Hydrocarbon-contaminated Sediments Research Articles

Marine Fungi Select and Transport Aerobic and Anaerobic Bacterial Populations from Polycyclic Aromatic Hydrocarbon-Contaminated Sediments.

The organization of microbial communities in marine sediment relies on complex biotic and abiotic interactions. Among them, the interaction between fungi and bacteria plays a crucial role building specific microbial assemblages, resulting in metabolic networks adapted to environmental conditions. The fungal-bacterial interaction (FBI) includes bacterial translocation via fungal mycelia, allowing bacterial dispersion, and ecological niche colonization. In order to demonstrate that the translocation of bacteria through fungal mycelia involves bacterial selection, the mycelia of two fungi isolated from marine coastal sediment, Alternaria destruens F10.81 and Fusarium pseudonygamai F5.76, showing different strategies for uptake of polycyclic aromatic hydrocarbon (PAH), homogenous internalization and vacuole forming respectively, were used to translocate bacteria through hydrophobic hydrocarbon contaminated sediments. A. destruens F10.81 selected four specific bacteria, while bacterial selection by F. pseudonygamai F5.76 was not evident. Among the bacteria selected by A. destruens F10.81, Spirochaeta litoralis, known as strictly anaerobic bacterium, was identified, indicating that A. destruens F10.81 selects and transports both aerobic and anaerobic bacteria. Such a result is consistent with the observed formation of anoxic micro-niches in areas surrounding and affected by fungal hyphae. Our findings provide new insights on the selection and dispersion of bacterial communities by fungi, which are crucial for the organization of microbial communities and their functioning in coastal PAH-contaminated sediments. IMPORTANCE The study provides advances for understanding fungal-bacterial relationships, particularly on the selection and dispersion of bacterial communities by fungi, which are crucial for the organization of microbial communities and their functioning in coastal PAH-contaminated sediments. The transportation of bacteria via fungal hyphae (fungal highway) results in bacterial selection; in particular, fungal hyphae offer adequate conditions for the transport of both aerobic and anaerobic bacteria through hydrophobic patches for the colonization of novel niches.

Data on hydrocarbons in sediment samples, and its body burden levels in tissues of Anomalocardia flexuosa from toxicity testing.

The analysis of hydrocarbons in terms of individual compounds is relevant to understand the origin and source of these substances, as well as its distribution in environmental compartments, including sediments and biota. Hydrocarbons concentrations were determined in sediments and in whole-body soft tissues of the tropical clam Anomalocardia flexuosa in sediment toxicity testing using samples of Mucuripe bay (Ceará State, NE Brazil) collected in 2011 during dredging events [1]. Data of target compounds included aliphatic (AHs) and aromatic hydrocarbons (PAHs), and linear alkylbenzenes (LABs). AHs compounds were determined on gas chromatography with flame ionization detector (GC-FID), while PAHs and LABs were determined on gas chromatography coupled to a mass spectrometer (GC/MS) in a selected ion mode (SIM). The potential of this dataset is baseline information on hydrocarbons contamination in sediments from a semi-arid region and the bioaccumulation of organic contaminants in marine organisms that can be used as models in ecotoxicological studies.

Characteristics of total petroleum hydrocarbon contamination in sediments in the Yangtze Estuary and adjacent sea areas

The spatial and temporal distribution characteristics of total petroleum hydrocarbon contamination in sediments in the Yangtze Estuary and adjacent sea areas were studied according to survey and monitoring data during the wet seasons of 2011–2016. The influencing mechanism was also analyzed. The average total petroleum hydrocarbon content was 176.25 mg/kg. This result indicated the absence of total petroleum hydrocarbon contamination in the sediments. With regard to spatial distribution, the total petroleum hydrocarbon content in the sediments decreased gradually from the coastal areas to the offshore areas. The spatial distribution of total petroleum hydrocarbon in the studied sea area can be divided into four sea areas, as supported by both multidimensional scaling index analysis and analysis of similarities. Sediments in the largest coastal turbidity zone presented the highest total petroleum hydrocarbon content, followed by those in coastal areas and mud areas successively. The total petroleum hydrocarbon content in offshore areas was low throughout the year.

