Organic Geochemical Evidence for the Formation of Condensate from Coaly Source Rocks in the Wumaying Buried Hill of the Huanghua Depression, Bohai Bay Basin.

Although oil and gas from coaly source rocks have been widely discovered worldwide, the role of oil generated from coal measures in marine-continental coaly deposits during the Carboniferous-Permian period in the Bohai Bay Basin has long been a subject of debate. The recent discovery of a condensate reservoir in the Wumaying buried hill within the Huanghua Depression of the Bohai Bay Basin offers new potential insights into this issue. In this study, we employed organic geochemical methods to explore the possibility of the Carboniferous-Permian coal deposit being a primary source of the condensate. The distribution of light hydrocarbons and the biomarker assemblage indicate that the condensate did not undergo significant secondary alterations such as thermal cracking, gas invasion fractionation, or biodegradation. The hydrocarbon generation potential of the Carboniferous-Permian coaly source rocks suggests that they could be an important contributor to the formation of condensate. High pristine/phytane ratios (1.0-7.5), an abundant presence of benzene series, and the dominance of C29 steranes (>50%) within the condensate could be indicative of coaly organic matter. These features are comparable to those found in coaly source rocks. Moreover, the stable carbon isotopic compositions of n-alkanes in the condensate, ranging from -26.0 to -30.0‰, correlate well with those from coaly mudstone (-25.4 to -30.0‰). This suggests that the condensate of the Wumaying buried hill may predominantly originate from the Carboniferous-Permian coaly mudstone. When integrated with the geological background, the results distinctly demonstrate that the Carboniferous-Permian coaly source rocks have significantly contributed to the formation of the condensate reservoir in the Wumaying buried hill. This provides an essential reference for future exploration of oil and gas resources derived from the carboniferous-Permian coaly source rocks in the Bohai Bay Basin.

A novel bioprospecting strategy via 13C-based high-throughput probing of active methylotrophs inhabiting oil reservoir surface soil.

Methane-oxidizing bacteria (MOB) have long been considered as a microbial indicator for oil and gas prospecting. However, due to the phylogenetically narrow breath of ecophysiologically distinct MOB, classic culture-dependent approaches could not discriminate MOB population at fine resolution, and accurately reflect the abundance of active MOB in the soil above oil and gas reservoirs. Here, we presented a novel microbial anomaly detection (MAD) strategy to quantitatively identify specific indicator methylotrophs in the surface soils for bioprospecting oil and gas reservoirs by using a combination of 13C-DNA stable isotope probing (SIP), high-throughput sequencing (HTS), quantitative PCR (qPCR) and geostatistical analysis. The Chunguang oilfield of the Junggar Basin was selected as a model system in western China, and type I methanotrophic Methylobacter was most active in the topsoil above the productive oil wells, while type II methanotrophic Methylosinus predominated in the dry well soils, exhibiting clear differences between non- and oil reservoir soils. Similar results were observed by quantification of Methylobacter pmoA genes as a specific bioindicator for the prediction of unknown reservoirs by grid sampling. A microbial anomaly distribution map based on geostatistical analysis further showed that the anomalous zones were highly consistent with petroleum, geological and seismic data, and validated by subsequent drilling. Over seven years, a total of 24 wells have been designed and drilled into the targeted anomaly, and the success rate via the MAD prospecting strategy was 83 %. Our results suggested that molecular techniques are powerful tools for oil and gas prospecting. This study indicates that the exploration efficiency could be significantly improved by integrating multi-disciplinary information in geophysics and geomicrobiology while reducing the drilling risk to a greater extent.

Identifying Active Rather than Total Methanotrophs Inhabiting Surface Soil Is Essential for the Microbial Prospection of Gas Reservoirs.

