scholarly journals Widespread microbial mercury methylation genes in the global ocean

2019 ◽  
Author(s):  
Emilie Villar ◽  
Lea Cabrol ◽  
Lars-Eric Heimbürger-Boavida
Keyword(s):  
Ecosystem Health ◽  
Inorganic Mercury ◽  
Global Ocean ◽  
Anaerobic Microorganisms ◽  
Antarctic Sea Ice ◽  
Anoxic Environments ◽  
Nitrite Oxidizing Bacteria ◽  
Subsurface Waters ◽  
High Concentrations ◽  
Methylmercury Production

AbstractMethylmercury is a neurotoxin that bioaccumulates from seawater to high concentrations in marine fish, putting human and ecosystem health at risk. High methylmercury levels have been found in the oxic subsurface waters of all oceans, yet only anaerobic microorganisms have been identified so far as efficient methylmercury producers in anoxic environments. The microaerophilic nitrite oxidizing bacteriaNitrospinahas been previously suggested as a possible mercury methylator in Antarctic sea ice. However, the microorganisms processing inorganic mercury into methylmercury in oxic seawater remain unknown. Here we show metagenomic evidence from open ocean for widespread microbial methylmercury production in oxic subsurface waters. We find high abundances of the key mercury methylating geneshgcABacross all oceans corresponding to taxonomic relatives of known mercury methylators from Deltaproteobacteria, Firmicutes and Chloroflexi. Our results identifyNitrospinaas the predominant and widespread key player for methylmercury production in the oxic subsurface waters of the global ocean.

Incorporating Concentration-Dependent Sediment Microbial Activity into Methylmercury Production Kinetics Modeling

2021 ◽  
Author(s):  
Grace E. Schwartz ◽  
Katherine A Muller ◽  
Saubhagya S Rathore ◽  
Regina L Wilpiszeski ◽  
Alyssa A Carrell ◽  
...  
Keyword(s):  
Gene Cluster ◽  
Microbial Activity ◽  
Inorganic Mercury ◽  
Anaerobic Microorganisms ◽  
Kinetics Modeling ◽  
Production Kinetics ◽  
Anoxic Environments ◽  
Kinetics Of ◽  
Methylmercury Production

In anoxic environments, anaerobic microorganisms carrying the hgcAB gene cluster can mediate the transformation of inorganic mercury (Hg(II)) to monomethylmercury (MMHg). The kinetics of Hg(II) transformation to MMHg in periphyton...

scholarly journals Large subglacial source of mercury from the southwestern margin of the Greenland Ice Sheet

2021 ◽  
Author(s):  
Jon R. Hawkings ◽  
Benjamin S. Linhoff ◽  
Jemma L. Wadham ◽  
Marek Stibal ◽  
Carl H. Lamborg ◽  
...  
Keyword(s):  
Natural Waters ◽  
Inorganic Mercury ◽  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
Annual Runoff ◽  
Arctic Ecosystems ◽  
High Mercury ◽  
Southwestern Margin ◽  
High Concentrations ◽  
Dissolved Mercury

AbstractThe Greenland Ice Sheet is currently not accounted for in Arctic mercury budgets, despite large and increasing annual runoff to the ocean and the socio-economic concerns of high mercury levels in Arctic organisms. Here we present concentrations of mercury in meltwaters from three glacial catchments on the southwestern margin of the Greenland Ice Sheet and evaluate the export of mercury to downstream fjords based on samples collected during summer ablation seasons. We show that concentrations of dissolved mercury are among the highest recorded in natural waters and mercury yields from these glacial catchments (521–3,300 mmol km−2 year−1) are two orders of magnitude higher than from Arctic rivers (4–20 mmol km−2 year−1). Fluxes of dissolved mercury from the southwestern region of Greenland are estimated to be globally significant (15.4–212 kmol year−1), accounting for about 10% of the estimated global riverine flux, and include export of bioaccumulating methylmercury (0.31–1.97 kmol year−1). High dissolved mercury concentrations (~20 pM inorganic mercury and ~2 pM methylmercury) were found to persist across salinity gradients of fjords. Mean particulate mercury concentrations were among the highest recorded in the literature (~51,000 pM), and dissolved mercury concentrations in runoff exceed reported surface snow and ice values. These results suggest a geological source of mercury at the ice sheet bed. The high concentrations of mercury and its large export to the downstream fjords have important implications for Arctic ecosystems, highlighting an urgent need to better understand mercury dynamics in ice sheet runoff under global warming.

