Spartina anglica lignocellulosic biomass was placed in a natural salt marsh (Welwick, Humber, UK) and allowed to decompose for 16 weeks. During weeks 1-6, 8, 10 and 16, biomass was harvested and phylogenetic metabarcoding was conducted. Five biological replicates (delineated A, B, C, D and E) were placed along a 300m transect. A day 0 sedimentary outgroup was included for a total of 46 datasets (5 replicates, 9 timepoints, 1 day 0).