, extent of, and recovery from disturbance. Funding for this project is being provided by the National Science Foundation.