Effects of seasonal succession and water pollution on the protozoan community structure in an eutrophic lake

The purpose of the research is to study the seasonal succession of protozoa community and the effect of water quality on the protozoa community to characterize biochemical processes occurring at a eutrophic Lake Donghu, a large shallow lake in Wuhan City, China. Samples of protozoa communities were obtained monthly at three stations by PFU (polyurethane foam unit) method over a year. Synchronously, water samples also were taken from the stations for the water chemical quality analysis. Six major variables were examined in a principal component analysis (PCA), which indicate the fast changes of water quality in this station I and less within-year variation and a comparatively stable water quality in stations II and III. The community data were analyzed using multivariate techniques, and we show that clusters are rather mixed and poorly separated, suggesting that the community structure is changing gradually, giving a slight merging of clusters form the summer to the autumn and the autumn to the winter. Canonical correspondence analysis (CCA) was used to infer the relationship between water quality variables and phytoplankton community structure, which changed substantially over the survey period. From the analysis of cluster and CCA, coupled by community pollution value (CPV), it is concluded that the key factors driving the change in protozoa community composition in Lake Donghu was water qualities rather than seasons.     

Effects of fenvalerate concentrations and its chiral isomers on bacterial community structure in the sediment environment of aquaculture ponds

To investigate the effect of chiral pesticide fenvalerate (FV) on the micro-ecological environment of aquaculture pond sediment, we used an indoor static experiment to observe the effects of FV added at different concentrations with different chiral isomers on the changes in the sediment bacterial community. The 16S rDNA high-throughput sequencing technique was used to conduct sequencing and analysis of the bacterial community structure as well as changes in aquaculture pond sediments after 4 weeks of cultivation. The results showed that the microbial alpha diversity indices (Sobs and Shannon indices) of the treated groups were significantly lower than those of the control group after 4 weeks (P < 0.05), and the values in the high-concentration group were significantly lower than those of the low-concentration group (P < 0.05). In terms of bacterial group composition, the proportion of abundance of Proteobacteria and Acidobacteria in the treated groups were greater than in the control group after 4 weeks, while the proportion of abundance of Bacteroidetes and Verrucomicrobia were lower. In the high-concentration FV treatment group, the proportion of abundance of Bacteroidetes, Acidobacteria, Chloroflexi, Nitrospinae, unclassified_k_norank, Ignavibacteriae, and Nitrospirae were significantly different from those of the other groups (P < 0.05). Principal coordinate analysis (PCoA) and ANONISIM/Adonis analysis showed that the cis-enantiomer had a stronger effect on the bacterial community as the concentration of FV increased. In addition, the linear discriminant analysis effect size (LEfSe) and linear discriminant analysis (LDA) results revealed differences in the level of enrichment of bacterial groups caused by FV at different concentrations and isomer levels. Collectively, this study showed that FV residue has a pronounced effect on bacterial communities in sediment, which becomes more significant with increasing exposure concentration. The effects of the cis- and trans-enantiomers of FV on the sediment environment are different; the cis-enantiomer has a stronger effect on the bacterial community.

     

Capability of the natural microbial community in a river water ecosystem to degrade the drug naproxen

The present work aims at evaluating the ability of the River Tiber natural microbial community to degrade naproxen in water samples collected downstream from a wastewater treatment plant. For this purpose, different water microcosms were set up (microbiologically active vs sterile ones) and treated with naproxen (100 μg/L) alone or in the co-presence of gemfibrozil in order to evaluate if the co-presence of the latter had an influence on naproxen degradation. The experiment was performed in the autumn and was compared with the same experimental set performed in spring of the same year to highlight if seasonal differences in the river water influenced the naproxen degradation. Pharmaceutical concentrations and microbial analysis (total cell number, viability, and microbial community composition) were performed at different times in the degradation experiments. The overall results show that the natural microbial community in the river water had a key role in the naproxen degradation. In fact, although there was a transient negative effect on the natural microbial community in all the experiments (3 h after adding the pharmaceutical), the latter was able to degrade naproxen within about 40 days. On the contrary, no decrease in the pharmaceutical concentration was observed in the sterile river water. Moreover, the co-presence of the two drugs lengthened the naproxen lag phase. As regards the natural microbial community composition detected by Fluorescence in situ Hybridization, Alpha and Gamma-Proteobacteria increased when the pharmaceutical halved, suggesting their role in the degradation. This study shows that with the concentration studied, naproxen was degraded by the natural microbial populations collected from a river chronically contaminated by this pharmaceutical.     

