Chemical characterization and toxicity of water-accommodated fraction of oil on the South American native species Hyalella curvispina

[Display omitted] •n-Alkanes were the main fraction in WAF, followed by toluene in the aromatic group.•Main hydrocarbon components in the WAF show dissipation half-lives between 65–200 h.•TPHs are significantly higher in the oil-impacted stream than in the reference site.•Different sensitivity to WAF is determined on amphipods from both sites.•Freshwater species protection limit for WAF acute toxicity is below 0.5 mg L−1. Chemical and toxicological crude oil analysis was performed on water-accommodated fraction of oil (WAF). This study characterized the chemical composition of WAF and its dissipation over a period of 192 h. Acute (96 h) and chronic (14 d) toxicity of WAF were evaluated on Hyalella curvispina from both reference (Los Barreales lake, LB) and hydrocarbon-contaminated (Durán stream, DS) sites. The total hydrocarbon (TPHs) concentration in WAF was 2.18 mg L−1. The dissipation rates of hydrocarbons in WAF showed a first-order kinetics, with half-lives ranging between 65 h-200 h. Amphipods from LB showed acute and chronic LC50 values of 0.33 and 0.018 mg L−1, respectively. Amphipods from DS exposed to pure WAF showed no mortality in either acute or chronic assays. Further biochemical and molecular research is required to determine the mechanisms underlying the resistance to WAF exposure on DS amphipods.