Indiscriminate use of pesticides in the modern agricultural practices leads to the contamination ... more Indiscriminate use of pesticides in the modern agricultural practices leads to the contamination of soils, surface and ground waters. The types of pesticides used in the agricultural watershed surrounding the complex Ichkeul Lake-Bizerte lagoon from Tunisia were identified and their quantity estimated. The survey of farmers and dealers of pesticides showed that the most commonly used active ingredients are iodosulfuron (2014 kg), mesosulfuron (1218 kg), 2.4D (4618 kg), glyphosate (2886 kg) and fenoxaprop (5300 kg) as herbicidal active ingredient; tebuconazole (9260 kg) and epoxiconazole (17168 kg) as a fungicide; and deltamethrin (341 kg), as insecticide. Herbicides are used twice a year (pre- and post-emergence), treatment with fungicides is a result of rust attacks, insecticides are applied against insects such as aphids, for example. The percentages of active ingredient were determined to establish a ranking according to the physical-chemical parameters of each active ingredient ...
Recent Advances in Geo-Environmental Engineering, Geomechanics and Geotechnics, and Geohazards, 2018
Petroleum Hydrocarbon Contamination (PHC) is a widespread environmental problem that can be found... more Petroleum Hydrocarbon Contamination (PHC) is a widespread environmental problem that can be found in many countries. Several contaminated land management approaches have been developed so far, all of which include some form of site investigation, risk assessment and remediation processes. Most of these approaches are often based on risk-based land management concepts. Most countries have a common framework for a risk assessment procedure for contaminated sites which endanger human health, involve ecological risk, and risks to water resources and construction materials. Usually, risk assessment of contaminated land is triggered by suspicious soil or groundwater contamination which is identified by Screening Values (SVs) approach. SVs specify generic quality standards for contaminated land. The application of SVs varies from adjusting long-term quality objectives, through making further investigations, to applying remedial actions. SVs derivation methods have scientific, geographical,...
This study was conducted to assess the impact and efficiency of the bioaugmentation as a bioremed... more This study was conducted to assess the impact and efficiency of the bioaugmentation as a bioremediation technique in annoying effects of a polycyclic aromatic hydrocarbon (phenanthrene) on a community of free-living nematodes from Bizerte bay (Tunisia). For this purpose, closed microcosms were exposed to three doses of phananthrene (0.1 μg kg-1, 1 μg kg-1 and 10 μg kg-1), in combination or not with a strain of Shewanella oneidensis. After 40 days of the exposure, results were obtained at the numerical, taxonomic and feeding levels. The results of univariate analyses revealed significant decreases in most univariate indices for phenanthrene treated communities compared to controls, with a discernible increase in the proportion of epistrate feeders. After bioaugmentation, similar patterns were observed for univariate and multivariate analyses, with the exception of the highest treatment, which showed no difference from the controls. The results obtained showed that the bioaugmentation with Shewanellea oneidensis was highly effective in reducing the negative impact of the highest dose of phenanthrene (10 μg kg-1 Dry Weight) tested on meiobenthic nematodes. Furthermore, a combination of Shewanellea oneidensis and four omnivore-carnivore nematode taxa could be suggested as an effective method in the bioremediation of phenanthrene-contaminated sediment.
Microbial communities inhabiting soil-water-sediment continuum in coastal areas provide important... more Microbial communities inhabiting soil-water-sediment continuum in coastal areas provide important ecosystem services. Their adaptation in response to environmental stressors, particularly mitigating the impact of pollutants discharged from human activities, has been considered for the development of microbial biomonitoring tools, but their use is still in the infancy. Here, chemical and molecular (16S rRNA gene metabarcoding) approaches were combined in order to determine the impact of pollutants on microbial assemblages inhabiting the aquatic network of a soil-water-sediment continuum around the Ichkeul Lake (Tunisia), an area highly impacted by human activities. Samples were collected within the soil-river-lake continuum at three stations in dry (summer) and wet (winter) seasons. The contaminant pressure index (PI), which integrates Polycyclic aromatic hydrocarbons (PAHs), alkanes, Organochlorine pesticides (OCPs) and metal contents, and the microbial pressure index microgAMBI, based on bacterial community structure, showed significant correlation with contamination level and differences between seasons. The comparison of prokaryotic communities further revealed specific assemblages for soil, river and lake sediments. Correlation analyses identified potential "specialist" genera for the different compartments, whose abundances were correlated with the pollutant type found. Additionally, PICRUSt analysis revealed the metabolic potential for pollutant transformation or degradation of the identified "specialist" species, providing information to estimate the recovery capacity of the ecosystem. Such findings offer the possibility to define a relevant set of microbial indicators for assessing the effects of human activities on aquatic ecosystems. Microbial indicators, including the detection of "specialist" and sensitive taxa, and their functional capacity, might be useful, in combination with integrative microbial indices, to constitute accurate biomonitoring tools for the management and restoration of complex coastal aquatic systems.