The use of benthic mesocosms for the assessment of sediment contamination.

The diagnostic capability of changes in the benthic macroinvertebrate community composition to determine the cause in contaminated sediments were addressed using box core mesocosms subjected to cadmium, atrazine and nutrient enrichment. Intact cores of lake sediment were collected from Lake Erie at four occasions during 1996 and were returned to laboratory where they were maintained and manipulated. The benthic community composition of the artificially polluted mesocosms was compared with field data, collected at the same time as the intact cores, and to untreated control boxes. Community composition was related to the measured environmental variables using multi-dimensional scaling (MDS) and principle axis correlation (PCC). Community responses to different treatments were both different and consistent, suggesting that the community structure of these mesocosms could be used to identify the primary source of impact.     

Dredging impact on an urbanized Florida bayou: effects on benthos and algal-periphyton.

Environmental effects of dredging events have been uncommonly reported for shallow, residential estuaries characteristic of the Gulf of Mexico region. The objective of this study was to determine the impact of hydraulic dredging on an urbanized estuary. Physicochemical quality, benthic community composition, whole sediment toxicity, periphytic algal community composition and trace metal tissue quality were determined prior to and after dredging. The effects on surface water pH, dissolved oxygen, and temperature were negligible but photosynthetically active radiation was decreased at several stations. Dredging significantly reduced benthic diversity and density (P < 0.05). However, the sediments were not acutely toxic to the epibenthic, Americamysis bahia (formerly Mysidopsis bahia); survival averaged 93% (post-dredging) and to 98% (pre-dredging). There were several post-dredging taxonomic structural changes in the diatom-dominated, periphyton community but differences in mean density and three diversity indices were not significant. Trace metal concentration in periphyton after dredging were reduced from an average of 4-65% and significantly for mercury, zinc and chromium in several areas. It was concluded that the environmental impact of small-scale dredging events in urbanized near-coastal areas, based on the selected parameters, are likely to be localized and of short-term environmental consequence. The choice of the target biota, response parameters and chemical analysis are important considerations in the environmental impact assessment of these periodic episodic events.     

A dynamic modelling approach for estimating critical loads of nitrogen based on plant community changes under a changing climate

A dynamic model of forest ecosystems was used to investigate the effects of climate change, atmospheric deposition and harvest intensity on 48 forest sites in Sweden (n = 16) and Switzerland (n = 32). The model was used to investigate the feasibility of deriving critical loads for nitrogen (N) deposition based on changes in plant community composition. The simulations show that climate and atmospheric deposition have comparably important effects on N mobilization in the soil, as climate triggers the release of organically bound nitrogen stored in the soil during the elevated deposition period. Climate has the most important effect on plant community composition, underlining the fact that this cannot be ignored in future simulations of vegetation dynamics. Harvest intensity has comparatively little effect on the plant community in the long term, while it may be detrimental in the short term following cutting. This study shows: that critical loads of N deposition can be estimated using the plant community as an indicator; that future climatic changes must be taken into account; and that the definition of the reference deposition is critical for the outcome of this estimate.     

