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Gérard Pergent - One of the best experts on this subject based on the ideXlab platform.
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Is Posidonia oceanica regression a general feature in the Mediterranean Sea
Mediterranean Marine Science, 2013Co-Authors: Marina Bonacorsi, Christine Pergent-martini, N. Breand, Gérard PergentAbstract:Over the last few years, a widespread regression of Posidonia oceanica meadows has been noticed in the Mediterranean Sea. However, the magnitude of this decline is still debated. The objectives of this study are (i) to assess the spatio-temporal evolution of Posidonia oceanica around Cap Corse (Corsica) over time comparing available ancient maps (from 1960) with a new (2011) detailed map realized combining different techniques (aerial photographs, SSS, ROV, scuba diving); (ii) evaluate the reliability of ancient maps; (iii) discuss observed regression of the meadows in relation to human pressure along the 110 km of coast. Thus, the comparison with previous data shows that, apart from sites clearly identified with the actual evolution, there is a relative stability of the surfaces occupied by the seagrass Posidonia oceanica . The recorded differences seem more related to changes in mapping techniques. These results confirm that in areas characterized by a moderate anthropogenic impact, the Posidonia oceanica meadow has no significant regression and that the changes due to the evolution of mapping techniques are not negligible. However, others facts should be taken into account before extrapolating to the Mediterranean Sea (e.g. actually mapped surfaces) and assessing the amplitude of the actual regression.
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metal contamination of Posidonia oceanica meadows along the corsican coastline mediterranean
Environmental Pollution, 2008Co-Authors: Celine Lafabrie, C Pergentmartini, Gérard PergentAbstract:Abstract The aim of this study is to determine metal (Cd, Co, Cr, Hg, Ni, Pb) concentrations in Posidonia oceanica tissues along the Corsican coastline. The results show that except for Cr, all the metals are preferentially accumulated in the blades; this is particularly interesting as it means that future metal analyses may be carried out only on the blades avoiding thus the removal of the shoots. Moreover, they show that metal concentrations may reflect the “background noise” of the Mediterranean Sea. Station 15 (Canari) can however be distinguished from the others due to its high Co, Cr and Ni concentrations. This result may be related to the presence of a previous asbestos mine, located near this station. Therefore, this study reinforces the usefulness and the relevance of Posidonia oceanica as a tracer of spatial metal contamination and as an interesting tool for water quality evaluation.
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Posidonia oceanica: A tracer of past mercury contamination
Environmental Pollution, 2007Co-Authors: Celine Lafabrie, Gérard Pergent, Christine Pergent-martini, A CapiomontAbstract:The aim of this study is to assess the relevance and the potential of Posidonia oceanica as a tracer of past mercury contamination. Shoots were collected on two sites, an impacted site, Rosignano (Tuscany, Italy), and a pristine site, Tonnara (Corsica, France). Lepidochronology was used to measure mercury concentrations in living sheaths and in the corresponding dead sheaths. The results show that there is an overestimation of mercury concentrations in dead sheaths (because of the degradation of this tissue due to its ageing), overestimation which stabilizes itself from the third lepidochronological year onwards (trend significant only for Rosignano). Thus, it is possible to estimate previous mercury concentrations and to date a contamination, by measuring mercury concentration in the dead sheaths of a given lepidochronological year and by taking into account the degradation of the sheaths. Therefore, Posidonia oceanica can be used to reconstruct the evolution of the past mercury contamination.
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Distribution and dynamics of Posidonia oceanica beds along the Albères coastline
Comptes Rendus De L Academie Des Sciences Serie Iii-sciences De La Vie-life Sciences, 2000Co-Authors: Laurent Ballesta, Gérard Pergent, Vanina Pasqualini, Christine Pergent-martiniAbstract:The location and dynamics of Posidonia oceanica beds were studied in the marine natural reserve of Cerbere–Banyuls-sur-Mer (eastern Pyrenees, France), through the mapping of bottom assemblages (transects and image processing) and the monitoring of fixed markers installed at the Posidonia oceanica lower limit. The surface area occupied by continuous beds is relatively limited and localized, whereas the presence of important areas of dead ‘matte’ would seem to indicate that bottom cover by Posidonia oceanica was more extensive in the past. Although the limited extension of the seagrass beds seems to be linked to both a high level of turbidity and severe hydrodynamic conditions, it is hypothesized that the regressions observed are due to lack of sediment.
