MUSSEL BEDS MODULATE WEATHERING REGIMES AND REDUCE THE EROSION OF FRIABLE INTERTIDAL PLATFORMS

JORGE LUIS CEFERINO GUTIERREZ; GONZALEZ, J. A.; COOMBES, M.A.; BAGUR, M.; SORIA, S. A.; PALOMO, M.G.

Mar del Plata

Congreso; XVIII Congreso Latinoamericano De Ciencias del Mar; 2019

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 sessile organisms that coverthe surface of intertidal platforms can have ―bioprotective‖ effects by reducing theimpacts of physical weathering and erosion agents (e.g., Coombes et al. 2017). Themid to high elevations of intertidal platforms fronting eroding cliffs in coastal BuenosAires Province (Santa Clara del Mar to Miramar; 37°50? to 38°20?S) are dominated bybed-forming mussels (Brachidontes rodriguezii). In this study we investigated whethermussel cover protects the friable, consolidated sediment platforms at PlayaCopacabana (38°14?S, 57° 46?W) from weathering and erosion. By means of musselremoval experiments we illustrated that mussel cover attenuates variations in platformsurface temperatures, enhances moisture retention during low tide, and reduces ratesof salt crystallization within the sediment pores. Mussel removal has also led to 10 %decreases in surface hardness and 2 mm reductions in platform height after 5 months.Collectively, our findings indicate that mussel beds reduce the potential for substratebreakdown via heating-cooling, wetting-drying, and salt crystallization, thus protectingfriable platforms from erosion. As intertidal platforms protect the cliffs behind from thehydraulic impact of waves (see Moses 2014), we posit that the protection of platformsby mussels might indirectly moderate coastline retreat rates.