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

GUTIÉRREZ, JORGE L.; GONZÁLEZ, JULIANA A. ; COOMBES, MARTIN A. ; BAGUR, MARÍA; SORIA, SABRINA A.; PALOMO, MARIA GABRIELA

Mar del Plata

Congreso; XVIII Congreso Latinoamericano de Ciencias del Mar-COLACMAR; 2019

The organisms inhabitingintertidal platforms can affect their weathering and erosion rates. Research onbiotic influences on platform integrity has traditionally emphasized the roleof bioeroders (i.e., organisms that scrap or bore into platforms via mechanica andchemical means). Yet, recent studies illustrate that sessile organisms thatcover the surface of intertidal platforms can have ―bioprotective‖ effects byreducing the impacts of physical weathering and erosion agents (e.g., Coombeset al. 2017). The mid to high elevations of intertidal platforms frontingeroding cliffs in coastal Buenos Aires Province (Santa Clara del Mar toMiramar; 37°50? to 38°20?S) are dominated by bed-forming mussels (Brachidontesrodriguezii). In this study we investigated whether mussel cover protectsthe friable, consolidated sediment platforms at Playa Copacabana (38°14?S, 57°46?W) from weathering and erosion. By means of mussel removal experiments weillustrated that mussel cover attenuates variations in platform surfacetemperatures, enhances moisture retention during low tide, and reduces rates ofsalt crystallization within the sediment pores. Mussel removal has also led to10 % decreases in surface hardness and 2 mm reductions in platform height after5 months. Collectively, our findings indicate that mussel beds reduce thepotential for substrate breakdown via heating-cooling, wetting-drying, and saltcrystallization, thus protecting friable platforms from erosion. As intertidalplatforms protect the cliffs behind from the hydraulic impact of waves (seeMoses 2014), we posit that the protection of platforms by mussels mightindirectly moderate coastline retreat rates.