Spatialized temporal dynamics of daily ozone concentrations: Identification of the main spatial differences.

Ground-level ozone (O3) is one of the most worrisome air pollutants regarding environmental and health impacts. There is a need for a deeper understanding of its spatial and temporal dynamics. Models are needed to provide continuous temporal and spatial coverage in ozone concentration data with a fine resolution. However, the simultaneous influence of each determinant of ozone dynamics, their spatial and temporal variations, and their interaction make the resulting dynamics of O3 concentrations difficult to understand. This study aimed to i) identify different classes of temporal dynamics of O3 at daily and 9 km2 resolution over a long-term period of 12 years, ii) identify the potential determinants of these dynamics and, iii) explore the spatial distribution of the potential classes of temporal dynamics on a spatial continuum and over about 1000 km2. Thus, 126 time series of 12-year daily ozone concentrations were classified using dynamic time warping (DTW) and hierarchical clustering (study area centered on Besançon, eastern France). The different temporal dynamics obtained differed on elevation, ozone levels, proportions of urbanized and vegetated surfaces. We identified different daily ozone temporal dynamics, spatially structured, that overlapped areas called urban, suburban and rural. Urbanization, elevation and vegetation acted as determinants simultaneously. Individually, elevation and vegetated surface were positively correlated with O3 concentrations (r = 0.84 and r = 0.41, respectively), while the proportion of urbanized area was negatively correlated with O3 (r = -0.39). An increasing ozone concentration gradient was observed from urban to rural areas and was reinforced by the elevation gradient. Rural areas were both subject to higher ozone levels (p < 0.001), least monitoring and lower predictability. We identified main determinants of the temporal dynamics of ozone concentrations. The joint influence of determinants was also synthesized. This study proposed a systematic, and reproducible way to build exposure area mapping.

Environmental noise exposure is associated with atherothrombotic risk.

There is growing evidence that environmental noise exposure could increase the risk of atherothrombotic events, including acute myocardial infarction (MI). We analysed the burden of environmental noise on atherothrombotic risk in MI patients. From the RICO survey, 879 consecutive MI patients included from 2004 to 2008 and living in an urban unit of > 237,000 inhabitants were analysed. Atherothrombotic risk was calculated using the TRS-2P score. TRS-2P categories were split into low (TRS-2P = 0/1) (40.8%), medium-low (TRS-2P = 2) (25.7%), medium-high (TRS-2P = 3) (21.8%) and high risk (TRS-2P ≥ 4) (11.6%). Noise exposure was associated with atherothrombotic risk, with the LAeq,24 h (OR (95% CI): 1.165 (1.026-1.324)) and Lnight (OR (95CI): 1.157 (1.031-1.298)), for each 10 dB(A) increase. After adjustment, noise exposure remained a predictor of atherothrombotic risk, with LAeq,24 h (OR (95% CI): 1.162 (1.011-1.337)) and with Lnight (OR (95% CI): 1.159 (1.019-1.317)). The relationship with transportation Lnight was significant for men (OR (95% CI): 1.260 (1.078-1.472)) but not for women (OR (95% CI): 0.959 (0.763-1.205)). We found a significant association between residential traffic noise exposure and atherothrombotic risk in men but not in women. These results could have major consequences for secondary prevention.

Improvement of downscaled ozone concentrations from the transnational scale to the kilometric scale: Need, interest and new insights.

