Variations in Stable Isotope Fractionation of Hg in Food Webs of Arctic Lakes

2009 ◽  
Vol 43 (24) ◽  
pp. 9148-9154 ◽  
Author(s):  
Nikolaus Gantner ◽  
Holger Hintelmann ◽  
Wang Zheng ◽  
Derek C. Muir
Keyword(s):  
Stable Isotope ◽  
Food Webs ◽  
Isotope Fractionation ◽  
Arctic Lakes ◽  
Stable Isotope Fractionation

scholarly journals Stable isotope fractionation reveals similar atomic level controls during aerobic and anaerobic microbial Hg transformation pathways

2021 ◽  
Author(s):  
Daniel S. Grégoire ◽  
Sarah E. Janssen ◽  
Noémie C. Lavoie ◽  
Michael T. Tate ◽  
Alexandre J. Poulain
Keyword(s):  
Stable Isotope ◽  
Food Webs ◽  
Isotope Fractionation ◽  
Atomic Level ◽  
Isotope Enrichment ◽  
Anoxygenic Photosynthesis ◽  
Physiological Processes ◽  
Stable Isotope Fractionation ◽  
Mercury Reduction ◽  
Heliobacterium Modesticaldum

Mercury (Hg) is a global pollutant and potent neurotoxin that bioaccumulates in food webs as monomethylmercury (MeHg). The production of MeHg is driven by anaerobic and Hg redox cycling pathways such as Hg reduction, which control the availability of Hg to methylators. Anaerobes play an important role in Hg reduction in methylation hotspots, yet their contributions remain underappreciated due to how challenging these pathways are to study in the absence of dedicated genetic targets and low levels of Hg 0 in anoxic environments. In this study we used Hg stable isotope fractionation to explore Hg reduction during anoxygenic photosynthesis and fermentation in the model anaerobe Heliobacterium modesticaldum Ice1. We show that cells preferentially reduce lighter Hg isotopes in both metabolisms leading to mass-dependent fractionation, but mass-independent fractionation commonly induced by UV-visible light is absent. Due to variability associated with replicated experiments, we could not discern whether dedicated physiological processes drive Hg reduction during photosynthesis and fermentation. However, we demonstrate that fractionation is affected by the interplay between pathways controlling Hg recruitment, accessibility, and availability alongside metabolic redox reactions. The combined contributions of these processes lead to isotopic enrichment during anoxygenic photosynthesis that is in between the values reported for anaerobic respiratory microbial Hg reduction and abiotic photoreduction. Isotope enrichment during fermentation is closer to what has been observed in aerobic bacteria that reduce Hg through dedicated detoxification pathways. Our work suggests that similar controls likely underpin diverse microbe-mediated Hg transformations that affect Hg’s fate in oxic and anoxic habitats. IMPORTANCE Anaerobic and photosynthetic bacteria that reduce mercury affect mercury delivery to microbes in methylation sites that drive bioaccumulation in food webs. Anaerobic mercury reduction pathways remain underappreciated in the current view of the global mercury cycle because they are challenging to study, bearing no dedicated genetic targets to establish physiological mechanisms. In this study we used stable isotopes to characterize the physiological processes that control mercury reduction during photosynthesis and fermentation in the model anaerobe Heliobacterium modesticaldum Ice1. The sensitivity of isotope analyses highlighted the subtle contribution of mercury uptake towards the isotope signature associated with anaerobic mercury reduction. When considered alongside the isotope signatures associated with microbial pathways for which genetic determinants have been identified, our findings underscore the narrow range of isotope enrichment that is characteristic of microbial mercury transformations. This suggests that there exist common atomic-level controls for biological mercury transformations across a broad range of geochemical conditions.

scholarly journals Unravelling the process of petroleum hydrocarbon biodegradation in different filter materials of constructed wetlands by stable isotope fractionation and labelling studies

2021 ◽  
Author(s):  
Andrea Watzinger ◽  
Melanie Hager ◽  
Thomas Reichenauer ◽  
Gerhard Soja ◽  
Paul Kinner
Keyword(s):  
Stable Isotope ◽  
Constructed Wetlands ◽  
Hydrogen Isotope ◽  
Petroleum Hydrocarbon ◽  
Isotope Fractionation ◽  
Isotope Effects ◽  
Filter Material ◽  
Hydrocarbon Biodegradation ◽  
Stable Isotope Fractionation ◽  
Filter Materials

