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Article scientifique
Accès libre
Anglais

Species-specific isotope tracking of mercury uptake and transformations by pico-nanoplankton in an eutrophic lake

Publié dansEnvironmental Pollution, vol. 288, no. 117771
Date de publication2021
Résumé

The present study aims to explore the bioaccumulation and biotic transformations of inorganic (iHg) and monomethyl mercury (MMHg) by natural pico-nanoplankton community from eutrophic lake Soppen, Switzerland. Pico-nanoplankton encompass mainly bacterioplankton, mycoplankton and phytoplankton groups with size between 0.2 and 20 μm. Species-specific enriched isotope mixture of 199iHg and 201MMHg was used to explore the accumulation, the subcellular distribution and transformations occurring in natural pico-nanoplankton sampled at 2 different depths (6.6 m and 8.3 m). Cyanobacteria, diatoms, cryptophyta, green algae and heterotrophic microorganisms were identified as the major groups of pico-nanoplankton with diatoms prevailing at deeper samples. Results showed that pico-nanoplankton accumulated both iHg and MMHg preferentially in the cell membrane/organelles, despite observed losses. The ratios between the iHg and MMHg concentrations measured in the membrane/organelles and cytosol were comparable for iHg and MMHg. Pico-nanoplankton demethylate added 201MMHg (~4 and 12% per day depending on cellular compartment), although the involved pathways are to further explore. Comparison of the concentrations of 201iHg formed from 201MMHg demethylation in whole system, medium and whole cells showed that 82% of the demethylation was biologically mediated by pico-nanoplankton. No significant methylation of iHg by pico-nanoplankton was observed. The accumulation of iHg and MMHg and the percentage of demethylated MMHg correlated positively with the relative abundance of diatoms and heterotrophic microorganisms in the pico-nanoplankton, the concentrations of TN, Mg2+, NO3−, NO2−, NH4+ and negatively with the concentrations of DOC, K+, Na+, Ca2+, SO42−. Taken together the results of the present field study confirm the role of pico-nanoplankton in Hg bioaccumulation and demethylation, however further research is needed to better understand the underlying mechanisms and interconnection between heterotrophic and autotrophic microorganisms. Graphical abstract

Financement
  • Swiss National Science Foundation - 175721
  • Autre - 17-CE34-0014-01
Citation (format ISO)
COSSART, Thibaut et al. Species-specific isotope tracking of mercury uptake and transformations by pico-nanoplankton in an eutrophic lake. In: Environmental Pollution, 2021, vol. 288, n° 117771. doi: 10.1016/j.envpol.2021.117771
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Article (Published version)
Identifiants
ISSN du journal0269-7491
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Informations techniques

Création09.09.2021 11:24:00
Première validation09.09.2021 11:24:00
Heure de mise à jour16.03.2023 01:16:27
Changement de statut16.03.2023 01:16:27
Dernière indexation12.02.2024 13:30:02
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