Dataset for manuscript: Burrowing crabs weaken mutualism between foundation species - Ecosystems 2018. The dataset contains the data on the experiment and field survey carried out in 2014 and 2015.The experiment lasted 16 months and was designed to test how the overlapping presence of two foundation species (cordgrass -Spartina alterniflora, and ribbed mussels -Geukensia demissa) in a southeastern US saltmarsh influenced the abundance of a facilitated species (fiddler crabs - Uca pugnax), and how this species affected each foundation species and their mutualistic interaction. In addition a field survey was conducted spanning 700 km of southeastern US coastline to assess the generality of the interactions found in the experiment. The full methodology can be found in the paper, linked below.