The presence of antibiotic/antimicrobial substances in the marine environment is of high concern since it potentially accelerates widespread bacterial antibiotic resistance (AR), and may have negative effects on non-pathogenic bacteria responsible for sustaining vital ecosystem functions. Our understanding of how antibiotics affect, and how AR develops and spreads in natural systems is very limited. Yet this knowledge is a prerequisite for the identification of sources and mechanisms involved in the global development of AR, which threatens to impair both ecosystem and human health. This research investigates 1) the occurrence and distribution of antibiotic resistance (AR) in marine sediment bacteria (MSB) in relation to environmental antibiotic exposure, 2) the physiological costs for sustaining AR, 3) the effect of antibiotics on MSB community structure and function and 4) the potential transfer of AR bacteria along marine food chains. Molecular methods will be applied when investigating presence of AR genes and structural changes in MSB in relation to antibiotic exposure. The outcome will contribute significantly to our knowledge on AR occurrence in MSB, effects of antibiotics on natural marine sediment systems, and show if marine sediments act as sources for AR and marine food chains as vectors for the transfer of AR bacteria to higher trophic levels.