Heavy metals Hg, Cd, and Pb in the body of sterlet (Acipenser ruthenus L.), the Lower Irtysh River

For assessing the possibility of using sterlet as a species-bioindicator of heavy metals' contamination in the bottom sediments, a study has been conducted on the distribution and accumulation of these pollutants in the fish body. The patterns of distribution of heavy metals (mercury, cadmium, lead) in the gills, muscles, liver and axial skeleton (chord) of sterlet living in the lower reaches of the Irtysh River have been investigated. The coefficient of biological accumulation in comparison with bottom sediments has been calculated, and heavy metal concentrations have been compared with allowable levels of these toxicants for raw fish. The concentrations of heavy metals (HM) have been determined by the atomic adsorption method. The maximum have been noted for lead, and among the analyzed organs and tissues, its greatest value are in the gills. The rows of HM distribution are as follows: Pb – gills > liver > muscles > skeleton, Hg – skeleton > gills > liver > muscles, Cd – gills > skeleton > liver > muscles. A statistically significant difference in distribution in the organs and tissues of fish is established only for Hg. Any statistically significant correlation between the distribution of the HM and the weight and size of the fish is not found. A comparative analysis of HM concentrations and sanitary-epidemiological regulations has established that Hg content in sterlet organs does not exceed the permissible level, for Cd in the gills and skeleton an excess of the permissible level is 25 and 9 %, respectively. For Pb in the body of sterlet, an excess of the permissible level in the gills is 48 %. It has been established that TM accumulation in the body of sterlet when compared with bottom sediments prevails over their elimination (> 1) for Cd in the gills, skeleton and liver, for Hg – in the skeleton and for Pb – in the gills. In other cases, the biological accumulation coefficient in the body of sterlet is < 1. The HM distribution for the fish organism and BS has a statistically significant, high direct correlation (RS = 0.95, p < 0.001), thereby we recommend using sterlet as a bioindicator of heavy metals' contamination in the bottom sediments.