Methane-oxidizing bacteria (MOB) have long been recognized as an important bioindicator for oil and gas exploration. However, due to their physiological and ecological diversity, the distribution of MOB in different habitats varies widely, making it challenging to authentically reflect the abundance of active MOB in the soil above oil and gas reservoirs using conventional methods. Here, we selected the Puguang gas field of the Sichuan Basin in Southwest China as a model system to study the ecological characteristics of methanotrophs using culture-independent molecular techniques. Initially, by comparing the abundance of the pmoA genes determined by quantitative PCR (qPCR), no significant difference was found between gas well and non-gas well soils, indicating that the abundance of total MOB may not necessarily reflect the distribution of the underlying gas reservoirs. 13C-DNA stable isotope probing (DNA-SIP) in combination with high-throughput sequencing (HTS) furthermore revealed that type II methanotrophic Methylocystis was the absolutely predominant active MOB in the non-gas-field soils, whereas the niche vacated by Methylocystis was gradually filled with type I RPC-2 (rice paddy cluster-2) and Methylosarcina in the surface soils of gas reservoirs after geoscale acclimation to trace- and continuous-methane supply. The sum of the relative abundance of RPC-2 and Methylosarcina was then used as specific biotic index (BI) in the Puguang gas field. A microbial anomaly distribution map based on the BI values showed that the anomalous zones were highly consistent with geological and geophysical data, and known drilling results. Therefore, the active but not total methanotrophs successfully reflected the microseepage intensity of the underlying active hydrocarbon system, and can be used as an essential quantitative index to determine the existence and distribution of reservoirs. Our results suggest that molecular microbial techniques are powerful tools for oil and gas prospecting.

Lipid biomarkers recording marine microbial community structure changes through the Frasnian-Famennian mass extinction event.

Studying the response and recovery of marine microbial communities during mass extinction events provides an evolutionary window through which to understand the adaptation and resilience of the marine ecosystem in the face of significant environmental disturbances. The goal of this study is to reconstruct changes in the marine microbial community structure through the Late Devonian Frasnian-Famennian (F-F) transition. We performed a multiproxy investigation on a drill core of the Upper Devonian New Albany Shale from the Illinois Basin (western Kentucky, USA). Aryl isoprenoids show green sulfur bacteria expansion and associated photic zone euxinia (PZE) enhancement during the F-F interval. These changes can be attributed to augmented terrigenous influxes, as recorded collectively by the long-chain/short-chain normal alkane ratio, carbon preference index, C30 moretane/C30 hopane, and diahopane index. Hopane/sterane ratios reveal a more pronounced dominance of eukaryotic over prokaryotic production during the mass extinction interval. Sterane distributions indicate that the microalgal community was primarily composed of green algae clades, and their dominance became more pronounced during the F-F interval and continued to rise in the subsequent periods. The 2α-methylhopane index values do not show an evident shift during the mass extinction interval, whereas the 3ß-methylhopane index values record a greater abundance of methanotrophic bacteria during the extinction interval, suggesting enhanced methane cycling due to intensified oxygen depletion. Overall, the Illinois Basin during the F-F extinction experienced heightened algal productivity due to intensified terrigenous influxes, exhibiting similarities to contemporary coastal oceans that are currently undergoing globalized cultural eutrophication. The observed microbial community shifts associated with the F-F environmental disturbances were largely restricted to the extinction interval, which suggests a relatively stable, resilient marine microbial ecosystem during the Late Devonian.

Linking the unique molecular complexity of dissolved organic matter to flood period in the Yangtze River mainstream.