The dire straits of Paratethys: Gateways to the anoxic giant of Eurasia

2021 ◽  
pp. SP523-2021-73
Author(s):  
D. V. Palcu ◽  
W. Krijgsman
Keyword(s):  
Carbon Sink ◽  
Global Climate ◽  
Water Masses ◽  
Source Rocks ◽  
Global Ocean ◽  
Tectonic Processes ◽  
Anoxic Environments ◽  
Geological Evolution ◽  
History Of ◽  
Tethys Ocean

AbstractA complex interplay of palaeoclimatic, eustatic and tectonic processes led to fragmentation and dissipation of the vast Tethys Ocean in Eocene-Oligocene times. The resulting Paratethys Sea occupied the northern Tethys region on Eurasia, grouping water masses of various subbasins, separated from each other and from the open ocean through narrow and shallow gateways and land bridges. Changes in marine gateway configuration and intra-basinal connectivity affected the regional hydrology, shifting most Paratethyan basins to extreme carbon-sink anoxic environments, anomalohaline evaporitic or brackish conditions or even endorheic lakes. Paratethys gateway restriction triggered the onset of a long-lasting (∼20 Myr) giant anoxic sea, characterised by stratified water masses and anoxic bottom water conditions, resulting in thick hydrocarbon source rocks. Here, we review the geological evolution of the “dire straits” of Paratethys that played a crucial role in the Eocene-Oligocene connectivity history of the Central Eurasian seas and we show that the main anoxic phases (Kuma and Maikop) correspond to restricted connectivity with the global ocean and a period of CO2 depletion in the atmosphere. Paratethys represents one of the largest carbon sinks of Earth's history and may thus have played a prominent role in global climate change.

Detecting Climate Fingerprints in Southern Ocean Carbon using a Biogeochemical Ocean Model

2021 ◽  
Author(s):  
Rebecca Wright ◽  
Corinne Le Quéré ◽  
Erik Buitenhuis ◽  
Dorothee Bakker
Keyword(s):  
Climate Change ◽  
Climate Variability ◽  
Southern Ocean ◽  
Observational Data ◽  
Ecosystem Dynamics ◽  
Global Ocean ◽  
Subsurface Waters ◽  
Climatic Drivers ◽  
Ocean Carbon ◽  
And Storage

<p>The Southern Ocean plays an important role in the uptake, transport and storage of carbon by the global oceans. These properties are dominated by the response to the rise in anthropogenic CO<sub>2</sub> in the atmosphere, but they are modulated by climate variability and climate change. Here we explore the effect of climate variability and climate change on ocean carbon uptake and storage in the Southern Ocean. We assess the extent to which climate change may be distinguishable from the anthropogenic CO<sub>2</sub> signal and from the natural background variability. We use a combination of biogeochemical ocean modelling and observations from the GLODAPv2020 database to detect climate fingerprints in dissolved inorganic carbon (DIC).</p><p>We conduct an ensemble of hindcast model simulations of the period 1920-2019, using a global ocean biogeochemical model which incorporates plankton ecosystem dynamics based on twelve plankton functional types. We use the model ensemble to isolate the changes in DIC due to rising anthropogenic CO<sub>2</sub> alone and the changes due to climatic drivers (both climate variability and climate change), to determine their relative roles in the emerging total DIC trends and patterns. We analyse these DIC trends for a climate fingerprint over the past four decades, across spatial scales from the Southern Ocean, to basin level and down to regional ship transects. Highly sampled ship transects were extracted from GLODAPv2020 to obtain locations with the maximum spatiotemporal coverage, to reduce the inherent biases in patchy observational data. Model results were sampled to the ship transects to compare the climate fingerprints directly to the observational data.</p><p>Model results show a substantial change in DIC over a 35-year period, with a range of more than +/- 30 µmol/L. In the surface ocean, both anthropogenic CO<sub>2</sub> and climatic drivers act to increase DIC concentration, with the influence of anthropogenic CO<sub>2</sub> dominating at lower latitudes and the influence of climatic drivers dominating at higher latitudes. In the deep ocean, the anthropogenic CO<sub>2</sub> generally acts to increase DIC except in the subsurface waters at lower latitudes, while climatic drivers act to decrease DIC concentration. The combined fingerprint of anthropogenic CO<sub>2</sub> and climatic drivers on DIC concentration is for an increasing trend at the surface and decreasing trends in low latitude subsurface waters. Preliminary comparison of the model fingerprints to observational ship transects will also be presented.</p>

scholarly journals Expanded Phylogenetic Diversity and Metabolic Flexibility of Mercury-Methylating Microorganisms

mSystems ◽  
2020 ◽  
Vol 5 (4) ◽  
Author(s):  
Elizabeth A. McDaniel ◽  
Benjamin D. Peterson ◽  
Sarah L. R. Stevens ◽  
Patricia Q. Tran ◽  
Karthik Anantharaman ◽  
...  
Keyword(s):  
Phylogenetic Diversity ◽  
Large Scale ◽  
Carbon Fixation ◽  
Anaerobic Bacteria ◽  
Inorganic Mercury ◽  
Metal Resistance ◽  
Metabolic Flexibility ◽  
Metabolic Diversity ◽  
Content Type ◽  
Methylmercury Production