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Preliminary data on the impact of fish farming facilities on Posidonia oceanica meadows in the Mediterranean
Oceanologica Acta, 2000Co-Authors: Gérard Pergent, Christine Pergent-martini, Stéphane Mendez, Vanina PasqualiniAbstract:While the extension of aquaculture along the coasts of the Mediterranean islands is today an economic priority, no data is available on the impact of these facilities on the littoral environment in general, and in particular on the Posidonia oceanica meadows that are responsible for the richness and diversity of these biotopes. The impact of fish farming facilities in the marine littoral environment is assessed at three Mediterranean sites in Corsica and Sardinia. Various parameters are considered: (i) the amount of light available, (ii) the nature of the sediment, and (iii) the vitality of the Posidonia oceanica beds. The findings confirm the impact of the aquaculture facilities within the water column (increase in turbidity, enrichment of the sediment in organic matter and nutrients), and it would appear that the Posidonia oceanica beds also undergo significant alterations. The decline in density of the meadows in the area influenced by aquaculture farming and their total disappearance beneath the facilities is particularly disturbing, even if the areas affected are not very extensive, at least for the smaller farms (a few hundred square metres), and if certain beneficial effects may be recorded (increase in benthic primary production). Because of its ability to record environmental alterations caused by these facilities (light, nutrients, trace metals), the Posidonia oceanica meadow is a good bioindicator for use in monitoring studies.
Carlos M. Duarte - One of the best experts on this subject based on the ideXlab platform.
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Posidonia oceanica changes in the Mediterranean sea
2013Co-Authors: Nuria Marba, Elena Díaz-almela, Carlos M. DuarteAbstract:Methodology: We compiled available data published in peer-review articles and grey literature reports until year 2009 as well as our own unpublished data. We searched for data with the engine ISI web of Knowledge, using the keywords Posidonia oceanica AND (regression OR decline OR progression OR recovery OR status OR cartography OR limits OR cover OR density OR biomass OR dynamics), and conducting a back search of cited papers. More information about the methodology to be found at: Calleja, M.L., N. Marba, C.M. Duarte (2007). The relationship between seagrass (Posidonia oceanica) decline and sulfide porewater concentration in carbonate sediments. Estuarine coastal and shelf science 73: 583-588; Waycott M, CM. Duarte, T.J. B. Carruthers, R.J. Orth, W.C. Dennison, S. Olyarnik, A. Calladine, J.W. Fourqurean, K.L. Heck, Jr, A.R.ll Hughes, G A. Kendrick, W. J Kenworthy, F T. Short, S L. Williams (2009). Accelerating loss of seagrasses across the globe threatens coastal ecosystems. Proceedings of the National Academy of Science USA 106: 12377–12381; Moreno, D., P. A. Aguilera, H. Castro (2001). Assessment of the conservation status of seagrass (Posidonia oceanica) meadows: implications for monitoring strategy and the decision-making process. Biological Conservation 102: 325-332.
