A Study to Characterize and Source Hydrocarbon Contamination of Sediments and Scallops in the Port au Port Bay, NL

The local fish harvesters of the Port au Port area noticed an increase in the number of dead/empty scallops (also known as ‘clappers’) in the Fall of 2012. By 2013 almost all of the scallops in the area were clappers. For example, in one catch, 160 of 176 scallops were clappers (Gale, 2014). This problem has been limited to the Port au Port area including Fox Island, Shag Island, and Long Point and Shoal Point areas (Hillier, 2014). However, clappers are not a problem in nearby St. George (Fig. 1a). Scallops have been tested and determined to be free of disease. However, testing has not been performed to determine if organic or inorganic contamination could have been the cause in the collapse of the scallops’ fishery in the Port-au-Port area in 2013. In the Port au Port area alone there are typically 12 to 15 scallop draggers from July to December, and it is estimated that the lost of the scallops in this area will cost these individuals 25% of their income (Hillier, 2014). The Port au Port Fishery Committee asked for help to identify the cause and potential remediation of loss of their scallop fishery. The Port au Port Fishery Committee identified a number of potential causes including seismic testing, environmental contamination due to dumping and drilling, and climate change

Isolation of nitrate-reducing bacteria from an offshore reservoir and the associated biosurfactant production

Biosurfactant producing nitrate-reducing bacteria (NRB) in anaerobic reservoir environments are closely associated with souring (H2S) control in the offshore oil and gas industry. Five NRB strains were screened from offshore produced water samples and all were identified as Pseudomonas stutzeri. Their biosurfactant producing abilities when fed on either glucose or glycerol media were investigated. P. stutzeri CX3 reduced the medium surface tension to 33.5 and 29.6 mN m−1, respectively, while growing on glucose or glycerol media. The CX3 strain was further inoculated to examine its growth performance, resulting in 32.4% and 94.5% of nitrate consumption over 228 hours of monitoring in two media, respectively. The composition analysis of the biosurfactant product generated by P. stutzeri CX3 was conducted through thin-layer chromatography, gas chromatography with a flame ionization detector (FID) and Fourier transform infrared spectroscopy (FT-IR). The biosurfactant product was identified as a mixture of a small part of lipopeptides and a large part of glycolipids while its critical micellar concentration (CMC) was as low as 35 mg L−1. The biosurfactant product demonstrated high stability over a wide range of temperature (4–121 °C), pH (2–10), and salinity (0–20% w/v) concentration. The results provided valuable technical and methodological support for effective offshore reservoir souring control and associated enhanced oil recovery activities

Geochemistry and geobiology of a present-day serpentinization site in California: The Cedars

Ultra-basic (pH 11–12) reducing (−656 to −585 mV) groundwater springs discharging from serpentinized peridotite of The Cedars, CA, were investigated for their geochemistry and geobiology. The spring waters investigated were of meteoric origin; however, geochemical modeling suggests that there were two sources of groundwater, a shallow source with sufficient contact with The Cedars’ peridotite body to be altered geochemically by serpentinization, and a deeper groundwater source that not only flows through the peridotite body but was also in contact with the marine sediments of the Franciscan Subduction Complex (FSC) below the peridotite body. We propose that the groundwater discharging from lower elevations (GPS1 and CS1) reflect the geochemistry of the deeper groundwater in contact with FSC, while groundwaters discharging from springs at higher elevations (NS1 and BSC) were a mixture of the shallow peridotite-only groundwater and the deeper groundwater that has been in contact with the FSC. Cell densities of suspended microbes within these waters were extremely low. In the NS1 and BSC spring fluids, cell densities ranged from 10^2 to 10^3 cells/ml, while suspended cells at GPS were lower than 10 cells/mL. However, glass slides incubated in the BSC and GPS1 springs for 2–3 weeks were colonized by cells with densities ranging from 10^6 to 10^7 cells/cm^2 attached to their surfaces. All of the springs were very low (⩽1 μM) in several essential elements and electron acceptors (e.g. nitrate/ammonium, sulfate, and phosphate) required for (microbial) growth, which is not uncommon at sites of continental serpentinization. Gases rich in N_2, H_2, and CH_4 were exsolving from the springs. The stable carbon isotope value (δ^(13)C_(CH4) = −68 ± 0.6‰) and the CH_4/C_(2+) (>10^3) of methane and other gaseous hydrocarbons exsolving from NS1 were typical of microbially sourced methane, whereas the isotope values and the CH_4/C_(2+) of BSC and CS1 springs were more enriched in ^(13)C and had CH_4/C_(2+) < 10^3, suggesting a mixture of microbial and non-microbial methane. The concentrations of aromatic compounds, and ethane, propane, iso- and n-butane were well described by simple physical mixing between the aromatic- and alkane-poor, shallow groundwater and the relatively aromatic, and alkane-rich groundwater that flows through both the peridotite and the FSC suggesting that these aromatic and alkane compounds originated in the deeper FSC groundwater and are not produced in the shallow peridotite-only groundwater. The aromatic compounds most probably originated from the diagenesis/degradation of organic matter in the marine sediments below the peridotite body, while the gaseous alkanes may have multiple sources including thermal degradation of the organic matter in the marine sediments below the peridotite body and possibly by abiogenic reactions occurring within the peridotite body. This geochemical study demonstrates the complexity of The Cedars, and the possible sources of hydrocarbons at continental sites of serpentinization

