Metal wastes have been repeatedly shown to significantly disturb periphytic communities. This stu... more Metal wastes have been repeatedly shown to significantly disturb periphytic communities. This study considers an industrial contamination site subjected to remediation processes since 2007. With the aim of finding relevant bioindicators of the restoration capacity of such impacted hydrosystems, this study focussed on biofilm and diatom recovery kinetics. Biofilms were colonised at a reference site and in parallel at a metal-contaminated site. After 24 days, contaminated biofilms were translocated to the reference site to study the biofilm recovery potential for 9 weeks under natural conditions. Analyses from the community level-measures of metal bioaccumulation, cell densities and taxonomic investigations-to the individual level-measures of teratological forms-were performed. The results showed that Zn and Cd contents were rapidly depurated, reaching reference levels 3 and 9 weeks after translocation, respectively. A Principal Response Curve (PRC) analysis enabled to see the fast evolution of diatom communities, with species specific to the reference site growing in decontaminated biofilms from the 3rd week. After 9 weeks, we estimated that diatom community restructuring was complete, based on measurements of biovolumes and teratological form rates which both decreased to reference levels in decontaminated biofilms throughout the experiment. The different teratological types appeared to be good bioindicators of biofilm contamination and shed light on the duration of contamination. According to these results, different criteria can provide information on the recovery potential of periphyton. Biofilms proved to be good bioindicators of metal recovery and diatoms proved to be good bioindicators of community recovery.
Distinguishing natural variations from human related changes becomes crucial in assessment, maint... more Distinguishing natural variations from human related changes becomes crucial in assessment, maintenance and restoration of aquatic ecosystems. The present work aims to focus on variation in the biogeographical frame of diatom assemblages in natural or near-natural conditions. First, 233 diatom samples collected from clean to less disturbed sites of the French hydrographic network were classified based on similarities of community
Les diatomées, micro-algues unicellulaires, colonisent une grande variété de substrats allant des... more Les diatomées, micro-algues unicellulaires, colonisent une grande variété de substrats allant des pierres et galets à des substrats vaseux et sableux, ou des plantes. L'échantillonnage en routine de ces communautés se faisant sur substrats durs, cette étude vise à comparer les communautés prélevées sur différents types de supports (naturels et artificiels), susceptibles de conditionner leur établissement. Bien que la structure spécifique des communautés présente une variabilité importante, en relation notamment avec les caractéristiques physiques du support et sa durée d'immersion, l'utilisation de substrats artificiels « neutres » assure une bonne représentativité des conditions environnementales estimées via les indices biologiques. Nous préconisons cependant d'effectuer simultanément des prélèvements sur substrats naturels, de manière à évaluer le plus correctement possible l'état des communautés diatomiques des cours d'eau.
Diatom species grown under non-limiting nutrient availability in multispecific biofilms were samp... more Diatom species grown under non-limiting nutrient availability in multispecific biofilms were sampled from glass substrates immersed in the field and in experimental freshwater microcosms, and their growth responses were determined. The major species that developed on the substrates were common to both experiments and the specific growth rates (k) ranged from 0.06 to 0.41 division day-1. An inverse relationship between k and cell sizes was observed, which is in accordance with allometry results reported by several authors. Although found in lower amounts, the large, slow-growing species accounted significantly in total community biovolume, underlying their significance for ecological purposes. From growth characteristics data, life history strategies were drawn for the dominant species recorded, from small pioneer species to large taxa that are more favoured by high resource supply. Kinetic data measured in both laboratory and in situ experiments stressed that the difficulties to mimic the field in laboratory experiments may have a strong impact on growth kinetics.
This study focuses on an industrial contamination site subjected to remediation processes since 2... more This study focuses on an industrial contamination site subjected to remediation processes since 2007 in the Riou-Mort watershed (southwest France). The purpose was to assess the first impacts of remediation on periphytic biofilms, and was performed during two years of biomonitoring. Periphytic biofilms were collected on glass slides immersed 24 days at different sites along the contamination gradient for 12 colonisation cycles. Metal contaminations (Cd and Zn) were analysed in biofilms and the evolution of diatom communities was assessed, integrating teratology quantifications. Despite remediation work initiated at the industrial site, this study demonstrated the persistence of metal contamination in water, as well as in biofilms. In addition, our data, showed that the remediation process was initially marked by an increase in metal contamination in the river, with increasing diatom community shifts. Metal-contaminated biofilms presented decreasing species diversities and were dominated by metal-resistant species such as Eolimna minima, whom abundances increased in 2010 reaching 57.2±10%. No significant decrease in metal accumulation was observed and total Cd content in biofilms collected downstream the industrial site ranged from 772.7±88 in July 2009 to 636.9±20 μg/gDW in July 2010. Results obtained on artificial substrates were compared with those of natural substrates and showed similar diatom communities and abundances of deformed diatoms but lower diversities. This ensured that glass slide subtrates gave a good representation of periphytic biofilm health. Finally, results were compared to studies performed before the remediation process and this did not reveal a decrease of metal accumulation in biofilms nor shifts in taxonomic composition of the communities, rather the remaining dominance of metal resistant species such as E. minima was confirmed.