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Thresholds of irradiance for seagrass Posidonia oceanica meadow metabolism
Marine Ecology Progress Series, 2012Co-Authors: Esperança Gacia, Nuria Marba, Just Cebrian, Raquel Vaquer-sunyer, Neus Garcias-bonet, Carlos M. DuarteAbstract:Meadows of the endemic seagrass Posidonia oceanica are threatened in the Mediter- ranean due to a general deterioration of the light environment that becomes critical when light irradiance is insufficient to meet the carbon requirements of the system. Here, we conduct a 3 wk, in situ shading experiment (8 levels plus controls) to determine the threshold of irradiance for bal- anced metabolism in a shallow P. oceanica meadow and further assess the recovery of the system 1 wk later. Reduced light irradiance decreased the net community production of the meadow, which may turn negative (i.e. respiration exceeded gross community primary production) under 338 μE m −2 s −1 . Shading throughout the experiment did not appear to cause sustained physiologi- cal damage to the system since values of net community production after the cessation of shading were similar to pre-experimental, ambient levels. Sediment acid volatile sulfide pools ranged between 0.002 and 0.058 mol m −2 across shading treatments, and the highest pools were observed in the most shaded sediments. At high light impairment, meristematic cell divisions were low, and carbohydrate content in young rhizomes decreased throughout the experiment. Eight days after the cessation of shading, reduced rhizome carbohydrate stores and elevated sediment sulfide lev- els still persisted in the previously intensively shaded areas. The present study provides evidence of resistance and resilience of the seagrass Posidonia oceanica to light impairment for short (3 wk) periods of time. Although the compensation irradiance of the system varied by ~2-fold, it provides a quantitative estimate of the irradiance threshold at which seagrass meadows may shift from being coastal carbon sinks to CO2 sources.
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endophytic bacterial community of a mediterranean marine angiosperm Posidonia oceanica
Frontiers in Microbiology, 2012Co-Authors: Neus Garciasbonet, Carlos M. Duarte, Jesus M Arrieta, Charles Novaes De Santana, Nuria MarbaAbstract:Bacterial endophytes are crucial for the survival of many terrestrial plants, but little is known about the presence and importance of bacterial endophytes of marine plants. We conducted a survey of the endophytic bacterial community of the long-living Mediterranean marine angiosperm Posidonia oceanica in surface-sterilized tissues (roots, rhizomes and leaves) by DGGE. A total of 26 Posidonia oceanica meadows around the Balearic Islands were sampled, and the band patterns obtained for each meadow were compared for the three sampled tissues. Endophytic bacterial sequences were detected in most of the samples analyzed. A total of 34 OTUs (Operational Taxonomic Units) were detected. The main OTUs of endophytic bacteria present in P. oceanica tissues belonged primarily to Proteobacteria (α, γ and δ subclasses) and Bacteroidetes. The OTUs found in roots significantly differed from those of rhizomes and leaves. Moreover, some OTUs were found to be associated to each type of tissue. Bipartite network analysis revealed differences in the bacterial endophyte communities present on different islands. The results of this study provide a pioneering step toward the characterization of the endophytic bacterial community associated with tissues of a marine angiosperm and reveal the presence of bacterial endophytes that differed among locations and tissue types.
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The effect of nutrient additions on bacterial activity in seagrass (Posidonia oceanica) sediments
Journal of Experimental Marine Biology and Ecology, 1998Co-Authors: Nancy I. López, Javier Romero, Carlos M. Duarte, Ferrán Vallespinós, Teresa AlcoverroAbstract:The influence of nutrient additions on benthic bacterial activity under seagrass meadows was tested by enriching five seagrass (Posidonia oceanica) meadows with nutrients over one year. We found a highly significant response of benthic bacterial activity to nutrient additions, which was reflected in greater (about two-fold) ammonification rates and, to a smaller extent, a significant tendency for a greater exoenzymatic activity. Nutrient additions significantly raised bacterial activity, without altering the seasonal changes in bacterial activity. As a result of the increased bacterial activity, the organic content of the sediments declined significantly, by about 33%, after one year of nutrient addition. Hence, nutrient additions to the seagrass meadows enhance seagrass production but also accelerate bacterial decomposition of seagrass carbon, thereby reducing the capacity of the sediments to store organic carbon. These results demonstrate that sediment nutrient availability limits bacterial activity in these Posidonia oceanica meadows, and identify bacteria as important nutrient consumers in these systems.