BACKGROUND: Ground-level ozone is a major public health issue worldwide. An accurate assessment of ozone exposure is necessary. Modeling tools have been developed to tackle this issue in large areas. However, these models could present inaccuracies at the local scale. OBJECTIVES: The objective of this study was i) to assess whether O3 concentrations estimated by transnational modeling at the kilometric scale (9 km2) could be improved, ii) to propose a potential correction of these downscaled ozone concentrations and iii) to evaluate the efficiency and applicability of such a correction. METHOD: The present work was carried out in three phases. First, the performance of a transnational modeling platform (PREV'EST) was assessed at 6 geographic points by comparison with data from 6 air quality monitoring stations. Performance indicators were used for this purpose (MBE (mean bias error), MAE (mean absolute error), RMSE (root mean square error), r (Pearson correlation coefficient), and target plots). Second, several corrections were developed using MARS (multivariate adaptive regression splines) and integrating different sets of variables (mean temperature, relative humidity, rainfall amount, wind speed, elevation, and date). Their performance was evaluated. Third, external validation of the corrections was conducted using the data from six additional air quality monitoring stations. RESULTS: The uncorrected PREV'EST model presented a lack of exactitude and precision. These concentrations did not reproduce the interday variability of the measurements, leading to a lack of temporal contrast in exposure data. For the best performance enhancement, the correction applied improved MBE, MAE, RMSE and r from 14.67, 19.23, 23.18 and 0.67 to 0.00, 8.00, 10.19 and 0.91, respectively. External validation confirmed the efficiency of the corrections at the regional scale. CONCLUSIONS: We propose a validated and efficient methodology integrating local environmental variables. The methodology is adaptable according to the context, needs and data available.

Association between moderated level of air pollution and fetal growth: the potential role of noise exposure.

This study aims to analyze, in a population of singletons, the potential confounding or modifying effect of noise on the relationship between fetal growth restriction (FGR) or small for gestational age (SGA) and environmental exposure to air pollution. All women with single pregnancies living in one of two medium-sized cities (Besançon, Dijon) and who delivered at a university hospital between 2005 and 2009 were included. FGR and SGA were obtained from medical records. Outdoor residential exposure to nitrogen dioxide (NO2) and particulate matter (PM10) was quantified at the mother's address at delivery over defined pregnancy periods; outdoor noise exposure was considered to be the annual average daily noise levels in the façade of building (LAeq,24 h). Adjusted odds ratios (ORa) were estimated by multivariable logistic regressions. Among the 8994 included pregnancies, 587 presented FGR and 918 presented SGA. In the two-exposure models, for SGA, the ORa for a 10-µg/m3 increase of PM10 during the two last months before delivery was 1.18, 95%CI 1.00-1.41 and for FGR, these ORa were for the first and the third trimesters, and the two last months before delivery: 0.77 (0.61-0.97), 1.38 (1.12-1.70), and 1.35 (1.11-1.66), respectively. Noise was not associated with SGA or FGR and did not confound the relationship between air pollution and SGA or FGR. These results are in favor of an association between PM10 exposure and fetal growth, independent of noise, particularly towards the end of pregnancy, and of a lack of association between noise and fetal growth.

Pneumothorax and the environment: A systematic review of the impact of air pollution and meteorology, and a meta-analysis on meteorology factors.

A relationship between the occurrence of spontaneous pneumothorax (SP) and meteorological factors has been observed but with contradictory results. The objectives of this systematic review was to synthesis the current body of evidence to the relationships between the occurrence of SP and environmental determinants such as meteorological factors and air pollutants. We conducted a systematic search of MEDLINE, Scopus, Cochrane Library and gray literature from inception up to 31st December 2020, to find published scientific research articles based on the following eligibility criteria: original studies and population-based articles describing the relationship between meteorological factors or air pollutants and the occurrence of SP. For the meta-analysis, studies involving a quantitative analysis of the exposure variable (atmospheric pressure, temperature, humidity and wind speed) and the impact of the occurrence of SP with comparable methodology were selected. General characteristics and methodological information for each study were assessed. The quality was evaluated according to the Newcastle-Ottawa Scale. Fourty four and 13 studies were respectively included in the qualitative and quantitative analyses. The variability of the study design with moderate quality and the different measurements of the exposure variables highlight the contrasting results. The results of the meta-analyses are in favor of a higher temperature observed in the day with SP than in the days without SP (maximum: MD 0.25 (-0.08, 0.58) p = 0.14; I2 = 26%, p = 0.21; mean: MD 0.22 (-0.15, 0.59) p = 0.24; I2 = 45%, p = 0.07). The small number of studies focused on air pollution did not allow us to conclude to determine the potential impact of exposure to air pollutants on the occurrence of SP. Meteorological conditions seem to be related to SP occurrence, especially increased temperature.