Analyses of organochlorine pesticides (OCPs), polycyclic aromatic hydrocarbons (PAHs), polychlori... more Analyses of organochlorine pesticides (OCPs), polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs), and butyl tins (BuSn) were conducted on sediments from Ichkeul Lake-Bizerte Lagoon watershed (Tunisia). A total of 59 compounds (16 PAHs, 12 PCBs, 22 OCPs and 9 BuSn) were measured in 40 surface sediment samples collected during two campaigns. High concentrations of total PAHs were identified in the lagoon ranging from 122 to 19600ng·g(-1). Several OCPs, including endrin, dieldrin, and lindane (Hexachlorocyclohexane or HCH or BHC) were found in high concentrations in Ichkeul Lake, ranging from 28 to 2012ngg(-1). PAHs and OCPs varied seasonally, in response to the complex hydrology of the watershed. The concentrations of total PCBs ranged between 0.04 and 10.653ngg(-1) and suggests low total PCBs sediment contamination, when compared to most international criteria. Total BuSn concentrations range between 67 and 526ng·g(-1), which are relatively low when compared to...
Benthic microorganisms are key players in the recycling of organic matter and recalcitrant compou... more Benthic microorganisms are key players in the recycling of organic matter and recalcitrant compounds such as polyaromatic hydrocarbons (PAHs) in coastal sediments. Despite their ecological importance, the response of microbial communities to chronic PAH pollution, one of the major threats to coastal ecosystems, has received very little attention. In one of the largest surveys performed so far on coastal sediments, the diversity and composition of microbial communities inhabiting both chronically contaminated and non-contaminated coastal sediments were investigated using high-throughput sequencing on the 18S and 16S rRNA genes. Prokaryotic alpha-diversity showed significant association with salinity, temperature, and organic carbon content. The effect of particle size distribution was strong on eukaryotic diversity. Similarly to alpha-diversity, beta-diversity patterns were strongly influenced by the environmental filter, while PAHs had no influence on the prokaryotic community struc...
Les objectifs de ce travail ont ete en premier lieu d’evaluer l’impact de la presence des HAPs et... more Les objectifs de ce travail ont ete en premier lieu d’evaluer l’impact de la presence des HAPs et des metaux sur la structure et la biodiversite des communautes bacteriennes presentes dans les sediments de la lagune de Bizerte, ainsi que l’effet de certains parametres du milieu. On a cherche egalement a caracteriser des souches bacteriennes capables de degrader les HAPs et resistantes aux metaux et aux antibiotiques ainsi qu’a detecter des genes impliques dans la degradation des HAPs. L’etude de la diversite bacterienne des sediments a ete realisee en combinant les approches culturales de microbiologie et des approches de biologie moleculaire. Les analyses statistiques combinees des parametres hydrobiologiques, de la teneur en HAPs et des empreintes genetiques des communautes bacteriennes par T-RFLP ont montre que la communaute bacterienne des sediments de la station la plus contaminee par les HAPs se differencie clairement de celles des autres stations. L’inventaire moleculaire des communautes bacteriennes des sediments des stations chargees en HAPs et en metaux traces a mis en evidence une difference significative dans la structure des communautes bacteriennes entre la station la plus polluee par les HAPs et celle la plus chargee en metaux traces. Les bacteries isolees sur du fluoranthene ont ete caracterisees par des tests morphologiques et biochimiques ainsi que par leurs antibioresistances et celle de la resistance aux metaux. Parmi celles selectionnees pour leur multiresistance, 75 % d’entre elles ont ete affiliees a la sous-classe des γ-Proteobacteries dont 67 % au genre Pseudomonas. Les dosages des HAPs ont montre que les souches selectionnees etaient capables de degrader les differents hydrocarbures testes. L’amplification par PCR a permis de detecter le gene nah codant pour la naphtalene dioxygenase chez ces souches selectionnees. De plus, les profils plasmidiques ont permis de mettre en evidence des plasmides de grandes tailles portant l’operon du gene nah.
RESUME Dans le but d'isoler des bactéries capables de dégrader les hydrocarbures aromatiques ... more RESUME Dans le but d'isoler des bactéries capables de dégrader les hydrocarbures aromatiques polycycliques et résistantes aux métaux lourds ainsi qu'aux antibiotiques, nous avons réalisé en mai 2004 des prélèvements d'eau et de sédiments dans la lagune de Bizerte au niveau de 16 stations réparties sur tout le plan d'eau. Nous avons procédé à l'isolement des bactéries par méthode d'enrichissement liquide utilisant un milieu minéral de base supplémenté en fluoranthène comme seule source de carbone et d'énergie. Des tests morphologiques et biochimiques ont été utilisés pour la sélection et l'identification de l'ensemble des bactéries cultivables (130 isolats). Les résultats préliminaires obtenus montrent que les bactéries dégradant les hydrocarbures aromatiques polycycliques appartiennent à différents groupes de bactéries Gram -et Gram + respectivement à des taux de 70 % et 30 %. Ce sont les bactéries de type bacilles Gram -qui sont prédominantes (74...
