Etang De Berre Research Articles

Using Bayesian networks for environmental health risk assessment.

The study investigated the potential relationships between air pollution, socio-economy, and proven pathologies (e.g., respiratory, cardiovascular) within an industrial area in Southern France (Etang de Berre), gathering steel industries, oil refineries, shipping, road traffic and experiencing a Mediterranean climate. A total of 178 variables were simultaneously integrated within a Bayesian model at intra-urban scale. Various unsupervised and supervised algorithms (maximum spanning tree, tree-augmented naive classifier) as well as sensitivity analyses were used to better understand the links between all variables, and highlighted correlations between population exposure to air pollutants and some pathologies. Adverse health effects (bronchus and lung cancers for 15-65 years old people) were observed for hydrofluoric acid at low background concentration (<0.003μgm-3) while exposure to particulate cadmium (0.210-0.250μgm-3) disrupts insulin metabolism for people over 65 years-old leading to diabetes. Bronchus and lung cancers for people over 65 years-old occurred at low background SO2 concentration (6μgm-3) below European limit values. When benzo[k]fluoranthene exceeded 0.672μgm-3, we observed a high number of hospital admissions for respiratory diseases for 15-65 years-old people. The study also revealed the important influence of socio-economy (e.g., single-parent family, people with no qualification at 15 years-old) on pathologies (e.g., cardiovascular diseases). Finally, a diffuse polychlorinated biphenyl (PCB) pollution was observed in the study area and can potentially cause lung cancers.

Wind-Induced Resuspension and Transport of Contaminated Sediment from the Rove Canal into the Etang De Berre, France

The present study concerns the erosion and transport of severely contaminated sediments in a Canal. It begins in the context of an engineering project aimed to re-introduce a forced convection at the entrance of this Canal by pumping marine water. The local wind is often strong enough to overpass the resuspension threshold; thus, there is a serious risk of downstream contamination of a Mediterranean lagoon. So, the goal is to evaluate this risk as a function of the pumping rate; this contamination is transported by the fine suspended particles. Different scenarios are investigated to determine the downstream transport of suspensions in terms of runoff. These scenarios (of 24 h) contains a succession of 3 periods: constant wind speed, wind slowdown and calm, for two opposite wind directions. Special attention is devoted to the modeling of complex mechanisms of erosion and resuspension during wind periods, deposition during windless periods and sediment consolidation. The main results concern the total flux of the suspended particles through the exit of the Canal at the confluence with the lagoon. It is shown that even for moderate runoff (&lt;6 m3/s) this total flux is large enough, not only during the wind period, but also after several hours of calm.

Discovery of a Pelophylax saharicus (Anura, Ranidae) population in Southern France: a new potentially invasive species of water frogs in Europe

Abstract We report the discovery of a population of the exotic North African Water Frog Pelophylax saharicus around the Etang de Berre, on the Mediterranean coast of France, about 25 km north-west of Marseille. The animals had been originally identified as P. perezi or P. kl. grafi by a combination of acoustic and morphological characters and their true identity was not revealed until three samples from one locality were included in a large-scale genomic work dedicated to the genus Pelophylax. Mitochondrial barcoding of the samples from other areas around Etang de Berre did not detect any native P. perezi or P. kl. grafi and confirmed that P. saharicus has spread to several localities, does reproduce and has been present since 2011 at least. We suggest that dedicated field work is needed as soon as possible to (i) map the extant of P. saharicus’s distribution around the Etang de Berre, (ii) establish if populations of the native P. perezi – kl. grafi system still persist around the Etang de Berre or not and (iii) check if P. saharicus has spread to neighboring areas or not. Depending on the answers to these three questions, local conservationists will need to evaluate the feasibility and relevance of any action to control the spread of this new invasive species and attempt to eradicate it.

