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Thawing permafrost in the Canadian Arctic tundra leads to peat erosion and slumping in narrow and shallow runnel ponds that surround more commonly studied polygonal ponds. Here we compared the methane production between runnel and polygonal ponds using stable isotope ratios, ¹⁴C signatures, and investigated potential methanogenic communities through high-throughput sequencing archaeal 16S rRNA genes. We found that runnel ponds had significantly higher methane and carbon dioxide emissions, produced from a slightly larger fraction of old carbon, compared to polygonal ponds. The methane stable isotopic signature indicated production through acetoclastic methanogenesis, but gene signatures from acetoclastic and hydrogenotrophic methanogenic Archaea were detected in both polygonal and runnel ponds. We conclude that runnel ponds represent a source of methane from potentially older C, and that they contain methanogenic communities able to use diverse sources of carbon, increasing the risk of augmented methane release under a warmer climate.

Polybrominated diphenyl ethers (PBDEs) and polychlorinated biphenyls (PCBs) were measured in sediments and benthic invertebrates near submarine municipal outfalls in Victoria and Vancouver, B.C., Canada, two areas with contrasting receiving environments. PBDE concentrations in wastewater exceeded those of the legacy PCBs by eight times at Vancouver and 35 times at Victoria. Total PBDE concentrations in benthic invertebrates were higher near Vancouver than Victoria, despite lower concentrations in sediments, and correlated with organic carbon-normalized concentrations in sediment. Principal Components Analysis indicated uptake of individual PBDE congeners was determined by sediment properties (organic carbon, grain size), while PCB congener uptake was governed by physico-chemical properties (octanol-water partitioning coefficient). Results suggest the utility of sediment quality guidelines for PBDEs and likely PCBs benefit if based on organic carbon-normalized concentrations. Also, where enhanced wastewater treatment increases the PBDEs to particulate organic carbon ratio in effluent, nearfield benthic invertebrates may face increased PBDE accumulation., (Crown Copyright © 2012. Published by Elsevier Ltd. All rights reserved.)

Polychlorinated biphenyl (PCB) biomagnification was characterized in a harbor seal food web in the Strait of Georgia, British Columbia, Canada. Trophic magnification factors (TMFs) for PCBs averaged 3.6, with a range of 0.7 to 9.4. The TMFs for individual congeners correlated with log K(OW) (r(2) = 0.56, p < 0.001), reflecting the role that physicochemical properties play in driving the biomagnification of PCBs in marine food webs. However, TMFs differed among PCB structure activity groups, clearly indicating an additional role for metabolic transformation of certain PCBs. The known feeding preferences of harbor seals enabled the calculation of trophic level-adjusted biomagnification factors (BMF(TL)) for PCBs in this species, which averaged 13.4 and ranged from 0.2 to 150.6. Metabolic transformation in seals explained some of the variation in congener-specific biomagnification, with lower BMF(TL) values for PCB congeners with meta- and parachlorine unsubstituted positions. Principal components analysis revealed the distinct roles played by trophic level, log K(OW), and metabolic transformation in explaining the notable differences in PCB patterns among harbor seals, their pups, and their prey. In the present study, the authors estimate there to be approximately 76 kg of PCBs in the biota of the Strait of Georgia, of which 1.6 kg is retained by harbor seals., (Copyright © 2012 SETAC.)

The fate of contaminants entering the marine environment through wastewater outfalls depends on the contaminant's persistence and affinity for particles. However, the physical characteristics of the receiving environment, for example, current velocity and sedimentary processes, may be even more important. Because of the complexity of natural settings and the lack of appropriate comparative settings, this is not frequently evaluated quantitatively. The authors investigated the near-field accumulation of particle-reactive polybrominated diphenyl ethers (PBDEs) entering coastal waters by way of two municipal outfalls: one discharging into a high-energy, low-sedimentation environment near Victoria, BC, Canada; the other into a low-energy, high-sedimentation environment, near Vancouver, BC. The authors used ²¹⁰Pb profiles in box cores together with an advection-diffusion model to determine surface mixing and sedimentation rates, and to model the depositional history of PBDEs at these sites. Surprisingly, 88 to 99% of PBDEs were dispersed beyond the near-field at both sites, but a greater proportion of PBDEs was captured in the sediment near the Vancouver outfall where rapid burial was facilitated by inorganic sediment supplied from the nearby Fraser River. Although the discharge of PBDEs was much lower from the Victoria outfall than from Vancouver, some sediment PBDE concentrations were higher near Victoria., (Copyright © 2011 SETAC.)