Environmental Science and Pollution Research, 2014
The objectives of this study were (1) to assess the responses of benthic nematodes to a polycycli... more The objectives of this study were (1) to assess the responses of benthic nematodes to a polycyclic aromatic hydrocarbon (PAH) contamination and (2) to test bioremediation techniques for their efficiency in PAH degradation and their effects on nematodes. Sediments with their natural nematofauna communities from Bizerte lagoon (Tunisia) were subjected to a PAH mixture (100 ppm) of phenanthrene, fluoranthene, and pyrene during 30 days. Nematode abundance and diversity significantly decreased, and the taxonomic structure was altered. Results from multivariate analyses of the species abundance data revealed that PAH treatments were significantly different from the control. Spirinia parasitifera became the dominant species (70 % relative abundance) and appeared to be an "opportunistic" species to PAH contamination while Oncholaimus campylocercoides and Neochromadora peocilosoma were strongly inhibited. Biostimulation (addition of mineral salt medium) and bioaugmentation (inoculation of a hydrocarbonoclastic bacterium) were used as bioremediation techniques. Bioremediation treatments enhanced degradation of all three PAHs, with up to 96 % degradation for phenanthrene resulting in a significant stimulation of nematode abundance relative to control microcosms. Nevertheless, these treatments, especially the biostimulation provoked a weak impact on the community structure and diversity index relative to the control microcosms suggesting their feasibility in biorestoration of contaminated sediments.
Environmental science and pollution research international, Jan 25, 2015
Sediments from Bizerta lagoon were used in an experimental microcosm setup involving three scenar... more Sediments from Bizerta lagoon were used in an experimental microcosm setup involving three scenarios for the bioremediation of anthracene-polluted sediments, namely bioaugmentation, biostimulation, and a combination of both bioaugmentation and biostimulation. In order to investigate the effect of the biotreatments on the benthic biosphere, 16S rRNA gene-based T-RFLP bacterial community structure and the abundance and diversity of the meiofauna were determined throughout the experiment period. Addition of fresh anthracene drastically reduced the benthic bacterial and meiofaunal abundances. The treatment combining biostimulation and bioaugmentation was most efficient in eliminating anthracene, resulting in a less toxic sedimentary environment, which restored meiofaunal abundance and diversity. Furthermore, canonical correspondence analysis showed that the biostimulation treatment promoted a bacterial community favorable to the development of nematodes while the treatment combining bio...
In order to estimate how pollution affects the bacterial community structure and composition of s... more In order to estimate how pollution affects the bacterial community structure and composition of sediments, chemical and molecular approaches were combined to investigate eight stations around the Bizerte lagoon. Terminal restriction fragment length polymorphism (T-RFLP) analysis of PCR-amplified 16S rRNA genes revealed that each station was characterized by a specific bacterial community structure. The combination of this data with those of chemical analysis showed a correlation between the bacterial fingerprint and the pollutant content, principally with hydrocarbon pollution. The composition of the bacterial community of two contrasted stations related to the pollution revealed sequences affiliated to α, β, γ, δ, ε subclass of the Proteobacteria, Actinobacteria, and Acidobacteria in both stations although in different extent. Gamma and delta subclass of the Proteobacteria were dominant and represent 70% of clones in the heavy-metalcontaminated station and 47% in the polyaromatic hydrocarbon (PAH)-contaminated. Nevertheless, most of the sequences found were unaffiliated to cultured bacteria. The adaptation of the bacterial community mainly to PAH compounds demonstrated here and the fact that these bacterial communities are mainly unknown suggest that the Bizerte lagoon is an interesting environment to understand the capacity of bacteria to cope with some pollutants.
Environmental Science and Pollution Research, 2012
Purpose The main goals of this study were to investigate (1) the behavior of microbial communitie... more Purpose The main goals of this study were to investigate (1) the behavior of microbial communities in response to lowdose bioavailable anthracene addition in lightly contaminated sediment from Bizerte Lagoon and (2) the effects of bioremediation treatments on microbial biomass, activity, and community structure. Methods Sediment microcosms amended with 1 ppm anthracene were incubated in triplicate during 30 days. Biostimulation (addition of nitrogen and phosphorus fertilizer) and bioaugmentation (inoculation of a hydrocarbonoclastic bacterium) were used as bioremediation treatments. Bacterial biomass was estimated using flow cytometry. Sediment oxygen consumption was measured with oxygen microelectrodes. Bacterial community structure was assessed by molecular fingerprints (terminal restriction fragment length polymorphism; T-RFLP) analysis. Results Anthracene contamination resulted in a significant reduction of bacterial abundance with an impact on cell integrity. Concomitantly, sediment oxygen consumption was strongly inhibited. Correspondence analysis on T-RFLP data indicated that bacterial community structures from anthracene-contaminated microcosms were different from that of the control. Interestingly, the changes observed in microbial biomass, structure, and activities as a result of anthracene contamination were not alleviated even with the use of biostimulation and combination of biostimulation and bioaugmentation strategy for anthracene bioremediation. Nevertheless, both treatment methods resulted in different community structures relative to the contaminated and control microcosms with the appearance of distinct populations. Conclusion Anthracene spiking severely affected microbial communities, suggesting dominance of nontolerant populations in this lightly-contaminated sediment. Although biostimulation and/or bioaugmentation treatments did not alleviate the anthracene toxic effects, the changes observed in microbial population and structure suggest that the proposed treatments might be promising to promote bacterial growth. Further works are still required to propose a more efficient strategy to stimulate biodegradation that takes into account the complex interactions between species for resource access.
