We estimated taxon-level body mass using a biological trait database of Northwest European benthos. The total biomass for each sample was then calculated as the sum of taxon-specific biomasses. We then calculated three diversity metrics: total abundance, species richness, and Pielou’s evenness. The mean individual body mass at each sample was calculated by dividing total biomass by total abundance. 
All taxa were assigned into one of the six feeding groups based on their dietary information: detritivore, scavenger, grazer, filter feeder, predator, and parasite. We assumed the exitstence of nine basal resources at all sampling sites (carrion, bacteria, CPOM, FPOM, fungi, macroalgae, and protists) and assigned subsets of them to primary consumers (detritivore, filter feeder, grazer, and scavenger). We established trophic interactions at the taxon level for predators and parasites using a metaweb approach. For each sample, the local food web was constructed as the subset of trophic interactions from this metaweb for taxa observed. We then calculated nine food web topological metrics: proportions of basal, intermediate, and top species, mean trophic level, standardized deviations of normalised generality and vulnerability, link richness, linkage density, and connectance. 
The 17 structures were split into three scenarios: 2 structures in scenario 1 (samples before decommissioning and short-term <1 year after decommissioning), 14 structures in scenario 2 (post-decommissioning samples at the medium term: 1-5 years after decommissioning), and 1 structure in scenario 3 (samples before decommissioning and long-term >5 years after decommissioning). The analysis adopted a difference-in-difference design to account for background environmental changes unrelated to decommissioning. We compared the changes in the impact zone with concurrent changes in the control zone for each scenario and quantified the effects based on Hedge’s g effect size. The magnitude and directionality of each effect size for each chemical variable and ecological metrics showed the effects of decommissioning.