Abstract
The organisms inhabiting intertidal platforms can affect their weathering and erosion rates. Research on biotic influences on platform integrity has traditionally emphasized the role of bioeroders (i.e., organisms that scrap or bore into platforms via mechanical and chemical means). Yet, recent studies illustrate that covers of sessile organisms on the surfaces of intertidal platforms can have bioprotective effects by reducing the efficacy of physical weathering and erosion agents. Eroding cliffs fronted by cohesive shore platforms are a pervasive feature along the continental Argentinean coastline (37–52°S). In this study, we investigated how mussel (Brachidontes rodriguezii) cover mediates weathering and erosion of a cohesive, consolidated silt platform at Playa Copacabana (5 km north of Miramar, Buenos Aires Province; 38° 14′ S, 57° 46′ W). By means of mussel removal experiments, we found that mussel cover attenuates variations in platform surface temperatures, enhances moisture retention during low tide, reduces rates of salt crystallization within the pores of the platform material, and attenuates hydrodynamic forcing on the platform surface. Mussel removal also led to a 10% decrease in surface hardness and a 2-mm reduction in platform height after 5 months. Collectively, our findings indicate that mussel beds limit substrate breakdown via heating-cooling, wetting-drying, and salt crystallization and provide some of the first experimental field evidence for the direct impacts of biotic cover on platform erosion. As intertidal platforms protect the cliffs behind from the hydraulic impact of waves, which may be enhanced with future sea-level rise, we posit that the protection of platforms by mussels indirectly moderates coastline retreat, especially on soft cohesive shores.
Highlights
Shore platforms are horizontal or gently sloping rock surfaces usually backed by cliffs that are widespread throughout the world’s intertidal zones (Trenhaile, 1987; Sunamura, 1992)
There is, no manipulative experimental field evidence for the direct impacts of biotic cover on platform weathering and erosion. Evaluating such effects is especially relevant on relatively soft cohesive shore platforms, where erosion can proceed quickly relative to the time taken for the recovery of some sessile organisms (e.g., 5 years for mussels and erect macroalgae; Micheli et al, 2016) following mortality and/or dislodgement (Charman et al, 2007; Moses, 2014)
Our findings illustrate that both weathering regimes and wave-driven processes can be attenuated by mussel cover on intertidal cohesive shore platforms
Summary
Shore platforms are horizontal or gently sloping rock surfaces usually backed by cliffs that are widespread throughout the world’s intertidal zones (Trenhaile, 1987; Sunamura, 1992). The evidence available to date indicates that covers of sessile organisms, such as seaweeds or barnacles, can limit the impacts of physical weathering agents on shore platforms via a range of mechanisms This includes moisture retention and buffering effects on temperature variations, which are thought to reduce the efficacy of substrate weathering via heatingcooling, wetting-drying, and salt crystallization (Stephenson and Kirk, 2000; Moura et al, 2012; Gowell et al, 2015). Improving our understanding of biogeomorphological processes is crucial to inform predictions of coastline responses to climate change, including shifts in the spatial arrangement of organisms and physical processes as a result of sea-level rise
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