A microcosm experiment was used to examine (1) the effects of different bioremediation schemes on... more A microcosm experiment was used to examine (1) the effects of different bioremediation schemes on degradation of anthracene and the structure of free-living marine nematodes in a lightly contaminated (4.5 lg g-1) sediment from Bizerte lagoon and (2) the responses of the nematode community upon an artificial spiking of a low dose anthracene (1 lg g-1). For that purpose sediment microcosms were incubated in laboratory for 40 days. Bioremediation techniques decreased the anthracene contamination, and interestingly, biodegradation were more efficient when anthracene was artificial supplied into the sediment suggesting that the addition of bioavailable anthracene stimulated the bacterial community to adjust towards a PAH-degrading community. Spiking with this low dose of anthracene provoked significant changes in the nematode community structure and abundance, with the elimination of specific species such as Mesacanthion diplechma, the decrease of the dominant species Oncholaimus campylocercoides and the increase in abundance of opportunistic species such as Spirinia parasitifera. This would suggest a low tolerance of the nematode community despite the presence of a weak anthracene contamination in the sediment that could have allow dominance of an anthracene tolerant nematode species. Anthracene toxicity was alleviated in biostimulation treatments, leading to a strong increase in nematode abundance, concomitantly with changes in the nematode community structure; Prochromadorella neapolitana became the most abundant species.
for the future use of biostimulation to reduce toxic effects of PAHs for meiofauna and bacteria i... more for the future use of biostimulation to reduce toxic effects of PAHs for meiofauna and bacteria in lagoon sediment.
Bulletin of environmental contamination and toxicology, Jan 21, 2016
A Quick, Easy, Cheap, Effective, Rugged and Safe (QuEChERS) method has been adapted and validated... more A Quick, Easy, Cheap, Effective, Rugged and Safe (QuEChERS) method has been adapted and validated for the simultaneous analysis of 16 PAHs, 12 PCBs and 9 OCPs in sediment. The sample preparation was adapted by modifying the nature of the extraction solvent, the extraction technique and the amount of sediment. The analytical performances were evaluated in terms of accuracy, linearity and quantification limits. The method was validated by the analysis of a reference marine sediment material (SRM 1941b). The obtained concentrations are in good agreement with the certified values with recoveries ranging 60 %-103 % for most of PAHs. Acceptable recoveries are obtained for PCBs, ranging 76 %-131 %, and for OCPs ranging 81 %-137 %. The method was applied to the analysis of sediments from the hydro-system Bizerte Lagoon/Ichkeul Lake (Tunisia). The Bizerte lagoon is mainly contaminated by PAHs whereas the Ichkeul lake is mainly by OCPs.
Microbes and Signaling Biomolecules Against Plant Stress, 2020
Environmental stress is the foremost limiting factor for agricultural productivity. It is essenti... more Environmental stress is the foremost limiting factor for agricultural productivity. It is essential to alleviate the distress caused by environmental and edaphic conditions in plants, failing to which would affect their growth, development, and productivity. Microorganisms have enormous metabolic capabilities to lessen the environmental stress and their interactions with plants provide a local and systemic defense under various biotic and abiotic stresses. Due to an increase in adverse external conditions, it is imperative to study plant-microbe relationships at the physiological and molecular level to provide deeper insights into the stressmitigating mechanisms.
Recent Advances in Geo-Environmental Engineering, Geomechanics and Geotechnics, and Geohazards, 2018
The residual sludge from the bottom of refinery crude oil storage tanks causes major environmenta... more The residual sludge from the bottom of refinery crude oil storage tanks causes major environmental and societal problems in Tunisia. Due to its high viscosity, it must be removed from the storage tanks in order to utilize the crude oil. However, its disposal in the environment leads to the infiltration of toxic metals into groundwater and eventual contamination of surface water bodies. The aim of this work was to characterize and treat sludge from Tunisian refinery by two different approaches (chemical and biological) and evaluate the economic efficiency of sludge remediation. Our results showed that both approaches are useful in terms of reducing the metal content of the sludge. However, the biological approach is more economically efficient and leads to better ecological outcomes.