Large rivers transport a significant amount of terrestrially derived dissolved organic matter (DOM) to coastal oceans, consisting of a critical component of the global biogeochemical cycle. Although high flow events usually introduce more terrestrial DOM than baseflow, the underlying molecular complexity and lability of DOM during high discharge are not well constrained, especially in large river ecosystems. By combining ultraviolet and fluorescent spectroscopy, and ultrahigh-resolution mass spectrometry, we found that stronger terrestrial DOM signal was detected during high discharge than normal discharge in the Yangtze River mainstream. The averaged DOC concentration was higher during high discharge than normal discharge. Optical properties confirmed higher aromaticity and relatively higher humic-like fluorescent components in DOM during high discharge. The molecular composition showed significantly higher molecular complexity, averaged molecular weight, aromaticity, relative abundances of polyphenols and highly unsaturated compounds of DOM during high discharge than normal discharge. A large set of unique molecular formulae (up to 4927) was only detected during high discharge. These unique molecular formulae were mostly lignin degradation products, likely due to more intensive soil leaching during high discharge. By comparing with incubation experiments and the Yangtze River mouth and East China Sea DOM molecular composition, some of these unique molecular formulae during high discharge are resistant to both bio- and photo-degradation, and persist during their transport to the East China Sea. Therefore, we suggest that high discharge will additionally introduce a relatively recalcitrant pool of DOM into the Yangtze River mainstream and persist during its journey to the ocean. Considering the projected increase of flood frequency, this study provides a preliminary foundation for further studies to better assess the underlying mechanisms how hydrology affect the biogeochemical cycling of DOM in large rivers.

Spatial changes in molecular composition of dissolved organic matter in the Yangtze River Estuary: Implications for the seaward transport of estuarine DOM.

The complexity of dissolved organic matter (DOM) limits our understanding of the estuarine carbon cycle. This study adopted a combination of bulk carbon isotope, optical techniques and ultra-high resolution mass spectrometry to study the spatial heterogeneity and compositional variations of DOM across a latitudinal transect of the Yangtze River Estuary (YRE). Results show that the whole section of YRE received high abundance of protein-like C4 fluorescent component (0.66 ± 0.08 R.U.) and high relative abundance of aliphatic compounds and peptides (8.28 ± 1.46%) from phytoplankton, which would contribute to the bioavailable DOM pool of the Eastern China Sea (ECS). However, multivariate analysis indicated that polycyclic aromatics and polyphenols from the Yangtze River experienced a significant decrease of 5% within the turbidity zone, creating a significant decrease of 0.08 in aromaticity index and modulating DOM content and compositions within the YRE. 1837 molecular formulae were identified to track dynamic behaviors of terrestrial DOM in the YRE. Molecular imprints showed the removal of terrestrial molecules in the turbidity zone indicated by the decrease of 753 in molecular quantity, when water masses mixing diluted the abundance of aromatic compounds. Adsorption and flocculation could serve important mechanisms to remove terrestrial DOM, promoting the burial of terrestrial DOM within estuarine sediments. Besides, some terrestrial molecular formulae were also detected in the ECS, suggesting the potential contribution of terrestrial DOM to the carbon stock of open seas after experiencing physical and photochemical transformations. This research provides a comprehensive insight into spatial variations of estuarine DOM composition, underlining the important role of estuaries in sorting and transporting DOM.

Hydrological management constraints on the chemistry of dissolved organic matter in the Three Gorges Reservoir.

Reservoirs are well known as a far-reaching human modification on the functions of natural river networks. However, changes in the chemistry and reactivity of dissolved organic matter (DOM) responding to hydrological management for water retention structures, and its influence on the river carbon cycle, remain poorly understood. Here we show that hydrological management does shape the molecular composition of DOM in the world's largest Three Gorges Reservoir, as revealed by optical spectroscopy and ultrahigh-resolution mass spectrometry. Relatively higher terrestrial input, molecular complexity, isomeric complexity, and environmental stability of DOM were observed during the storage period, whereas the inverse occurred during the drainage period. The results demonstrate that the hydrodynamic processes, which are mainly controlled by water intrusion from mainstream to tributaries, are likely the underlying mechanism controlling DOM chemistry. Integrated with observations from worldwide river reservoirs, the DOM degradation experiments suggest that reservoir hydrological management would enhance DOM mineralization, thereby increase CO2 emission and change the river carbon cycle.

