Assessments of Bioaccumulation Factor (BAF) for heavy metals (Pb and Hg) in an aquatic insect Laccotrephesruber: A major faunal component for three contrasting freshwater aquatic ecosystems of West Bengal and Odisha

Abstract

Although insects harbor almost all the terrestrial habitats but occur with negligible abundance in the aquatic environment mainly because of their tracheal mode of respiration. The present paper has attempted to find out the Bioaccumulation Factor (BAF) of a major aquatic insect species, Laccotrephesruber which inhabits in higher densities in three distantly located freshwater bodies having contrasting ecological factors overcoming even different environmental odds, especially the loads of two toxic heavy metals such as lead (Pb) and mercury (Hg).Collection and preservation of the aquatic insects alongwith estimation of different water quality parameters were made following standard methodologies (APHA, 2005). The heavy metals of the water, soil, selected aquatic plants and insect species were determined by Atomic Absorption Spectroscopy (AAS) from three selected study sites of [(1) a water impoundment – Rissia Dam in Odisha, (2) a large water body at Tamluk, West Bengal, and (3) a large pond at Haldia, West Bengal].In this study, above three study sites were selected in order to determine the concentrations and variation of two heavy metals (Pb and Hg) and their trend of accumulation in water, soil, aquatic plants and one aquatic insect species. After undertaking a yearlong (March’2019 – February’2020) field survey, Bioaccumulation Factors (BAF) of those heavy metals in an aquatic insect species, Laccotrephesruber and were deducted along with the recording ofdifferent pronounced ecological parameters (water quality – pH, temperature, conductivity and Total Dissolved Solids). It was seen that, lead (Pb) was found to be higher than mercury (Hg) in all the structural components (water, soil, vegetation and insect) of the three aquatic ecosystems including within the body of Laccotrephesruber of all (slight exception for soil of Rissia Dam). Besides, the concentrations of both the heavy metals were highest in the study site 3 (within industrial belt) followed by study site 2 (under the human activities) and study site 1 (in the natural undisturbed environment).From the BAFanalysis of Laccotrephesruber, it is seen that – (i) Hg is very bioaccumulative than Pb in Rissia Dam; (ii) Pb is moderately bioaccumulative than Hg in Tamluk; and (iii) Pb is very much bioaccumulative thanHg in Haldia.