Short term association between air pollution (PM10, NO2 and O3) and secondary spontaneous pneumothorax.

Secondary spontaneous pneumothorax (SSP) occurs in the context of underlying pulmonary disease. Our objectives were to estimate the relationship between SSP and short term air pollution exposure with nitrogen dioxide (NO2), ozone (O3) and particulate matter with a diameter ≤ 10 µm (PM10). Patients with SSP were included between June 1, 2009 and May 31, 2013, in 14 Emergency Departments in France. In this case-crossover design study, PM10, NO2, and O3 data were collected hourly from monitoring stations. Quantitative values, fast increase in air pollutant concentration, and air quality threshold exceedance were retained. These assessments were calculated for each of the 4 days prior to the event (Lag 1-Lag 4) for all case and control period, and for the entire exposure period. A total of 135 patients with SSP were included, with a mean age of 55.56 (SD 18.54) years. For short term exposure of PM10, NO2 and O3, no differences were observed between case and control periods in terms of quantitative values of air pollutant exposure (P > 0.68), fast increase in concentration (P > 0.12) or air quality threshold exceedance (P > 0.68). An association between O3 exposures cannot be ruled out, especially when considering the Lag 2 prior to the event and in warm seasons.

Pregnancy vulnerability in urban areas: a pragmatic approach combining behavioral, medico-obstetrical, socio-economic and environmental factors.

Multiple risk factors are associated with adverse pregnancy outcomes (APO), but how all these different factors combine and accumulate remains unknown. The objective of this observational retrospective study was to describe the accumulation of multiple vulnerability markers in pregnant women living in an urban area. Women living in Besançon (France) who delivered between 2005 and 2009 were included. Individual data were collected from the obstetrical records while environmental exposures were collected using environmental prediction models. The accumulation of 15 vulnerability markers, grouped into six dimensions (maternal age, smoking, body mass index (BMI), socio-economic, medico-obstetrical and environmental vulnerabilities) was described and analyzed in comparison with four APO. Among the 3686 included women, 20.8% were aged under 20 or over 34 and 21.9% had an extreme pre-pregnancy BMI. 18.8% declared smoking during pregnancy. Women exposed to socio-economic, medico-obstetrical or environmental vulnerability were 14.2%, 31.6% and 42.4% respectively. While 20.6% were not exposed to any marker, 18.8% accumulated three or more dimensions. The risk of APO increased significantly with the cumulative number of vulnerabilities. Define and validate a vulnerability score could be useful to identify vulnerable women, adapt their pregnancy monitoring and help policy makers to implement appropriate education or health promotion programs.

Does air pollution really impact the onset of spontaneous pneumothorax? A French case-crossover study.

RATIONALE: A link is established between air pollution and respiratory diseases. Very few studies evaluated this link with primary spontaneous pneumothorax (PSP). Contrasted results, low statistical power and methodological limits of these studies brought us to evaluate in a more thorough way this link. OBJECTIVES: (1) to estimate the relation between PSP and air pollutants namely nitrogen dioxide (NO2), ozone (O3) and particulate matter with a diameter ≤ 10 µm (PM10); (2) to investigate a time lag effect between these pollutants and occurrence of PSP. METHODS: This study has a case-crossover design. Subjects aged ≥18 years admitted from 1st June 2009 to 31st May 2013, in 14 Emergency Departments centers on the French territory. Were excluded: patients with traumatic, secondary, recurrent or history of previous pneumothorax. NO2, O3 and PM10 data were collected hourly in monitoring stations. Three exposure assessments were retained: quantitative values, fast increase concentration of air pollutants and peak of pollution. These assessments were calculated for the entire exposure period and for each of the four days of all case and control periods. RESULTS: 948 subjects included. Whatever the pollutant considered, no differences were observed between case and control periods, regardless of whether the quantitative values of air pollutants exposure (p > 0.09), fast increase concentration (p > 0.46) and peak of pollution (p > 0.20). CONCLUSIONS: We failed to show a relation between PSP and short-term air pollution exposure to low levels of NO2 and PM10. An association between O3 exposure and PSP cannot be ruled out. An impact at higher exposure level, and/or a potentiating effect of different meteorological factors remain to be demonstrated.