Processing of dissolved organic matter from surface waters to sediment pore waters in a temperate coastal wetland.

Coastal wetlands are active transitional ecotones between land and ocean, and are considered as hot spots of organic matter processing within the global carbon cycle, which dissolved organic matter (DOM) plays a critical role. In this study, combined use of ultrahigh-resolution mass spectrometry (FT-ICR MS) and complementary optical techniques was conducted to assess the detailed molecular composition of DOM in the temperate Liaohe coastal wetland (LCW), NE China in respect to the differences in DOM composition from surface water to sediment pore water. Significant positive correlations between salinity and dissolved organic carbon (DOC) concentrations were observed in both surface waters and pore waters. Pore water DOM is generally characterized by lower protein-like fluorescence and biological index, but higher humification and humic-like fluorescent components than those in surface water DOM. Corresponding to the optical properties, FT-ICR MS measurements show that pore water DOM has higher proportions of heteroatoms, aromaticity index, O/C ratios, unsaturated aliphatics, and peptides, but lower average H/C ratios compared to surface water DOM across locations with different marsh plant species (rice (Oryza sativa), reed (Phragmites australis), Seablite (Suaeda Salsa)) and salinity (0.5 to 51.5 psu). The results suggest that selective preservation for polyphenols, lignin degradation intermediates (highly unsaturated compounds), and microbial resynthesis of heteroatomic compounds are involved in the processing of DOM from surface water to pore water, leading to the formation of higher molecular weight and sulfur-containing molecules. The abundant CHOS compounds could be related to the early diagenetic sulfurization of DOM in sediments. Our unique data set should provide new clues for a comprehensive understanding of the molecular dynamics of DOM in coastal wetlands.

Source identification of chromium in the sediments of the Xiaoqing River and Laizhou Bay: A chromium stable isotope perspective.

Hexavalent chromium, Cr(VI), is a heavy metal contaminant and the reduction of Cr(VI) is accompanied by large isotopic fractionation. In this study, the sources of Cr were explored using the Cr isotopic composition of sediments from the Xiaoqing River, a heavily polluted river located in the Shandong Province of China, which flows into Laizhou Bay. The results show that δ53Cr values of the sediments are the highest upstream near the pollution source, and gradually decrease along the river toward the range for igneous reservoirs observed near the estuary. Based on the calculation of authigenic Cr isotopic composition (δ53Crauth) using the detrital index and leaching experiments, we suggest that the authigenic Cr in the sample near the pollution source with the highest δ53Crauth value mainly comes from the reduction of Cr(VI) discharged by anthropogenic activity, and authigenic Cr in other samples in the midstream with δ53Crauth values slightly higher than the range of igneous reservoirs may come from natural oxidative Cr weathering products. By introducing a Rayleigh model, we calculate that at least 31%-55% of Cr(VI) in the river water had been reduced to Cr(III) near the pollution source. Due to the self-purification ability of the river, Cr(VI) was reduced; thus, there is no record of high δ53Crauth values in the downstream of the Xiaoqing River and Laizhou Bay, indicating no obvious Cr pollution in these locations. The limited variation of δ53Cr values for samples from a sediment core in Laizhou Bay is also indicative of no obvious Cr pollution in the history. The Cr isotopic compositions of the river sediments are useful for the identification of Cr sources and can be used to advise environmental remediation on Cr pollution.

Optical and Molecular Signatures of Dissolved Organic Matter Reflect Anthropogenic Influence in a Coastal River, Northeast China.

