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Abstract Title: Exploring the Capacity of Diatom Cyclotella Meneghiniana in Contributing to the Aquatic Hg Species Transformations
Presenter Name: Joao Santos
Company/Institution: Faculty of Sciences, Earth and Environment Sciences, Department F.-A. Forel for Environmental and Aquatic Sciences, University of Geneva
Session: Mercury in Freshwater Ecosystems
Co-Authors: Joao Santos

Abstract Information :

Mercury is a persistent contaminant that can cause serious damage to human and environmental health. Despite the low concentration levels, mercury can bioaccumulate in aquatic organisms, and in the case of methylmercury, it can be biomagnified through the aquatic food web, posing serious health issues to fish consumers. Phytoplankton species are at the base of the food web, therefore playing a crucial role in the entry of Hg in the food webs and its trophic transfer. The aim of the present study is to explore mercury species bioaccumulation and biotransformation capability of diatoms, as representative phytoplankton species. Species-specific isotope tracer?s technique was used to quantify the uptake, methylation and demethylation by diatom Cyclotella meneghiniana. The changes in the 199Hg(II) and/or 201CH3Hg concentrations over exposure time were followed by gas chromatography coupled with inductively coupled plasma mass spectrometry (GC-ICP MS). To account for the contribution of the abiotic transformation, a comparison was made with the system in the absence of diatoms. Results demonstrated a significant accumulation of both Hg(II) and CH3Hg by C. meneghiniana and CH3Hg demethylation. Additionally, 199Hg(II) loss due to Hg(II) reduction to Hg0, ultimately released into the atmosphere (via volatilization process), was detected and quantified. The implications of the results found are with respect to the mercury incorporation at the base of the food webs and the potential contribution of diatoms in Hg cycling.

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