Enhanced Weathering and Erosion of a Cohesive Shore Platform Following the Experimental Removal of Mussels

GONZALEZ, JULIANA A.; COOMBES, MARTIN A.; PALOMO, M. GABRIELA; ISLA, FEDERICO I.; SORIA, SABRINA A.; GUTIÉRREZ, JORGE L.

FRONTIERS IN MARINE SCIENCE

Frontiers Media SA

Año: 2021 vol. 8

2296-7745

The organisms inhabiting intertidal platforms can affect their weathering and erosionrates. Research on biotic influences on platform integrity has traditionally emphasizedthe role of bioeroders (i.e., organisms that scrap or bore into platforms via mechanicaland chemical means). Yet, recent studies illustrate that covers of sessile organismson the surfaces of intertidal platforms can have bioprotective effects by reducing theefficacy of physical weathering and erosion agents. Eroding cliffs fronted by cohesiveshore platforms are a pervasive feature along the continental Argentinean coastline(37?52◦S). In this study, we investigated how mussel (Brachidontes rodriguezii) covermediates weathering and erosion of a cohesive, consolidated silt platform at PlayaCopacabana (5 km north of Miramar, Buenos Aires Province; 38◦ 140 S, 57◦ 460 W).By means of mussel removal experiments, we found that mussel cover attenuatesvariations in platform surface temperatures, enhances moisture retention during lowtide, reduces rates of salt crystallization within the pores of the platform material, andattenuates hydrodynamic forcing on the platform surface. Mussel removal also led toa 10% decrease in surface hardness and a 2-mm reduction in platform height after5 months. Collectively, our findings indicate that mussel beds limit substrate breakdownvia heating-cooling, wetting-drying, and salt crystallization and provide some of the firstexperimental field evidence for the direct impacts of biotic cover on platform erosion. Asintertidal platforms protect the cliffs behind from the hydraulic impact of waves, whichmay be enhanced with future sea-level rise, we posit that the protection of platforms bymussels indirectly moderates coastline retreat, especially on soft cohesive shores.