Paracyclops chiltoni inhabiting water highly contaminated with arsenic: Water chemistry, population structure, and arsenic distribution within the organism

Abstract

We investigated population structure and arsenic bioaccumulation and distribution in zooplankton inhabiting highly contaminated freshwater with arsenic. We collected water and zooplankton samples over a 4 year period, determined environmental temperature as well as water temperature, pH, electrical conductivity (EC), total dissolved solids (TDS), oxidation-reduction potential (ORP), dissolved oxygen (DO), major cations and anions and total arsenic concentration. We identified zooplankton species and determined their abundance, length, sex ratios, and arsenic bioaccumulation and distribution in exposed organisms. At the study site, an extremophile, Paracyclops chiltoni, was found to survive in an environment with high concentration of arsenic, sulfate and fluoride in freshwater as a well-adapted organism. Results showed that the average arsenic concentration in freshwater was 53.64 ± 10.58 mg/L. Exposed organisms of Paracyclops chiltoni showed arsenic accumulation (up to 9.6 ± 5.4 mgAs/kg) in its body, likely in the digestive tract as well as typical abundance and length, which showed a relationship to environmental temperature and oxic conditions in freshwater. Metallotolerant copepods might help to better understand if arsenic methylation processes occur in freshwater aquatic organisms.

Keywords: Hydrogeochemistry; Metallotolerant; Paracyclops chiltoni; Water pollution; Zooplankton.