The roles of biological interactions and pollutant contamination in shaping microbial benthic community structure

Biological interactions between metazoans and the microbial community play a major role in structuring food webs in aquatic sediments. Pollutants can also strongly affect the structure of meiofauna and microbial communities. This study aims investigating, in a non-contaminated sediment, the impact of meiofauna on bacteria facing contamination by a mixture of three PAHs (fluoranthene, phenanthrene and pyrene). Sediment microcosms were incubated in the presence or absence of meiofauna during 30 days. Bioremediation treatments, nutrient amendment and addition of a hydrocarbon-degrading bacterium, were also tested to enhance PAH biodegradation. Results clearly show the important role of meiofauna as structuring factor for bacterial communities with significant changes observed in the molecular fingerprints. However, these structural changes were not concomitant with changes in biomass or function. PAH contamination had a severe impact on total meiofaunal abundance with a strong decrease of nematodes and the complete disappearance of polychaetes and copepods. In contrast, correspondence analysis, based on T-RFLP fingerprints, showed that contamination by PAH resulted in small shifts in microbial composition, with or without meiofauna, suggesting a relative tolerance of bacteria to the PAH cocktail. The PAH bioremediation treatments were highly efficient with more than 95% biodegradation. No significant difference was observed in presence or absence of meiofauna. Nutrient addition strongly enhanced bacterial and meiofaunal abundances as compared to control and contaminated microcosms, as well as inducing important changes in the bacterial community structure. Nutrients thus were the main structural factor in shaping bacterial community composition, while the role of meiofauna was less evident.     

Monitoring microbial community in a subsurface soil contaminated with hydrocarbons by quinone profile

A natural attenuation experiment was carried out using a lysimeter for 308 days after contaminating the subsoil with hydrocarbons (HCs) and the changes in the structures of microbial community in the hydrocarbon (HC) contaminated subsoil were monitored by quinone profile analysis. The residues of HCs remained for 217 days in the subsoil after the contamination. The amount of total quinones (TQ), an indicator of microbial biomass, significantly increased in the HC contaminated subsoil for 217 days, comparing with that of the background subsoil or the subsoil before the addition of HCs. The major quinone species and the quinone composition, indicators of community structure, were significantly different between the HC contaminated soil and the background soil for 217 days. The major increased quinine species in the HC contaminated soil were menaquinone-8(H4), menaquinone-9(H2) and ubiquinone-9, indicating the propagation of Gram-positive bacteria with high guanine and cytosine content and gamma-subclass of Proteobacteria and fungi. There was no significant difference in the diversity of the quinone species (DQ), an indicator of taxonomic diversity of microbial community, except for the decrease in DQ in the shallow subsoil after 35 days when a high concentration of HCs was detected. After 308 days when the HCs in the subsoil disappeared, TQ returned to the level of the background soil, and no significant difference in quinone composition were observed between the HC contaminated soil and the background soil. The results suggested that respiratory quinones are effective biomarkers for characterizing the temporal changes of microbial community in the HC contaminated subsoil.     

Forecasting Alpine Vegetation Change Using Repeat Sampling and a Novel Modeling Approach

Global change affects alpine ecosystems by, among many effects, by altering plant distributions and community composition. However, forecasting alpine vegetation change is challenged by a scarcity of studies observing change in fixed plots spanning decadal-time scales. We present in this article a probabilistic modeling approach that forecasts vegetation change on Niwot Ridge, CO using plant abundance data collected from marked plots established in 1971 and resampled in 1991 and 2001. Assuming future change can be inferred from past change, we extrapolate change for 100 years from 1971 and correlate trends for each plant community with time series environmental data (1971–2001). Models predict a decreased extent of Snowbed vegetation and an increased extent of Shrub Tundra by 2071. Mean annual maximum temperature and nitrogen deposition were the primary a posteriori correlates of plant community change. This modeling effort is useful for generating hypotheses of future vegetation change that can be tested with future sampling efforts.     

