A note on the possibility of monitoring the biological effects of chronic exposure to heavy metals from purified sewage discharged into the Neva Bay
A study of chronic (6 months) effects of biologically treated sewage water on the functional state of crayfish Astacus leptodactylus (Esch.) was carried out. Crayfish were used as test organisms in the "BioArgus-WW" bioelectronic system installed at the South-West Wastewater Treatment Plant of the State Unitary Enterprise "Vodokanal of St. Petersburg". Crayfish of the same species were used as a control group, being a part of the "BioArgus-W" bioelectronic system of monitoring the overall toxicity of the Neva River water entering the water intake at the Main Waterworks of the State Unitary Enterprise "Vodokanal of St. Petersburg". During the exposure process, the heart rate of these crayfish was continuously measured. At the end of the exposure, cadmium, nickel and copper accumulation was measured in the soft tissues of the crayfish. The study revealed no significant changes in the functional state of the crayfish, as well as no increased accumulation of the studied metals (Cd, Cu, Ni) in the muscle and hepatopancreas of the crayfish-bioindicators, contained in the biologically treated sewage water, as compared to the control group of crayfish. This indicates a low content of these heavy metals in the biologically treated sewage water discharged into the Neva Bay. Crayfish that have long been used as test-organisms in bioelectronic systems for real-time monitoring of the quality of the biologically treated sewage water were shown to be suitable as bioindicators of chronic contamination of these waters with heavy metals.