Multiple pregnancies and air pollution in moderately polluted cities: Is there an association between air pollution and fetal growth?

BACKGROUND: Multiple pregnancies (where more than one fetus develops simultaneously in the womb) are systematically excluded from studies of the impact of air pollution on pregnancy outcomes. This study aims to analyze, in a population of multiple pregnancies, the relationship between fetal growth restriction (FGR), small for gestational age (SGA) and exposure to air pollution in moderately polluted cities. METHODS: All women with multiple pregnancies living in the city of Besançon or in the urban area of Dijon and who delivered at a university hospital between 2005 and 2009 were included. FGR and SGA were obtained from medical records. Outdoor residential nitrogen dioxide (NO2) exposure was assessed using the mother's address, considering a 50 m radius buffer over the following defined pregnancy periods: each trimester, entire pregnancy and two months before delivery. Logistic regression analyses were performed. RESULTS: This study included 249 multiple pregnancies with 506 newborns. The median of NO2 concentration considering a 50 m radius buffer during entire pregnancy was 23.1 µg/m3 (minimum at 10.1 µg/m3 and maximum at 46.7 µg/m3). No association was observed between NO2 and SGA whatever the pregnancy period (the odds ratio (OR) range 0.78 to 0.88). Regarding FGR, the OR associated with an increase of 10 µg/m3 of NO2 exposure during entire pregnancy was 1.52 (95% Confidence Interval (CI): 1.02-2.26). Similar results were observed for NO2 exposure during the various pregnancy periods. CONCLUSIONS: These results are in line with an association between NO2 and fetal growth in multiple pregnancies for an exposure mostly below the threshold set out in European legislation.

Does low to moderate environmental exposure to noise and air pollution influence preterm delivery in medium-sized cities?

Background: Preterm birth (PB) is an important predictor of childhood morbidity and educational performance. Beyond the known risk factors, environmental factors, such as air pollution and noise, have been implicated in PB. In urban areas, these pollutants coexist. Very few studies have examined the effects of multi-exposure on the pregnancy duration. The objective of this study was to analyse the relationship between PB and environmental chronic multi-exposure to noise and air pollution in medium-sized cities. Methods: A case-control study was conducted among women living in the city of Besançon (121 671 inhabitants) or in the urban unit of Dijon (243 936 inhabitants) and who delivered in a university hospital between 2005 and 2009. Only singleton pregnancies without associated pathologies were considered. Four controls were matched to each case in terms of the mother's age and delivery location. Residential noise and nitrogen dioxide (NO2) exposures were calculated at the mother's address. Conditional logistic regression models were applied, and sensitivity analyses were performed. Results: This study included 302 cases and 1204 controls. The correlation between noise and NO2 indices ranged from 0.41 to 0.59. No significant differences were found in pollutant exposure levels between cases and controls. The adjusted odds ratios ranged between 0.96 and 1.08. Sensitivity analysis conducted using different temporal and spatial exposure windows demonstrated the same results. Conclusions: The results are in favour of a lack of connection between preterm delivery and multi-exposure to noise and air pollution in medium-sized cities for pregnant women without underlying disease.

Origin and diversity of testate amoebae shell composition: Example of Bullinularia indica living in Sphagnum capillifolium.

