Some species of seagrasses (e.g., Zostera marina and Posidonia oceanica) have declined in the Med... more Some species of seagrasses (e.g., Zostera marina and Posidonia oceanica) have declined in the Mediterranean, at least locally. Others are progressing, helped by sea warming, such as Cymodocea nodosa and the non-native Halophila stipulacea. The decline of one seagrass can favor another seagrass. All in all, the decline of seagrasses could be less extensive and less general than claimed by some authors. Natural recolonization (cuttings and seedlings) has been more rapid and more widespread than was thought in the 20th century; however, it is sometimes insufficient, which justifies transplanting operations. Many techniques have been proposed to restore Mediterranean seagrass meadows. However, setting aside the short-term failure or half-success of experimental operations, long-term monitoring has usually been lacking, suggesting that possible failures were considered not worthy of a scientific paper. Many transplanting operations (e.g., P. oceanica) have been carried out at sites where...
Human activities generate large volumes of waste that supply marine coastal environments in patho... more Human activities generate large volumes of waste that supply marine coastal environments in pathogens, organic matter, nutrients and toxicants. Among the wide range of toxicants are trace elements. Since the latter are toxic for aquatic organisms from threshold levels and as they are therefore likely to cause multiple damage to the population, the community and the ecosystem levels, their environmental occurrence has to be accurately monitored in order to guarantee appropriate environmental management of coastal zones and to preserve marine coastal ecosystems and the goods and services they provide. In the framework of the STARECAPMED project, the present study aimed to monitor, for the first time, the coastal contamination of the entire Mediterranean by As, Ag, Cd, Cu, Hg, Ni and Pb, using Posidonia oceanica as bioindicator species. But sustainable coastal management also requires the development of appropriate contamination classification systems intended, among other purposes, fo...
The meadows formed by the Mediterranean seagrass Posidonia oceanica are subjected to various natu... more The meadows formed by the Mediterranean seagrass Posidonia oceanica are subjected to various natural (e.g., water movement, light availability, sedimentation) and anthropogenic (e.g., anchoring, trawling, fish farms, explosives) phenomena that erode them and create diverse types of patches. The assemblage of the P. oceanica matrix and these patches creates particular seascapes. On the basis of this assessment, we aimed to investigate the importance of the patch type in structuring P. oceanica seascapes and to offer new prospects in the large scale studies of seagrass meadows. Five sites encompassing large P. oceanica meadows ranging from 1.86 km² to 4.42 km² along the Corsican coast (France) were considered. Eleven patch types with different sizes, shapes and origins were identified using side scan sonar images (sonograms). Five were recognized as natural and five as anthropogenic. One can be of both origins. The resolution of the sonograms allowed to detect patches of various sizes...
The coastal vegetation, and in particular the seagrasses, plays a major role in the fixation of c... more The coastal vegetation, and in particular the seagrasses, plays a major role in the fixation of carbon. Posidonia oceanica, a species endemic to the Mediterranean, is of particular interest because of the constitution of a particular structure, the matte, which enables the sequestration of carbon over long periods of time. An initial assessment of the stocks of carbon sequestrated within the matte has been undertaken in two sectors of the NATURA 2000 site “Grand Herbier de la Plaine Orientale”, Biguglia in the north and Aléria in the south. The surface area of the meadow has been measured by means of the combined use of aerial remote sensing (shallow zone) and side-scan sonar (deep zone). The thickness of the matte has been assessed by means of seismic reflection using a 2.5 KHz sediment probe and a sparker. The calibration of the seismic data was performed by scuba diving at the level of intermatte cliffs, clearly visible on the seismic profiles. The seagrass meadow at the NATURA 2...