Sources and molecular composition of dissolved organic matter (DOM) in coastal rivers have been tightly linked with its reactivity and fate, thus influencing element and nutrient cycling. The DOM in coastal rivers is usually sourced from both terrestrial and marine inputs, with further complication by anthropogenic activities, which is less understood in coastal rivers located near populated industrial regions. In this study, DOM in a typical anthropogenically influenced coastal river, Daliao River, was analyzed for optical analyses and for molecular composition via Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) to give a better scope of composition and sources of DOM. The DOM was enriched in autochthonous and anthropogenic inputs at upstream sites according to high chlorophyll a concentrations, strong protein-like fluorescence, and nonoxygen heteroatomic CHOS formulae (19-24% by relative peak intensity) detected by FT-ICR MS analysis. A series of surfactant-like formulae, indicative of wastewater inputs, were identified and showed a decreasing trend from upstream to the river mouth. Compared with large world rivers, the DOM of Daliao River is characterized by higher abundances of heteroatomic (excluding O) formulae and molecular lability, which is likely caused by strong autochthonous and anthropogenic inputs. In general, we demonstrate that in addition to optical properties, the molecular composition can assess the specific anthropogenic imprints and molecular lability of DOM, which is essential for constraining sources and identifying processes during the transit of DOM from the river to estuary with increasing urbanization and industrialization.

Geochemical Evidence of First Forestation in the Southernmost Euramerica from Upper Devonian (Famennian) Black Shales.

The global dispersal of forests and soils has been proposed as a cause for the Late Devonian mass extinctions of marine organisms, but detailed spatiotemporal records of forests and soils at that time remain lacking. We present data from microscopic and geochemical analyses of the Upper Devonian Chattanooga Shale (Famennian Stage). Plant residues (microfossils, vitrinite and inertinite) and biomarkers derived from terrestrial plants and wildfire occur throughout the stratigraphic section, suggesting widespread forest in the southern Appalachian Basin, a region with no macro plant fossil record during the Famennian. Inorganic geochemical results, as shown by increasing values of SiO2/Al2O3, Ti/Al, Zr/Al, and the Chemical Index of Alteration (CIA) upon time sequence, suggest enhanced continental weathering that may be attributed to the invasion of barren lands by rooted land plants. Our geochemical data collectively provide the oldest evidence of the influences of land plants from the southernmost Appalachian Basin. Our synthesis of vascular plant fossil record shows a more rapid process of afforestation and pedogenesis across south-central Euramerica during the Frasnian and Famennian than previously documented. Together, these results lead us to propose a new hypothesis that global floral dispersal had progressed southward along the Acadian landmass rapidly during the Late Devonian.

Optical and molecular signatures of dissolved organic matter in Xiangxi Bay and mainstream of Three Gorges Reservoir, China: Spatial variations and environmental implications.

With the on-going boom in the construction of dam reservoirs all over the world, the sources and composition of dissolved organic matter (DOM) in fluvial networks are expected to be altered. Considering the importance of DOM as a key biogeochemical component in inland waters, this might bring important ecological and environmental influences. However, limited information is available on the molecular composition of DOM in dam reservoirs. In this study, the spatial characteristics of DOM composition were investigated in Xiangxi tributary and mainstream of the Three Gorges Reservoir (TGR), the largest freshwater reservoir in the world. The concentration alteration of conservative cations revealed the water intrusion from mainstream into Xiangxi tributary, which mainly controlled the hydrological gradient. One tyrosine-like (C4), one tryptophan-like (C2), and two humic-like (C1 and C3) fluorescent components were identified in fluorescent DOM (FDOM) by parallel factor analysis (PAFACAC), potentially indicating algal, anthropogenic, and terrestrial inputs, respectively. Decreasing trends of C1, C3 and C4 components and an increasing trend of C2 component were observed from Xiangxi tributary to mainstream, indicating higher terrestrial and algal inputs but lower anthropogenic inputs in Xiangxi tributary compared to mainstream. The Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) characterization further revealed substantial heterogeneity of DOM at the molecular level. Interestingly, S-containing compounds related to synthetic surfactants were consistently detected, and their relative abundances showed an increasing trend from Xiangxi tributary to mainstream, in agreement with the distribution of the anthropogenic derived C2 component. Meanwhile, numerous lignin-like S-containing compounds were identified, likely the result of the incorporation of sulfide ions to lignin-like CHO compounds. This study represents the first molecular level characterization of DOM in the TGR system, which should aid the design and implementation of more detailed future studies.