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The influence of herbivores on Posidonia oceanica epiphytes
Aquatic Botany, 1997Co-Authors: Teresa Alcoverro, Carlos M. Duarte, Javier RomeroAbstract:Abstract The biomass seasonality of the seagrass Posidonia oceanica (L.) Delile epiphytes was examined at five sites in NE Spain to assess the relative importance of large-scale versus local factors in controlling the seasonal pattern observed. Large-scale seasonal forcing, resulting from changes in light and temperature associated with the solar cycle, was assessed from the coherence of seasonal epiphytic biomass changes among meadows and accounted for 38% of total variance. Most of this variability was explained by seasonal variability in Posidonia oceanica shoot size, as shown by the reduction in the variance explained by seasonality when shoot biomass of the host was used as a covariate. Differences among sites were also highly significant, both considered as differences in yearly biomass values (accounting for 30% of total variance) and as the differences in the annual time course of epiphyte biomass among meadows, which accounted for 26% of the variability. Nutrient effect seemed to be mostly seasonal, thus contributing to the large-scale variability. In contrast, consumption by herbivores seemed to play a major role in inducing among-site variability of epiphyte biomass, but no similar role in influencing Posidonia oceanica shoot size. This is due to the within-shoot epiphyte distribution, such that the removal of relatively small amounts of leaf standing biomass (e.g. 10–20%) results in the removal of a large amount of epiphyte biomass (e.g. 40–50%). These findings support the hypothesis that epiphyte biomass is primarily controlled by seasonal changes in seagrass shoot size and hence ultimately by the solar cycle and secondarily by local environmental changes, among which herbivory seems the most important.
Nuria Marba - One of the best experts on this subject based on the ideXlab platform.
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Posidonia oceanica changes in the Mediterranean sea
2013Co-Authors: Nuria Marba, Elena Díaz-almela, Carlos M. DuarteAbstract:Methodology: We compiled available data published in peer-review articles and grey literature reports until year 2009 as well as our own unpublished data. We searched for data with the engine ISI web of Knowledge, using the keywords Posidonia oceanica AND (regression OR decline OR progression OR recovery OR status OR cartography OR limits OR cover OR density OR biomass OR dynamics), and conducting a back search of cited papers. More information about the methodology to be found at: Calleja, M.L., N. Marba, C.M. Duarte (2007). The relationship between seagrass (Posidonia oceanica) decline and sulfide porewater concentration in carbonate sediments. Estuarine coastal and shelf science 73: 583-588; Waycott M, CM. Duarte, T.J. B. Carruthers, R.J. Orth, W.C. Dennison, S. Olyarnik, A. Calladine, J.W. Fourqurean, K.L. Heck, Jr, A.R.ll Hughes, G A. Kendrick, W. J Kenworthy, F T. Short, S L. Williams (2009). Accelerating loss of seagrasses across the globe threatens coastal ecosystems. Proceedings of the National Academy of Science USA 106: 12377–12381; Moreno, D., P. A. Aguilera, H. Castro (2001). Assessment of the conservation status of seagrass (Posidonia oceanica) meadows: implications for monitoring strategy and the decision-making process. Biological Conservation 102: 325-332.
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Thresholds of irradiance for seagrass Posidonia oceanica meadow metabolism
Marine Ecology Progress Series, 2012Co-Authors: Esperança Gacia, Nuria Marba, Just Cebrian, Raquel Vaquer-sunyer, Neus Garcias-bonet, Carlos M. DuarteAbstract:Meadows of the endemic seagrass Posidonia oceanica are threatened in the Mediter- ranean due to a general deterioration of the light environment that becomes critical when light irradiance is insufficient to meet the carbon requirements of the system. Here, we conduct a 3 wk, in situ shading experiment (8 levels plus controls) to determine the threshold of irradiance for bal- anced metabolism in a shallow P. oceanica meadow and further assess the recovery of the system 1 wk later. Reduced light irradiance decreased the net community production of the meadow, which may turn negative (i.e. respiration exceeded gross community primary production) under 338 μE m −2 s −1 . Shading throughout the experiment did not appear to cause sustained physiologi- cal damage to the system since values of net community production after the cessation of shading were similar to pre-experimental, ambient levels. Sediment acid volatile sulfide pools ranged between 0.002 and 0.058 mol m −2 across shading treatments, and the highest pools were observed in the most shaded sediments. At high light impairment, meristematic cell divisions were low, and carbohydrate content in young rhizomes decreased throughout the experiment. Eight days after the cessation of shading, reduced rhizome carbohydrate stores and elevated sediment sulfide lev- els still persisted in the previously intensively shaded areas. The present study provides evidence of resistance and resilience of the seagrass Posidonia oceanica to light impairment for short (3 wk) periods of time. Although the compensation irradiance of the system varied by ~2-fold, it provides a quantitative estimate of the irradiance threshold at which seagrass meadows may shift from being coastal carbon sinks to CO2 sources.