Risk of wind-driven resuspension and transport of contaminated sediments in a narrow marine channel confluencing a wide lagoon

This work concerns the wind-driven resuspension in a narrow marine channel and the risk of transport of contaminated bottom sediments in a wide brackish lagoon in the context of a planned anthropogenic infrastructure (with forced convection, by pumping sea water). It is based on the modelling and 3D numerical simulation of salinity, current distributions and bottom shear stress (BSS). The goal is to demonstrate that, even for narrow channels of a few tens of meter of width, a wind of 10–20 m/s is sufficient to create intensive currents, to resuspend muddy bottom sediments and transport polluted sediments downstream. Several model scenarios are considered for such wind speeds in two dominant and opposite wind directions, for a channel whose bottom sediments are mainly constituted of fine particles, typically 85% of mud and 15% of fine sand. It is known that finer sediments usually play an important role to transport contaminants (due to larger surface area of smaller particles). Our main results concern the bottom shear stress along such a long and narrow channel; namely the Rove channel which confluences the Etang de Berre lagoon, and for which a project of forced current circulation is planned by pumping sea water. Our numerical results show that the mobility threshold can be easily overpassed for the muddy sediments in the Rove channel. For a bottom roughness of 5 μm (coarse silt) and a wind speed of 20 m/s, BSS can reach 0.18 N/m2 for the N-NW wind in the median part of the channel, and even 0.21 N/m2 in one enlargement for the S-SE wind, while BSScr is about 0.1 N/m2. We conclude that these local winds can permit floc erosion and even surface erosion of fine sediments in the Rove channel.Concerning the resuspension of muddy sediments, our results are consistent with the experimental study presented by Carlin et al. (2016) for a windy shallow lagoon. They are also consistent with the conclusion of Mengual et al. (2017), from erodimetry experiment for estuarine sediments, that the sediment behaves like a pure mud if the percentage of the mud fraction is more than 70%, and that the critical BSS for mobility of such bed sediments is of the order of 0.1 N/m2. Such a lower critical BSS when the mixture is muddier is opposite to trends most often published.

Wind effect on bottom shear stress, erosion and redeposition on Zostera noltei restoration in a coastal lagoon; part 2

This paper concerns wind effect on bottom shear stress (BSS), resuspension and redeposition of bottom sediments in the nearshore areas of the Etang de Berre (EB), a semi-enclosed lagoon, in the context of Zostera noltei (Z.n.) restoration. As in our previous paper, the first step is to compare BSS with its threshold, BSScr, for a wind speed of 21 m/s. But, here, a new simulation is performed for 16 wind directions regularly spaced. It permits to analyze the combined effect, over one year, of these winds on the erosion risk. For that, a mean value of |BSS|, i.e., a weighted average based on the frequency of each wind directions, has been determined and compared to BSScr for a class of roughness parameters. A similar averaging of BSS→ has been also evaluated to obtain the direction of an average bottom current.Then, the most important contribution of the present paper concerns the modelling of the wind-induced sediment erosion, transport and redeposition. The specific module SEDIM/MARS3D is used to determine how the thickness of a given mud-sand sedimentary layer can be changed by the wind-induced current during typical periods of 3 days of constant wind. This numerical study is performed for three wind speeds in the two main wind directions: N-NW and S-SE. The time evolution of this initial sedimentary layer permits to determine where and when the erosion would be large enough to be a stressor for the Z.n. restoration.For an extreme erosion rate of 10−3 kg/m2/s, for a strong wind speed of 21 m/s and an initial sedimentary layer of 15 cm, all this layer would be eroded in several nearshore areas after 3 days. The erosion risk is maximum along the eastern shore, where an additive effect of the two opposite winds can be expected. Indeed, S-SE and N-NW winds create coastal jets of opposite direction and of about the same intensity exerting alongshore erosion and deposition at about the same places.The present results concerning the time evolution of erosion depth induced by the wind improve our knowledge of the erosion risk on the Z.n. restoration in EB. They will be useful to appropriately orient the action of politics and managers for a future restoration program.

Contribution to remediation of brackish lagoon: 3D simulation of salinity, bottom currents and resuspension of bottom sediments by strong winds

This work concerns the modelling and numerical simulation of the 3D salinity and current distribution in a very shallow Mediterranean lagoon subject to strong winds which create intensive resuspension of polluted bottom sediments. We consider wind speeds of 10 m/s and 20 m/s in the two dominant wind directions (N-NW and S-SE). This study is made for different scenarios of flow exchanges with the surrounding hydrosystems: a brackish lagoon on the North (the Etang de Berre), the Cadiere River on the East, and a brackish channel on the South (the Rove channel). The bottom shear stress (BSS) are compared to the BBS threshold given in the literature in terms of the bottom roughness. It permits to determine which kind of bottom sediments (muds and sands) will be resuspended by each wind. The bottom currents permit to predict in which direction the suspended sediments will be moved and where are the sedimentary deposit zones. It provides a guide for the specialists of remediation of the lagoon for a mechanical extraction of sediments in such zones.In addition, numerical experiments have been performed to understand how the salinity distribution depends on the flow exchanges with the two brackish surrounding hydrosystems. This new knowledge will permit the owner of this lagoon to know how to maintain efficiently the level of salinity in the suitable range.