Biological indicators have the capacity to integrate the temporal changes of contaminants, concen... more Biological indicators have the capacity to integrate the temporal changes of contaminants, concentrations or fluxes over various time-scales, and are thus considered as interesting tools for water quality biomonitoring. Since the mid-70ies, French programs have developed water monitoring approaches based on the use of bivalve molluscs; and recently the natural background and the extent of water contamination were bioassessed at the scale of the whole western Mediterranean. But even if bivalve molluscs are viewed as reliable bioindicators, their use is not always made easy as a result of their absence in numerous coastal regions that force their transplantation (cages) during several months before their sampling and analysis. This weakness led several scientists to evaluate the bioindicator abilities of other marine organisms. Seagrasses, whose ability to bioaccumulate contaminants proportionally to environmental contamination levels has been clearly demonstrated, have thus been prop...
Intensive anchoring of leisure boats in seagrass meadows leads to mechanical damages. This anthro... more Intensive anchoring of leisure boats in seagrass meadows leads to mechanical damages. This anthropogenic impact creates bare mat patches that are not easily recolonized by the plant. Several tools are used to study human impacts on the structure of seagrass meadows but they are not able to assess the indirect and long term implication of mechanical destruction. We chose to investigate the possible changes in the substrate chemistry given contrasted boat impacts. Our observations show that hydrogen sulfide concentrations remain high at 15 and 20m depth (42.6μM and 18.8μM) several months after the highest period of anchoring during the summer. Moreover, our multidisciplinary study reveals that anchoring impacts of large boats at 15 and 20m depth can potentially change the seascape structure. By taking into account both structural and chemical assessments, different managing strategies must be applied for coastal areas under anthropogenic pressures.
The Biotic Index based on Posidonia oceanica (BiPo) is a classification system for evaluation of ... more The Biotic Index based on Posidonia oceanica (BiPo) is a classification system for evaluation of the ecological status in Mediterranean coastal waters, developed in accordance with the EU Water Framework requirements. The aim of this study is to verify the applicability and reliability of the BiPo index to different geographical areas of the northwestern Mediterranean (France, Spain and Italy), to understand whether such a classification system may be applied more extensively, as so far it has only been applied to coastal waters in Corsica. The ecological status determined for sites is verified against pressures revealed from satellite imagery and from trace metal contamination of plants, to identify the sources of pressure that may be responsible for a low ecological status. The results of this study indicate that: (i) the BiPo index responds reliably to pressures, in different areas of the Mediterranean; (ii) sites with an ecological quality ratio (EQR) close to the good/moderate boundary require particular attention to identify and reduce causes of deterioration; (iii) the support of chemical indicators, in this case metal contamination, is relevant to identify potential sources of pressure.
The concentration of phenolic compound was measured in the seagrass Posidonia oceanica when inter... more The concentration of phenolic compound was measured in the seagrass Posidonia oceanica when interacting with two Bryopsidophyceae, Caulerpa taxifolia and Caulerpa racemosa, between May 1999 and May 2000. These measurements were performed on adult and intermediate leaves and in sheaths of the seagrass. Sampling was carried out at three stations subject to increasing levels of interaction with Caulerpa. The number of tannin cells was also analysed. Five phenolic compounds were identified in P. oceanica, with a predominance of caffeic acid in the adult and intermediate leaves. For a given level of interaction (and for both Caulerpa sp.), a significant seasonal variation in phenolic compounds was shown in the adult leaves (higher in November and lower in September and March for example for the interaction with C. taxifolia). Only for two compounds (corresponding to a mixture containing ferulic acid and the ester methyl 12-acetoxyricinoleate) were significant differences observed as a function of the level of interaction with C. taxifolia, and only in the adult leaves: higher concentrations of phenols were observed with increasing level of interaction. Thus, adult leaves gave values of 55.5 ± 14.1 lg g À1 dm without interaction (0Ct) and 94.9 ± 23.4 lg g À1 dm with high interaction (2Ct), corresponding to an increase of 70%. No significant difference was observed with intermediate leaves and sheaths, or for interaction with C. racemosa. The number of tannin cells (supposed to produce the phenolic compounds) largely increased in the adult and intermediate leaves when the degree of interaction with C. taxifolia increased: 90 mm above the base of the sheath (in adult leaves), 16.7 ± 10.6 tannin cells cm À2 were found without interaction (0Ct), and 57.8 ± 21.2 tannin cells cm À2 with high interaction (2Ct). No significant difference was found for C. racemosa interaction. It thus appears that when the seagrass P. oceanica is in interaction with C. taxifolia, it accelerates its production of secondary metabolites so as to limit invasion of the beds.