Effects of residue incorporation and plant growth on soil labile organic carbon and microbial function and community composition under two soil moisture levels

This study investigates the effects of residue incorporation coupled with plant growth and soil moisture level on wheat biomasses, soil nutrients, labile organic carbon (LOC), microbial metabolic profiles, and community composition. Four management practices were used in a 180-day pot experiment: (1) control (CON), (2) maize (Zea mays L.) residue incorporation without plants (MR), (3) wheat (Triticum aestivum L.) plants without maize residue (WP), and (4) maize residue incorporation with wheat plants (MRWPs). Each management practice included soil moisture at both 40 and 80% of field capacity. At wheat harvest, soil nutrient contents in the WP and MRWP treatments were significantly lower than in the CON and MR treatments. In comparison with the CON treatment, MR, WP, and MRWP treatments resulted in 35, 23, and 67% increases in dissolved organic carbon content; 17, 12, and 34% increases in hot-water extractable organic carbon content; and 78, 50, and 150% increases in microbial biomass carbon content. Furthermore, microbial utilizations of carboxylic acids and polymer carbon sources in the MR, WP, and MRWP treatments were 261 and 88%, 239 and 105%, and 300 and 126% higher than in the CON treatment. The MR and CON treatments had similar phospholipid fatty acid (PLFA) content but the WP and MRWP treatments had significantly increased gram-negative content and changes to community composition compared with the CON and MR treatments. The wheat biomass, LOC, and PLFA contents significantly increased with greater soil moisture. Overall, these results suggest an additive effect of residue incorporation and plant growth on LOC contents, primarily due to the changes in microbial utilization of carbon sources and community composition.     

Changes in the wet precipitation of sodium and chloride over the continental United States, 1984–2006

Data on wet-only precipitation from the National Atmospheric Deposition Program/National Trends Network were analysed for trends in the sodium and chloride fluxes over the United States between 1 January 1984 and 31 December 2006. The data were first checked for consistency and for ionic balance. It was necessary to correct for changes in bicarbonate due to changes in atmospheric CO₂ levels over the study period, in order to obtain a balance. The fluxes were calculated and the trends determined by linear regression in the log domain. The significance of the trends was checked using both F- and t-tests. At 154 sites having reasonably continuous records over the assessment period, the sodium flux fell significantly at 139 and increased significantly at only one. The chloride flux similarly fell significantly at 140 and increased significantly at the same one as the sodium flux increased. At coastal sites the chloride to sodium ratio was the same as that in sea water, within experimental limits. Further from the coast the ratio changed apparently due to changes in the entire aerosol chemistry. The findings are discussed in terms of the simplicity and robustness of the methodology employed to determine the trends; the oceanic origin of most observable sodium even in the interior of the continent, probably because it occurs as a fine (<1 micron) aerosol which is poorly scavenged by precipitation; and the possibility that the drop in sodium and chloride fluxes might be driven by climate change.     

Functional and community-level soil microbial responses to zinc addition may depend on test system biocomplexity

The effect of zinc on soil nitrification and composition of the microbial community in soil was investigated using a full factorial experiment with five zinc concentrations and four levels of biological complexity (microbes only, microbes and earthworms (Eisenia fetida), microbes and Italian ryegrass (Lolium multiflorum var. Macho), and microbes, ryegrass and earthworms). After 6 weeks of exposure, the activity of soil nitrifying bacteria was measured and the microbial community structure was characterized by phospholipid fatty acid (PLFA) analysis. Soil nitrification and several PLFA markers were significantly influenced by either zinc addition and/or the presence of earthworms or ryegrass, and one of the most pronounced changes was the increase of fungi and decrease of bacteria with increasing concentrations of zinc. Of particular interest, however, was the potential interaction between the presence of plants and/or earthworms and the effect of zinc, which the factorial study design allowed us to explore. Such an effect was observed in two cases: Earthworms reduced the positive effect of zinc on the fungal biomass (ANOVA, p=0.03), and the effect of earthworms on the soil nitrification activity depended on zinc concentration (ANOVA, p<0.05). The effect of earthworm presence was not very large, but it does show that multispecies tests might give information about metal toxicity or bioavailability that cannot be predicted from single-species tests.     

