Distribution of thiols in the northwest Atlantic Ocean

Kading, Tristan

doi:10.1575/1912/5711

Cited by 3 publications

(7 citation statements)

References 73 publications

(101 reference statements)

Supporting

Mentioning

Contrasting

Order By: Relevance

“…In estuarine, coastal and open ocean waters, their concentrations typically fall in the low nM range. Cys concentrations in the marine environments are typically lower, for instance 0.3 to 2.11 nM in the North Pacific (Dupont et al, 2006) and < 0.1 to 1.5 nM in the North Atlantic (Kading, 2013; Swarr et al, 2016). These Cys concentrations are about 2 orders of magnitude lower than those (> 100 nM) that reduced MeHg uptake in our study.…”

Section: Discussionmentioning

confidence: 99%

“…In contrast to Cys, our study showed that MeHg uptake was decreased by 30% in the presence of 10 nM of GSH, a concentration approaching levels observed in marine environments, especially estuarine and coastal waters. Reported concentrations of GSH ranged from < 1 to 15 nM in the North-East Atlantic (Le Gall and van den Berg, 1998), 0.7 to 3.6 nM in coastal England (Al-Farawati and van den Berg, 2001), < 0.1 to 2.21 nM in the North Atlantic (Kading, 2013; Swarr et al, 2016), 0.01 to 0.76 in the North Pacific (Dupont et al, 2006), 0.23 to 6.23 nM in Galveston Bay, Texas (Tang et al, 2000), 0.17 to 0.79 nM in San Diego Bay, California (Tang et al, 2004), 0.08 to 0.13 nM in Cape Gear Estuary, North Carolina (Tang et al, 2004), and 0.37 to 0.45 nM in Norfolk Estuary, Virginia (Tang et al, 2004); however electro-analytical methods used in some of these studies may lead to over-estimates of GSH concentrations due to indiscriminate quantification (the authors assumed GSH was the primary component in total thiols). Notably, rather than GSH, γEC (γ-glutamylcysteine, a precursor of GSH) was found to be the most abundant thiol species (2 to 15 nM) in the North Pacific (Dupont et al, 2006).…”

Section: Discussionmentioning

confidence: 99%

See 1 more Smart Citation

Bioaccumulation of methylmercury in a marine diatom and the influence of dissolved organic matter

Lee

Fisher

2017

Marine Chemistry

View full text Add to dashboard Cite

The largest bioconcentration step of most metals, including methylmercury (MeHg), in aquatic biota is from water to phytoplankton, but the extent to which dissolved organic matter (DOM) affects this process for MeHg largely remains unexplored in marine systems. This study investigated the influence of specific sulfur-containing organic compounds and naturally occurring DOM on the accumulation of MeHg in a marine diatom Thalassiosira pseudonana. Initial uptake rate constants and volume concentration factors (VCFs) of MeHg were calculated to evaluate MeHg enrichment in algal cells in the presence of a range of organic compound concentrations. At environmentally realistic and higher concentrations, the addition of glycine and methionine had no effect on algal MeHg uptake, but thiol-containing compounds such as cysteine and thioglycolic acid reduced MeHg accumulation in algal cells at high added concentrations (> 100 times higher than naturally occurring concentrations). However, environmentally realistic concentrations of glutathione, another thiol-containing compound as low as 10 nM, resulted in a decline of ~ 30% in VCFs, suggesting its possible importance in natural waters. Humic acid additions of 0.1 and 0.5 mg C/L also reduced MeHg VCFs by ~ 15% and ~ 25%, respectively. The bioaccumulation of MeHg for T. pseudonana in coastal waters with varying levels of dissolved organic carbon (DOC) was inversely correlated with bulk DOC concentrations. Generally, naturally occurring DOM, particularly certain thiol-containing compounds, can reduce MeHg uptake by phytoplankton.

show abstract

Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Bioaccumulation of methylmercury in a marine diatom and the influence of dissolved organic matter

Lee

Fisher

2017

Marine Chemistry

View full text Add to dashboard Cite

show abstract

“…Before analysis, frozen seawater samples were thawed overnight in a refrigerator and acidified to 15 mM with methanesulfonic acid (MSA). Samples (50 mL) were derivatized and analyzed according to the methods of Tang and colleagues (2003) with a few modifications (Kading, 2013). Changes to the Tang protocol included use of tris(2-carboxyethyl)phosphine (TCEP) as the reducing agent, and addition of the reducing agent after neutralization, rather than before.…”

Section: Derivitizationmentioning

confidence: 99%

“…As the primary source of thiols is biogenic production, co-variation between dissolved thiols and chlorophyll a (Chl a) concentrations might be expected and indeed has been observed in the surface coastal ocean (Al-Farawati and van den Berg, 2001). However, thiol concentrations were unrelated to Chl a in surface water from both the northwest Pacific and 4 northwest Atlantic (Dupont et al, 2006;Kading, 2013), which suggests that the sinks (primarily photo-oxidation and biological uptake) for thiols may be just as influential as biogenic production in determining ambient concentrations, especially in oligotrophic surface waters and at depths below the photic zone. For example, photochemical destruction of the thiol pool in the surface ocean has been demonstrated to be on the order of hours (Flock et al, 1997;Winterbourn and Metodiewa, 1999;Laglera and van den Berg, 2006;Moingt et al, 2010).…”

