Introduction of Relative Abundance Distribution (RAD) Indices, Estimated from the Rank-Frequency Diagrams (RFD), to Assess Changes in Community Diversity

Quantifying a relative abundance distribution based on thesampling of a set of species is a widespread problem in ecology.A number of diversity indices have been proposed and used in numerous works in spite of a lack of statistical characteristics and tests of comparison. The relative abundancedistribution can also be described using rank-frequency diagrams but fitting these diagrams to mathematical models such as the Zipf-Mandelbrot model remains problematic. Strong correlation between the Zipf-Mandelbrot model parameters prevent their estimation by optimization algorithm. In light of this, new indices of sampled communities are introduced here. These indices are two linear regression slopes estimated from rank-frequency diagrams. The numerous statistical studies that have been carried out on linear regression models are used to compare sampled communities. These new indices possesscharacteristic properties with an ecological meaning.Correlations between these indices, the Zipf-Mandelbrot modelparameters and an evenness diversity index are examined. Anecological application is made using entomological data as anexample. This example consists of a transect from the edge of apond to a dry forest along which 60,000 insects were sampledfrom six different sampling stations. Using the new indicesdescribed here, station C, located at the edge of that areasubject to influence from the pond, is differentiated from theother stations. This station would seem to present the lowestdegree of niche diversity and the lowest evenness, and recent observations confirm the deterioration of this station.     

How to Take into Account Uncertainty in Species Extinction Probabilities for Phylogenetic Conservation Prioritization

In this article, we are concerned with the general problem of choosing from a set of taxa T a subset S to protect in order to try to contribute to halting biodiversity loss as efficiently as possible given limited resources. The protection of a taxon decreases its extinction probability, and the impact of protecting the taxa of S is measured by the resulting expected phylogenetic diversity (ePD) of the set T. The primary challenge posed by this approach lies in determining the extinction probability of a taxon (protected or unprotected). To deal with this difficulty, the uncertainty about the extinction probabilities can be described through a set of possible scenarios, each corresponding to different extinction probability values for each taxon. We show how to determine an “optimal robust set” of taxa to protect, defined as the set of taxa that minimizes the maximum “regret,” i.e., the maximum relative gap, over all the scenarios, between (1) the ePD of T obtained by protecting the taxa of this set and (2) the ePD of T which would be produced by protecting the subset of taxa optimal for the considered scenario. In our experimental conditions covering 100 cases, this gap is almost always less than 1%. Consequently, the ePD of T obtained by protecting the taxa of the optimal robust set is not far from the maximum ePD of T that could have been obtained if we had known the true scenario. In other words, a way of escaping (in large part, at least) from the uncertainty related to the extinction probabilities of the taxa consists of choosing to protect those belonging to the optimal robust set. We also compare the optimal robust set to other relevant subsets of T.     

Designing Connected and Compact Nature Reserves

It is generally accepted that for many species, the ability to get around a reserve promotes their long-term persistence. Here, we measure the ease with which species can move by two spatial criteria: (i) the connectivity of the reserve, that is to say, the possibility to go through the whole reserve without leaving it, and (ii) the compactness of the reserve, that is to say, the remoteness of the sites in relation to each other, the distance between two sites being measured by the shortest distance to travel to get from one site to another without leaving the reserve. To protect the reserve of external disturbances, we also impose a connectivity constraint for the area outside the reserve. This article presents a method based on integer linear programming to define connected and compact reserves. Computational experiments carried out on artificial instances with 400 sites and 100 species are presented to illustrate the effectiveness of the approach.     

Dissolved organic matter from treated effluent of a major wastewater treatment plant: characterization and influence on copper toxicity

A combination of reverse osmosis (RO) concentration and DAX-8/XAD-4 resin adsorption techniques is used to isolate the various constituents of urban dissolved organic matter (DOM) from inorganic salts. Three fractions: hydrophobic (HPO), transphilic (TPI) and hydrophilic (HPI) accounting respectively for 35%, 20% and 45% of extracted carbon, are isolated from effluents of a major French wastewater treatment plant. This atypical DOC distribution, in comparison with natural water where the HPO fraction dominates, shows the significance of HPI fraction which often gets neglected because of extraction difficulties. A number of analytical techniques (elemental, spectroscopic: UV, FTIR) allow highlighting the weak aromaticity of wastewater effluent DOM (EfOM) due to fewer degradation and condensation processes and the strong presence of proteinaceous structures indicative of intense microbial activity. Copper toxicity in the presence of DOM is estimated using an acute toxicity test on Daphnia Magna (Strauss). Results reveal the similar protective role of each EfOM fraction compared to reference Suwannee river fulvic acid despite lower EfOM aromaticity (i.e. specific UV absorbance). The environmental implications of these results are discussed with respect to the development of site-specific water quality criteria.     

