Trophic fate of inorganic and methyl-mercury in a macrophyte-chironomid food chain

• Published in: Journal of hazardous materials Vol. 338; pp. 140 - 147
• Main Authors: Beauvais-Flück, Rebecca, Gimbert, Frédéric, Méhault, Ophélie, Cosio, Claudia
• Format: Journal Article
• Language: English
• Published: Netherlands Elsevier B.V 15.09.2017; Elsevier
• Subjects: Animals; Bioaccumulation; Biodegradation, Environmental; Biological Availability; Cell wall; Chironomidae - drug effects; Chironomidae - growth & development; Chironomidae - metabolism; Depuration; Ecotoxicology; Food Chain; Geologic Sediments - chemistry; Hydrocharitaceae - metabolism; Inorganic Chemicals - analysis; Inorganic Chemicals - metabolism; Inorganic Chemicals - toxicity; Intracellular; Larva - metabolism; Life Sciences; Methylmercury Compounds - analysis; Methylmercury Compounds - metabolism; Methylmercury Compounds - toxicity; Subcellular Fractions - metabolism; Toxicokinetics; Toxicology; Toxicokinetics; Intracellular; Bioaccumulation; Depuration; Cell wall
• ISSN: 0304-3894; 1873-3336
• DOI: 10.1016/j.jhazmat.2017.05.028

•Hg was transferred from cell wall and intracellular fractions of E. nuttallii to chironomids.•In chironomids, MMHg was in the cytosol, while IHg in the insoluble fraction.•MMHg demethylation was concomitant with IHg reallocation to the insoluble fraction.•Macrophytes are a new identified dietary source of Hg for benthic larvae. Dietary transfer of mercury (Hg) is central for its effects on higher trophic animals, nonetheless, its driving parameters and characteristics are not well understood. Here we measured Hg species transfer (uptake) from the macrophyte Elodea nuttallii −mimicking tissues incorporation in sediments after decay- to Chironomus riparius. Methyl-Hg (MMHg) was more transferable than inorganic Hg (IHg) from plant’s intracellular and cell wall compartments. After 10-d-long exposure, MMHg was predominantly found in MMHg form in the cytosolic compartment (S) of chironomids, while IHg showed similar concentrations in S and insoluble debris (P) compartments. After cessation of Hg species exposure (depuration), only MMHg resulted in a bioaccumulation factor >1. Toxicokinetics modelling indicated a demethylation of MMHg in the S fraction and its concomitant storage in the P fraction as IHg during both uptake and depuration, revealing an elimination and detoxification mechanism. Our data support that MMHg is more transferable than IHg to sensitive subcellular targets as well as bioavailable fraction in chironomids, in line with field studies showing higher MMHg transfer than IHg in food webs. Hence our data point out macrophytes as a potential Hg source to benthic food webs to be considered for enhancing aquatic environment protection during phytoremediation programs.