The aim of the experiment was to test if surface oxidation of the plastic polymer (polyethylene) would result in different microbial communities in comparison to untreated polyethylene or glass. Oxidation of plastic polymers introduces chain scissions, adds functional groups, such as carbonyl and ultimately reduces molecular weight. Previous laboratory experiments have shown that such degradation processes may allow biodegradation. To test the hypothesis that microbial communities on weathered plastic harbour higher relative abundances of known obligate hydrocarbon degrading bacteria, samples were incubated in situ in coastal water in the mediterranean (Mallorca) for two and nine days. Results showed that incidence of known oil degraders was highest after two days on the weathered plastics compared to untreated plastic and glass. These differences however, were no longer observable on day nine, suggesting that carbon from polyethylene was not a driving factor in community composition.