ABSTRACT Methylmercury is a potent bioaccumulating neurotoxin that is produced by specific microorganisms that methylate inorganic mercury. Methylmercury production in diverse anaerobic bacteria and archaea was recently linked to the hgcAB genes. However, the full phylogenetic and metabolic diversity of mercury-methylating microorganisms has not been fully unraveled due to the limited number of cultured experimentally verified methylators and the limitations of primer-based molecular methods. Here, we describe the phylogenetic diversity and metabolic flexibility of putative mercury-methylating microorganisms by hgcAB identification in publicly available isolate genomes and metagenome-assembled genomes (MAGs) as well as novel freshwater MAGs. We demonstrate that putative mercury methylators are much more phylogenetically diverse than previously known and that hgcAB distribution among genomes is most likely due to several independent horizontal gene transfer events. The microorganisms we identified possess diverse metabolic capabilities spanning carbon fixation, sulfate reduction, nitrogen fixation, and metal resistance pathways. We identified 111 putative mercury methylators in a set of previously published permafrost metatranscriptomes and demonstrated that different methylating taxa may contribute to hgcA expression at different depths. Overall, we provide a framework for illuminating the microbial basis of mercury methylation using genome-resolved metagenomics and metatranscriptomics to identify putative methylators based upon hgcAB presence and describe their putative functions in the environment. IMPORTANCE Accurately assessing the production of bioaccumulative neurotoxic methylmercury by characterizing the phylogenetic diversity, metabolic functions, and activity of methylators in the environment is crucial for understanding constraints on the mercury cycle. Much of our understanding of methylmercury production is based on cultured anaerobic microorganisms within the Deltaproteobacteria, Firmicutes, and Euryarchaeota. Advances in next-generation sequencing technologies have enabled large-scale cultivation-independent surveys of diverse and poorly characterized microorganisms from numerous ecosystems. We used genome-resolved metagenomics and metatranscriptomics to highlight the vast phylogenetic and metabolic diversity of putative mercury methylators and their depth-discrete activities in thawing permafrost. This work underscores the importance of using genome-resolved metagenomics to survey specific putative methylating populations of a given mercury-impacted ecosystem.

scholarly journals Argon as a Tracer of Cross-Isopycnal Mixing in the Thermocline

2006 ◽  
Vol 36 (11) ◽  
pp. 2090-2105 ◽  
Author(s):  
Cara C. Henning ◽  
David Archer ◽  
Inez Fung
Keyword(s):  
General Circulation Model ◽  
General Circulation ◽  
Vertical Mixing ◽  
Circulation Model ◽  
Ocean General Circulation Model ◽  
Global Ocean ◽  
Equatorial Pacific Ocean ◽  
Subsurface Waters ◽  
Different Temperatures ◽  
Ocean Gyre

Abstract Noble gases such as argon are unaffected by chemical reactions in the ocean interior, but a number of physical mechanisms can lead to measurable sea level atmospheric disequilibrium in subsurface waters of the ocean. One such mechanism is the mixing of waters of different temperatures, which can lead to supersaturation in the ocean interior. The authors simulate the supersaturation mixing signature in the thermocline in a global ocean general circulation model, Parallel Ocean Program model, version 1.4 (POP 1.4). In contrast to existing mixing diagnostics such as dye tracers or microstructure measurements, which yield the local, recent rate of diabatic mixing, argon disequilibrium traces an integrated lifetime history of subsurface mixing. A theoretical model of the subtropical Atlantic Ocean gyre is built, based on the competing time scales of horizontal and vertical mixing, that agrees well with the full general circulation model argon supersaturation gradient in the thermocline. These results suggest that gyre-scale argon data from the real ocean could be similarly interpreted. The variation of the argon supersaturation with diffusivity in the equatorial Pacific Ocean is also investigated.