Complete Genome Sequence of Exiguobacterium sp. Strain N4-1P, a Psychrophilic Bioemulsifier Producer Isolated from a Cold Marine Environment in North Atlantic Canada.

ABSTRACTHere, we present the complete genome sequence of Exiguobacterium sp. strain N4-1P, a psychrophilic bacterium that produces bioemulsifier, isolated for the first time from petroleum hydrocarbon-contaminated sediment samples from shoreline Newfoundland, Canada. Many strains of the genus Exiguobacterium are extremophiles and have properties of biotechnological interest.

Glycerol-enhanced microwave heating for ultra-rapid effective remediation of marine sediments highly contaminated with hydrocarbons

Abstract In this study, a new enhanced MW heating treatment using glycerol was proposed and investigated in the remediation of marine sediments highly contaminated with hydrocarbons. The heating and contaminant removal performance of different treatments using varying glycerol doses were compared. The results showed that the addition of glycerol in sediments largely promoted the MW absorbing performance that corresponded to a large increase in temperature (up to ∼120 °C) with a maximum sediment temperature of 342 °C. This allowed much faster contaminant removal kinetic to be obtained. A glycerol dose of 5% led to drastically lowered contaminant residual concentrations of 6454 (R = ∼81%), 770 (R = ∼98%) and 12 (R > 99%) mg kg −1 after 3, 5 and 10 min, respectively, demonstrating that ∼5 min were sufficient to reach the regulatory remediation target. A further dose increase (10%) led to a required time of 3 min (R > 99%), which corresponded to almost half of the MW energy required respect to the unenhanced MW. The main advantage of MW/glycerol treatment is the possibility to obtain a very rapid and effective decontamination process potentially reducing energy costs, also in the case of a very high initial hydrocarbon concentration, without producing additional by-products (respect to MW alone), which in some cases can be toxic. A comparison with other available clean-up alternatives revealed that literature does not report similar rapid and at the same time effective treatments for hydrocarbon-contaminated sediments.

Microbial Communities Associated with Zones of Elevated Magnetic Susceptibility in Hydrocarbon-Contaminated Sediments

ABSTRACTRecent studies suggest that magnetic susceptibility (MS) measurements can play an important role in identifying zones where microbial-mediated iron mineral transformations are occurring. Here we investigated the microbial community variations within zones of elevated MS in a petroleum hydrocarbon-contaminated aquifer near Bemidji, Minnesota, USA. Our main objective was to 1) identify the key microbial populations that may play a role in hydrocarbon degradation, 2) analyze which microbial populations could be connected to the elevated MS and 3) explore the use of non-destructive geophysical techniques as a tool to guide microbial sampling. Clone libraries based on the 16S rRNA gene revealed the presence of iron-reducing β-Proteobacteria in the vadose zone, whereas the free petroleum phase on the water table was characterized by a methanogenic consortium, in which the syntrophic δ-proteobacterium Smithella and the hydrogenotrophic Methanoregula predominated. Nonmetric multidimensional scaling (NMDS) found a close relationship between elevated MS values and the methanogenic hydrocarbon-degrading consortium. Our results suggest that magnetic susceptibility measurements can guide microbiologists to zones of active microbial biodegradation in aged petroleum spills.

Magnetite Formation by the Novel Fe(III)-reducing Geothrix fermentans Strain HradG1 Isolated from a Hydrocarbon-Contaminated Sediment with Increased Magnetic Susceptibility

Surface sediments at the former military base Hradcany, Czech Republic, heavily contaminated with hydrocarbons, were remediated over years by air-sparging. The sediments show a strong magnetic enhancement at the groundwater fluctuation zone. Here we describe the isolation of a new Fe(III)-reducing and magnetite-producing bacterial strain Geothrix fermentans HradG1from this magnetic and redox-dynamic layer. This isolation underlines that the genus Geothrix is a relevant group of bacteria in hydrocarbon-contaminated environments that undergo dynamic oxic-anoxic redox fluctuations. The Fe(III)-reducing metabolic activity of these organisms potentially leads to changing magnetic soil properties that can potentially be used to identify biogeochemical hotspots.