Data Revues 16310691 V335i10 11 S1631069112002466, Oct 1, 2012
Coralligenous habitat and rhodoliths beds are very important in terms of biodiversity in the Medi... more Coralligenous habitat and rhodoliths beds are very important in terms of biodiversity in the Mediterranean Sea. During an oceanographic campaign, carried out in northern Cap Corse, new coralligenous structures have been discovered. These structures, never previously identified in the Mediterranean Sea, are named "coralligenous atolls" because of their circular shape. The origin and growth dynamics of these atolls are still unknown but their form does not appear to result from hydrodynamic action and an anthropogenic origin also seems unlikely. However, this kind of shape seems rather closer to that of other circular structures (e.g. pockmarks) the origin of which is related to gaseous emissions. Further studies are needed to confirm this hypothesis through chemical analysis.
Comptes Rendus De L Academie Des Sciences Series Iii Sciences De La Vie, Apr 30, 2000
The location and dynamics of Posidonia oceanica beds were studied in the marine natural reserve o... more The location and dynamics of Posidonia oceanica beds were studied in the marine natural reserve of Cerbère-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 'matter' 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.
International Journal of Environment and Pollution, Mar 20, 2015
New ways of evaluating the quality of the coastal marine environment in a practical, dependable a... more New ways of evaluating the quality of the coastal marine environment in a practical, dependable and cost-efficient manner are continually sought. It would thus appear of some value to make use of bioindicator species that reflect both the average levels and the temporal variations of contaminants at a given site. Owing to their extensive distribution in the littoral zone and the ecological importance of such populations, it is of interest to examine the potential of marine phanerogams as indicator species of metal contamination in the marine environment. Based on results obtained in the Mediterranean, it would appear that the accumulation by marine phanerogams of metallic elements present in the environment is both extensive and specific. The levels accumulated vary according to the metal, the species and the tissue type examined. In addition, the plant's physiology, which will vary with the season and/or the age of the tissues, has a significant effect on the stocking process. Nevertheless, a number of laboratory and in situ experiments seem to indicate that the levels of contaminants that are accumulated are a good reflection of environmental contamination. Recent studies offer new research outlooks with the possibility of (i) using biochemical parameter measurements as a means of early detection and estimation of metal contaminant levels, and (ii) evaluating the current and past contamination levels for a given site by making use of the dating and memorization capacities that are characteristic of certain phanerogam species .
