Faunal engineering stimulates landscape-scale accretion in southeastern US salt marshes

Abstract

The fate of coastal ecosystems depends on their ability to keep pace with sealevel rise-yet projections of accretion widely ignore effects of engineering fauna. Here, we quantify effects of the mussel, Geukensia demissa, on southeastern US saltmarsh accretion. Multi-season and -tidal stage surveys, in combination with field experiments, reveal that deposition is 2.8-10.7-times greater on mussel aggregations than any other marsh location. Our Delft-3DBIVALVES model further predicts that mussels drive substantial changes to both the magnitude (+/-<0.1 cm center dot yr(-1)) and spatial patterning of accretion at marsh domain scales. We explore the validity of model predictions with a multi-year creekshed musselmanipulation of >200,000 mussels and find that this faunal engineer drives far greater changes to relative marsh accretion rates than predicted (+/->0.4 cm center dot yr(-1)). Thus, we highlight an urgent need for empirical, experimental, and modeling work to resolve the importance of faunal engineers in directly and indirectly modifying the persistence of coastal ecosystems globally.