Spatiotemporal variability of hydrocarbons in surface sediments from an intensively human-impacted Xiaoqing River-Laizhou Bay system in the eastern China: Occurrence, compositional profile and source apportionment.

Hydrocarbons in coastal sediments record organic matter sources, and thus are widely used to elucidate both natural and anthropogenic inputs and for the estimation of pollution levels. Surface sediments were taken from Xiaoqing River and Laizhou Bay of eastern China in spring and summer of 2014, and were analyzed to determine the characteristics of aliphatic and aromatic hydrocarbons. Various hydrocarbons were identified, including n-alkanes, monomethylated alkanes (MMAs), isoprenoid alkanes, linear alkylbenzenes (LABs), hopanes, steranes and polycyclic aromatic hydrocarbons (PAHs). They were used to track both biogenic (terrestrial plant and microbial inputs) and anthropogenic inputs (petroleum and fossil fuel or biomass burning) in this ecosystem. The major part of hydrocarbons identified came from anthropogenic inputs including petroleum residues and synthetic detergents related hydrocarbons (16.2-90.3%), followed by higher plant (4.5-80.5%) and microbial inputs (0.8-57.5%). Interestingly, significant differences in hydrocarbon concentrations and distributions were observed between spring and summer. In particular, significant higher percentages of microbially derived hydrocarbons, but lower percentages of anthropogenic and vascular plant derived hydrocarbons were observed in summer than spring. Further principal component analyses suggested that the overall distribution of aliphatic hydrocarbons was mainly controlled by seasonality instead of spatiality. In contrast, the distribution of PAHs showed insignificant spatial and seasonal differences. Physical processes such as atmospheric transportation and further deposition, may be factors influencing the distribution of PAHs in the study area with widely biomass and fossil fuel burning. The decoupled distributions of aliphatic and aromatic hydrocarbons warrant further study for a comprehensive understanding of long term sedimentary hydrocarbon sources and input dynamics with increasing human activities. MAJOR FINDING: Seasonal difference in aliphatic hydrocarbon composition was observed in surface sediments of Laizhou Bay, which is mainly caused by stronger phytoplankton and microbial inputs in summer under the overall high pollution background.

Cyanobacterial blooms in oil-contaminated subtidal sediments revealed by integrated approaches.

Cyanobacteria are important primary producers on the surface of oceans and are susceptible to oil spills. However, their tolerance to oil and their roles in the bioremediation of crude oil remain elusive. We analysed the response of microbial communities to a simulated oil spill in estuarine sediment microcosms under a series of oil concentrations (0, 25, 125, and 250 g kg-1 dry wt.). Cyanobacterial blooms only occurred on the sediment surface in the low oil (LO, 25 g kg-1 dry wt.) group, and cyanobacteria grew from very small amounts to enriched levels according to an internal mechanism. The dominant phylotypes enriched in the oil-contaminated sediments on day 35 were Leptolyngbya, Oscillatoria, Arthrospira (Spirulina), Geitlerinema and Cyanothece, and the majority were capable of fixing nitrogen. Gammaproteobacterial blooms occurred during the early stage, and Oceanospirillales dominated the sediment surface. The annotation of unassembled metatranscriptomic data revealed an increase in nitrogen metabolism, particularly photosynthesis (antenna proteins) during the later stage, together with depletion of fatty acid metabolism. In summary, high concentrations of crude oil are toxic to cyanobacteria but can facilitate the emergence of cyanobacterial aggregation at low concentrations (crude oil concentration < 25 g kg-1 dry wt.).

Using fecal sterols to assess dynamics of sewage input in sediments along a human-impacted river-estuary system in eastern China.