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endophytic bacterial community of a mediterranean marine angiosperm Posidonia oceanica
Frontiers in Microbiology, 2012Co-Authors: Neus Garciasbonet, Carlos M. Duarte, Jesus M Arrieta, Charles Novaes De Santana, Nuria MarbaAbstract:Bacterial endophytes are crucial for the survival of many terrestrial plants, but little is known about the presence and importance of bacterial endophytes of marine plants. We conducted a survey of the endophytic bacterial community of the long-living Mediterranean marine angiosperm Posidonia oceanica in surface-sterilized tissues (roots, rhizomes and leaves) by DGGE. A total of 26 Posidonia oceanica meadows around the Balearic Islands were sampled, and the band patterns obtained for each meadow were compared for the three sampled tissues. Endophytic bacterial sequences were detected in most of the samples analyzed. A total of 34 OTUs (Operational Taxonomic Units) were detected. The main OTUs of endophytic bacteria present in P. oceanica tissues belonged primarily to Proteobacteria (α, γ and δ subclasses) and Bacteroidetes. The OTUs found in roots significantly differed from those of rhizomes and leaves. Moreover, some OTUs were found to be associated to each type of tissue. Bipartite network analysis revealed differences in the bacterial endophyte communities present on different islands. The results of this study provide a pioneering step toward the characterization of the endophytic bacterial community associated with tissues of a marine angiosperm and reveal the presence of bacterial endophytes that differed among locations and tissue types.
Ante Žuljević - One of the best experts on this subject based on the ideXlab platform.
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Underwater documentary "save Posidonia oceanica meadows - treasury of biological diversity of the Adriatic Sea"
2006Co-Authors: B. Mikac, Ante ŽuljevićAbstract:This 15 minutes underwater documentary was made in 2003. within the project "Public awareness raising about importance and protection of endemic meadows of sea-grass Posidonia oceanica". First part of the film talks about importance and irreplaceable roles which Posidonia oceanica is playing in the marine ecosystem. Different animals inhabiting Posidonia oceanica meadows are appearing: fishes, mussels, snails, sea urchins, octopus and others. Second part of the film is alerting people on different human activities that are nowdays threatening this vulnerable marine biotope. Audience is introduced with the project concerning protection of Posidonia oceanica meadows led by the NGO Green Istria (Croatia). The awareness raising campaign about importance and protection of Posidonia oceanica meadows is aimed for the inhabitants of Medulin and Ližnjan (Istria, Croatia), communities where the last Posidonia oceanica meadows in Istrian peninsula (Croatia) are left. Tourists which are visiting Medulin and Ližnjan Community and whose activities (anchorig, waste water disposal etc.) are greately affecting Posidonia oceanica meadows are the target population of this campaign as well. There are English, German and Italian translation of the film. Film was already presented in Medulin, Banjole, Pula, Zagreb (Croatia), Netherlands, France, Belgrade (Serbia), Cyprus, Turkey, Chech Republic and Italy. In Octobar 2004. film was participating on the World Festival of Underwater Pictures in Antibes (France). In December 2004. it won the Special Prize on the 8. International Underwater Film Festval in Belgrade (Serbia). It was shown in Zagreb (Croatia) in January 2005. during the Festival "Freedom to Creativity!" In April 2005. it was presented and won the 3. Prize in the Professional Underwater Documentary Category on the "First Eastern Mediterranean Underwater Photography and Film Festival" in Cyprus. Several months later it was awarded on the "Marmara Festival" of underwater photography and film in Istanbul (Turkey). Many schools and diving clubs included this film in their regular education.
