A little bit of light goes a long way: the role of phototrophs on mercury cycling

Grégoire, Daniel S.; Poulain, Alexandre J.

doi:10.1039/c3mt00312d

Cited by 56 publications

(54 citation statements)

References 159 publications

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“…In addition, presence of mer operon, responsible for enzymatic Hg reduction, has not been confirmed in phototrophic organisms [ Barkay et al , 2010; Grégoire and Poulain , ]. This could indicate that the DGM increase we observed was in fact due either to chemical reactions by secreted metabolites or was reduction conducted by associated heterotrophic community [ Grégoire and Poulain , ].…”

Section: Resultsmentioning

confidence: 99%

Mercury presence and speciation in the South Atlantic Ocean along the 40°S transect

Bratkič

Vahčič

Kotnik

et al. 2016

Global Biogeochemical Cycles

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Mercury (Hg) natural biogeochemical cycle is complex and a significant portion of biological and chemical transformation occurs in the marine environment. To better understand the presence and abundance of Hg species in the remote ocean regions, waters of South Atlantic Ocean along 40°S parallel were investigated during UK-GEOTRACES cruise GA10. Total mercury (THg), methylated mercury (MeHg), and dissolved gaseous mercury (DGM) concentrations were determined. The concentrations were very low in the range of pg/L (femtomolar). All Hg species had higher concentration in western than in eastern basin. THg did not appear to be a useful geotracer. Elevated methylated Hg species were commonly associated with low-oxygen water masses and occasionally with peaks of chlorophyll a, both involved with carbon (re)cycling. The overall highest MeHg concentrations were observed in the mixed layer (500 m) and in the vicinity of the Gough Island. Conversely, DGM concentrations showed distinct layering and differed between the water masses in a nutrient-like manner. DGM was lowest at surface, indicating degassing to the atmosphere, and was highest in the Upper Circumpolar Deep Water, where the oxygen concentration was lowest. DGM increased also in Antarctic Bottom Water. At one station, dimethylmercury was determined and showed increase in region with lowest oxygen saturation. Altogether, our data indicate that the South Atlantic Ocean could be a source of Hg to the atmosphere and that its biogeochemical transformations depend primarily upon carbon cycling and are thereby additionally prone to global ocean change.

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Section: Resultsmentioning

confidence: 99%

Mercury presence and speciation in the South Atlantic Ocean along the 40°S transect

Bratkič

Vahčič

Kotnik

et al. 2016

Global Biogeochemical Cycles

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“…In conditions such as those in the euphotic zones of coastal and marine waters, light can stimulate phototrophic organisms to reduce HgII to Hg0, thus reducing the pool of inorganic Hg available to methylation organisms and exerting a crucial role in regulating levels of MeHg in surface waters (Grégoire and Poulain 2014). However, light also stimulates photosynthetic activity, which in turn influences the release of labile DOM that encourages methylating microbial activity.…”

Section: Lightmentioning

confidence: 99%

Recent advances in the study of mercury methylation in aquatic systems

Paranjape

Hall

2017

FACETS

121

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With increasing input of neurotoxic mercury to environments as a result of anthropogenic activity, it has become imperative to examine how mercury may enter biotic systems through its methylation to bioavailable forms in aquatic environments. Recent development of stable isotope-based methods in methylation studies has enabled a better understanding of the factors controlling methylation in aquatic systems. In addition, the identification and tracking of the hgcAB gene cluster, which is necessary for methylation, has broadened the range of known methylators and methylation-conducive environments. Study of abiotic factors in methylation with new molecular methods (the use of stable isotopes and genomic methods) has helped elucidate the confounding influences of many environmental factors, as these methods enable the examination of their direct effects instead of merely correlative observations. Such developments will be helpful in the finer characterization of mercury biogeochemical cycles, which will enable better predictions of the potential effects of climate change on mercury methylation in aquatic systems and, by extension, the threat this may pose to biota.

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“…The increase in MeHg following re-exposure of surface waters to sunlight may also be attributable to phototrophic blooms, which can create environments that can facilitate methylation of Hg. 62 Therefore, if PD occurred, it may have been obscured by in situ…”

Section: Ecosystem-scale Observations Of Photodemethylationmentioning

confidence: 99%

Photodemethylation of Methylmercury in Eastern Canadian Arctic Thaw Pond and Lake Ecosystems

Girard

Leclerc

Amyot

2016

Environ. Sci. Technol.

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Permafrost thaw ponds of the warming Eastern Canadian Arctic are major landscape constituents and often display high levels of methylmercury (MeHg). We examined photodegradation potentials in high-dissolved organic matter (DOC) thaw ponds on Bylot Island (BYL) and a low-DOC oligotrophic lake on Cornwallis Island (Char Lake). In BYL, the ambient MeHg photodemethylation (PD) rate over 48 h of solar exposure was 6.1 × 10 -3 m 2 E -1 , and the rate in MeHg amended samples was 9.3 × 10 -3 m 2 E -1 . In contrast, in low-DOC Char Lake, PD was only observed in the first 12 hours, which suggests that PD may not be an important loss process in polar desert lakes. Thioglycolic acid addition slowed PD, while glutathione and chlorides did not impact northern PD rates. During an ecosystem-wide experiment conducted in a covered BYL pond, there was neither net MeHg increase in the dark nor loss attributable to PD following reexposure to sunlight. We propose that high-DOC Arctic thaw ponds are more prone to MeHg PD than nearby oligotrophic lakes, likely through photoproduction of reactive species rather than via thiol complexation. However, at the ecosystem level, these ponds, which are widespread through the Arctic, remain likely sources of MeHg for neighbouring systems.3

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A little bit of light goes a long way: the role of phototrophs on mercury cycling

Cited by 56 publications

References 159 publications

Mercury presence and speciation in the South Atlantic Ocean along the 40°S transect

Mercury presence and speciation in the South Atlantic Ocean along the 40°S transect

Recent advances in the study of mercury methylation in aquatic systems

Photodemethylation of Methylmercury in Eastern Canadian Arctic Thaw Pond and Lake Ecosystems

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