Numerical simulation of the wind influence on bottom shear stress and salinity fields in areas of Zostera noltei replanting in a Mediterranean coastal lagoon

The paper concerns the numerical simulation of the wind influence on bottom shear stress and salinity fields in a semi-enclosed coastal lagoon (Etang de Berre) which is connected to the Mediterranean through a long and narrow channel (called Caronte). Two different scenarios are considered. The first scenario (scen.#1), starting with a homogeneous salinity of S=20 PSU and without wind forcing, studies a stratification process under the influence of a periodic seawater inflow and a strong freshwater inflow from a hydropower plant (250m3/s). Then, in the second scenario (scen.#2), we study how a strong wind of 80km/h can destroy the haline stratification obtained at the end of scen.#1. The MARS3D numerical model is used to analyze the 3D current and salinity distribution induced by these three meteorological, oceanic and anthropogenic forcings in this lagoon and in the Caronte channel.The main goal is to determine the bottom shear stress (BSS) in the nearshore areas of Zostera noltei replanting, and to compare it with the threshold for erosion of the bottom sediments for different bottom roughness parameters.The most interesting results concern the four nearshore replanting areas; two are situated on the eastern side of EB and two on the western side. The results of scen.#2 show that all these areas are subject to a downwind coastal jet. The destratification process is very beneficial; salinity always remains greater than 12 PSU for a N-NW wind of 80km/h and a hydropower runoff of 250m3/s. Concerning BSS, it presents a maximum near the shoreline and decreases along transects perpendicular to the shoreline. There exists a zone, parallel to the shoreline, where BSS presents a minimum (where BSS=0). When comparing the BSS value at the four control points with the critical value, BSScr, at which the sediment mobility would occur, we see that for the smaller bottom roughness values (ranging from z0=3.5×10−4mm, to 3.5×10−2mm) BSS largely surpasses this critical value. For a N-NW wind speed of 40km/h (which is blowing for around 100days per year), BSS still largely surpasses BSScr - at least for the silt sediments (ranging from z0=3.5×10−4mm, to 3.5×10−3mm). This confirms the possibility that the coastal jet could be a stressor for SAV replanting.

The effect of wind induced bottom shear stress and salinity on Zostera noltii replanting in a Mediterranean coastal lagoon

The paper concerns the wind influence on bottom shear stress and salinity levels in a Mediterranean semi-enclosed coastal lagoon (Etang de Berre), with respect to a replanting program of Zostera noltii. The MARS3D numerical model is used to analyze the 3D current, salinity and temperature distribution induced by three meteorological, oceanic and anthropogenic forcings in this lagoon. The numerical model has been carefully validated by comparison with daily observations of the vertical salinity and temperature profiles at three mooring stations, for one year. Then, two modelling scenarios are considered. The first scenario (scen.#1), starting with a homogeneous salinity of S = 20 PSU and without wind forcing, studies a stratification process under the influence of a periodic seawater inflow and a strong freshwater inflow from a hydropower plant (250 m3/s). Then, in the second scenario (scen.#2), we study how a strong wind of 80 km/h can mix the haline stratification obtained at the end of scen.#1. The most interesting results concern four nearshore replanting areas; two are situated on the eastern side of EB and two on the western side. The results of scen.#2 show that all these areas are subject to a downwind coastal jet. Concerning bottom salinity, the destratification process is very beneficial; it always remains greater than 12 PSU for a N-NW wind of 80 km/h and an hydropower runoff of 250 m3/s.Special attention is devoted to the bottom shear stress (BSS) for different values of the bottom roughness parameter (for gravels, sands and silts), and to the bottom salinity. Concerning BSS, it presents a maximum near the shoreline and decreases along transects perpendicular to the shoreline. There exists a zone, parallel to the shoreline, where BSS presents a minimum (close to zero). When comparing the BSS value at the four replanting areas with the critical value, BSScr, at which the sediment mobility would occur, we see that for the smaller roughness values (ranging from z0 = 3.5 × 10−4 mm, to 3.5 × 10−2 mm) BSS largely surpasses this critical value. For a N-NW wind speed of 40 km/h (which is blowing for around 100 days per year), BSS still largely surpasses BSScr - at least for the silt sediments (ranging from z0 = 3.5 × 10−4 mm, to 3.5 × 10−3 mm). This confirms the possibility that the coastal jet could generate sediment mobility which could have a negative impact for SAV replanting.