Alkane biodegradation and dynamics of phylogenetic subgroups of sulfate-reducing bacteria in an anoxic coastal marine sediment artificially contaminated with oil

For 503 days, unoiled control and artificially oiled sediments were incubated in situ at 20m water depth in a Mediterranean coastal area. Degradation of the aliphatic fraction of the oil added was followed by GC-MS. At the same time, terminal restriction fragment length polymorphism (T-RFLP) of 16S rRNA encoding genes was used to detect dynamics in the sulfate-reducing bacteria (SRB) community in response to the oil contamination. Specific polymerase chain reaction (PCR) primer sets for five generic or suprageneric groups of SRB were used for PCR amplification of DNA extracted from sediments. During the experiment, hydrocarbons from C(17) to C(30) were significantly degraded even in strictly anoxic sediment layers. Of the five SRB groups, only two groups were detected in the sediments (control and oiled), namely the Desulfococcus-Desulfonema-Desulfosarcina-like group and the Desulfovibrio-Desulfomicrobium-like group. Statistical analysis of community patterns revealed dynamic changes over time within these two groups following the contamination. Significant differences in community patterns were recorded in artificially oiled compared with control sediments. Cloning and sequencing of 16S rRNA encoding genes performed after 503 days showed that many of the most abundant sequences were closely related to hydrocarbonoclastic SRB which could have played an active role in the observed biodegradation of aliphatic hydrocarbons. Results from the present study provide useful information on the dynamics of dominant SRB in heavily oil-contaminated sediments and their potential for anaerobic biodegradation for the treatment of spilled oil in anoxic marine environments.     

Plant and Vegetation Dynamics on Disko Island,West Greenland: Snapshots Separated by Over 40 Years

We report on a revisit in 2009 to sites where vegetation was recorded in 1967 and 1970 on Disko Island, West Greenland. Re-sampling of the same clones of the grass Phleum alpinum after 39 years showed complete stability in biometrics but dramatic earlier onset of various phenological stages that were not related to changes in population density. In a fell-field community, there was a net species loss, but in a herb-slope community, species losses balanced those that were gained. The type of species establishing and increasing in frequency and/or cover abundance at the fell-field site, particularly prostrate dwarf shrubs, indicates a possible start of a shift towards a heath, rather than a fell-field community. At the herb-slope site, those species that established or increased markedly in frequency and/or cover abundance indicate a change to drier conditions. This is confirmed both by the decrease in abundance of Alchemilla glomerulans and Epilobium hornemanii, and the drying of a nearby pond. The causes of these changes are unknown, although mean annual temperature has risen since 1984.     

Insight into the dynamic microbial community and core bacteria in composting from different sources by advanced bioinformatics methods

Microbial communities are important for high composting efficiency and good quality composts. This study was conducted to compare the changes of physicochemical and bacterial characteristics in composting from different raw materials, including chicken manure (CM), duck manure (DM), sheep manure (SM), food waste (FW), and vegetable waste (VW). The role and interactions of core bacteria and their contribution to maturity in diverse composts were analyzed by advanced bioinformatics methods combined sequencing with co-occurrence network and structural equation modeling (SEM). Results indicated that there were obviously different bacterial composition and diversity in composting from diverse sources. FW had a low pH and different physiochemical characteristics compared to other composts but they all achieved similar maturity products. Redundancy analysis suggested total organic carbon, phosphorus, and temperature governed the composition of microbial species but key factors were different in diverse composts. Network analysis showed completely different interactions of core bacterial community from diverse composts but Thermobifida was the ubiquitous core bacteria in composting bacterial network. Sphaerobacter and Lactobacillus as core genus were presented in the starting mesophilic and thermophilic phases of composting from manure (CM, DM, SM) and municipal solid waste (FW, VW), respectively. SEM indicated core bacteria had the positive, direct, and the biggest (>?80%) effects on composting maturity. Therefore, this study presents theoretical basis to identify and enhance the core bacteria for improving full-scale composting efficiency facing more and more organic wastes.