Aquatic ecosystems are increasingly subject to human-induced pressures, which significantly jeopa... more Aquatic ecosystems are increasingly subject to human-induced pressures, which significantly jeopardise ecosystem conservation. The use of ecological indicators is considered at present the most adequate tool to assess water status, as they supply information about the state of the ecosystem and, if chosen accurately, reflect changes in environmental quality (Blandin, 1986; Dauer, 1993). The main criteria that should be considered when selecting an ecological indicator are its sensitivity to disturbance, its ability to synthesise complex information in a reliable way, its easiness and simplicity of application, its applicability in extensive geographical areas, and its relevance to policy and management requirements (Blandin, 1986; Dale and Beyeler, 2001; Salas et al., 2006). Seagrass are increasingly used as ecological indicators, because of their wide distribution, their ecological role, and their sensitivity to disturbance (Pergent et al., 1995; Short and Wyllie-Echeverria, 1996; Krause-Jensen et al., 2005). The seagrass P. oceanica is widely distributed in Mediterranean coastal waters (Procaccini et al., 2003) and its specific responses to anthropogenic disturbance are acknowledged (Balestri et al., 2004; Ruiz and Romero, 2003; Leoni et al., 2006). However information and data remain heterogeneous, and are rarely synthesised or associated with a meadow quality assessment (Lopez y Royo et al., 2007). The use of seagrass as tool for an ecological evaluation of coastal waters has recently been highlighted in European legislation by the Water Framework Directive (WFD) (EC, 2000). The Directive establishes the basis for monitoring, protection and enhancement of all aquatic ecosystems in European Member States (MS), by setting ecological quality objectives (i.e. ''good water status'' for all European waters by 2015) which require to assess water quality status using a combination of ecological indicators in priority. Angiosperms are one of the four biological quality elements required for the evaluation of ecological status. Given its policy relevance, it is therefore essential, for seagrass in Europe, to consider WFD requirements when developing an ecological index. The WFD requires the establishment of assessment systems, based on pressures and impacts on the ecosystems and their relevant components, and sets precise criteria and a stepwise procedure for their development (EC, 2000). The main requirements being: (i) the use of specific biological elements (BQE) supported by physico-chemical elements, (ii) the development of the classification on the basis of the relationship between BQE and disturbance, (iii) the quantification of ecological status on the basis Ecological Indicators 10 (2010) 380-389
The location and dynamics of Posidonia oceanica beds were studied in the marine natural reserve o... more The location and dynamics of Posidonia oceanica beds were studied in the marine natural reserve of Cerbère-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 'matter' 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.
Some species of seagrasses (e.g., Zostera marina and Posidonia oceanica) have declined in the Med... more Some species of seagrasses (e.g., Zostera marina and Posidonia oceanica) have declined in the Mediterranean, at least locally. Others are progressing, helped by sea warming, such as Cymodocea nodosa and the non-native Halophila stipulacea. The decline of one seagrass can favor another seagrass. All in all, the decline of seagrasses could be less extensive and less general than claimed by some authors. Natural recolonization (cuttings and seedlings) has been more rapid and more widespread than was thought in the 20th century; however, it is sometimes insufficient, which justifies transplanting operations. Many techniques have been proposed to restore Mediterranean seagrass meadows. However, setting aside the short-term failure or half-success of experimental operations, long-term monitoring has usually been lacking, suggesting that possible failures were considered not worthy of a scientific paper. Many transplanting operations (e.g., P. oceanica) have been carried out at sites where...
Human activities generate large volumes of waste that supply marine coastal environments in patho... more Human activities generate large volumes of waste that supply marine coastal environments in pathogens, organic matter, nutrients and toxicants. Among the wide range of toxicants are trace elements. Since the latter are toxic for aquatic organisms from threshold levels and as they are therefore likely to cause multiple damage to the population, the community and the ecosystem levels, their environmental occurrence has to be accurately monitored in order to guarantee appropriate environmental management of coastal zones and to preserve marine coastal ecosystems and the goods and services they provide. In the framework of the STARECAPMED project, the present study aimed to monitor, for the first time, the coastal contamination of the entire Mediterranean by As, Ag, Cd, Cu, Hg, Ni and Pb, using Posidonia oceanica as bioindicator species. But sustainable coastal management also requires the development of appropriate contamination classification systems intended, among other purposes, fo...
The meadows formed by the Mediterranean seagrass Posidonia oceanica are subjected to various natu... more The meadows formed by the Mediterranean seagrass Posidonia oceanica are subjected to various natural (e.g., water movement, light availability, sedimentation) and anthropogenic (e.g., anchoring, trawling, fish farms, explosives) phenomena that erode them and create diverse types of patches. The assemblage of the P. oceanica matrix and these patches creates particular seascapes. On the basis of this assessment, we aimed to investigate the importance of the patch type in structuring P. oceanica seascapes and to offer new prospects in the large scale studies of seagrass meadows. Five sites encompassing large P. oceanica meadows ranging from 1.86 km² to 4.42 km² along the Corsican coast (France) were considered. Eleven patch types with different sizes, shapes and origins were identified using side scan sonar images (sonograms). Five were recognized as natural and five as anthropogenic. One can be of both origins. The resolution of the sonograms allowed to detect patches of various sizes...
