Molecular biomarkers of Dreissena polymorpha for evaluation of renaturation success of a formerly sewage polluted stream

The renaturation success of an urban stream, formally used for discharge of treated sewage waters was investigated by active biomonitoring with Dreissena polymorpha based on molecular biomarkers and compared to a semi-natural stream and laboratory controls. Response to pollution charges were analyzed by reverse transcriptase-PCR of heat-shock protein (hsp70), P-glycoprotein (P-gp), catalase (CAT) and pi class glutathione S-transferase (piGST). Hsp70 transcription was similarly induced at both sites, indicating protein damage. At the semi-natural stream CAT and P-gp were induced, indicating oxidative stress and increased discharge of pollutants, which correlated to high amounts of aluminum at this site. piGST was induced at one sampling date at the renaturated stream only, but identification of the causing pollutant was not achieved. Results confirm regeneration of the formerly sewage polluted stream, because induction of the tested biomarkers was either at or below the levels of the semi-natural stream.