Testate amoebae are free-living shelled protists that build a wide range of shells with various sizes, shapes, and compositions. Recent studies showed that xenosomic testate amoebae shells could be indicators of atmospheric particulate matter (PM) deposition. However, no study has yet been conducted to assess the intra-specific mineral, organic, and biologic grain diversity of a single xenosomic species in a natural undisturbed environment. This study aims at providing new information about grain selection to develop the potential use of xenosomic testate amoebae shells as bioindicators of the multiple-origin mineral/organic diversity of their proximal environment. To fulfil these objectives, we analysed the shell content of 38 Bullinularia indica individuals, a single xenosomic testate amoeba species living in Sphagnum capillifolium, by scanning electron microscope (SEM) coupled with X-ray spectroscopy. The shells exhibited high diversities of mineral, organic, and biomineral grains, which confirms their capability to recycle xenosomes. Mineral grain diversity and size of B. indica matched those of the atmospheric natural mineral PM deposited in the peatbog. Calculation of grain size sorting revealed a discrete selection of grains agglutinated by B. indica. These results are a first step towards understanding the mechanisms of particle selection by xenosomic testate amoebae in natural conditions.

Cinderella's helping pigeons of the microbial world: The potential of testate amoebae for identifying cryptotephra.

Cryptotephra (particles <125µm) is a key record for monitoring past and current volcanic activity. However, its extraction from the host sediment and analysis is often long and difficult because of its small size. Finding a simple method to extract cryptotephra from environmental samples would therefore make its analysis much easier. We hypothesized that arcellinid testate amoebae may hold such a potential. These free-living shelled protists are among the earliest microorganisms to colonize volcanic tephra, and build their shell by agglutinating minerals from their environment. We analyzed by X-ray Spectrometry the mineral signature of tephra from the 2011 Puyehue-Cordon Caulle Volcanic Complex (Chile) eruption ash fallout and compared it to that of the shells of 51 individual testate amoebae (three individuals from each of 17 species) from 13 samples collected at different distances from the active vent. The mineral composition of particles within shells closely matched that of similar size class particles from their environment. The capacity of testate amoebae to randomly use mineral grains from their environment makes it possible to use their shells to assess the mineral composition of cryptotephra from soil, peat or sediment samples. Testate amoebae therefore represent the microbial world's version of Cinderella's helping pigeons.

Do outdoor environmental noise and atmospheric NO2 levels spatially overlap in urban areas?

The urban environment holds numerous emission sources for air and noise pollution, creating optimum conditions for environmental multi-exposure situations. Evaluation of the joint-exposure levels is the main obstacle for multi-exposure studies and one of the biggest challenges of the next decade. The present study aims to describe the noise/NO2 multi-exposure situations in the urban environment by exploring the possible discordant and concordant situations of both exposures. Fine-scale diffusion models were developed in the European medium-sized city of Besançon (France), and a classification method was used to evaluate the multi-exposure situations in the façade perimeter of 10,825 buildings. Although correlated (Pearson's r = 0.64, p < 0.01), urban spatial distributions of the noise and NO2 around buildings do not overlap, and 30% of the buildings were considered to be discordant in terms of the noise and NO2 exposure levels. This discrepancy is spatially structured and associated with variables describing the building's environment. Our results support the presence of several co-existing, multi-exposure situations across the city impacted by both the urban morphology and the emission and diffusion/propagation phases of each pollutant. Identifying the mechanisms of discrepancy and convergence of multi-exposure situations could help improve the health risk assessment and public health.

Modelling and mapping trace element accumulation in Sphagnum peatlands at the European scale using a geomatic model of pollutant emissions dispersion.

Trace elements (TEs) transported by atmospheric fluxes can negatively impact isolated ecosystems. Modelling based on moss-borne TE accumulation makes tracking TE deposition in remote areas without monitoring stations possible. Using a single moss species from ombrotrophic hummock peatlands reinforces estimate quality. This study used a validated geomatic model of particulate matter dispersion to identify the origin of Cd, Zn, Pb and Cu accumulated in Sphagnum capillifolium and the distance transported from their emission sources. The residential and industrial sectors of particulate matter emissions showed the highest correlations with the TEs accumulated in S. capillifolium (0.28(Zn)-0.56(Cu)) and (0.27(Zn)-0.47(Cu), respectively). Distances of dispersion varied depending on the sector of emissions and the considered TE. The greatest transportation distances for mean emissions values were found in the industrial (10.6 km when correlating with all TEs) and roads sectors (13 km when correlating with Pb). The residential sector showed the shortest distances (3.6 km when correlating with Cu, Cd, and Zn). The model presented here is a new tool for evaluating the efficacy of air pollution abatement policies in non-monitored areas and provides high-resolution (200 × 200 m) maps of TE accumulation that make it possible to survey the potential impacts of TEs on isolated ecosystems.