Sedimentary fecal sterols and other sterol biomarkers, combined with bulk total organic carbon (TOC) and its stable carbon isotope were applied to characterize the sewage contamination across a ca. 280 km transect from the Xiaoqing River to the Laizhou Bay, a typical river-estuary system subjected to extensive anthropogenic stress due to rapid regional urbanization and industrialization in eastern China. Two sampling events were performed in both spring and summer seasons in the Laizhou Bay adjacent to the Xiaoqing River in order to assess the potential seasonal variation. Fecal sterols such as coprostanol and epicoprostanol, which are typical indicators of anthropogenic sewage input, displayed high concentrations of up to 63.2 µg g-1 dry weight (dw) and 13.1 µg g-1 dw, respectively. Results suggested that most of the stations along the Xiaoqing River were severely contaminated by fecal inputs with a decreasing trend from the river to the estuary that was mainly explained by the increasing distance from the diffuse sewage sources and the gradual dilution by sea water. Although there was no significant difference in fecal sterol concentrations between spring and summer in the Laizhou Bay, suggestive of no significant difference in sewage abundance, significantly higher average epicoprostanol/coprostanol and lower coprostanol/epicoprostanol ratios were observed in spring than summer, indicative of different sewage sources (e.g., human vs. non-human). Seasonal discharge and land-runoff, air temperature related to microbial activity differences and different extend of animal manure irrigation during agricultural planting could be additional reasons and need further investigation. Nevertheless, fecal sterol concentrations, distributions and diagnostic ratios should all be taken into consideration to better understand sewage inputs and source dynamics in river-estuary ecosystems.

Periodically spilled-oil input as a trigger to stimulate the development of hydrocarbon-degrading consortia in a beach ecosystem.

In this study, time-series samples were taken from a gravel beach to ascertain whether a periodic oil input induced by tidal action at the early stage of an oil spill can be a trigger to stimulate the development of hydrocarbon-degrading bacteria under natural in situ attenuation. High-throughput sequencing shows that the microbial community in beach sediments is characterized by the enrichment of hydrocarbon-degrading bacteria, including Alcanivorax, Dietzia, and Marinobacter. Accompanying the periodic floating-oil input, dynamic successions of microbial communities and corresponding fluctuations in functional genes (alkB and RDH) are clearly indicated in a time sequence, which keeps pace with the ongoing biodegradation of the spilled oil. The microbial succession that accompanies tidal action could benefit from the enhanced exchange of oxygen and nutrients; however, regular inputs of floating oil can be a trigger to stimulate an in situ "seed bank" of hydrocarbon-degrading bacteria. This leads to the continued blooming of hydrocarbon-degrading consortia in beach ecosystems. The results provide new insights into the beach microbial community structure and function in response to oil spills.

[Changes of microbial abundance and functional genes in oil and gas under gaseous hydrocarbon condition].

Objective: Hydrocarbon microseepage is a natural phenomenon that hydrocarbon gases of subsurface petroleum accumulations migrate upward by reservoir pressure. The detection of the activity and distribution of these highly specialized populations can be used to forecast the existence of oil and gas deposits. However, the hydrocarbon-oxidizing bacterial population are usually not predominant in soil samples above the typical onshore oil and gas reservoirs. It is hard to assess the abundance of hydrocarbon-oxidizing bacteria. Methods: In this study, changes of microbial abundance and functional genes were studied. Results: Under gaseous hydrocarbon condition, changes of methane and butane oxidizing bacteria were different. Furthermore, changes of functional genes indicated that genome analysis was more proper for microbial anomalies detection. Conclusion: The profiling data of this study provide a comprehensive insight into gene expression profiles and lay the foundation for optimizing the microbial prospecting technology.

Polybrominated diphenyl ethers (PBDEs) and alternative brominated flame retardants (aBFRs) in sediments from four bays of the Yellow Sea, North China.