Section: Introductionmentioning

confidence: 98%

Dissolved low-molecular weight thiol concentrations from the U.S. GEOTRACES North Atlantic Ocean zonal transect

Swarr

Kading

Lamborg

et al. 2016

Deep Sea Research Part I: Oceanographic Research Papers

Self Cite

View full text Add to dashboard Cite

Low-molecular weight thiols, including cysteine and glutathione, are biomolecules involved in a variety of metabolic pathways and act as important antioxidant and metal buffering agents. In this last capacity, they represent a potential mechanism for modulating the bioavailability and biogeochemistry of many trace elements in the ocean, particularly for chalcophilic elements (e.g., Cu, Zn, Cd, Ag and Hg). For this reason, and in the context of the international GEOTRACES program that seeks to understand the biogeochemistry of trace elements in the ocean, we measured the concentration of individual dissolved low-molecular weight thiols during the U.S. GEOTRACES North Atlantic Zonal Transect (USGNAZT). Only two thiols were identified, cysteine and glutathione, in contrast to results from the northeast subarctic Pacific Ocean, where the dipeptides glycine-cysteine and arginine-cysteine were also present and -glutamylcysteine was dominant. Concentrations of cysteine and glutathione in the North Atlantic Ocean were lower than in the Pacific and ranged from below detection (~0.01 nM) to 0.61 nM of cysteine and up to 1.0 nM of glutathione, with cysteine generally more abundant than glutathione. Vertical profiles of cysteine and glutathione were broadly consistent with their biological production, being more abundant in surface water and usually below detection at

show abstract

“…The potential for stimulation of methylation in natural systems by thiol availability has not been investigated, but may be limited in oxic marine waters. Thiol mediated enhancement or suppression of Hg(II) uptake is specific to reduced species [Schaefer and Morel, 2009; and thiols found in marine waters may be oxidized in its primary role as a copper-binding ligand in low Hg marine waters [Kading, 2013]. Although previous measurements of dissolved thiols in marine waters have found that up to half may persist in their reduced forms [Dupont et al, 2006], distributions of small thiols such as cysteine and glutathione are found at nanomolar concentrations in the surface ocean, with depletion at depth [Kading, 2013;Swarr et al, 2012].…”

Section: Temporal Trends In Dissolved Mercury Speciationmentioning

confidence: 99%

Transformations of mercury in the marine water column

Munson¹

2014

View full text Add to dashboard Cite

Methylation of mercury (Hg) in the marine water column has been hypothesized to serve as the primary source of the bioaccumulating chemical species monomethylmercury (MMHg) to marine food webs. Despite decades of research describing mercury methylation in anoxic sediments by anaerobic bacteria, mechanistic studies of water column methylation are severely limited. These essential studies have faced analytical challenges associated with quantifying femtomolar concentrations of the methylated Hg species dimethylmercury (DMHg) and MMHg in marine systems. In addition, the complex biogeochemical cycling of Hg in natural systems require consideration of gaseous, dissolved, and particulate species of Hg in order to probe potential controls on its ultimate transfer into marine food webs.The presented work provides a comprehensive study of Hg chemical speciation and transformations in Tropical Pacific waters. We developed an analytical method for MMHg determination from seawater that has the potential to ease measurements of MMHg distributions, as well as mechanistic studies of Hg species transformations.We used this method, in addition to previously established methods, to measure dissolved and particulate Hg species distributions and fluxes along a transect of the Pacific Ocean. Over significant gradients in oxygen utilization and primary productivity, we observed a region of methylated Hg species focused in the Equatorial Pacific that appeared spatially separated from higher concentrations in North Pacific Intermediate Waters. From the first full water column depth profiles of this region, we also observed the intrusion of elevated Hg into deep waters of the Equatorial and South Pacific Ocean.In addition we observed substantial potential rates of mercury methylation in subsurface and low oxygen waters along the Pacific transect as well as the Sargasso Sea using Hg isotope tracers. We observed dynamic production and decomposition of methylated Hg in low productivity waters, despite low ambient methylated Hg concentrations. From the addition of bulk organic matter as well as individual compounds important for methylation in anaerobic bacteria, we observe no simple limitation of Hg methylation in marine waters but highly dynamic conversion of Hg between methylated and inorganic species. List of Tables 13 Chapter 1: Introduction 15Chapter 2: Determination of monomethylmercury from seawater with ascorbic acidassisted direct ethylation Despite these guidelines, it is estimated that 0.6-11% of US women ages 16-49 have blood mercury (Hg) levels above the recommended limit for safe exposure [Mahaffey et al, 2004].Estimates of fish sources suggest that up to 90% of fish consumed in the US are from marine and estuarine environments [Sunderland, 2007]. As a result, understanding the factors that controlMMHg sources and transfer in marine environments is crucial for minimizing potential health threats to humans and marine life. Mercury from Marine Waters to BiotaThe need to quantify MMHg sources in natural waters is r...

show abstract

Distribution of thiols in the northwest Atlantic Ocean

Cited by 3 publications

References 73 publications

Bioaccumulation of methylmercury in a marine diatom and the influence of dissolved organic matter

Bioaccumulation of methylmercury in a marine diatom and the influence of dissolved organic matter

Dissolved low-molecular weight thiol concentrations from the U.S. GEOTRACES North Atlantic Ocean zonal transect

Transformations of mercury in the marine water column

Contact Info

Product

Resources

About