Global gradients of coral exposure to environmental stresses and implications for local management

Background: The decline of coral reefs globally underscores the need for a spatial assessment of their exposure to multiple environmental stressors to estimate vulnerability and evaluate potential counter-measures. Methodology/Principal Findings: This study combined global spatial gradients of coral exposure to radiation stress factors (temperature, UV light and doldrums), stress-reinforcing factors (sedimentation and eutrophication), and stress-reducing factors (temperature variability and tidal amplitude) to produce a global map of coral exposure and identify areas where exposure depends on factors that can be locally managed. A systems analytical approach was used to define interactions between radiation stress variables, stress reinforcing variables and stress reducing variables. Fuzzy logic and spatial ordinations were employed to quantify coral exposure to these stressors. Globally, corals are exposed to radiation and reinforcing stress, albeit with high spatial variability within regions. Based on ordination of exposure grades, regions group into two clusters. The first cluster was composed of severely exposed regions with high radiation and low reducing stress scores (South East Asia, Micronesia, Eastern Pacific and the central Indian Ocean) or alternatively high reinforcing stress scores (the Middle East and the Western Australia). The second cluster was composed of moderately to highly exposed regions with moderate to high scores in both radiation and reducing factors (Caribbean, Great Barrier Reef (GBR), Central Pacific, Polynesia and the western Indian Ocean) where the GBR was strongly associated with reinforcing stress. Conclusions/Significance: Despite radiation stress being the most dominant stressor, the exposure of coral reefs could be reduced by locally managing chronic human impacts that act to reinforce radiation stress. Future research and management efforts should focus on incorporating the factors that mitigate the effect of coral stressors until long-term carbon reductions are achieved through global negotiations

Ephemeroptera communities as bioindicators of the suitability of headwater streams for restocking with white-clawed crayfish, Austropotamobius pallipes

Currently, the distribution of the European native white-clawed crayfish (Austropotamobius pallipes) is restricted and fragmented over its range. Many European countries have active programmes for conservation of the species, including reintroduction programmes. Here, we have studied four brooks that were restocked with crayfish coming from population rescue from the Brissionnières after a drought in summer 2009. The aim was to validate the use of Ephemeropteran communities as potential bioindicators to select brooks for crayfish restocking. Restocked brooks were surveyed in 2010 and 2012. All brooks showed chemical and physical parameters in accordance with A. pallipes requirements. Three brooks which had high Ephemeropteran richness including Leptophlebiidae species (Habrophlebia lauta and Paraleptophlebia submarginata) have been restocked successfully. No crayfish were observed during the survey in Le Peu, which had only two Ephemeropteran species tolerant of reduced water quality and had no Leptophlebiidae species. Ecological characteristics of Ephemeropteran species and the limitations of their use as bioindicators to select brook for restocking are discussed

Modelling geosmin concentrations in three sources of raw water in Quebec, Canada

International audienceThe presence of off-flavour compounds such as geosmin, often found in raw water, significantly reduces the organoleptic quality of distributed water and diverts the consumer from its use. To adapt water treatment processes to eliminate these compounds, it is necessary to be able to identify them quickly. Routine analysis could be considered a solution, but it is expensive and delays associated with obtaining the results of analysis are often important, thereby constituting a serious disadvantage. The development of decision-making tools such as predictive models seems to be an economic and feasible solution to counterbalance the limitations of analytical methods. Among these tools, multi-linear regression and principal component regression are easy to implement. However, due to certain disadvantages inherent in these methods (multicollinearity or non-linearity of the processes), the use of emergent models involving artificial neurons networks such as multi-layer perceptron could prove to be an interesting alternative. In a previous paper (Parinet et al., Water Res 44: 5847-5856, 2010), the possible parameters that affect the variability of taste and odour compounds were investigated using principal component analysis. In the present study, we expand the research by comparing the performance of three tools using different modelling scenarios (multi-linear regression, principal component regression and multi-layer perceptron) to model geosmin in drinking water sources using 38 microbiological and physicochemical parameters. Three very different sources of water, in terms of quality, were selected for the study. These sources supply drinking water to the Qu,bec City area (Canada) and its vicinity, and were monitored three times per month over a 1-year period. Seven different modelling methods were tested for predicting geosmin in these sources. The comparison of the seven different models showed that simple models based on multi-linear regression provide sufficient predictive capacity with performance levels comparable to those obtained with artificial neural networks. The multi-linear regression model (R (2) = 0.657, < 0.001) used only four variables (phaeophytin, sum of green algae, chlorophyll-a and potential Redox) in comparison with ten variables (potassium, heterotrophic bacteria, organic nitrogen, total nitrogen, phaeophytin, total organic carbon, sum of green algae, potential Redox, UV absorbance at 254 nm and atypical bacteria) for the best model obtained with artificial neural networks (R (2) = 0.843)

Insights into Mechanistic Models for Evaporation of Organic Liquids in the Environment Obtained by Position-Specific Carbon Isotope Analysis