Iranian Journal of Chemistry & Chemical Engineering-international English Edition, 2020
This study aims to determine the major elements of Portland cement type I and II (CEMI and CEMII)... more This study aims to determine the major elements of Portland cement type I and II (CEMI and CEMII) in a cement factory in north Tunisia and which metal elements are introduced into the production process. We determine also the metal input rate and their distribution at the entrance and exit of the process. The major elements were analyzed and the trace elements (Arsenic, barium, lead, mercury, boron, strontium, Cadmium, Chromium, copper, manganese, nickel, and zinc) were identified. The concentrations of heavy metals in CEMI showed no significant difference p
Indiscriminate use of pesticides in the modern agricultural practices leads to the contamination ... more Indiscriminate use of pesticides in the modern agricultural practices leads to the contamination of soils, surface and ground waters. The types of pesticides used in the agricultural watershed surrounding the complex Ichkeul Lake-Bizerte lagoon from Tunisia were identified and their quantity estimated. The survey of farmers and dealers of pesticides showed that the most commonly used active ingredients are iodosulfuron (2014 kg), mesosulfuron (1218 kg), 2.4D (4618 kg), glyphosate (2886 kg) and fenoxaprop (5300 kg) as herbicidal active ingredient; tebuconazole (9260 kg) and epoxiconazole (17168 kg) as a fungicide; and deltamethrin (341 kg), as insecticide. Herbicides are used twice a year (pre- and post-emergence), treatment with fungicides is a result of rust attacks, insecticides are applied against insects such as aphids, for example. The percentages of active ingredient were determined to establish a ranking according to the physical-chemical parameters of each active ingredient ...
Recent Advances in Geo-Environmental Engineering, Geomechanics and Geotechnics, and Geohazards, 2018
Petroleum Hydrocarbon Contamination (PHC) is a widespread environmental problem that can be found... more Petroleum Hydrocarbon Contamination (PHC) is a widespread environmental problem that can be found in many countries. Several contaminated land management approaches have been developed so far, all of which include some form of site investigation, risk assessment and remediation processes. Most of these approaches are often based on risk-based land management concepts. Most countries have a common framework for a risk assessment procedure for contaminated sites which endanger human health, involve ecological risk, and risks to water resources and construction materials. Usually, risk assessment of contaminated land is triggered by suspicious soil or groundwater contamination which is identified by Screening Values (SVs) approach. SVs specify generic quality standards for contaminated land. The application of SVs varies from adjusting long-term quality objectives, through making further investigations, to applying remedial actions. SVs derivation methods have scientific, geographical,...
This study was conducted to assess the impact and efficiency of the bioaugmentation as a bioremed... more This study was conducted to assess the impact and efficiency of the bioaugmentation as a bioremediation technique in annoying effects of a polycyclic aromatic hydrocarbon (phenanthrene) on a community of free-living nematodes from Bizerte bay (Tunisia). For this purpose, closed microcosms were exposed to three doses of phananthrene (0.1 μg kg-1, 1 μg kg-1 and 10 μg kg-1), in combination or not with a strain of Shewanella oneidensis. After 40 days of the exposure, results were obtained at the numerical, taxonomic and feeding levels. The results of univariate analyses revealed significant decreases in most univariate indices for phenanthrene treated communities compared to controls, with a discernible increase in the proportion of epistrate feeders. After bioaugmentation, similar patterns were observed for univariate and multivariate analyses, with the exception of the highest treatment, which showed no difference from the controls. The results obtained showed that the bioaugmentation with Shewanellea oneidensis was highly effective in reducing the negative impact of the highest dose of phenanthrene (10 μg kg-1 Dry Weight) tested on meiobenthic nematodes. Furthermore, a combination of Shewanellea oneidensis and four omnivore-carnivore nematode taxa could be suggested as an effective method in the bioremediation of phenanthrene-contaminated sediment.
Microbial communities inhabiting soil-water-sediment continuum in coastal areas provide important... more Microbial communities inhabiting soil-water-sediment continuum in coastal areas provide important ecosystem services. Their adaptation in response to environmental stressors, particularly mitigating the impact of pollutants discharged from human activities, has been considered for the development of microbial biomonitoring tools, but their use is still in the infancy. Here, chemical and molecular (16S rRNA gene metabarcoding) approaches were combined in order to determine the impact of pollutants on microbial assemblages inhabiting the aquatic network of a soil-water-sediment continuum around the Ichkeul Lake (Tunisia), an area highly impacted by human activities. Samples were collected within the soil-river-lake continuum at three stations in dry (summer) and wet (winter) seasons. The contaminant pressure index (PI), which integrates Polycyclic aromatic hydrocarbons (PAHs), alkanes, Organochlorine pesticides (OCPs) and metal contents, and the microbial pressure index microgAMBI, based on bacterial community structure, showed significant correlation with contamination level and differences between seasons. The comparison of prokaryotic communities further revealed specific assemblages for soil, river and lake sediments. Correlation analyses identified potential "specialist" genera for the different compartments, whose abundances were correlated with the pollutant type found. Additionally, PICRUSt analysis revealed the metabolic potential for pollutant transformation or degradation of the identified "specialist" species, providing information to estimate the recovery capacity of the ecosystem. Such findings offer the possibility to define a relevant set of microbial indicators for assessing the effects of human activities on aquatic ecosystems. Microbial indicators, including the detection of "specialist" and sensitive taxa, and their functional capacity, might be useful, in combination with integrative microbial indices, to constitute accurate biomonitoring tools for the management and restoration of complex coastal aquatic systems.
