Content of Fe and Mn in waters and zebra mussel (Dressena polymorpha) from Ovcharitsa Dam, Stara Zagora region, Bulgaria

Elica Valkova, Vasil Atanasov and Petya Veleva

Abstract: The main objective of this study is to determine the levels of heavy metals iron (Fe) and manganese (Mn) in the waters and muscles of the “Zebra” mussel (Dreissena polymorpha) from Ovcharitsa Dam, Stara Zagora, Bulgaria. Iron concentrations measured in the waters of Ovcharitsa Dam in November, 2018 are 4.5 times higher than the requirement for YAV in accordance with Regulation H-4 of the Bulgarian legislation. Concentrations measured during this period indicate the presence of possible temporary pollution in November, 2018. These values fully correspond to the concentrations of the same element measured in the muscle of the Zebra mussel in January, 2019 of 104.36 mg/kg (16.5 units above the arithmetic mean) due to the passage of iron ions from water into the mussel organism. Higher Fe values are also characterized by specimens of mussels inhabiting the Ovcharitsa Dam in August, 2018. Mn levels measured in the waters of the studied water body in November, 2018 are some times higher (5 times) than the YAV regulated by Regulation H-4 of the Bulgarian legislation. The reported data confirm the existence of possible permanent contamination with Mn during all months of the survey except for March, 2019. The reported amounts of manganese in mussels indicate that Dreissena polymorpha mainly accumulates the metal in August, 2018 and March 2019. The concentration of this element in the musculature of the examined mussels is gradually increasing, with the lowest value (5.33 mg/kg) established in November, 2018 and the highest (11.74 mg/kg) in March, 2019. Iron and manganese concentrations found in water can indicate the state of the hydroecosystems at the time of sampling. Aquatic organisms (including Dreissena polymorpha mussels) have the ability to accumulate heavy metals over time, making them a more reliable biological indicator of hydroecosystem pollution than conventional water monitoring.

Keywords: heavy metals; hydroecosystem; musculature; water body; zebra mussel

Date published: 2020-08-31