Environmental Chemistry Environmental Chemistry Society
Environmental problems - Chemical approaches
RESEARCH ARTICLE

Kinetics of mercury accumulation by freshwater biofilms

Perrine Dranguet A B , Vera I. Slaveykova A and Séverine Le Faucheur A C
+ Author Affiliations
- Author Affiliations

A University of Geneva, Faculty of Sciences, Earth and Environment Sciences, Department F.-A. Forel for Environmental and Aquatic Sciences, Environmental Biogeochemistry and Ecotoxicology, Uni Carl Vogt, 66 Bvd Carl-Vogt, CH 1211, Geneva, Switzerland.

B Present address: Département de Sciences Biologiques, Université de Montréal, Pavillon Marie-Victorin C.P. 6128, Succ. Centre-Ville, Montréal, QC H3C 3J7, Canada.

C Corresponding author. Email: severine.lefaucheur@unige.ch

Environmental Chemistry - https://doi.org/10.1071/EN17073
Submitted: 28 October 2016  Accepted: 29 June 2017   Published online: 22 January 2018

Environmental context. Mercury (Hg) is a major environmental contaminant due to its toxicity, accumulation and biomagnification along the food chain. We demonstrate that Hg accumulation by biofilms, one possible entry point for Hg into food webs, is rapid and depends on biofilm structure and composition. These findings have important implications for the understanding of Hg bioavailability and effects towards aquatic microorganisms.

Abstract. Mercury contamination is of high concern due to its bioaccumulation, toxicity and biomagnification along the food chain. Biofilms can accumulate Hg and contribute to its incorporation in freshwater food webs. Nevertheless, the accumulation kinetics of Hg by biofilms is not well described and understood. The aim of the present study was thus to gain mechanistic understanding of Hg accumulation by biofilms. Kinetics of Hg uptake by biofilms of different ages (e.g. different compositions) was characterised by determining Hg contents in biofilms with and without a cysteine-washing step. Hg accumulation was rapid in both biofilms, with the uptake rate constant of the younger biofilm 10 times higher than that of the older biofilm. Moreover, accumulated Hg reached a plateau at 24 h exposure in the younger biofilm, whereas it increased linearly in the older biofilm. The observed difference in Hg uptake by the studied biofilms is likely a result of the difference in biofilm thickness (and thus Hg diffusion inside the biofilm matrix) and microbial composition. These findings have important implications for the understanding of Hg bioavailability and effects towards aquatic microorganisms.

Additional keywords: hgcA gene, merA gene, mercury uptake rate constant, periphyton.


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