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Underwater documentary "save Posidonia oceanica meadows - treasury of biological diversity of the Adriatic Sea"
2006Co-Authors: B. Mikac, Ante ŽuljevićAbstract:This 15 minutes underwater documentary was made in 2003. within the project "Public awareness raising about importance and protection of endemic meadows of sea-grass Posidonia oceanica". First part of the film talks about importance and irreplaceable roles which Posidonia oceanica is playing in the marine ecosystem. Different animals inhabiting Posidonia oceanica meadows are appearing: fishes, mussels, snails, sea urchins, octopus and others. Second part of the film is alerting people on different human activities that are nowdays threatening this vulnerable marine biotope. Audience is introduced with the project concerning protection of Posidonia oceanica meadows led by the NGO Green Istria (Croatia). The awareness raising campaign about importance and protection of Posidonia oceanica meadows is aimed for the inhabitants of Medulin and Ližnjan (Istria, Croatia), communities where the last Posidonia oceanica meadows in Istrian peninsula (Croatia) are left. Tourists which are visiting Medulin and Ližnjan Community and whose activities (anchorig, waste water disposal etc.) are greately affecting Posidonia oceanica meadows are the target population of this campaign as well. There are English, German and Italian translation of the film. Film was already presented in Medulin, Banjole, Pula, Zagreb (Croatia), Netherlands, France, Belgrade (Serbia), Cyprus, Turkey, Chech Republic and Italy. In Octobar 2004. film was participating on the World Festival of Underwater Pictures in Antibes (France). In December 2004. it won the Special Prize on the 8. International Underwater Film Festval in Belgrade (Serbia). It was shown in Zagreb (Croatia) in January 2005. during the Festival "Freedom to Creativity!" In April 2005. it was presented and won the 3. Prize in the Professional Underwater Documentary Category on the "First Eastern Mediterranean Underwater Photography and Film Festival" in Cyprus. Several months later it was awarded on the "Marmara Festival" of underwater photography and film in Istanbul (Turkey). Many schools and diving clubs included this film in their regular education.
Christine Pergent-martini - One of the best experts on this subject based on the ideXlab platform.
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Is Posidonia oceanica regression a general feature in the Mediterranean Sea
Mediterranean Marine Science, 2013Co-Authors: Marina Bonacorsi, Christine Pergent-martini, N. Breand, Gérard PergentAbstract:Over the last few years, a widespread regression of Posidonia oceanica meadows has been noticed in the Mediterranean Sea. However, the magnitude of this decline is still debated. The objectives of this study are (i) to assess the spatio-temporal evolution of Posidonia oceanica around Cap Corse (Corsica) over time comparing available ancient maps (from 1960) with a new (2011) detailed map realized combining different techniques (aerial photographs, SSS, ROV, scuba diving); (ii) evaluate the reliability of ancient maps; (iii) discuss observed regression of the meadows in relation to human pressure along the 110 km of coast. Thus, the comparison with previous data shows that, apart from sites clearly identified with the actual evolution, there is a relative stability of the surfaces occupied by the seagrass Posidonia oceanica . The recorded differences seem more related to changes in mapping techniques. These results confirm that in areas characterized by a moderate anthropogenic impact, the Posidonia oceanica meadow has no significant regression and that the changes due to the evolution of mapping techniques are not negligible. However, others facts should be taken into account before extrapolating to the Mediterranean Sea (e.g. actually mapped surfaces) and assessing the amplitude of the actual regression.
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Posidonia oceanica: A tracer of past mercury contamination
Environmental Pollution, 2007Co-Authors: Celine Lafabrie, Gérard Pergent, Christine Pergent-martini, A CapiomontAbstract:The aim of this study is to assess the relevance and the potential of Posidonia oceanica as a tracer of past mercury contamination. Shoots were collected on two sites, an impacted site, Rosignano (Tuscany, Italy), and a pristine site, Tonnara (Corsica, France). Lepidochronology was used to measure mercury concentrations in living sheaths and in the corresponding dead sheaths. The results show that there is an overestimation of mercury concentrations in dead sheaths (because of the degradation of this tissue due to its ageing), overestimation which stabilizes itself from the third lepidochronological year onwards (trend significant only for Rosignano). Thus, it is possible to estimate previous mercury concentrations and to date a contamination, by measuring mercury concentration in the dead sheaths of a given lepidochronological year and by taking into account the degradation of the sheaths. Therefore, Posidonia oceanica can be used to reconstruct the evolution of the past mercury contamination.