     

Investigation of interactions between surface water and petroleum-type pollutants

Background, Aims and Scope In oil spill investigations, one of the most important steps is a proper choice of approaches that imply an investigation of samples taken from different sedimentary environments, samples of oil contaminants taken in different periods of time and samples taken at different distances from the oil spill. In all these cases, conclusion on the influence of the environment, microorganisms or migration on the oil contaminants' composition can be drawn from the comparison of chemical compositions of the investigated contaminants. However, in case of water contaminants, it is very important to define which part of organic matter has been analyzed. Namely, previous investigations showed that there were some differences in chemical composition of the same oil contaminant depending on the intensity of its contact with ground water. The aim of this work is to define more precisely the interactions between oil contaminant and water, i.e. the influence of the intensity of interaction between the oil contaminant and water on its chemical composition. The study was based on a comparison of four fractionated extracts of an oil pollutant, after they had been analyzed in details. Methods Oil polluted surface water (wastewater canal, Pančevo, Serbia) was investigated. The study was based on a comparison of four extracts of an oil contaminant: extract 1 (decanted part), and extracts 2, 3 and 4 (extracted by shaking for 1 minute, 5 minutes and 24 hours, respectively). The fractionated extracts were saponified with a solution of KOH in methanol, and neutralized with 10% hydrochloric acid. The products were dissolved in a mixture of dichloromethane and hexane, and individually fractionated by column chromatography on alumina and silica gel (saturated hydrocarbon, aromatic, alcohol and fatty acid fractions). n-Alkanes and isoprenoid aliphatic alkanes, polycyclic alkanes of sterane and triterpane types, alcohols and fatty acids were analyzed using gas chromatography (GC) and gas chromatography-mass spectrometry (GC-MS). δ13CPDB values of individual n-alkanes in the aliphatic fractions were determined using gas chromatography-isotope ratio monitoring-mass spectrometry (GC-irmMS). Results and discussion. Extracts 1 and 2 are characterized by uniform distribution of n-alkanes, whereas extract 3 is characterized by an even-numbered members dominating the odd-ones, and extract 4 showed a bimodal distribution. Extract 1 is characterized by the least negative δ13CPDB values of C19-C26 n-alkanes. Sterane and triterpane analysis confirmed that all extracts originated from the same oil contaminant. n-Fatty acids, C19-C24, in all extracts are very low, being somewhat higher in extract 4. Even-numbered n-alcohols, C12–C16, were identified in the highest concentration in extract 3. It was assumed that algae were responsible for the composition of extract 3. Furthermore, a possible reason for higher concentrations of C19–C26 n-alkanes and C19–C24 fatty acids in extract 4 is the formation of inclusion compounds with colloidal micelles formed between the oil contaminant's NSO-compounds and water. Conclusion It was undoubtedly confirmed that there were specific differences in the compositions of the different extracts depending on the intensity of the interaction between the oil contaminant and the surface water. Recommendation and Outlook. When comparing the composition of oil contaminants from different water samples (regardless of the ultimate investigation goal) it is necessary to compare the extracts isolated under the same conditions, in other words, extracts that were in the same or very similar interaction with water.     