Analyses of organochlorine pesticides (OCPs), polycyclic aromatic hydrocarbons (PAHs), polychlori... more Analyses of organochlorine pesticides (OCPs), polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs), and butyl tins (BuSn) were conducted on sediments from Ichkeul Lake-Bizerte Lagoon watershed (Tunisia). A total of 59 compounds (16 PAHs, 12 PCBs, 22 OCPs and 9 BuSn) were measured in 40 surface sediment samples collected during two campaigns. High concentrations of total PAHs were identified in the lagoon ranging from 122 to 19600ng·g(-1). Several OCPs, including endrin, dieldrin, and lindane (Hexachlorocyclohexane or HCH or BHC) were found in high concentrations in Ichkeul Lake, ranging from 28 to 2012ngg(-1). PAHs and OCPs varied seasonally, in response to the complex hydrology of the watershed. The concentrations of total PCBs ranged between 0.04 and 10.653ngg(-1) and suggests low total PCBs sediment contamination, when compared to most international criteria. Total BuSn concentrations range between 67 and 526ng·g(-1), which are relatively low when compared to...
Benthic microorganisms are key players in the recycling of organic matter and recalcitrant compou... more Benthic microorganisms are key players in the recycling of organic matter and recalcitrant compounds such as polyaromatic hydrocarbons (PAHs) in coastal sediments. Despite their ecological importance, the response of microbial communities to chronic PAH pollution, one of the major threats to coastal ecosystems, has received very little attention. In one of the largest surveys performed so far on coastal sediments, the diversity and composition of microbial communities inhabiting both chronically contaminated and non-contaminated coastal sediments were investigated using high-throughput sequencing on the 18S and 16S rRNA genes. Prokaryotic alpha-diversity showed significant association with salinity, temperature, and organic carbon content. The effect of particle size distribution was strong on eukaryotic diversity. Similarly to alpha-diversity, beta-diversity patterns were strongly influenced by the environmental filter, while PAHs had no influence on the prokaryotic community struc...
Les objectifs de ce travail ont ete en premier lieu d’evaluer l’impact de la presence des HAPs et... more Les objectifs de ce travail ont ete en premier lieu d’evaluer l’impact de la presence des HAPs et des metaux sur la structure et la biodiversite des communautes bacteriennes presentes dans les sediments de la lagune de Bizerte, ainsi que l’effet de certains parametres du milieu. On a cherche egalement a caracteriser des souches bacteriennes capables de degrader les HAPs et resistantes aux metaux et aux antibiotiques ainsi qu’a detecter des genes impliques dans la degradation des HAPs. L’etude de la diversite bacterienne des sediments a ete realisee en combinant les approches culturales de microbiologie et des approches de biologie moleculaire. Les analyses statistiques combinees des parametres hydrobiologiques, de la teneur en HAPs et des empreintes genetiques des communautes bacteriennes par T-RFLP ont montre que la communaute bacterienne des sediments de la station la plus contaminee par les HAPs se differencie clairement de celles des autres stations. L’inventaire moleculaire des communautes bacteriennes des sediments des stations chargees en HAPs et en metaux traces a mis en evidence une difference significative dans la structure des communautes bacteriennes entre la station la plus polluee par les HAPs et celle la plus chargee en metaux traces. Les bacteries isolees sur du fluoranthene ont ete caracterisees par des tests morphologiques et biochimiques ainsi que par leurs antibioresistances et celle de la resistance aux metaux. Parmi celles selectionnees pour leur multiresistance, 75 % d’entre elles ont ete affiliees a la sous-classe des γ-Proteobacteries dont 67 % au genre Pseudomonas. Les dosages des HAPs ont montre que les souches selectionnees etaient capables de degrader les differents hydrocarbures testes. L’amplification par PCR a permis de detecter le gene nah codant pour la naphtalene dioxygenase chez ces souches selectionnees. De plus, les profils plasmidiques ont permis de mettre en evidence des plasmides de grandes tailles portant l’operon du gene nah.
RESUME Dans le but d'isoler des bactéries capables de dégrader les hydrocarbures aromatiques ... more RESUME Dans le but d'isoler des bactéries capables de dégrader les hydrocarbures aromatiques polycycliques et résistantes aux métaux lourds ainsi qu'aux antibiotiques, nous avons réalisé en mai 2004 des prélèvements d'eau et de sédiments dans la lagune de Bizerte au niveau de 16 stations réparties sur tout le plan d'eau. Nous avons procédé à l'isolement des bactéries par méthode d'enrichissement liquide utilisant un milieu minéral de base supplémenté en fluoranthène comme seule source de carbone et d'énergie. Des tests morphologiques et biochimiques ont été utilisés pour la sélection et l'identification de l'ensemble des bactéries cultivables (130 isolats). Les résultats préliminaires obtenus montrent que les bactéries dégradant les hydrocarbures aromatiques polycycliques appartiennent à différents groupes de bactéries Gram -et Gram + respectivement à des taux de 70 % et 30 %. Ce sont les bactéries de type bacilles Gram -qui sont prédominantes (74...
