Although physiological and genetic adaptation to toxic stress has been the focus of recent research, the role of lifestyle in pollution tolerance has received less attention. In this study, copper tolerance of benthic and epi-benthic species of harpacticoid copepods was investigated. Concentration-response curves were generated for populations of both species but collected at contaminated and uncontaminated estuaries. The population of the benthic species from the contaminated site showed higher tolerance than its population from the uncontaminated site. The epi-benthic species showed no inter-specific differences in tolerance. The comparison of tolerance between field collected animals of the benthic species and animals from the same population but reared in the laboratory for two generations suggested the existence of a genetic inherited tolerance. Results revealed the importance that lifestyle may have on the generation of tolerance to toxic substances and highlight a potential unforeseen role of it in maintenance of biodiversity on contaminated habitats.