The impact of municipal solid waste management on greenhouse gas emissions in the United States

Technological advancements, environmental regulations, and emphasis on resource conservation and recovery have greatly reduced the environmental impacts of municipal solid waste (MSW) management, including emissions of greenhouse gases (GHGs). This study was conducted using a life-cycle methodology to track changes in GHG emissions during the past 25 years from the management of MSW in the United States. For the baseline year of 1974, MSW management consisted of limited recycling, combustion without energy recovery, and landfilling without gas collection or control. This was compared with data for 1980, 1990, and 1997, accounting for changes in MSW quantity, composition, management practices, and technology. Over time, the United States has moved toward increased recycling, composting, combustion (with energy recovery) and landfilling with gas recovery, control, and utilization. These changes were accounted for with historical data on MSW composition, quantities, management practices, and technological changes. Included in the analysis were the benefits of materials recycling and energy recovery to the extent that these displace virgin raw materials and fossil fuel electricity production, respectively. Carbon sinks associated with MSW management also were addressed. The results indicate that the MSW management actions taken by U.S. communities have significantly reduced potential GHG emissions despite an almost 2-fold increase in waste generation. GHG emissions from MSW management were estimated to be 36 million metric tons carbon equivalents (MMTCE) in 1974 and 8 MMTCE in 1997. If MSW were being managed today as it was in 1974, GHG emissions would be approximately 60 MMTCE.     

Changes in the grassland-forest boundary at Ta-Ta-Chia long term ecological research (LTER) site detected by stable isotope ratios of soil organic matter

The carbon isotope analysis [delta13C values] of organic samples can be a useful research in ecological studies because delta13C values are indicative of the plant source. This study investigated the changes in plant communities along the grassland-forest boundary in the alpine forest at Ta-Ta-Chia long term ecological research (LTER) site in central Taiwan using carbon isotope data. The aim of this study was focused on the forest fire affected the change of vegetation community. Four pedons from grassland dominated by Miscanthus transmorrisonensis (pedons 1 and 2), transition zone by Tsuga and Yushania nittakeyamensis (pedon 3), and forest zone by Tsuga and nittakeyamensis (pedon 4) were examined. Soil organic matter (SOM) delta13C values in the upper soil horizon were similar to delta13C values of the overlaying vegetation types. This indicates that the boundary between these plant communities remained the same in the past decades. The delta13C values of the grassland SOM ranged from -19.4 per thousand to -24.1 per thousand, showing decrease with soil depth. This suggests that C4 plants (transmorrisonensis) have replaced C3 plants of Tsuga and nittakeyamensis. The delta13C values of the Tsuga forest area (pedon 4) range from -27.0 per thousand to -23.5 per thousand and showed only slight change with soil depth, implying that C3 plants have remained the major species in the forest.     

Microbial indicators of heavy metal contamination in urban and rural soils

Urban soils and especially their microbiology have been a neglected area of study. In this paper, we report on microbial properties of urban soils compared to rural soils of similar lithogenic origin in the vicinity of Aberdeen city. Significant differences in basal respiration rates, microbial biomass and ecophysiological parameters were found in urban soils compared to rural soils. Analysis of community level physiological profiles (CLPP) of micro-organisms showed they consumed C sources faster in urban soils to maintain the same level activity as those in rural soils. Cu, Pb, Zn and Ni were the principal elements that had accumulated in urban soils compared with their rural counterparts with Pb being the most significant metal to distinguish urban soils from rural soils. Sequential extraction showed the final residue after extraction was normally the highest proportion except for Pb, for which the hydroxylamine-hydrochloride extractable Pb was the largest part. Acetic acid extractable fraction of Cd, Cu, Ni, Pb and Zn were higher in urban soils and aqua regia extractable fraction were lower suggesting an elevated availability of heavy metals in urban soils. Correlation analyses between different microbial indicators (basal respiration, biomass-C, and sole C source tests) and heavy metal fractions indicated that basal respiration was negatively correlated with soil Cd, Cu, Ni and Zn inputs while soil microbial biomass was only significantly correlated with Pb. However, both exchangeable and iron- and manganese-bound Ni fractions were mostly responsible for shift of the soil microbial community level physiological profiles (sole C source tests). These data suggest soil microbial indicators can be useful indicators of pollutant heavy metal stress on the health of urban soils.