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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·yr−1) and spatial patterning of accretion at marsh domain scales. We explore the validity of model predictions with a multi-year creekshed mussel manipulation of >200,000 mussels and find that this faunal engineer drives far greater changes to relative marsh accretion rates than predicted (±>0.4 cm·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.

Crotty, S.M., Pinton, D., Canestrelli, A., Fischman, H., Ortals, C., Dahl, N.R., Williams, S.L., Bouma, T.J. and Angelini, C. 2023. Faunal engineering stimulates landscape-scale accretion in southeastern US salt marshes. Nature Communications. 14(881). (DOI: 10.1038/s41467-023-36444-w)