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

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