Air pollution in moderately polluted urban areas: How does the definition of "neighborhood" impact exposure assessment?

Environmental health studies commonly quantify subjects' pollution exposure in their neighborhood. How this neighborhood is defined can vary, however, leading to different approaches to quantification whose impacts on exposure levels remain unclear. We explore the relationship between neighborhood definition and exposure assessment. NO2, benzene, PM10 and PM2.5 exposure estimates were computed in the vicinity of 10,825 buildings using twelve exposure assessment techniques reflecting different definitions of "neighborhood". At the city scale, its definition does not significantly influence exposure estimates. It does impact levels at the building scale, however: at least a quarter of the buildings' exposure estimates for a 400 m buffer differ from the estimated 50 m buffer value (±1.0 µg/m(3) for NO2, PM10 and PM2.5; and ±0.05 µg/m(3) for benzene). This variation is significantly related to the definition of neighborhood. It is vitally important for investigators to understand the impact of chosen assessment techniques on exposure estimates.

Assessing residential exposure to urban noise using environmental models: does the size of the local living neighborhood matter?

Environmental epidemiological studies rely on the quantification of the exposure level in a surface defined as the subject's exposure area. For residential exposure, this area is often the subject's neighborhood. However, the variability of the size and nature of the neighborhoods makes comparison of the findings across studies difficult. This article examines the impact of the neighborhood's definition on environmental noise exposure levels obtained from four commonly used sampling techniques: address point, façade, buffers, and official zoning. A high-definition noise model, built on a middle-sized French city, has been used to estimate LAeq,24 h exposure in the vicinity of 10,825 residential buildings. Twelve noise exposure indicators have been used to assess inhabitants' exposure. Influence of urban environmental factors was analyzed using multilevel modeling. When the sampled area increases, the average exposure increases (+3.9 dB), whereas the SD decreases (-1.6 dB) (P<0.01). Most of the indicators differ statistically. When comparing indicators from the 50-m and 400-m radius buffers, the assigned LAeq,24 h level varies across buildings from -9.4 to +22.3 dB. This variation is influenced by urban environmental characteristics (P<0.01). On the basis of this study's findings, sampling technique, neighborhood size, and environmental composition should be carefully considered in further exposure studies.

Exposure chambers for studying the partitioning of atmospheric PAHs in environmental compartments: validation and calibration using experimental and computational approaches.

The environmental partitioning of atmospheric polycyclic aromatic hydrocarbons (PAHs) conditions their entry into food chains and subsequent risks for human health. The need for new experimental exposure devices for elucidating the mechanisms governing ecosystemic PAH transfer motivated the elaboration of an original small-scale exposure chamber (EC). A dual approach pairing experimentation and computational fluid dynamics (CFD) was selected to provide comprehensive validation of this EC as a tool to study the transfer and biological effects of atmospheric PAH pollution in microsystems. Soil samples and passive air samplers (PASs) were exposed to atmospheric pollution by phenanthrene (PHE), a gaseous PAH, for 2 weeks in examples of the EC being tested, set up under different conditions. Dynamic concentrations of atmospheric PHE and its uptake by PASs were simulated with CFD, results showing homogeneous distribution and constant atmospheric PHE concentrations inside the ECs. This work provides insight into the setting of given concentrations and pollution levels when using such ECs. The combination of experimentation and CFD is a successful ECs calibration method that should be developed with other semivolatile organic pollutants, including those that tend to partition in the aerosol phase.