Molecular Changes in Dissolved Organic Matter After Soil Rewetting

2021 ◽  
Author(s):  
Alice Orme ◽  
Simon Benk ◽  
Markus Lange ◽  
Christian Zerfaß ◽  
Georg Pohnert ◽  
...  
Keyword(s):  
Organic Matter ◽  
Dissolved Organic Matter ◽  
Mass Spectrometry Analysis ◽  
Microbial Decomposition ◽  
Molecular Changes ◽  
Spectrometry Analysis ◽  
Subsurface Waters ◽  
High Production ◽  
High Concentrations ◽  
Over Time

<p>The intensity and occurrence of droughts is projected to increase due to climate change. Dried soils release high concentrations of dissolved organic matter (DOM) into subsurface waters when they are rewet, the so-called rewetting peak. To more accurately predict the role of rewetting of soils after drought on the carbon cycle in a changing climate, it is important to understand the processes behind this DOM release.</p><p>The DOM rewetting peak origin is disputed between soil organic matter (SOM) from breakdown of soil particles; accumulated root exudates; and microbial release due to a change in osmotic potential through osmolytes or cell bursting. To better understand the origin of the rewetting DOM peak, we took a rewetting series of soil water samples from different vegetation types between December 2018 and April 2019 for targeted and untargeted metabolomics. Initial results using untargeted ultrahigh-resolution mass spectrometry analysis revealed a clear temporal trend, indicating that vegetation-independent molecular changes occur following rewetting. An increase in O/C and a decrease in H/C over time was observed which is attributed to microbial decomposition, supported by a decrease in m/z over time. We also observed an increase in the content of lipidic compounds (R > 0.6) following rewetting. This indicates that cells do not burst upon rewetting and, over time, microbial activity increases, suggesting that the DOM rewetting peak is caused by a lack of decomposition, rather than a high production, of organic matter.</p>

scholarly journals Anaerobic Microbial Degradation of Hydrocarbons: From Enzymatic Reactions to the Environment

2016 ◽  
Vol 26 (1-3) ◽  
pp. 5-28 ◽  
Author(s):  
Ralf Rabus ◽  
Matthias Boll ◽  
Johann Heider ◽  
Rainer U. Meckenstock ◽  
Wolfgang Buckel ◽  
...  
Keyword(s):  
Microbial Degradation ◽  
Field Studies ◽  
Stable Isotope Probing ◽  
Special Topic ◽  
Enzymatic Reactions ◽  
Gene Markers ◽  
Anaerobic Microorganisms ◽  
Anoxic Environments ◽  
Benzylsuccinate Synthase

Hydrocarbons are abundant in anoxic environments and pose biochemical challenges to their anaerobic degradation by microorganisms. Within the framework of the Priority Program 1319, investigations funded by the Deutsche Forschungsgemeinschaft on the anaerobic microbial degradation of hydrocarbons ranged from isolation and enrichment of hitherto unknown hydrocarbon-degrading anaerobic microorganisms, discovery of novel reactions, detailed studies of enzyme mechanisms and structures to process-oriented in situ studies. Selected highlights from this program are collected in this synopsis, with more detailed information provided by theme-focused reviews of the special topic issue on ‘Anaerobic biodegradation of hydrocarbons' [this issue, pp. 1-244]. The interdisciplinary character of the program, involving microbiologists, biochemists, organic chemists and environmental scientists, is best exemplified by the studies on alkyl-/arylalkylsuccinate synthases. Here, research topics ranged from in-depth mechanistic studies of archetypical toluene-activating benzylsuccinate synthase, substrate-specific phylogenetic clustering of alkyl-/arylalkylsuccinate synthases (toluene plus xylenes, <i>p</i>-cymene, <i>p</i>-cresol, 2-methylnaphthalene, <i>n</i>-alkanes), stereochemical and co-metabolic insights into <i>n</i>-alkane-activating (methylalkyl)succinate synthases to the discovery of bacterial groups previously unknown to possess alkyl-/arylalkylsuccinate synthases by means of functional gene markers and in situ field studies enabled by state-of-the-art stable isotope probing and fractionation approaches. Other topics are Mo-cofactor-dependent dehydrogenases performing O<sub>2</sub>-independent hydroxylation of hydrocarbons and alkyl side chains (ethylbenzene, <i>p</i>-cymene, cholesterol, <i>n</i>-hexadecane), degradation of <i>p</i>-alkylated benzoates and toluenes, glycyl radical-bearing 4-hydroxyphenylacetate decarboxylase, novel types of carboxylation reactions (for acetophenone, acetone, and potentially also benzene and naphthalene), W-cofactor-containing enzymes for reductive dearomatization of benzoyl-CoA (class II benzoyl-CoA reductase) in obligate anaerobes and addition of water to acetylene, fermentative formation of cyclohexanecarboxylate from benzoate, and methanogenic degradation of hydrocarbons.