We measured persistent organic pollutant (POP) concentrations in chinook salmon (Oncorhynchus tshawytscha) in order to characterize dietary exposure in the highly contaminated, salmon-eating northeastern Pacific resident killer whales. We estimate that 97 to 99% of polychlorinated biphenyls (PCBs), polychlorinated dibenzo-p-dioxins (PCDDs), polychlorinated dibenzofurans (PCDFs), dichlorodiphenyltrichloroethane (DDT), and hexachlorocyclohexane (HCH) in returning adult chinook were acquired during their time at sea. Highest POP concentrations (including PCBs, PCDDs, PCDFs, and DDT) and lowest lipids were observed in the more southerly chinook sampled. While feeding by salmon as they enter some more POP-contaminated near-shore environments inevitably contribute to their contamination, relationships observed between POP patterns and both lipid content and delta13C also suggest a migration-related metabolism and loss of the less-chlorinated PCB congeners. This has implications for killer whales, with the more PCB-contaminated salmon stocks in the south partly explaining the 4.0 to 6.6 times higher estimated daily intake for sigmaPCBs in southern resident killer whales compared to northern residents. We hypothesize that the lower lipid content of southerly chinook stocks may cause southern resident killer whales to increase their salmon consumption by as much as 50%, which would further increase their exposure to POPs.

We report atmospheric methane carbon isotope ratios (delta13CH4) from the Western Greenland ice margin spanning the Younger Dryas-to-Preboreal (YD-PB) transition. Over the recorded approximately 800 years, delta13CH4 was around -46 per mil (per thousand); that is, approximately 1 per thousand higher than in the modern atmosphere and approximately 5.5 per thousand higher than would be expected from budgets without 13C-rich anthropogenic emissions. This requires higher natural 13C-rich emissions or stronger sink fractionation than conventionally assumed. Constant delta13CH4 during the rise in methane concentration at the YD-PB transition is consistent with additional emissions from tropical wetlands, or aerobic plant CH4 production, or with a multisource scenario. A marine clathrate source is unlikely.

Methanotrophic bacteria play an important role in global cycling of carbon and co-metabolism of contaminants. Methanotrophs from pristine regions of the Snake River Plain Aquifer (SRPA; Idaho, USA) were studied in order to gain insight into the native groundwater communities' genetic potential to carry out TCE co-metabolism. Wells were selected that were proximal to a TCE plume believed to be undergoing natural attenuation. Methane concentrations ranged from 1 to >1000 nM. Carbon isotope ratios and diversity data together suggest that the SRPA contains active communities of methanotrophs that oxidize microbially produced methane. Microorganisms removed from groundwater by filtration were used as inocula for enrichments or frozen immediately and DNA was subsequently extracted for molecular characterization. Primers that specifically target methanotroph 16S rRNA genes or genes that code for subunits of soluble or particulate methane monooxygenase, mmoX and pmoA, respectively, were used to characterize the indigenous methanotrophs via PCR, cloning, RFLP analysis, and sequencing. Type I methanotroph clones aligned with Methylomonas, Methylocaldum, and Methylobacter sequences and a distinct 16S rRNA phylogenetic lineage grouped near Methylobacter. The majority of clone sequences in type II methanotroph 16S rRNA, pmoA, and mmoX gene libraries grouped closely with sequences in the Methylocystis genus. A subset of the type II methanotroph clones from the aquifer had sequences that aligned most closely to Methylosinus trichosporium OB3b and Methylocystis spp., known TCE-co-metabolizing methanotrophs.

Characteristics of an obligately methylotrophic coccoid methanogen (strain GS-16) previously isolated from estuarine sediment are described. Growth was demonstrated on dimethyl sulfide (DMS) or trimethylamine (TMA), but not on methane thiol, methane thiol plus hydrogen, dimethyl disulfide, or methionine. DMS-grown cells were able to metabolize DMS and TMA simultaneously when inoculated into media containing substrate levels of these compounds. However, TMA-grown cells could not metabolize [C]DMS to CH(4), although they could convert [C]methanol to CH(4). These results suggest that metabolism of DMS proceeds along a somewhat different route than that of TMA and perhaps also that of methanol. The organism exhibited doubling times of 23 and 32 h for growth (25 degrees C) in mineral media on TMA and DMS, respectively. Doubling times were more rapid ( approximately 6 h) when the organisms were grown on TMA in complex broth. In mineral media, the fastest growth on DMS occurred between pH levels of 7.0 and 8.7, at 29 degrees C, and with 0.2 to 0.4 M Na and 0.04 M Mg. Somewhat different results occurred for growth on TMA in complex broth. Cells had a moles percent G+C value of 44.5% for their DNA. Growth on DMS, TMA, and methanol yielded stable carbon isotope fractionation factors of 1.044, 1.037, and 1.063, respectively. Fractionation factors for hydrogen were 1.203 (DMS) and 1.183 (TMA).