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IS GLUTATHIONE TRANSFERASE (GST) ACTIVITY IN Posidonia oceanica A STRESS RESPONSE TO MERCURY EXPOSURE?
Bulletin of Marine Science, 2002Co-Authors: Lila Ferrat, Christine Pergent-martini, Catherine Fernandez, Michele RoméoAbstract:Today, efficient monitoring of the environment is increasingly depend on the use of bio-indicator species. Marine phanerogams, and in particular Posidonia oceanica, would appear to be potentially valuable bioindicators of metal pollutants. Although correlations have been found between the mercury levels accumulated in the plant tissue and the concentrations of this metal in the water column, it would be of interest to identify early signs of the stress response induced by this xenobiotic. Thus, mercury concentrations and GST activity in Posidonia oceanica (L.) Delile from contaminated and pristine sites were measured. These results demonstrate that an increase in mercury level is correlated with an increase in GST activity, particularly in the sheaths of P. oceanica shoots. The sites contaminated by mercury were also those sites for which the highest enzyme activity was recorded. An even better correlation was found between the mercury levels and GST activity, if a 2 mo lag in the effect of mercury on GST activity is assumed.
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Distribution and dynamics of Posidonia oceanica beds along the Albères coastline
Comptes Rendus De L Academie Des Sciences Serie Iii-sciences De La Vie-life Sciences, 2000Co-Authors: Laurent Ballesta, Gérard Pergent, Vanina Pasqualini, Christine Pergent-martiniAbstract:The location and dynamics of Posidonia oceanica beds were studied in the marine natural reserve of Cerbere–Banyuls-sur-Mer (eastern Pyrenees, France), through the mapping of bottom assemblages (transects and image processing) and the monitoring of fixed markers installed at the Posidonia oceanica lower limit. The surface area occupied by continuous beds is relatively limited and localized, whereas the presence of important areas of dead ‘matte’ would seem to indicate that bottom cover by Posidonia oceanica was more extensive in the past. Although the limited extension of the seagrass beds seems to be linked to both a high level of turbidity and severe hydrodynamic conditions, it is hypothesized that the regressions observed are due to lack of sediment.
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Preliminary data on the impact of fish farming facilities on Posidonia oceanica meadows in the Mediterranean
Oceanologica Acta, 2000Co-Authors: Gérard Pergent, Christine Pergent-martini, Stéphane Mendez, Vanina PasqualiniAbstract:While the extension of aquaculture along the coasts of the Mediterranean islands is today an economic priority, no data is available on the impact of these facilities on the littoral environment in general, and in particular on the Posidonia oceanica meadows that are responsible for the richness and diversity of these biotopes. The impact of fish farming facilities in the marine littoral environment is assessed at three Mediterranean sites in Corsica and Sardinia. Various parameters are considered: (i) the amount of light available, (ii) the nature of the sediment, and (iii) the vitality of the Posidonia oceanica beds. The findings confirm the impact of the aquaculture facilities within the water column (increase in turbidity, enrichment of the sediment in organic matter and nutrients), and it would appear that the Posidonia oceanica beds also undergo significant alterations. The decline in density of the meadows in the area influenced by aquaculture farming and their total disappearance beneath the facilities is particularly disturbing, even if the areas affected are not very extensive, at least for the smaller farms (a few hundred square metres), and if certain beneficial effects may be recorded (increase in benthic primary production). Because of its ability to record environmental alterations caused by these facilities (light, nutrients, trace metals), the Posidonia oceanica meadow is a good bioindicator for use in monitoring studies.