Environmental Science and Pollution Research, 2014
The objectives of this study were (1) to assess the responses of benthic nematodes to a polycycli... more The objectives of this study were (1) to assess the responses of benthic nematodes to a polycyclic aromatic hydrocarbon (PAH) contamination and (2) to test bioremediation techniques for their efficiency in PAH degradation and their effects on nematodes. Sediments with their natural nematofauna communities from Bizerte lagoon (Tunisia) were subjected to a PAH mixture (100 ppm) of phenanthrene, fluoranthene, and pyrene during 30 days. Nematode abundance and diversity significantly decreased, and the taxonomic structure was altered. Results from multivariate analyses of the species abundance data revealed that PAH treatments were significantly different from the control. Spirinia parasitifera became the dominant species (70 % relative abundance) and appeared to be an "opportunistic" species to PAH contamination while Oncholaimus campylocercoides and Neochromadora peocilosoma were strongly inhibited. Biostimulation (addition of mineral salt medium) and bioaugmentation (inoculation of a hydrocarbonoclastic bacterium) were used as bioremediation techniques. Bioremediation treatments enhanced degradation of all three PAHs, with up to 96 % degradation for phenanthrene resulting in a significant stimulation of nematode abundance relative to control microcosms. Nevertheless, these treatments, especially the biostimulation provoked a weak impact on the community structure and diversity index relative to the control microcosms suggesting their feasibility in biorestoration of contaminated sediments.
Environmental science and pollution research international, Jan 25, 2015
Sediments from Bizerta lagoon were used in an experimental microcosm setup involving three scenar... more Sediments from Bizerta lagoon were used in an experimental microcosm setup involving three scenarios for the bioremediation of anthracene-polluted sediments, namely bioaugmentation, biostimulation, and a combination of both bioaugmentation and biostimulation. In order to investigate the effect of the biotreatments on the benthic biosphere, 16S rRNA gene-based T-RFLP bacterial community structure and the abundance and diversity of the meiofauna were determined throughout the experiment period. Addition of fresh anthracene drastically reduced the benthic bacterial and meiofaunal abundances. The treatment combining biostimulation and bioaugmentation was most efficient in eliminating anthracene, resulting in a less toxic sedimentary environment, which restored meiofaunal abundance and diversity. Furthermore, canonical correspondence analysis showed that the biostimulation treatment promoted a bacterial community favorable to the development of nematodes while the treatment combining bio...
In order to estimate how pollution affects the bacterial community structure and composition of s... more In order to estimate how pollution affects the bacterial community structure and composition of sediments, chemical and molecular approaches were combined to investigate eight stations around the Bizerte lagoon. Terminal restriction fragment length polymorphism (T-RFLP) analysis of PCR-amplified 16S rRNA genes revealed that each station was characterized by a specific bacterial community structure. The combination of this data with those of chemical analysis showed a correlation between the bacterial fingerprint and the pollutant content, principally with hydrocarbon pollution. The composition of the bacterial community of two contrasted stations related to the pollution revealed sequences affiliated to α, β, γ, δ, ε subclass of the Proteobacteria, Actinobacteria, and Acidobacteria in both stations although in different extent. Gamma and delta subclass of the Proteobacteria were dominant and represent 70% of clones in the heavy-metalcontaminated station and 47% in the polyaromatic hydrocarbon (PAH)-contaminated. Nevertheless, most of the sequences found were unaffiliated to cultured bacteria. The adaptation of the bacterial community mainly to PAH compounds demonstrated here and the fact that these bacterial communities are mainly unknown suggest that the Bizerte lagoon is an interesting environment to understand the capacity of bacteria to cope with some pollutants.
Environmental Science and Pollution Research, 2012
Purpose The main goals of this study were to investigate (1) the behavior of microbial communitie... more Purpose The main goals of this study were to investigate (1) the behavior of microbial communities in response to lowdose bioavailable anthracene addition in lightly contaminated sediment from Bizerte Lagoon and (2) the effects of bioremediation treatments on microbial biomass, activity, and community structure. Methods Sediment microcosms amended with 1 ppm anthracene were incubated in triplicate during 30 days. Biostimulation (addition of nitrogen and phosphorus fertilizer) and bioaugmentation (inoculation of a hydrocarbonoclastic bacterium) were used as bioremediation treatments. Bacterial biomass was estimated using flow cytometry. Sediment oxygen consumption was measured with oxygen microelectrodes. Bacterial community structure was assessed by molecular fingerprints (terminal restriction fragment length polymorphism; T-RFLP) analysis. Results Anthracene contamination resulted in a significant reduction of bacterial abundance with an impact on cell integrity. Concomitantly, sediment oxygen consumption was strongly inhibited. Correspondence analysis on T-RFLP data indicated that bacterial community structures from anthracene-contaminated microcosms were different from that of the control. Interestingly, the changes observed in microbial biomass, structure, and activities as a result of anthracene contamination were not alleviated even with the use of biostimulation and combination of biostimulation and bioaugmentation strategy for anthracene bioremediation. Nevertheless, both treatment methods resulted in different community structures relative to the contaminated and control microcosms with the appearance of distinct populations. Conclusion Anthracene spiking severely affected microbial communities, suggesting dominance of nontolerant populations in this lightly-contaminated sediment. Although biostimulation and/or bioaugmentation treatments did not alleviate the anthracene toxic effects, the changes observed in microbial population and structure suggest that the proposed treatments might be promising to promote bacterial growth. Further works are still required to propose a more efficient strategy to stimulate biodegradation that takes into account the complex interactions between species for resource access.