Distinguishing natural variations from human related changes becomes crucial in assessment, maint... more Distinguishing natural variations from human related changes becomes crucial in assessment, maintenance and restoration of aquatic ecosystems. The present work aims to focus on variation in the biogeographical frame of diatom assemblages in natural or near-natural conditions. First, 233 diatom samples collected from clean to less disturbed sites of the French hydrographic network were classified based on similarities of community
The relationships between diatom species and cadmium (Cd) accumulated in biofilms of the Riou-Mor... more The relationships between diatom species and cadmium (Cd) accumulated in biofilms of the Riou-Mort River (SW, France) were studied in July 2004 and March 2005. Biofilms were sampled from artificial substrates immersed along a metallic pollution gradient during 20 days. Dynamics of diatom communities and cadmium accumulation were followed by collecting samples after 4, 7, 14 and 20 days of biofilm colonization. Cd accumulation in biofilms during experiment was significantly higher in Cd polluted station (Joanis) than in reference station (Firmi) for both seasons. Periphytic diatom composition varied between sites and seasons. At Firmi station, seasonal dynamics of diatom communities were stable with the dominance of Cyclotella meneghiniana and Melosira varians in July and Surirellabrebissonnii and Navicula gregaria in March. At Joanis station, diatom communities mainly responded to high levels of metal by a high proportion of small, adnate species. Positive correlations between Eolimna minima, Nitzschia palea, Encyonema minutum, Surirella angusta, and Gomphonema parvulum and cadmium accumulation were observed, indicating that these species are tolerant to high levels of cadmium. On the other hand, negative correlations of C. meneghiniana, N. gregaria, Navicula lanceolata, M. varians and Nitzschia dissipata with cadmium qualify them as sensitive diatom species. Periphytic diatom composition through the presence of specific species highlight metal tolerant indicator diatom groups which will be meaningful for biomonitoring pollution in natural aquatic systems.
Metal wastes have been repeatedly shown to significantly disturb periphytic communities. This stu... more Metal wastes have been repeatedly shown to significantly disturb periphytic communities. This study considers an industrial contamination site subjected to remediation processes since 2007. With the aim of finding relevant bioindicators of the restoration capacity of such impacted hydrosystems, this study focussed on biofilm and diatom recovery kinetics. Biofilms were colonised at a reference site and in parallel at a metal-contaminated site. After 24 days, contaminated biofilms were translocated to the reference site to study the biofilm recovery potential for 9 weeks under natural conditions. Analyses from the community level-measures of metal bioaccumulation, cell densities and taxonomic investigations-to the individual level-measures of teratological forms-were performed. The results showed that Zn and Cd contents were rapidly depurated, reaching reference levels 3 and 9 weeks after translocation, respectively. A Principal Response Curve (PRC) analysis enabled to see the fast evolution of diatom communities, with species specific to the reference site growing in decontaminated biofilms from the 3rd week. After 9 weeks, we estimated that diatom community restructuring was complete, based on measurements of biovolumes and teratological form rates which both decreased to reference levels in decontaminated biofilms throughout the experiment. The different teratological types appeared to be good bioindicators of biofilm contamination and shed light on the duration of contamination. According to these results, different criteria can provide information on the recovery potential of periphyton. Biofilms proved to be good bioindicators of metal recovery and diatoms proved to be good bioindicators of community recovery.
Distinguishing natural variations from human related changes becomes crucial in assessment, maint... more Distinguishing natural variations from human related changes becomes crucial in assessment, maintenance and restoration of aquatic ecosystems. The present work aims to focus on variation in the biogeographical frame of diatom assemblages in natural or near-natural conditions. First, 233 diatom samples collected from clean to less disturbed sites of the French hydrographic network were classified based on similarities of community
Les diatomées, micro-algues unicellulaires, colonisent une grande variété de substrats allant des... more Les diatomées, micro-algues unicellulaires, colonisent une grande variété de substrats allant des pierres et galets à des substrats vaseux et sableux, ou des plantes. L'échantillonnage en routine de ces communautés se faisant sur substrats durs, cette étude vise à comparer les communautés prélevées sur différents types de supports (naturels et artificiels), susceptibles de conditionner leur établissement. Bien que la structure spécifique des communautés présente une variabilité importante, en relation notamment avec les caractéristiques physiques du support et sa durée d'immersion, l'utilisation de substrats artificiels « neutres » assure une bonne représentativité des conditions environnementales estimées via les indices biologiques. Nous préconisons cependant d'effectuer simultanément des prélèvements sur substrats naturels, de manière à évaluer le plus correctement possible l'état des communautés diatomiques des cours d'eau.