Environmental impacts of hydroelectric power and other anthropogenic developments on the hydromorphology and ecology of the Durance channel and the Etang de Berre, southeast France

The generation of electricity through hydropower can, along with other anthropogenic activities, degrade river hydromorphology and ecosystems. In this case, water for power generation is diverted from the River Durance to a canal, which services a chain of 17 power stations, with the lower three being in the catchment of the Etang de Berre. This means that excess water and sediments are discharged into the salt-water lagoon with enormous consequences for ecosystems there. This paper summarizes the impacts of HEP and other human activities on both the river and lagoonal systems. It also considers agency and government attempts to understand and counter the degradation of these systems, both to date and in the future, with the latter catering for the potential impacts of future human development and global warming.

Ring-hydroxylating dioxygenase (RHD) expression in a microbial community during the early response to oil pollution

The early functional response of a bacterial community from the sediments of a chronically oil-polluted retention basin located at the Etang de Berre (France) was investigated just after petroleum addition. After removing hydrocarbon compounds by natural abiotic and biotic processes, the sediments were maintained in microcosms and Vic Bilh petroleum was added. The diversity and the expression of genes encoding ring-hydroxylating dioxygenases (RHD) were examined just after the petroleum addition until 14days focussing on the first hours following the contamination. RHD gene copy numbers and diversity were maintained throughout all the incubation period; however, transcripts were detected only during the first 2days. One dominant RHD gene, immediately and specifically expressed in response to petroleum contamination, was related to RHD gene carried by a plasmid found in Pseudomonas spp. The expression of the RHD genes was correlated with high biodegradation levels observed for low molecular weight PAHs at 7days of incubation. The study shows that the bacterial metabolism induced just after the oil input is a key stage that could determine the bacterial community structure changes. Monitoring the expression of RHD genes, key genes involved in hydrocarbon degradation, may provide useful information for managing bioremediation processes.

Numerical realization of the three-dimensional model of hydrodynamics for shallow water basins on a high-performance system

The paper is dedicated to the development and application of the 3D shallow water hydrodynamics model. Parallel realization of the deepest descent the symmetric successive over relaxation (SSOR) algorithm is presented for solving finite-difference equations obtained after discretization of the initial problem. Estimates for speeding up and increasing the efficiency of the parallel algorithm are given, and the flow velocity distribution for the Azov Sea (South of Russia) and the Lagoon Etang de Berre (South of France) are presented.

Confocal Laser Scanning Microscopy Image Analysis for Cyanobacterial Biomass Determined at Microscale Level in Different Microbial Mats

We recently published a new method based on determining cyanobacterial biomass by confocal laser scanning microscopy image analysis (CLSM-IA) (Solé et al., Ultramicrosc 107:669-673, 2007). CLSM-IA allows biomass calculation for microorganisms of a small size, since the limit of the technique's resolution is that generated by a voxel, the smallest unit of a three-dimensional digital image, equivalent to 1.183 x 10(-3) mgC/cm(3) of sediment. This method is especially suitable for the quantitative analysis of a large number of CLSM images generated from benthic sediments in which complex populations of cyanobacteria are abundant, such as microbial mats. In order to validate the new CLSM approach, mats with varying structural characteristics were studied. We have grouped them into three types: Microcoleus mats (laminated), sandy mats (nonlaminated and composed of well-sorted quartz sands), and oil-polluted mats. In this work, we applied CLSM-IA in natural [the Ebro delta and Sant Jordi colony (Spain), Salins-de-Giraud and Etang de Berre (France), and Orkney Islands (Scotland)] and artificial [mesocosms (Israel)] microbial mats. A total of 4,103 confocal images were obtained in order to determine total and individual cyanobacteria biomass profiles, at microscale level. The data presented in this paper show the efficacy of the method, as it can be applied to highly diverse mat samples.