A microcosm experiment was used to examine (1) the effects of different bioremediation schemes on... more A microcosm experiment was used to examine (1) the effects of different bioremediation schemes on degradation of anthracene and the structure of free-living marine nematodes in a lightly contaminated (4.5 lg g-1) sediment from Bizerte lagoon and (2) the responses of the nematode community upon an artificial spiking of a low dose anthracene (1 lg g-1). For that purpose sediment microcosms were incubated in laboratory for 40 days. Bioremediation techniques decreased the anthracene contamination, and interestingly, biodegradation were more efficient when anthracene was artificial supplied into the sediment suggesting that the addition of bioavailable anthracene stimulated the bacterial community to adjust towards a PAH-degrading community. Spiking with this low dose of anthracene provoked significant changes in the nematode community structure and abundance, with the elimination of specific species such as Mesacanthion diplechma, the decrease of the dominant species Oncholaimus campylocercoides and the increase in abundance of opportunistic species such as Spirinia parasitifera. This would suggest a low tolerance of the nematode community despite the presence of a weak anthracene contamination in the sediment that could have allow dominance of an anthracene tolerant nematode species. Anthracene toxicity was alleviated in biostimulation treatments, leading to a strong increase in nematode abundance, concomitantly with changes in the nematode community structure; Prochromadorella neapolitana became the most abundant species.
for the future use of biostimulation to reduce toxic effects of PAHs for meiofauna and bacteria i... more for the future use of biostimulation to reduce toxic effects of PAHs for meiofauna and bacteria in lagoon sediment.
Bulletin of environmental contamination and toxicology, Jan 21, 2016
A Quick, Easy, Cheap, Effective, Rugged and Safe (QuEChERS) method has been adapted and validated... more A Quick, Easy, Cheap, Effective, Rugged and Safe (QuEChERS) method has been adapted and validated for the simultaneous analysis of 16 PAHs, 12 PCBs and 9 OCPs in sediment. The sample preparation was adapted by modifying the nature of the extraction solvent, the extraction technique and the amount of sediment. The analytical performances were evaluated in terms of accuracy, linearity and quantification limits. The method was validated by the analysis of a reference marine sediment material (SRM 1941b). The obtained concentrations are in good agreement with the certified values with recoveries ranging 60 %-103 % for most of PAHs. Acceptable recoveries are obtained for PCBs, ranging 76 %-131 %, and for OCPs ranging 81 %-137 %. The method was applied to the analysis of sediments from the hydro-system Bizerte Lagoon/Ichkeul Lake (Tunisia). The Bizerte lagoon is mainly contaminated by PAHs whereas the Ichkeul lake is mainly by OCPs.
Microbes and Signaling Biomolecules Against Plant Stress, 2020
Environmental stress is the foremost limiting factor for agricultural productivity. It is essenti... more Environmental stress is the foremost limiting factor for agricultural productivity. It is essential to alleviate the distress caused by environmental and edaphic conditions in plants, failing to which would affect their growth, development, and productivity. Microorganisms have enormous metabolic capabilities to lessen the environmental stress and their interactions with plants provide a local and systemic defense under various biotic and abiotic stresses. Due to an increase in adverse external conditions, it is imperative to study plant-microbe relationships at the physiological and molecular level to provide deeper insights into the stressmitigating mechanisms.
Recent Advances in Geo-Environmental Engineering, Geomechanics and Geotechnics, and Geohazards, 2018
The residual sludge from the bottom of refinery crude oil storage tanks causes major environmenta... more The residual sludge from the bottom of refinery crude oil storage tanks causes major environmental and societal problems in Tunisia. Due to its high viscosity, it must be removed from the storage tanks in order to utilize the crude oil. However, its disposal in the environment leads to the infiltration of toxic metals into groundwater and eventual contamination of surface water bodies. The aim of this work was to characterize and treat sludge from Tunisian refinery by two different approaches (chemical and biological) and evaluate the economic efficiency of sludge remediation. Our results showed that both approaches are useful in terms of reducing the metal content of the sludge. However, the biological approach is more economically efficient and leads to better ecological outcomes.
Iranian Journal of Chemistry & Chemical Engineering-international English Edition, 2020
This study aims to determine the major elements of Portland cement type I and II (CEMI and CEMII)... more This study aims to determine the major elements of Portland cement type I and II (CEMI and CEMII) in a cement factory in north Tunisia and which metal elements are introduced into the production process. We determine also the metal input rate and their distribution at the entrance and exit of the process. The major elements were analyzed and the trace elements (Arsenic, barium, lead, mercury, boron, strontium, Cadmium, Chromium, copper, manganese, nickel, and zinc) were identified. The concentrations of heavy metals in CEMI showed no significant difference p
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