Exposure assessment of French women and their newborn to brominated flame retardants: determination of tri- to deca- polybromodiphenylethers (PBDE) in maternal adipose tissue, serum, breast milk and cord serum

In the frame of a French monitoring program, tri- to deca- polybromodiphenylethers (PBDE) have been measured in maternal and cord serum, adipose tissue, and breast milk samples, collected from 93 volunteer women during caesarean deliveries. The seven major tri- to heptaBDE (BDE-28, 47, 99, 100, 153, 154, and 183) were detected in adipose tissue and breast milk with cumulated median values of 2.59 and 2.51 ng g⁻¹ l w. Nine highly brominated octa- to decaBDE (BDE-196, 197, 201, 202, 203, 206, 207, 208 and 209) was performed in the same samples, with cumulated median values of 2.73 and 3.39 ng g⁻¹ l w in adipose tissue and breast milk, respectively. At this opposite, median levels of octa- to decaBDE in maternal and cord serum appeared significantly higher than the levels of tri- to heptaBDE in the same matrices, i.e. 8.85 and 12.34 versus 0.98 and 0.69 ng g⁻¹ l w, respectively.     

Realistic approach of pesticide residues and French consumer exposure within fruit & vegetable intake

The increase of fruit and vegetable (F&V) intake contributes to the prevention of chronic diseases, but could also significantly increase pesticide exposure and may thus be of health concern. Following a previous pesticide exposure assessment study, the present study was carried out to determine actual levels of pesticides within 400 g of F&V intake and to evaluate consumer risk. Forty-three Active Substances (AS) exceeding 10 % of the Acceptable Daily Intake (ADI) in balanced menus established for our previous theoretical study were considered. Fifty-six pooled food samples were analyzed: 28 fruit samples and 28 vegetable samples. Pesticide values were compared to Maximum Residue Levels (MRL) and to the "toxicological credit" derived from ADI. It was observed that 23 out of the 43 retained AS were never detected, 5 were detected both in F&V samples, 12 only in fruits and 3 only in vegetables. The most frequently detected AS were carbendazim, iprodione and dithiocarbamates. When detected, AS were more frequently found in fruit samples (74 %) than in vegetable samples (26 %). A maximum of 3 AS were detected at once in a given sample. Overall, we observed 8 and 14 overruns of the MRL in 1204 measures in pooled vegetable and fruit samples, respectively (0.7 % and 1.2 % of cases, respectively). Chronic exposure for adults was the highest for dithiocarbamates but did not exceed 23.7 % of the ADI in F&V. It was concluded that raising both F&V consumption up to 400 g/day (~5 F&V/day) according to recommendations of the national health and nutrition plan, does not induce pesticide overexposure and should not represent a risk for the consumer.     

Thermodynamic and kinetic study of phenol degradation by a non-catalytic wet air oxidation process

This work is dedicated to an accurate evaluation of thermodynamic and kinetics aspects of phenol degradation using wet air oxidation process. Phenol is a well known polluting molecule and therefore it is important having data of its behaviour during this process. A view cell is used for the experimental study, with an internal volume of 150 mL, able to reach pressures up to 30 MPa and temperatures up to 350 °C. Concerning the thermodynamic phase equilibria, experimental and modelling results are obtained for different binary systems (water/nitrogen, water/air) and ternary system (water/nitrogen/phenol). The best model is the Predictive Soave Redlich Kwong one. This information is necessary to predict the composition of the gas phase during the process. It is also important for an implementation in a process simulation. The second part is dedicated to kinetics evaluation of the degradation of phenol. Different compounds have been detected using GC coupled with a MS. A kinetic scheme is deduced, taking into account the evolution of phenol, hydroquinones, catechol, resorcinol and acetic acid. The kinetic parameters are calculated for this scheme. These data are important to evaluate the evolution of the concentration of the different polluting molecules during the process. A simplified kinetic scheme, which can be easily implemented in a process simulation, is also determined for the direct degradation of phenol into H₂O and CO₂. The Arrhenius law data obtained for the phenol disappearance are the following: k = 1.8 × 10⁶ ± 3.9 × 10⁵ M⁻¹ s⁻¹ (pre-exponential factor) and E_a = 77 ± 8 kJ mol⁻¹ (activation energy).     

Spread of the native grass <Emphasis Type="Italic">Elymus athericus</Emphasis> in salt marshes of Mont-Saint-Michel bay as an unusual case of coastal eutrophication

Contrary to many estuaries where the increase in inputs of nitrogenous nutrients results in a macro-algal or phytoplanktonic bloom, no proliferation of this kind has ever been observed in the waters of Mont-Saint-Michel bay (north-western France) owing to a very high turbidity which greatly limits light penetration. On the other hand, it is well known that the factor that usually limits the growth of vascular plants in salt marshes is not the light resource but nitrogen availability; these plant species are therefore able to benefit fully from the enrichment of water by nitrogenous compounds. This seems to be the case of the sea couch grass Elymus athericus that has spread very rapidly on the salt marshes of this site since the mid-1980s. Firstly, the present study (i) accurately documents, from a compilation of data from administrative archives, the changes in agricultural land use in the major watersheds during the period 1970–2010, together with related changes in the nitrate contents of the rivers flowing into the bay; (ii) quantifies the spatial spread of sea couch grass between 1984 and 2013 from the five maps made during this period. In the second part, using in-depth analysis based on the findings of previous studies, it shows that the expansion of this native grass corresponds to a biological invasion phenomenon, for which nitrogen enrichment of the bay seems to be the only plausible explanation.