The distribution characteristics and potential sources of polybrominated diphenyl ethers (PBDEs) and alternative brominated flame retardants (aBFRs) were investigated in 54 surface sediment samples from four bays (Taozi Bay, Sishili Bay, Dalian Bay, and Jiaozhou Bay) of North China's Yellow Sea. Of the 54 samples studied, 51 were collected from within the four bays and 3 were from rivers emptying into Jiaozhou Bay. Decabromodiphenylethane (DBDPE) was the predominant flame retardant found, and concentration ranged from 0.16 to 39.7 ng g(-1) dw and 1.13-49.9 ng g(-1) dw in coastal and riverine sediments, respectively; these levels were followed by those of BDE 209, and its concentrations ranged from n.d. to 10.2 ng g(-1) dw and 0.05-7.82 ng g(-1) dw in coastal and riverine sediments, respectively. The levels of DBDPE exceeded those of decabromodiphenyl ether (BDE 209) in most of the samples in the study region, whereas the ratio of DBDPE/BDE 209 varied among the four bays. This is indicative of different usage patterns of brominated flame retardants (BFRs) and also different hydrodynamic conditions among these bay areas. The spatial distribution and composition profile analysis indicated that BFRs in Jiaozhou Bay and Dalian Bay were mainly from local sources, whereas transport from Laizhou Bay by coastal currents was the major source of BFRs in Taozi Bay and Sishili Bay. Both the ∑PBDEs and ∑aBFRs (sum of pentabromotoluene (PBT), 2,3-diphenylpropyl-2,4,6-tribromophenyl ether (DPTE), pentabromoethylbenzene (PBEB), and hexabromobenzene (HBB)) were at low concentrations in all the sediments. This is probably attributable to a combination of factors such as low regional usage of these products, atmospheric deposition patterns, coastal currents transportation patterns, and degradation processes for higher BDE congeners. This paper is the first study that has investigated the levels of DBDPE in the coastal sediments of China's Yellow Sea.

Combining molecular fingerprints with multidimensional scaling analyses to identify the source of spilled oil from highly similar suspected oils.

Oil fingerprints have been a powerful tool widely used for determining the source of spilled oil. In most cases, this tool works well. However, it is usually difficult to identify the source if the oil spill accident occurs during offshore petroleum exploration due to the highly similar physiochemical characteristics of suspected oils from the same drilling platform. In this report, a case study from the waters of the South China Sea is presented, and multidimensional scaling analysis (MDS) is introduced to demonstrate how oil fingerprints can be combined with mathematical methods to identify the source of spilled oil from highly similar suspected sources. The results suggest that the MDS calculation based on oil fingerprints and subsequently integrated with specific biomarkers in spilled oils is the most effective method with a great potential for determining the source in terms of highly similar suspected oils.

Activity, distribution, and abundance of methane-oxidizing bacteria in the near surface soils of onshore oil and gas fields.

Methane-oxidizing bacteria (MOB) have long been used as an important biological indicator for oil and gas prospecting, but the ecological characteristics of MOB in hydrocarbon microseep systems are still poorly understood. In this study, the activity, distribution, and abundance of aerobic methanotrophic communities in the surface soils underlying an oil and gas field were investigated using biogeochemical and molecular ecological techniques. Measurements of potential methane oxidation rates and pmoA gene copy numbers showed that soils inside an oil and gas field are hot spots of methane oxidation and MOB abundance. Correspondingly, terminal restriction fragment length polymorphism analyses in combination with cloning and sequencing of pmoA genes also revealed considerable differences in the methanotrophic community composition between oil and gas fields and the surrounding soils. Principal component analysis ordination furthermore indicated a coincidence between elevated CH4 oxidation activity and the methanotrophic community structure with type I methanotrophic Methylococcus and Methylobacter, in particular, as indicator species of oil and gas fields. Collectively, our results show that trace methane migrated from oil and gas reservoirs can considerably influence not only the quantity but also the structure of the methanotrophic community.