The results from the comparison between the two summer periods, coming from all the biotic indices, pointed out that, the A3 site (treatment site), revealed a clear improvement in summer 2019, about a year after the installation of bioeremediators, showing an unexpected change especially from a qualitative point of view, Some of the previous species desappeared, (Capitella capitata) while other, more indicative of “good healt environmental situation” appeared. This is the case of for instance of the polychaete Spiochaetopterus costarum. become instead more abundant.