The coastal vegetation, and in particular the seagrasses, plays a major role in the fixation of c... more The coastal vegetation, and in particular the seagrasses, plays a major role in the fixation of carbon. Posidonia oceanica, a species endemic to the Mediterranean, is of particular interest because of the constitution of a particular structure, the matte, which enables the sequestration of carbon over long periods of time. An initial assessment of the stocks of carbon sequestrated within the matte has been undertaken in two sectors of the NATURA 2000 site “Grand Herbier de la Plaine Orientale”, Biguglia in the north and Aléria in the south. The surface area of the meadow has been measured by means of the combined use of aerial remote sensing (shallow zone) and side-scan sonar (deep zone). The thickness of the matte has been assessed by means of seismic reflection using a 2.5 KHz sediment probe and a sparker. The calibration of the seismic data was performed by scuba diving at the level of intermatte cliffs, clearly visible on the seismic profiles. The seagrass meadow at the NATURA 2...
Biological indicators have the capacity to integrate the temporal changes of contaminants, concen... more Biological indicators have the capacity to integrate the temporal changes of contaminants, concentrations or fluxes over various time-scales, and are thus considered as interesting tools for water quality biomonitoring. Since the mid-70ies, French programs have developed water monitoring approaches based on the use of bivalve molluscs; and recently the natural background and the extent of water contamination were bioassessed at the scale of the whole western Mediterranean. But even if bivalve molluscs are viewed as reliable bioindicators, their use is not always made easy as a result of their absence in numerous coastal regions that force their transplantation (cages) during several months before their sampling and analysis. This weakness led several scientists to evaluate the bioindicator abilities of other marine organisms. Seagrasses, whose ability to bioaccumulate contaminants proportionally to environmental contamination levels has been clearly demonstrated, have thus been prop...
Intensive anchoring of leisure boats in seagrass meadows leads to mechanical damages. This anthro... more Intensive anchoring of leisure boats in seagrass meadows leads to mechanical damages. This anthropogenic impact creates bare mat patches that are not easily recolonized by the plant. Several tools are used to study human impacts on the structure of seagrass meadows but they are not able to assess the indirect and long term implication of mechanical destruction. We chose to investigate the possible changes in the substrate chemistry given contrasted boat impacts. Our observations show that hydrogen sulfide concentrations remain high at 15 and 20m depth (42.6μM and 18.8μM) several months after the highest period of anchoring during the summer. Moreover, our multidisciplinary study reveals that anchoring impacts of large boats at 15 and 20m depth can potentially change the seascape structure. By taking into account both structural and chemical assessments, different managing strategies must be applied for coastal areas under anthropogenic pressures.
The Biotic Index based on Posidonia oceanica (BiPo) is a classification system for evaluation of ... more The Biotic Index based on Posidonia oceanica (BiPo) is a classification system for evaluation of the ecological status in Mediterranean coastal waters, developed in accordance with the EU Water Framework requirements. The aim of this study is to verify the applicability and reliability of the BiPo index to different geographical areas of the northwestern Mediterranean (France, Spain and Italy), to understand whether such a classification system may be applied more extensively, as so far it has only been applied to coastal waters in Corsica. The ecological status determined for sites is verified against pressures revealed from satellite imagery and from trace metal contamination of plants, to identify the sources of pressure that may be responsible for a low ecological status. The results of this study indicate that: (i) the BiPo index responds reliably to pressures, in different areas of the Mediterranean; (ii) sites with an ecological quality ratio (EQR) close to the good/moderate boundary require particular attention to identify and reduce causes of deterioration; (iii) the support of chemical indicators, in this case metal contamination, is relevant to identify potential sources of pressure.
