Does geology matter? The relative importance of substrates and their properties to rocky intertidal communities

Understanding the effects of geology and geologic history on communities and species is imperative for interpreting community structure and species interactions.  Rocky intertidal communities, which have been a hotbed for conceptual advances in community ecology, exist in a mosaic of rock types that differ in a variety of ways.  Surprisingly, the role of substrates and their properties on shaping communities has not been adequately tested, despite increasing alteration to the world’s coastlines in the face of growing populations and industry and the replacement of natural substrates with artificial ones.  In addition to comparing communities on different substrates, this study begins to 1) identify and characterize rock properties that may be important for supporting unique communities and biofilms, and 2) investigate the role of substratum on recruitment of important herbivores, patellogastropod limpets.  Results demonstrate a clear difference between communities on natural and artificial substrates and reveal important species-specific responses to rock type and surface roughness. Additionally, surface microstructure, mineral composition, and grain size and shape may be important to communities by influencing water retentions, biofilm communities, and erosion.  Preliminary results suggest that patellogastropod recruitment and juvenile mortality may be strongly influenced by these features, which are determined by the rock properties characterized here.