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An experiment was conducted using microcosms with connected sedimentary compartments to assess the effects of three polycyclic aromatic hydrocarbons (PAHs) on free-living marine nematodes from Bizerte Bay (northeastern Tunisia). Over 30 days, the nematofauna were exposed to four treatment sediments, including one with chrysene (150 ppb), chrysene (150 ppb) plus fluoranthene (75 ppb), chrysene (150 ppb) and phenanthrene (15 ppb), and an uncontaminated reference. Numerical and qualitative community simplifications occurred in contaminated sediments relative to the reference. The diversity of nematodes differed based on hydrocarbon combinations. Multivariate analyses revealed communities in contaminated compartments differed from those in the initial natural sediment and reference. Differences in sensitivities of nematodes to hydrocarbons and in migratory abilities occurred. Rhabditis sp., Calamicrolaimus honestus, and Oncholaimus campylocercoides were in all compartments and classified as tolerant to PAHs. Nematodes observed only in control compartments, including Parasphaerolaimus paradoxus, Encheliidae (sp.), Trichotheristus mirabilis, and Theristus pertenuis were considered sensitive. Keywords: Microcosm, Free-living marine nematodes, Polycyclic aromatic hydrocarbons, Migration, Abundance, Species diversity