To what extent do food preferences explain the trophic position of heterotrophic and mixotrophic microbial consumers in a Sphagnum peatland?

Although microorganisms are the primary drivers of biogeochemical cycles, the structure and functioning of microbial food webs are poorly studied. This is the case in Sphagnum peatlands, where microbial communities play a key role in the global carbon cycle. Here, we explored the structure of the microbial food web from a Sphagnum peatland by analyzing (1) the density and biomass of different microbial functional groups, (2) the natural stable isotope (δ(13)C and δ(15)N) signatures of key microbial consumers (testate amoebae), and (3) the digestive vacuole contents of Hyalosphenia papilio, the dominant testate amoeba species in our system. Our results showed that the feeding type of testate amoeba species (bacterivory, algivory, or both) translates into their trophic position as assessed by isotopic signatures. Our study further demonstrates, for H. papilio, the energetic benefits of mixotrophy when the density of its preferential prey is low. Overall, our results show that testate amoebae occupy different trophic levels within the microbial food web, depending on their feeding behavior, the density of their food resources, and their metabolism (i.e., mixotrophy vs. heterotrophy). Combined analyses of predation, community structure, and stable isotopes now allow the structure of microbial food webs to be more completely described, which should lead to improved models of microbial community function.

Above- and belowground linkages in Sphagnum peatland: climate warming affects plant-microbial interactions.

Peatlands contain approximately one third of all soil organic carbon (SOC). Warming can alter above- and belowground linkages that regulate soil organic carbon dynamics and C-balance in peatlands. Here we examine the multiyear impact of in situ experimental warming on the microbial food web, vegetation, and their feedbacks with soil chemistry. We provide evidence of both positive and negative impacts of warming on specific microbial functional groups, leading to destabilization of the microbial food web. We observed a strong reduction (70%) in the biomass of top-predators (testate amoebae) in warmed plots. Such a loss caused a shortening of microbial food chains, which in turn stimulated microbial activity, leading to slight increases in levels of nutrients and labile C in water. We further show that warming altered the regulatory role of Sphagnum-polyphenols on microbial community structure with a potential inhibition of top predators. In addition, warming caused a decrease in Sphagnum cover and an increase in vascular plant cover. Using structural equation modelling, we show that changes in the microbial food web affected the relationships between plants, soil water chemistry, and microbial communities. These results suggest that warming will destabilize C and nutrient recycling of peatlands via changes in above- and belowground linkages, and therefore, the microbial food web associated with mosses will feedback positively to global warming by destabilizing the carbon cycle. This study confirms that microbial food webs thus constitute a key element in the functioning of peatland ecosystems. Their study can help understand how mosses, as ecosystem engineers, tightly regulate biogeochemical cycling and climate feedback in peatlands.

Using testate amoeba as potential biointegrators of atmospheric deposition of phenanthrene (polycyclic aromatic hydrocarbon) on "moss/soil interface-testate amoeba community" microecosystems.

Microecosystem models could allow understanding of the impacts of pollutants such as polycyclic aromatic hydrocarbons on ecosystem functioning. We studied the effects of atmospheric phenanthrene (PHE) deposition on the microecosystem "moss/soil interface-testate amoebae (TA) community" over a 1-month period under controlled conditions. We found that PHE had an impact on the microecosystem. PHE was accumulated by the moss/soil interface and was significantly negatively correlated (0.4 < r(2) < 0.7) with total TA abundance and the abundance of five species of TA (Arcella sp., Centropyxis sp., Nebela lageniformis, Nebela tincta and Phryganella sp.). Among sensitive species, species with a superior trophic level (determined by the test aperture size) were more sensitive than other TA species. This result suggests that links between microbial groups in the microecosystems are disrupted by PHE and that this pollutant had effects both direct (ingestion of the pollutant or direct contact with cell) and/or indirect (decrease of prey) on the TA community. The TA community seems to offer a potential integrative tool to understand mechanisms and processes by which the atmospheric PHE deposition affects the links between microbial communities.