Bioaccumulation of Polycyclic Aromatic Hydrocarbons and Mercury in Oysters (Crassostrea rhizophorae) from Two Brazilian Estuarine Zones

Nowadays, organisms are increasingly being used in biomonitoring to assess bioavailability and bioaccumulation of contaminants. This approach can use both native and transplanted organisms in order to accomplish this task. In Brazil, most of the studies related to bioaccumulation of contaminants in oysters deal with metals. The present work employs this kind of test in Brazilian coastal estuaries (Santos and Paranaguá) to evaluate total mercury and polycyclic aromatic hydrocarbon contamination in sediments and oysters (native and caged Crassostrea rhizophorae). The methodologies employed were based on known USEPA methods. Results have shown a significant contamination in Santos sediments and consequent bioavailability of organisms. Paranaguá sediments presented lower contamination in sediments, but native oysters were able to accumulate total Hg. The experiments done with caged oysters did not show significant bioaccumulation of Hg and PAHs in the Paranaguá site, but proved to be an excellent tool to assess bioavailability in the Santos estuary since they were able to bioaccumulate up to 1,600% of total PAH in the samples from the inner part of this estuary when compared to control organisms. Multivariate statistical analyses employed to these results have separated the sites evaluated and the most contaminated samples from the least contaminated.

Microbial Community Analysis of a Coastal Salt Marsh Affected by the Deepwater Horizon Oil Spill

Coastal salt marshes are highly sensitive wetland ecosystems that can sustain long-term impacts from anthropogenic events such as oil spills. In this study, we examined the microbial communities of a Gulf of Mexico coastal salt marsh during and after the influx of petroleum hydrocarbons following the Deepwater Horizon oil spill. Total hydrocarbon concentrations in salt marsh sediments were highest in June and July 2010 and decreased in September 2010. Coupled PhyloChip and GeoChip microarray analyses demonstrated that the microbial community structure and function of the extant salt marsh hydrocarbon-degrading microbial populations changed significantly during the study. The relative richness and abundance of phyla containing previously described hydrocarbon-degrading bacteria (Proteobacteria, Bacteroidetes, and Actinobacteria) increased in hydrocarbon-contaminated sediments and then decreased once hydrocarbons were below detection. Firmicutes, however, continued to increase in relative richness and abundance after hydrocarbon concentrations were below detection. Functional genes involved in hydrocarbon degradation were enriched in hydrocarbon-contaminated sediments then declined significantly (p<0.05) once hydrocarbon concentrations decreased. A greater decrease in hydrocarbon concentrations among marsh grass sediments compared to inlet sediments (lacking marsh grass) suggests that the marsh rhizosphere microbial communities could also be contributing to hydrocarbon degradation. The results of this study provide a comprehensive view of microbial community structural and functional dynamics within perturbed salt marsh ecosystems.

Enhanced biodegradation of hydrocarbon-contaminated sediments using microbial fuel cells

A sediment microbial fuel cell (MFC) was tested to determine if electron transfer from the anaerobic zone of contaminated sediments to the overlying aerobic water could facilitate an enhanced and aerobic equivalent degradation of total petroleum hydrocarbons (TPH). Results indicate that voltages as high as 190mV (2162mW/m3) were achieved in a sediment MFC with an anode buried in sediments containing TPH concentrations at approximately 16,000mgkg−1. Additionally, after approximately 66 days, the TPH degradation rates were 2% and 24% in the open-circuit control sediment MFC and active sediment MFC, respectively. Therefore, it appears that applying MFC technology to contaminated sediments enhances natural biodegradation by nearly 12 fold. Additionally, a novel sediment MFC was designed to provide a cost-effective method of passive oxidation or indirect aerobic degradation of contaminants in an otherwise anaerobic environment. In addition, the use of a wicking air cathode in this study maintained dissolved oxygen concentrations 1–2mgl−1 higher than submerged cathodes, demonstrating that this technology can be applied to environments with either aerobic or anaerobic overlying water and an anaerobic matrix, such as shallow lagoon, ponds, and marshes, and groundwater.