Diatom species grown under non-limiting nutrient availability in multispecific biofilms were samp... more Diatom species grown under non-limiting nutrient availability in multispecific biofilms were sampled from glass substrates immersed in the field and in experimental freshwater microcosms, and their growth responses were determined. The major species that developed on the substrates were common to both experiments and the specific growth rates (k) ranged from 0.06 to 0.41 division day-1. An inverse relationship between k and cell sizes was observed, which is in accordance with allometry results reported by several authors. Although found in lower amounts, the large, slow-growing species accounted significantly in total community biovolume, underlying their significance for ecological purposes. From growth characteristics data, life history strategies were drawn for the dominant species recorded, from small pioneer species to large taxa that are more favoured by high resource supply. Kinetic data measured in both laboratory and in situ experiments stressed that the difficulties to mimic the field in laboratory experiments may have a strong impact on growth kinetics.
This study focuses on an industrial contamination site subjected to remediation processes since 2... more This study focuses on an industrial contamination site subjected to remediation processes since 2007 in the Riou-Mort watershed (southwest France). The purpose was to assess the first impacts of remediation on periphytic biofilms, and was performed during two years of biomonitoring. Periphytic biofilms were collected on glass slides immersed 24 days at different sites along the contamination gradient for 12 colonisation cycles. Metal contaminations (Cd and Zn) were analysed in biofilms and the evolution of diatom communities was assessed, integrating teratology quantifications. Despite remediation work initiated at the industrial site, this study demonstrated the persistence of metal contamination in water, as well as in biofilms. In addition, our data, showed that the remediation process was initially marked by an increase in metal contamination in the river, with increasing diatom community shifts. Metal-contaminated biofilms presented decreasing species diversities and were dominated by metal-resistant species such as Eolimna minima, whom abundances increased in 2010 reaching 57.2±10%. No significant decrease in metal accumulation was observed and total Cd content in biofilms collected downstream the industrial site ranged from 772.7±88 in July 2009 to 636.9±20 μg/gDW in July 2010. Results obtained on artificial substrates were compared with those of natural substrates and showed similar diatom communities and abundances of deformed diatoms but lower diversities. This ensured that glass slide subtrates gave a good representation of periphytic biofilm health. Finally, results were compared to studies performed before the remediation process and this did not reveal a decrease of metal accumulation in biofilms nor shifts in taxonomic composition of the communities, rather the remaining dominance of metal resistant species such as E. minima was confirmed.
Distinguishing natural variations from human related changes becomes crucial in assessment, maint... more Distinguishing natural variations from human related changes becomes crucial in assessment, maintenance and restoration of aquatic ecosystems. The present work aims to focus on variation in the biogeographical frame of diatom assemblages in natural or near-natural conditions. First, 233 diatom samples collected from clean to less disturbed sites of the French hydrographic network were classified based on similarities of community
The relationships between diatom species and cadmium (Cd) accumulated in biofilms of the Riou-Mor... more The relationships between diatom species and cadmium (Cd) accumulated in biofilms of the Riou-Mort River (SW, France) were studied in July 2004 and March 2005. Biofilms were sampled from artificial substrates immersed along a metallic pollution gradient during 20 days. Dynamics of diatom communities and cadmium accumulation were followed by collecting samples after 4, 7, 14 and 20 days of biofilm colonization. Cd accumulation in biofilms during experiment was significantly higher in Cd polluted station (Joanis) than in reference station (Firmi) for both seasons. Periphytic diatom composition varied between sites and seasons. At Firmi station, seasonal dynamics of diatom communities were stable with the dominance of Cyclotella meneghiniana and Melosira varians in July and Surirellabrebissonnii and Navicula gregaria in March. At Joanis station, diatom communities mainly responded to high levels of metal by a high proportion of small, adnate species. Positive correlations between Eolimna minima, Nitzschia palea, Encyonema minutum, Surirella angusta, and Gomphonema parvulum and cadmium accumulation were observed, indicating that these species are tolerant to high levels of cadmium. On the other hand, negative correlations of C. meneghiniana, N. gregaria, Navicula lanceolata, M. varians and Nitzschia dissipata with cadmium qualify them as sensitive diatom species. Periphytic diatom composition through the presence of specific species highlight metal tolerant indicator diatom groups which will be meaningful for biomonitoring pollution in natural aquatic systems.
Uploads
Papers by Coste Michel