Nonequilibrium clumped isotope signals in microbial methane

Methane is a key component in the global carbon cycle with a wide range of anthropogenic and natural sources. Although isotopic compositions of methane have traditionally aided source identification, the abundance of its multiply-substituted “clumped” isotopologues, e.g., 13CH3D, has recently emerged as a proxy for determining methane-formation temperatures; however, the impact of biological processes on methane’s clumped isotopologue signature is poorly constrained. We show that methanogenesis proceeding at relatively high rates in cattle, surface environments, and laboratory cultures exerts kinetic control on 13CH3D abundances and results in anomalously elevated formation temperature estimates. We demonstrate quantitatively that H2 availability accounts for this effect. Clumped methane thermometry can therefore provide constraints on the generation of methane in diverse settings, including continental serpentinization sites and ancient, deep groundwaters.National Science Foundation (U.S.) (EAR-1250394)National Science Foundation (U.S.) (EAR-1322805)Deep Carbon Observatory (Program)Natural Sciences and Engineering Research Council of CanadaDeutsche Forschungsgemeinschaft (Gottfried Wilhelm Leibniz Program)United States. Dept. of Defense (National Defense Science and Engineering Graduate Fellowship)Neil & Anna Rasmussen FoundationGrayce B. Kerr Fund, Inc. (Fellowship)MIT Energy Initiative (Shell-MITEI Graduate Fellowship)Shell International Exploration and Production B.V. (N. Braunsdorf and D. Smit of Shell PTI/EG grant

Solution behavior of reduced C-O-H volatiles in silicate melts at high pressure and temperature

The solubility and solution mechanisms of reduced Csingle bondOsingle bondH volatiles in Na2Osingle bondSiO2 melts in equilibrium with a (H2 + CH4) fluid at the hydrogen fugacity defined by the iron-wüstite + H2O buffer [fH2(IW)] have been determined as a function of pressure (1–2.5 GPa) and silicate melt polymerization (NBO/Si: nonbridging oxygen per silicon) at 1400 °C. The solubility, calculated as CH4, increases from ∼0.2 wt% to ∼0.5 wt% in the melt NBO/Si-range ∼0.4 to ∼1.0. The solubility is not significantly pressure-dependent, probably because fH2(IW) in the 1–2.5 GPa range does not vary greatly with pressure. Carbon isotope fractionation between methane-saturated melts and (H2 + CH4) fluid varied by ∼14‰ in the NBO/Si-range of these melts. The (C..H) and (O..H) speciation in the quenched melts was determined with Raman and 1H MAS NMR spectroscopy. The dominant (C..H)-bearing complexes are molecular methane, CH4, and a complex or functional group that includes entities with Ctriple bond; length of mdashCsingle bondH bonding. Minor abundance of complexes that include Sisingle bondOsingle bondCH3 bonding is tentatively identified in some melts. There is no spectroscopic evidence for Sisingle bondC or Sisingle bondCH3. Raman spectra indicate silicate melt depolymerization (increasing NBO/Si). The [CH4/Ctriple bond; length of mdashCsingle bondH]melt abundance ratio is positively correlated with NBO/Si, which is interpreted to suggest that the (Ctriple bond; length of mdashCsingle bondH)-containing structural entity is bonded to the silicate melt network structure via its nonbridging oxygen. The ∼14‰ carbon isotope fractionation change between fluid and melt is because of the speciation changes of carbon in the melt

Investigations of potential microbial methanogenic and carbon monoxide utilization pathways in ultra-basic reducing springs associated with present-day continental serpentinization: the Tablelands, NL, CAN

Ultra-basic reducing springs at continental sites of serpentinization act as portals into the biogeochemistry of a subsurface environment with H2 and CH4 present. Very little, however, is known about the carbon substrate utilization, energy sources, and metabolic pathways of the microorganisms that live in this ultra-basic environment. The potential for microbial methanogenesis with bicarbonate, formate, acetate, and propionate precursors and carbon monoxide (CO) utilization pathways were tested in laboratory experiments by adding substrates to water and sediment from the Tablelands, NL, CAD, a site of present-day continental serpentinization. Microbial methanogenesis was not observed after bicarbonate, formate, acetate, or propionate addition. CO was consumed in the live experiments but not in the killed controls and the residual CO in the live experiments became enriched in 13C. The average isotopic enrichment factor resulting from this microbial utilization of CO was estimated to be 11.2 ± 0.2‰. Phospholipid fatty acid concentrations and δ13C values suggest limited incorporation of carbon from CO into microbial lipids. This indicates that in our experiments, CO was used primarily as an energy source, but not for biomass growth. Environmental DNA sequencing of spring fluids collected at the same time as the addition experiments yielded a large proportion of Hydrogenophaga-related sequences, which is consistent with previous metagenomic data indicating the potential for these taxa to utilize CO