Stimulating the anaerobic degradation of aromatic hydrocarbons in contaminated sediments by providing an electrode as the electron acceptor

The possibility that electrodes might serve as an electron acceptor to simulate the degradation of aromatic hydrocarbons in anaerobic contaminated sediments was investigated. Initial studies with Geobacter metallireducens demonstrated that although toluene was rapidly adsorbed onto the graphite electrodes it was rapidly oxidized to carbon dioxide with the electrode serving as the sole electron acceptor. Providing graphite electrodes as an electron acceptor in hydrocarbon-contaminated sediments significantly stimulated the removal of added toluene and benzene. Rates of toluene and benzene removal accelerated with continued additions of toluene and benzene. [(14)C]-Toluene and [(14)C]-benzene were quantitatively recovered as [(14)C]-CO(2), demonstrating that even though the graphite adsorbed toluene and benzene they were degraded. Introducing an electrode as an electron acceptor also accelerated the loss of added naphthalene and [(14)C]-naphthalene was converted to [(14)C]-CO(2). The results suggest that graphite electrodes can serve as an electron acceptor for the degradation of aromatic hydrocarbon contaminants in sediments, co-localizing the contaminants, the degradative organisms and the electron acceptor. Once in position, they provide a permanent, low-maintenance source of electron acceptor. Thus, graphite electrodes may offer an attractive alternative for enhancing contaminant degradation in anoxic environments.

Spectral induced polarization for the characterization of free‐phase hydrocarbon contamination of sediments with low clay content

ABSTRACTThe identification of organic pollutants in the soil and the subsurface is a goal of primary importance in the management of contaminated sites. However, only a few non‐invasive techniques can be useful towards this goal. One such technique is spectral induced polarization. In this study, we investigate the spectral induced polarization effect of changing fluid saturation in a well‐characterized porous medium, analysing the difference between air and hydrocarbons, at different degrees of water saturation. The experiments were conducted on fine eolic sand samples coming from an experimental site near Turin, Italy. Octanol and benzene were used as non‐aqueous phase liquids. Samples were initially saturated with water having controlled electrical conductivity and subsequently de‐saturated stepwise with injection of air at known pressure. The eolic sand samples were then re‐saturated with the same water contaminated with hydrocarbons and then a non‐aqueous phase liquid phase (either octanol or benzene) was injected in volumetric steps, in order to compare the effects of air and non‐aqueous phase liquid invasion. At each saturation step, spectral induced polarization measurements were conducted in the 0.01 Hz to 1 kHz range using the ZEL‐SIP04 impedance meter developed at the Forschungszentrum Juelich. The measurement setup guaranteed a 1 mrad phase precision for the entire frequency measurement range. Measurements were conducted under temperature controlled conditions at 20 (±0.5)° C. All spectral induced polarization curves show a peak in the range 0.01–1 Hz that changes in intensity and frequency with varying saturation and a high‐frequency phase shift increase dominated by capacitive coupling effects of the measuring system. A multiple Cole‐Cole model was fitted to the data. The effects of de‐saturation on the low‐frequency Cole‐Cole parameters are that a) resistivity increases with decreasing water saturation but increases less with non‐aqueous phase liquid than with the same volume of air; b) chargeability increases with decreasing water saturation but in presence of non‐aqueous phase liquids its value is sometimes lower, sometimes higher and sometimes similar to the one observed in presence of air; c) the time constant τ increases with decreasing water saturation and is consistently larger with non‐aqueous phase liquid than with air. These differences between air and non‐aqueous phase liquid injection can be explained in terms of differences in non‐aqueous phase distribution within the porous medium, as observed by X‐ray micro‐CT: while air is homogeneously distributed, non‐aqueous phase liquids segregate under density effects. In summary, all spectral induced polarization effects of air and non‐aqueous phase liquid injection in the considered porous medium are volumetric, i.e., are not due to interaction with grain surfaces or other electrical‐chemical effects but are caused by pore obstruction by the electrically non‐conductive phase.

