Estuarine oiling increases a long-term decline in mussel growth

The ribbed mussel, Geukensia granosissima, cycles nutrients, contributes to soil stability, and can be a major component of predator-prey communities in salt marshes. Mussels were exposed the 2010 Deepwater Horizon oil spill Gulf Mexico, marshes remain contaminated eight years later. We hypothesized that oiled mussels had reduced annual growth, altered population size frequency, perhaps changed valve morphometrics. sampled 10 near Port Sulphur, LA, measure morphometrics 133 their age-specific growth rate, also marsh content percent vegetative cover. relationships between weight, length biomass weight stable as aged. A Year 1 decline from 1994 2018 is not easily explained by estuarine acidification, flooding, temperature rise; freshening waters suggested probable causal factor declining rate. average dry per declined with oiling 2010. multiple regression equation using cover concentration described 70% variation length. Sites highest few 14 bands more younger compared sites lowest oiling. Valve for four after was compensated higher rates older mussels. Annual below amount predicted five spill. Mussel populations may have been structured predators responsive subtle ways.