Marine biofilms were established on glass beads with or without deliberate pre-exposure to LAS (20 mg/L) in Spain (Cadiz) and Sweden (Kristineberg). The ability of each community to mineralize LAS (100 mg/L) was then assessed in biometers at four experimental temperatures (between 6 and 21 1C). Genetic diversity and biomass of the biofilms were assessed by genetic fingerprinting (DGGE) and direct bacterial counts. With biofilms fromSweden, where LAS was not detected in seawater (n¼3), deliberate pre-exposure to LAS resulted in lower genetic diversity and higher mineralization rate constant; however, with biofilms from Spain, where 6.473.9 mgLAS/L (n¼3) was measured during the colonization, pre-exposure did not affect the bacterial community. Bacterial acclimation therefore appeared to have been induced at environmental concentrations o6 mgLAS/L. Environmental pre-exposure was not a pre-requisite for featuring the full consortia of LAS degraders in the biometers. The mineralization rate was described using an Arrhenius equation at experimental temperatures within the typical annual range; however, they departed from this model below this range. ; info:eu-repo/semantics/published