Towards bioremediation of toxic unresolved complex mixtures of hydrocarbons: identification of bacteria capable of rapid degradation of alkyltetralins

Unresolved complex mixtures (UCMs) of aromatic hydrocarbons are widespread, but often overlooked, environmental contaminants. Since UCMs are generally rather resistant to bacterial degradation, bioremediation of UCM-contaminated sites by bacteria is a challenging goal. Branched chain alkyltetralins are amongst the individual classes of components of aromatic UCMs which have been identified in hydrocarbon-contaminated sediments and a number of synthetic alkyltetralins have proved toxic in laboratory studies. Thus, alkyltetralins should perhaps be amongst the targets for UCM bioremediation strategies. The slow degradation of several alkyltetralins by a microbial consortium has been reported previously; however, the bacteria involved remain unidentified and no single strain capable of alkyltetralin biodegradation has been isolated. The present project therefore aimed to enrich and identify bacterial consortia and single strains of bacteria from a naturally hydrocarbon-contaminated site (Whitley Bay, UK), which were capable of the degradation of two synthetic alkyltetralins (6-cyclohexyltetralin (CHT) and 1-(3’-methylbutyl)-7-cyclohexyltetralin (MBCHT)). Bacteria were enriched from sediment collected from Whitley Bay, UK by culturing with CHT and MBCHT for a period of 4 months. Biodegradation experiments were then established and degradation of model compounds monitored by gas chromatography–mass spectrometry. Internal standards allowed the generation of quantitative data. 16S rRNA gene clone libraries were constructed from individual enrichments to allow assessment of microbial community structure. Selective media containing MBCHT were used to isolate single bacterial strains. These strains were then tested in liquid culture for their ability to degrade MBCHT. The consortia obtained through enrichment culture were able to degrade 87% of CHT and 76% of MBCHT after only 46 days compared with abiotic controls. The 16S ribosomal RNA gene clone libraries of these bacteria were dominated by sequences of Rhodococcus spp. Using selective media, a strain of Rhodococcus was then isolated that was also able to biodegrade 63% of MBCHT in only 21 days. The present report describes the isolation of a single bacterial strain able to degrade the resistant MBCHT. Although significant losses of MBCHT were observed, putative metabolites were not detectable. Rhodococcus sp. have been reported previously to be able to biodegrade a range of hydrocarbon compounds. Due to their environmental persistence and toxicity, aromatic UCMs require bioremediation. The culturing and identification of such bacteria capable of rapid degradation of alkyltetralins may be an important step toward the development of bioremediation strategies for sites contaminated with toxic UCMs.

Diversity of hydrocarbon-degradingKlebsiellastrains isolated from hydrocarbon-contaminated estuaries