Molecular diversity studies of bacterial communities of oil polluted microbial mats from the Etang de Berre (France)

The biodiversity of microbial mats inhabiting the oil-contaminated lagoon Etang de Berre was determined by molecular approaches. The fingerprint of denaturing gradient gel electrophoresis (DGGE) and automatic ribosomal intergenic spacer analysis (ARISA) of mats exposed to different pollution levels showed specific microbial communities for each site but similar diversity richness. Species composition of the mats were compared by constructing 16S rRNA libraries. Amplified rDNA restriction analysis (ARDRA) of clone libraries confirmed their similar level of diversity richness. Phylogenetic analysis of the 16S rRNA sequences showed that the classes gamma and alpha of Proteobacteria were abundantly present in both sites whereas phylotypes related to the delta-Proteobacteria and to the uncultured WS3 group were mainly found in the site with the highest pollution. Identification of the species involved in oil degradation by combining culture-based approaches and DGGE, showed that enrichment cultures were constituted by members of the Rhodobacterales and species related to Rhodococcus, Sphingomonas, Xanthomonas and Microbacterium, all of them known for their ability to degrade hydrocarbons. Our findings suggest that oil pollution has not affected the biodiversity richness of the mats. However, the populations involved in hydrocarbon degradation represent a minor fraction of the mat communities in the Etang de Berre.

A comparative study of cyanobacterial diversity in polluted and unpolluted microbial mats by means CLSM

Abstract This paper is a summary of the results obtained from a study of the diversity of cyanobacteria in oil polluted and unpolluted natural environments. Our work group identified the different genera of cyanobacteria by means of CLSM, as this technique is specifically appropriate for studying the diversity of these microorganisms in stratified bentonic environments (microbial mats). The cyanobacteria identified in pristine ecosystems show that the most abundant cyanobacteria correspond to the genera: Microcoleus chthonoplastes, Oscillatona sp., Lyngbya sp., Leptolyngbya sp., and Limnothrix sp. Phormidium sp.and Pseudanabaena sp. were also identified, although they were less abundant. On the other hand, in the ecosystems heavily polluted with oil (Etang de Berre) neither Microcoleus chthonoplastes nor Oscillatoria sp. were detected, although the other genera mentioned were. With respect to coccoid cyanobacteria, the most abundant groups in the Ebro delta were Gloeocapsa sp. and Synechocystis sp. and al...

Genetic diversity of oxygenic phototrophs in microbial mats exposed to different levels of oil pollution

Abstract This paper presents a genetic diversity inventory of oxygenic phototrophs (cyanobacteria and eukaryotic algae) of nine selected microbial mat communities from four distinct geographical areas along the European coast. The communities were exposed to different levels of oil pollution. PCR-DGGE analysis of 16S rRNA gene fragments revealed a unique banding pattern for each sampling site. The number of bands which indicates the genetic richness, varied from one to twelve per site. Comparative analysis of DNA sequences obtained from the excised DGGE bands showed the identity of the oxygenic phototrophs present in the different mats. The relative abundance of diatoms, inferred from the band intensity, decreased with increasing oil pollution in the Etang de Berre mats (France). Cyanobacteria related to members of the genera Phormidium and Planktotrix were present in both the light and mediated polluted site, indicating oil tolerance. In the heavily polluted mat, only Oscillatoria-related cyanobacteria a...

L'habitat rural dans la Provence Antique : villa, vicus et mansio. Etudes de cas

This file originates from a reflection on rural settlements in Provence. These which have not been made the object of a specific paper are regrouped here and presented in their micro-regional space : the "Moyenne Durance" and the valley of Buëch, the depression of Maillanne between the plain of Arles and the Durance, the valley of Argens and the « dépression permienne» in the var department. The study of the sites located on the "Etang de Berre" shores draws attention to the diffusion of villa, maritima on the Provence littoral.

