Variable toxicity of inorganic mercury compounds to Artemia elicited by coexposure with dissolved organic matter

Abstract

The chemical behavior of mercury (Hg) and its interactions with naturally occurring ligands shape its environmental fate and impact. The neurotoxic properties of Hg are widely known and studied both in vitro and in vivo. However, there continues to be limited information on the influence of chelation with large organic ligands on the toxicity to marine macro-organisms. This work examined the effect of Hg complexed with various types of dissolved organic matter (DOM) on the mortality and hatching success of Artemia sp. nauplii under varying marine media conditions. The results confirmed both, an alleviating as well as additive, DOM-specific, effect on mortality. DOM coexposure resulted in a compound specific decreased or increased toxicity in comparison with single exposure in artificial seawater, with LC₅₀ values ranging from 2.11 to 62.89 µM. Hatching success under conditions of Hg exposure was almost two orders of magnitude more sensitive than toxicity in hatched individuals. Elevated DOM concentrations had no statistically significant impact on hatching success with computed EC₅₀ values ranging from 196 to 324 nM.

Keywords: Bioaccumulation; Ecotoxicology; Hatching assay; Marine environment.

Fig. 1

FTIR spectra of three types of organic matter. Raw absorbance spectra data were transformed to transmittance data and normalized against 100% transmittance

Fig. 2

Lethal effects in Instar I Artemia sp. after 24 h coexposure to A HgCl₂ and B HgOAc₂ with DOM#1–3 media (see respective colors). Assays were conducted in independent triplicate, solid lines show the combined four parameter logistic fit, and error bars show the standard error of the mean

Fig. 3

Mercury body burden measured in the A bioaccumulation assay and B the adsorption assay using Instar I nauplii of Artemia sp. Assays were conducted in independent triplicate. Solid lines denote A the one compartment accumulation model and B the non-linear pseudo-second order kinetic adsorption model

Fig. 4

Literature 24 h LC₅₀ values derived from Artemia Instar I (yellow half) and Instar II + III nauplii (blue half) after exposure to Hg. Values are given as mean and the error bars denote the 95% confidence interval if provided. Red and blue datapoints were derived from HgCl₂ exposure, orange datapoints were derived with HgOAc₂

Fig. 5

Hatching success of Artemia sp. cysts after 24 h coexposure to A HgCl₂ and B HgOAc₂ with DOM#1–3 media (see respective colors). Assays were conducted in independent triplicate, solid lines show the combined four parameter logistic fit, and error bars denote the standard error of the mean