To examine invertebrate resiliency after the 2010 Deepwater Horizon oil spill, we monitored the recovery of macroinfauna in replicated reference, moderately and heavily oiled salt marshes in Barataria Bay Louisiana for 8.5 y after the spill. Plants suffered near 100% mortality in heavily oiled marshes, profoundly altering the sedimentary environment. Plants in moderately oiled marshes did not suffer extensive mortality but experienced reduced above- and belowground plant biomass. A community analysis based on 40 macroinfaunal taxa was conducted during early, 2011–2012, middle, 2013–2017 and late, 2017–2018, stages of recovery. The early stage was marked by very low taxonomic diversity and low total macroinfaunal abundance in all marshes, while the middle stage was denoted by relatively high diversity and very high abundances in heavily oiled marshes where densities far exceeded reference and regional means. The community in the heavily oiled marshes diverged from reference and moderately oiled marshes during the middle recovery period when the crustaceans Apocorophium louisianum and Leptochelia rapax, the polychaete Alitta succinea, and oligochaetes dramatically increased in abundance, while at the same time, abundance increases of the polychaetes Manayunkia aestuarina, Streblospio gynobrachiata, and Capitellidae sp. lagged behind increasing trends at reference and moderately oiled sites. Macroinfaunal community similarity in moderately oiled marshes differed from reference and heavily oiled marshes in all three recovery stages but did not differ from reference sites on the last collection date. Heavily oiled community similarity not only differed from moderately oiled and reference marshes in all three recovery stages but remained different from reference sites on the last collection date. These observations indicate that moderately oiled marshes recovered by about 8 years, but that heavily oiled marshes require more than a decade to achieve resiliency.
