Far from Boring: Grazing the Surface of Tide Pool Topography and Bioerosion

Tide pools are havens for ecosystems high in species richness and diversity. Though the rocky topography that hosts these pools has been extensively studied, the interactions between topography and intertidal ecology is poorly constrained. Past work advocates for bidirectional feedbacks between rocky coast topography and intertidal organisms. For example, a location's patina of organisms might affect weathering and erosion rates due to biologic processes (i.e., boring, grazing, and chemical cementation) completed throughout numerous life cycles. Here, we seek to examine the feedbacks among substrate strength, topography, and intertidal organisms. We collected data in six locations along the Oregon Coast that have a wide range of rock types and strength. At each site, we documented intertidal species, rock hardness, and topography along transects that varied between 40m and 100m long, oriented perpendicular to the shoreline. Intertidal organisms were grouped by their interaction with the substrate, i.e. plucking, grazing, or boring. To determine whether intertidal organisms control rock strength and topography (or vice versa), we performed multivariate statistics (e.g., ANOVA, MRA, and URT) on the dataset, including confounding abiotic variables that may affect rock strength, such as wetness, aspect, and rock type. Preliminary results suggest a relationship between rock hardness and organism-driven erosion, and indicate that organism type varies with rock type. These results suggest that biology facilitates erosion, and that this role may be more central than generally recognized. However, our work also indicates that rock type is a primary control in dictating habitat suitability, analogous to the manner in which tidal zone can determine species composition. This work points to a set of complex feedbacks between intertidal ecosystems and rocky coast topography, that when integrated over geologic time, may have implications for the preservation and erosion of marine terraces.