tA meso-scale pilot plant was set up to test the efficiency of a bioremediation scheme applied to marinesediments contaminated by heavy metals and hydrocarbons. The experiment was implemented forthree years in two stages using two remediation agents: plants (Paspalum vaginatum and Tamarix gal-lica) and earthworms (Eisenia fetida). DNA and RNA-based methodologies were applied to elucidate thedynamics of the bacterial population and were related to improving biological and chemical conditionsof the sediments. Bioremediation strategies were successful in removing pollutants from the contami-nated sediments and specialization within the bacterial community related to the type of contaminationpresent was detected in the different stages of the process. The highest response of Gram-positive PAH-degraders to the contamination was detected at the beginning and after the first stage of the experiment,corresponding to the uppermost values of degradation.