Macrofaunal colonization of mine tailings impacted sediments.

•Effects of mine tailings on benthic colonization were experimentally studied.•All sediments capped with mine tailings were successfully colonized within 6 months.•Abundances of annelids were lower, while mollusks were higher in tailings treatments.•Fine-grained tailings with remnants of flotation chemicals had most profound effects.•In the mixing zone outside the STD, the extent of effects will vary between tailings.