To investigate the diversity and the catabolic capacity of oil-degrading Klebsiella strains isolated from hydrocarbon-contaminated sediments in Santos-São Vicente estuary systems in Brazil. Klebsiella strains obtained from the estuary were characterized using 16S rRNA gene sequencing and BOX-PCR patterns, testing their catabolic capacity to degrade toluene, xylene, naphthalene and nonane, and identifying the catabolic genes present in the oil-degrading strains. Results show that Klebsiella strains were widespread in the estuary. Twenty-one isolates from the Klebsiella genus were obtained; 14 had unique BOX patterns and were further investigated. Among four distinct catabolic genes tested (todC1, ndoB, xylE and alkB1), only the todC1 gene could be amplified in two Klebsiella strains. The biodegradation assay showed that most of the strains had the ability to degrade all of the tested hydrocarbons; however, the strains displayed different efficiencies. The oil-degrading Klebsiella isolates obtained from the estuary were closely related to Klebsiella pneumoniae and Klebsiella ornithinolytica. The isolates demonstrated a substantial degree of catabolic plasticity for hydrocarbon degradation. The results of this study show that several strains from the Klebsiella genus are able to degrade diverse hydrocarbon compounds. These findings indicate that Klebsiella spp. can be an important part of the oil-degrading microbial community in estuarine areas exposed to sewage.

Monitoring nutrient impact on bacterial community composition during bioremediation of anoxic PAH-contaminated sediment

Marine harbor sediments are frequently polluted with significant amount of polycyclic aromatic hydrocarbons (PAHs) some of which are naturally toxic, recalcitrant, mutagenic, and carcinogenic. To stimulate biodegradation of PAHs in PAH-contaminated sediments collected from near Gwangyang Bay, Korea, lactate was chosen as a supplementary carbonaceous substrate. Sediment packed into 600 ml air-tight jar was either under no treatment condition or lactate amended condition (1%, w/v). Microbial community composition was monitored by bacteria-specific and archaea-specific PCR-terminal restriction fragment length polymorphism (T-RFLP), in addition to measuring the residual PAH concentration. Results showed that lactate amendment enhanced biodegradation rate of PAHs in the sediment by 4 to 8 times, and caused a significant shift in archaebacterial community in terms of structure and diversity with time. Phylogenetic analysis of 23 archaeal clones with distinctive RFLP patterns among 288 archaeal clones indicated that majority of the archaeal members were closest to unculturable environmental rDNA clones from hydrocarbon-contaminated and/or methanogenesis-bearing sediments. Lactate amendment led to the enrichment of some clones that were most closely related to PAH-degrading Methanosarcina species. These results suggest a possible contribution of methanogenic community to PAH degradation and give us more insights on how to effectively remediate PAH-contaminated sediments.

Benthic community response to petroleum-associated components in Arctic versus temperate marine sediments

We assessed the effects of crude oil and drill cuttings on sediment oxygen demand (SOD) of marine benthic communities from Arctic (Barents Sea) and temperate (Oslofjord) areas of the Norwegian continental shelf. Field-collected cores in both areas were subjected to three different treatments: two concentrations of hydrocarbon-contaminated sediments, and drill cuttings (DC). Cores were incubated for 21 days at 5°C (Barents Sea) and at 10°C (Oslofjord) during which SOD was measured five times. We observed significantly higher SOD in the high oil concentration (HOC) and DC treatments compared to control cores from the Arctic, but not in the temperate Oslofjord. No difference was observed between the low oil concentration (LOC) and control at either location. The clear differences in the response of Arctic benthic communities to petroleum compounds compared to temperate benthic communities is likely related to differences in community structure, sensitivity of individual taxa to petroleum-related compounds and different contamination history of the two study areas.

Alternative methodology for isolation of biosurfactant-producing bacteria

Wide biosurfactant application on biorremediation is limited by its high production cost. The search for cheaper biossurfactant production alternatives has guided our study. The use of selective media containing sucrose (10 g x L(-1)) and Arabian Light oil (2 g x L(-1)) as carbon sources showed to be effective to screen and maintain biosurfactant-producing consortia isolated from mangrove hydrocarbon-contaminated sediment. The biosurfactant production was assayed by kerosene, gasoline and Arabian Light Emulsification activity and the bacterial growth curve was determined by bacterial quantification. The parameters analyzed for biosurfactant production were the growth curve, salinity concentration, flask shape and oxygenation. All bacteria consortia screened were able to emulsify the petroleum derivatives tested. Biosurfactant production increased according to the incubation time; however the type of emulsification (non-aqueous phase or aqueous phase) did not change with time but with the compound tested. The methodology was able to isolate biosurfactant-producing consortia from superficial mangrove sediment contaminated by petroleum hydrocarbons and was recommended for selection of biosurfactant producing bacteria in tropical countries with low financial resources.