scholarly journals Isolation of Mercury-binding Peptides in Vegetative Parts of Chromolaena odorata

2005 ◽  
Vol 60 (3-4) ◽  
pp. 252-259 ◽  
Author(s):  
Malona P. Velasco-Alinsug ◽  
Gilda C. Rivero ◽  
Titos Anacleto O. Quibuyen
Keyword(s):  
Inorganic Mercury ◽  
Ionization Mass ◽  
Chromolaena Odorata ◽  
Isolation Techniques ◽  
Rp Hplc ◽  
Binding Peptides ◽  
Stems And Leaves ◽  
High Concentrations ◽  
Prominent Peak

Abstract Mercury-binding peptides from roots, stems, and leaves of Hg-treated Chromolaena odorata plants were isolated and partially characterized using RP-HPLC and ESI-MS. Upon exposure of C. odorata plants to high concentrations of 1.0 and 2.0 μᴍ Hg(NO3)2 treatments from 0-28 days, they accumulated as much as 125 mg/g (dry wt) Hg in the roots, 15.280 mg/g (dry wt) Hg in the stems, and 0.800 mg/g (dry wt) Hg in the leaves indicating that C. odorata has a high potential as a phytoremediation agent of inorganic mercury. The plant’s ability to accumulate and sequester Hg ions was primarily attributed to the production of Hgbinding peptides, which were initially detected through the use of Ellman’s reagent. Isolation techniques using RP-HPLC equipped with a C18 column manifested a single prominent peak consistently appearing at a retention time of 2.6-2.8 min in all the plant samples treated with different Hg concentrations at varying lengths of exposure. Further characterization of this prominent peak using electrospray ionization mass spectrometry revealed the presence of a peptide containing several cysteine residues with the highest peak concentration recorded at 91 mV and 89 mV in roots and stems of plants treated with 2.0 μᴍ Hg(NO3)2 for 4 wk (P < 0.05) and 85 mV in leaves treated with 1.0 μᴍ Hg(NO3)2 for 1 wk.

Modification de la bioaccumulation du sélénium chez Mytilus edulis en présence du mercure organique et inorganique

1986 ◽  
Vol 43 (1) ◽  
pp. 203-210 ◽  
Author(s):  
Emilien Pelletier
Keyword(s):  
Methyl Mercury ◽  
Animal Species ◽  
Blue Mussel ◽  
Accumulation Rate ◽  
Inorganic Mercury ◽  
Toxic Effects ◽  
Organic Selenium ◽  
Inorganic Selenium ◽  
High Concentrations ◽  
The Impact

Studies of the simultaneous bioaccumulation of selenium and mercury in the blue mussel, Mytilis edulis, in the presence of TiO2 as carrier have shown that there is an interaction between the two elements. We measured the bioaccumulation rates of dissolved selenite (Na2SeO3) and adsorbed organic selenium (C8H7O2Se)2 and determined the impact of the presence of mercury (HgCl2 and [(CH3Hg)3O]OH) in the environment. Mussels measuring 3.6 ± 0.2 cm were distributed in nine contamination tanks with continuously circulating seawater and were exposed to organic or inorganic selenium at a concentration of 50 μg Se∙L−1 for periods of 15–50 d. Some of the tanks were simultaneously exposed to high concentrations of organic and inorganic mercury (3.0 and 30 μg Hg∙L−1, respectively). When mercury was not present, the mussels accumulated the inorganic selenium at a slow rate (0.12 ng Se∙g−1∙d−1), but did not accumulate the organic selenium. When inorganic mercury was added to the water at 30 μg Hg∙L−1, the accumulation rate of inorganic selenium doubled (0.24 ng Se∙g−1d−1), while it tripled (0.40 ng Se∙g−1d−1) when methyl mercury was added at 3.0 μg Hg∙L−1. Even the adsorbed organic selenium seemed to become bioavailable in the presence of methyl mercury, and was accumulated at a rate of 0.15 ng Se∙g−1d−1. However, the phenomenon is not reciprocal, that is, the presence of selenium, no matter what its concentration or chemical nature, had no effect on the accumulation rate of mercury. No toxic effects were observed where selenium was administered alone, but the toxic effects of mercury were observed in all mussels exposed to it. Selenium showed none of the adverse effects previously observed in other animal species.

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