Vineyard areas are important causes of water ecosystems contamination, especially by pesticides residues. These compounds could markedly disturb the aquatic biocenosis particularly the photosynthetic organisms that are targeted by herbicides. On the Long Term Ecological Research (LTER) Ardières Morcille watershed, an area impacted by Beaujolais vineyard (SE France), biofilms and diatoms were used as bioindicators for quality assessment, during the pesticide spreading period (April-May 2008). Along the increasing up- to downstream gradient of trophic (mainly orthophosphate) and pesticide pollution, biofilm communities were allowed to settle on glass slides for 4 or 8 weeks at three sites. After a 4-week colonisation some samples from the two contaminated downstream sites were transferred upstream in the clean site for four weeks and the other stayed in the same place. Periphytic communities were always dominated by brown algae. From up- to downstream, biofilm biomass and diatom species richness decreased; normalized diatom indices (including the French standard BDI) expressed quite well the increase in trophy. Species composition of the assemblages was used to discriminate between the effects of nutrients and toxicants, which increased simultaneously along the river. The biofilm samples transferred upstream recovered quite differently, depending on the location of their original site in the contamination gradient. Most of the quantitative descriptors reached a level comparable to that of the reference communities (grown for 8 weeks at the reference site), but the diatom assemblages (cell densities per colonized surface unit, taxonomic composition of the samples) varied between dates and along the gradient. These communities did not entirely recover a reference structure but the increase in diversity, associated with the settlement of sensitive species, suggested an elevated resilience potential.