Establishing cause–effect relationships in hydrocarbon‐contaminated sediments using a sublethal response of the benthic marine alga, Entomoneis CF Punctulata

A sublethal whole-sediment toxicity test that uses flow cytometry to measure inhibition of esterase activity in the marine microalga Entomoneis cf punctulata was applied to the assessment of hydrocarbon-contaminated sediments and toxicity identification and evaluation (TIE). Concentration-response relationships were developed, and a 20% effect concentration for total polycyclic aromatic hydrocarbons (PAHs) of 60 mg/kg normalized to 1% total organic carbon was calculated. Relationships between toxic effects and sediment organic carbon concentrations, organic carbon forms (e.g., black carbon), and sediment particle size indicated that further normalization of hydrocarbon concentrations to sediment particle size may improve concentration-response relationships. The algal toxicity test was applied as a rapid whole-sediment TIE procedure that involved the addition to sediment of powdered coconut charcoal (PCC), a hydrophobic, carbon-based material that strongly adsorbs PAHs and decreases the pore-water exposure pathway. Sediments with PCC concentrations of up to 15% (w/w) provided acceptable responses in control sediments. For six sediments with total PAH concentrations of 1,060, 4,060, 5,120, 9,150, 9,900, and 15,900 mg/kg, inhibition of E. cf punctulata esterase activity (% of control) was 75, 97, 94, 93, 100, and 97%, respectively. Following a 15% PCC amendment to these sediments, inhibition of esterase activity was 0, 1, 11, 69, 32, and 68%, respectively, indicating a decrease in toxicity in all sediments. Because the alga E. cf punctulata is exposed to toxicants via both pore water and overlying water, the reduction in toxicity achieved by 15% PCC additions can be related to the efficient removal of dissolved hydrocarbons released from sediment particles. The sediment-PCC manipulations coupled with algal whole-sediment toxicity tests provided an effective and rapid TIE method to determine whether hydrocarbon contaminants are responsible for toxicity in sediments.

Monitoring the Natural Recovery of Hydrocarbon-Contaminated Sediments with Chemical Fingerprinting

†Drs. Scott A. Stout, Gregory S. Douglas, and Allen D. Uhler are principals at NewFields Environmental Forensics Practice, LLC, in Rockland, Massachusetts. They each have over 15 years experience in the chemical characterization of petroleum and related contaminants in the environment. Their firm specializes in the application of chemical fingerprinting and other forensic tools in assessing liability associated with environmental contamination in soils, groundwater, surface water, and sediments, including expert consulting and technical support in the course of litigation.

Investigation of bacterial diversity in Brazilian tropical estuarine sediments reveals high actinobacterial diversity

Phylogenetic and statistical analyses of 16S rRNA gene libraries were used for the investigation of actinobacterial communities present in two tropical estuarine sediments (Santos-São Vicente estuary, Brazil). The libraries were constructed from samples collected at the brackish end of the estuary, highly hydrocarbon-contaminated, and at the marine end, uncontaminated. Clones from the marine end of the estuary were all related to sequences from non-cultured Actinobacteria and unidentified bacteria recovered from a wide range of environmental samples, whereas clones from the brackish end were mainly related to sequences from cultured Actinobacteria. Statistical analyses showed that the community recovered from the hydrocarbon-contaminated sediment sample, at the brackish end, was less diverse than the uncontaminated one, at the marine end, and that the communities from the two libraries were differently structured, suggesting that these may have not originated from the same community. The recognition of the spatial pattern of actinobacterial distribution in a natural environment is a first step towards understanding the way these communities are organized, providing valuable data for further investigations of their taxonomic and functional diversity.