AbstractMaintaining and supporting complete biodegradation during remediation of petroleum hydrocarbon contaminated groundwater in constructed wetlands is vital for the final destruction and removal of contaminants. We aimed to compare and gain insight into biodegradation and explore possible limitations in different filter materials (sand, sand amended with biochar, expanded clay). These filters were collected from constructed wetlands after two years of operation and batch experiments were conducted using two stable isotope techniques; (i) carbon isotope labelling of hexadecane and (ii) hydrogen isotope fractionation of decane. Both hydrocarbon compounds hexadecane and decane were biodegraded. The mineralization rate of hexadecane was higher in the sandy filter material (3.6 µg CO2 g−1 day−1) than in the expanded clay (1.0 µg CO2 g−1 day−1). The microbial community of the constructed wetland microcosms was dominated by Gram negative bacteria and fungi and was specific for the different filter materials while hexadecane was primarily anabolized by bacteria. Adsorption / desorption of petroleum hydrocarbons in expanded clay was observed, which might not hinder but delay biodegradation. Very few cases of hydrogen isotope fractionation were recorded in expanded clay and sand & biochar filters during decane biodegradation. In sand filters, decane was biodegraded more slowly and hydrogen isotope fractionation was visible. Still, the range of observed apparent kinetic hydrogen isotope effects (AKIEH = 1.072–1.500) and apparent decane biodegradation rates (k = − 0.017 to − 0.067 day−1) of the sand filter were low. To conclude, low biodegradation rates, small hydrogen isotope fractionation, zero order mineralization kinetics and lack of microbial biomass growth indicated that mass transfer controlled biodegradation.

Effects of food quality, starvation and life stage on stable isotope fractionation in Collembola

Pedobiologia ◽  
2005 ◽  
Vol 49 (3) ◽  
pp. 229-237 ◽  
Author(s):  
Dominique Haubert ◽  
Reinhard Langel ◽  
Stefan Scheu ◽  
Liliane Ruess
Keyword(s):  
Stable Isotope ◽  
Food Quality ◽  
Isotope Fractionation ◽  
Life Stage ◽  
Stable Isotope Fractionation

Magnesium stable isotope fractionation in marine biogenic calcite and aragonite

2011 ◽  
Vol 75 (19) ◽  
pp. 5797-5818 ◽  
Author(s):  
F. Wombacher ◽  
A. Eisenhauer ◽  
F. Böhm ◽  
N. Gussone ◽  
M. Regenberg ◽  
...  
Keyword(s):  
Stable Isotope ◽  
Isotope Fractionation ◽  
Stable Isotope Fractionation

Compound-Specific Stable Isotope Fractionation of Pesticides and Pharmaceuticals in a Mesoscale Aquifer Model

2016 ◽  
Vol 50 (11) ◽  
pp. 5729-5739 ◽  
Author(s):  
Heide K. V. Schürner ◽  
Michael P. Maier ◽  
Dominik Eckert ◽  
Ramona Brejcha ◽  
Claudia-Constanze Neumann ◽  
...  
Keyword(s):  
Stable Isotope ◽  
Isotope Fractionation ◽  
Stable Isotope Fractionation

Cadmium uptake and transport processes in rice revealed by stable isotope fractionation and Cd-related gene expression

2022 ◽  
Vol 806 ◽  
pp. 150633
Author(s):  
Songxiong Zhong ◽  
Xiaomin Li ◽  
Fangbai Li ◽  
Yingmei Huang ◽  
Tongxu Liu ◽  
...  
Keyword(s):  
Gene Expression ◽  
Stable Isotope ◽  
Isotope Fractionation ◽  
Transport Processes ◽  
Cadmium Uptake ◽  
Related Gene ◽  
Stable Isotope Fractionation ◽  
Uptake And Transport

Zinc stable isotope fractionation upon accelerated oxidative weathering of sulfidic mine waste

2014 ◽  
Vol 487 ◽  
pp. 97-101 ◽  
Author(s):  
R. Matthies ◽  
L. Krahé ◽  
D.W. Blowes
Keyword(s):  
Stable Isotope ◽  
Isotope Fractionation ◽  
Mine Waste ◽  
Stable Isotope Fractionation

Redox Driven Stable Isotope Fractionation

2011 ◽  
pp. 345-359 ◽  
Author(s):  
Jay R. Black ◽  
Jeffrey A. Crawford ◽  
Seth John ◽  
Abby Kavner
Keyword(s):  
Stable Isotope ◽  
Isotope Fractionation ◽  
Stable Isotope Fractionation
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