International audiencePosition-specific isotope effects (PSIEs) have been measured by isotope ratio monitoring C-13 nuclear magnetic resonance spectrometry during the evaporation of 10 liquids of different polarities under 4 evaporation modes (passive evaporation, air-vented evaporation, low pressure evaporation, distillation). The observed effects are used to assess the validity of the Craig-Gordon isotope model for organic liquids. For seven liquids the overall isotope effect (IE) includes a vapor-liquid contribution that is strongly position specific in polar compounds but less so in apolar compounds and a diffusive IE that is not position-specific, except in the alcohols, ethanol and propan-1-ol. The diffusive IE is diminished under forced evaporation. The position-specific isotope pattern created by liquid-vapor IEs is manifest in five liquids, which have an air-side limitation for volatilization. For the alcohols, undefined processes in the liquid phase create additional PSIEs. Three other liquids with limitations on the liquid side have a lower, highly position-specific, bulk diffusive IE. It is concluded that evaporation of organic pollutants creates unique position-specific isotope patterns that may be used to assess the progress of remediation or natural attenuation of pollution and that the Craig-Gordon isotope model is valid for the volatilization of nonpolar organic liquids with air-side limitation of the volatilization rate

Enhanced forensic discrimination of pollutants by position-specific isotope analysis using isotope ratio monitoring by C-13 nuclear magnetic resonance spectrometry

International audienceIn forensic environmental investigations the main issue concerns the inference of the original source of the pollutant for determining the liable party. Isotope measurements in geochemistry, combined with complimentary techniques for contaminant identification, have contributed significantly to source determination at polluted sites. In this work we have determined the intramolecular C-13 profiles of several molecules well-known as pollutants. By giving additional analytical parameters, position-specific isotope analysis performed by isotope ratio monitoring by C-13 nuclear magnetic resonance (irm-C-13 NMR) spectrometry gives new information to help in answering the major question: what is the origin of the detected contaminant? We have shown that isotope profiling of the core of a molecule reveals both the raw materials and the process used in its manufacture. It also can reveal processes occurring between the contamination site `source' and the sampling site. Thus, irm-C-13 NMR is shown to be a very good complement to compound-specific isotope analysis currently performed by mass spectrometry for assessing polluted sites involving substantial spills of pollutant. (C) 2015 Elsevier B.V. All rights reserved

Position-specific Carbon Isotope Fractionation gives Insights into Mechanistic Models for Evaporation of Organic Liquids in the Environment

AbstractThis work describes position-specific isotope effects (IE) measured by iq 13C-NMR during the evaporation of 8 different liquids of different polarities under 4 evaporation modes (passive evaporation, air-vented evaporation, low pressure evaporation and distillation). The observed effects are used to assess the question whether for carbon isotopes in organic liquids the use of the Craig-Gordon isotope model is valid. It is shown for five liquids that the overall IE include vapour-liquid IE which are strongly position-specific in polar compounds and less specific in apolar compounds, and a diffusive effect for which is not position-specific. The diffusive effect is diminished under wind and low pressure. After evaporation, the position-specific isotope pattern created by liquid-vapour IE is still quite reasonably preserved in these five liquids, which have, like water, an air-side limitation for volatilisation. Three other liquids in this study with limitations rather or fully on the liquid side differed from this pattern. It is concluded that evaporation of organic pollutants creates a unique position-specific isotope pattern that may be used to assess the progress of remediation or natural attenuation, and that the Craig-Gordon isotope model is valid for the volatilization of organic liquids with air-side limitation of the volatilization rate

Predicting equilibrium vapour pressure isotope effects by using artificial neural networks or multi-linear regression - A quantitative structure property relationship approach

International audienceWe aim at predicting the effect of structure and isotopic substitutions on the equilibrium vapour pressure isotope effect of various organic compounds (alcohols, acids, alkanes, alkenes and aromatics) at intermediate temperatures. We attempt to explore quantitative structure property relationships by using artificial neural networks (ANN); the multi-layer perceptron (MLP) and compare the performances of it with multi-linear regression (MLR). These approaches are based on the relationship between the molecular structure (organic chain, polar functions, type of functions, type of isotope involved) of the organic compounds, and their equilibrium vapour pressure. A data set of 130 equilibrium vapour pressure isotope effects was used: 112 were used in the training set and the remaining 18 were used for the test/validation dataset Two sets of descriptors were tested, a set with all the descriptors: number of C-12, C-13, O-16, O-18, H-1, H-2, OH functions, OD functions, C=O functions, Connolly Solvent Accessible Surface Area (CSA) and temperature and a reduced set of descriptors. The dependent variable (the output) is the natural logarithm of the ratios of vapour pressures (ln R), expressed as light/heavy as in classical literature. Since the database is rather small, the leave-one-out procedure was used to validate both models. Considering higher determination coefficients and lower error values, it is concluded that the multi-layer perceptron provided better results compared to multi-linear regression. The stepwise regression procedure is a useful tool to reduce the number of descriptors. To our knowledge, a Quantitative Structure Property Relationship (QSPR) approach for isotopic studies is novel. (C) 2014 Elsevier Ltd. All rights reserved

Position-Specific Isotope Analysis by Isotopic NMR Spectrometry: New Insights on Environmental Pollution Studies

AbstractThe common practice of measuring the change in isotope ratio for the whole molecule using isotope ratio measurement by mass spectrometry leads to the loss of significant information of potential interest, since it is the position-specific fractionation which most closely reflects the effect of physicochemical processes. We have shown for MTBE, a common ground water contaminant, that isotopic quantitative 13C NMR spectrometry can be effectively applied to obtain this position-specific data. It is found that different characteristic position-specific isotope fractionation patterns are introducedby different types of evaporative process or by oxidative degradation

A multi-omics strategy to depict and compare the hepatotoxic mechanisms of chlordecone and its metabolite chlordecol

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