Analysis of oxygen rate time series in a strongly polluted lagoon using a regression tree method

This article presents results on daily forecasts of dissolved oxygen rates in a lagoon, the ‘Etang de Berre’, situated close to the French Mediterranean sea coast and submitted to particular meteorological conditions and freshwater inputs. To provide estimates of the response variable y (dissolved oxygen), a set of jointed decision rules is constructed by successive binary splitting of the predictor space composed of wind speed and freshwater flow data. The prediction model is displayed in the shape of a binary decision tree. We propose a transfer procedure in order to improve the prediction error of the tree model. Results obtained on the ‘Etang de Berre’ data set allow to describe and precise the effects of the environmental variables on the dissolved oxygen dynamics. The transfer procedure applied after the tree building process gives gains of prediction accuracy of about 17%.

Gross channel changes along the Durance River, Southern France, over the last 100 years using cartographic data

Gross channel changes for the Durance were determined using topographic maps from the 1890s and 1980s. Various width parameters were measured at 1 km intervals over 189 km from the Rhône junction at Avignon to La Saulce, some 31 km downstream of the dam at Serre Ponc¸on. During this period channel size has been considerably reduced. This can be attributed to four factors, two natural and two human induced. Firstly, there was a reduction in effective runoff at the end of the Little Ice Age (late 19th century). Secondly, runoff was further reduced with lower precipitation after about 1940. Thirdly, channel widths have been reduced by bank protection and by flood mitigation works. Finally, large-scale river regulation by EDF (Electricité de France), completed in the early 1960s, includes large dams to store alpine runoff, concrete canals to convey released water through some 20 power stations, and barrages to intercept tributary runoff and divert flows into the canals. In the lower Mediterranean part of the river, some of the diverted waters are discharged into irrigation and urban water canals (about 114 m3 s−1) and the rest into the Etang de Berre. Only about 1% of the mean discharge now reaches the Rhône. Discussion of available research provides insight into the four impacts, including additional comparative post-regulatory evidence from the Syndicat Mixte, a group concerned with environmental problems in the lower river. Evidence for channel change in lower parts of tributaries and for bed incision was found to be less conclusive. Such impacts may have been reduced by the interruptions of long-profile continuity by barrages and dams, and by lower discharges. Such discontinuities have adversely affected the ecology, low environmental flows and treated sewage dispersion. With some exceptions, environmental sustainability has not been a major issue because the Durance is such an important economic resource in terms of power, urban and irrigation waters, and building materials. Copyright © 2000 John Wiley & Sons, Ltd.

Forecasting physicochemical variables by a classification tree method. Application to the Berre Lagoon (south France).

The dynamics of the "Etang de Berre", a brackish lagoon situated close to the French Mediterranean sea coast, is strongly disturbed by freshwater inputs coming from an hydroelectric power station. The system dynamics has been described as a sequence of daily typical states from a set of physicochemical variables such as temperature, salinity and dissolved oxygen rates collected over three years by an automatic sampling station. Each daily pattern summarizes the evolution, hour by hour of the physicochemical variables. This article presents results of forecasts of the states of the system subjected to the simultaneous effects of meteorological conditions and freshwater releases. We recall the main step of the classification tree method used to build up the predictive model (Classification and Regression Trees, Breiman et al., 1984) and we propose a transfer procedure in order to test the stability of the model. Results obtained on the Etang de Berre data set allow us to describe and predict the effects of the environmental variables on the system dynamics with a margin of error. The transfer procedure applied after the tree building process gives a maximum gain in prediction accuracy of about 15%.

Relationship between heavy metals and magnetic properties in a large polluted catchment: The Etang de Berre (south of France)

The purpose of this study was to test possible extension of the relationship found by several authors between heavy metals enriched materials and magnetic properties to environmental system by the analysis of various materials of mixed anthropic and natural origins. The samples studied came from the Berre lake (pre-industrial sediments, recent surface sediments, saltmarsh materials, atmospheric dusts) and from other sources such as leaves of plane trees and Marseille urban sewage sludge. Clear correlations between metallic pollutants (mainly Zn, Cd & Cr with r2 > 0.75, and weaker correlation for Cu, Ni, Pb & Fe) concentrations and simple magnetic parameters (Saturation Isothermal Remanent Magnetisation, Susceptibility), are observed. The results show that correlation factors are frequently higher between magnetic parameters and metallic pollutants than between iron and the same metallic elements. For the same chemical element, SIRM values are frequently better correlated than x values. Nature of magnetic grains involved is discussed.