The concentration of phenolic compound was measured in the seagrass Posidonia oceanica when inter... more The concentration of phenolic compound was measured in the seagrass Posidonia oceanica when interacting with two Bryopsidophyceae, Caulerpa taxifolia and Caulerpa racemosa, between May 1999 and May 2000. These measurements were performed on adult and intermediate leaves and in sheaths of the seagrass. Sampling was carried out at three stations subject to increasing levels of interaction with Caulerpa. The number of tannin cells was also analysed. Five phenolic compounds were identified in P. oceanica, with a predominance of caffeic acid in the adult and intermediate leaves. For a given level of interaction (and for both Caulerpa sp.), a significant seasonal variation in phenolic compounds was shown in the adult leaves (higher in November and lower in September and March for example for the interaction with C. taxifolia). Only for two compounds (corresponding to a mixture containing ferulic acid and the ester methyl 12-acetoxyricinoleate) were significant differences observed as a function of the level of interaction with C. taxifolia, and only in the adult leaves: higher concentrations of phenols were observed with increasing level of interaction. Thus, adult leaves gave values of 55.5 ± 14.1 lg g À1 dm without interaction (0Ct) and 94.9 ± 23.4 lg g À1 dm with high interaction (2Ct), corresponding to an increase of 70%. No significant difference was observed with intermediate leaves and sheaths, or for interaction with C. racemosa. The number of tannin cells (supposed to produce the phenolic compounds) largely increased in the adult and intermediate leaves when the degree of interaction with C. taxifolia increased: 90 mm above the base of the sheath (in adult leaves), 16.7 ± 10.6 tannin cells cm À2 were found without interaction (0Ct), and 57.8 ± 21.2 tannin cells cm À2 with high interaction (2Ct). No significant difference was found for C. racemosa interaction. It thus appears that when the seagrass P. oceanica is in interaction with C. taxifolia, it accelerates its production of secondary metabolites so as to limit invasion of the beds.
Data Revues 16310691 V335i10 11 S1631069112002466, Oct 1, 2012
Coralligenous habitat and rhodoliths beds are very important in terms of biodiversity in the Medi... more Coralligenous habitat and rhodoliths beds are very important in terms of biodiversity in the Mediterranean Sea. During an oceanographic campaign, carried out in northern Cap Corse, new coralligenous structures have been discovered. These structures, never previously identified in the Mediterranean Sea, are named "coralligenous atolls" because of their circular shape. The origin and growth dynamics of these atolls are still unknown but their form does not appear to result from hydrodynamic action and an anthropogenic origin also seems unlikely. However, this kind of shape seems rather closer to that of other circular structures (e.g. pockmarks) the origin of which is related to gaseous emissions. Further studies are needed to confirm this hypothesis through chemical analysis.
Comptes Rendus De L Academie Des Sciences Series Iii Sciences De La Vie, Apr 30, 2000
The location and dynamics of Posidonia oceanica beds were studied in the marine natural reserve o... more The location and dynamics of Posidonia oceanica beds were studied in the marine natural reserve of Cerbère-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 'matter' 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.
International Journal of Environment and Pollution, Mar 20, 2015
New ways of evaluating the quality of the coastal marine environment in a practical, dependable a... more New ways of evaluating the quality of the coastal marine environment in a practical, dependable and cost-efficient manner are continually sought. It would thus appear of some value to make use of bioindicator species that reflect both the average levels and the temporal variations of contaminants at a given site. Owing to their extensive distribution in the littoral zone and the ecological importance of such populations, it is of interest to examine the potential of marine phanerogams as indicator species of metal contamination in the marine environment. Based on results obtained in the Mediterranean, it would appear that the accumulation by marine phanerogams of metallic elements present in the environment is both extensive and specific. The levels accumulated vary according to the metal, the species and the tissue type examined. In addition, the plant's physiology, which will vary with the season and/or the age of the tissues, has a significant effect on the stocking process. Nevertheless, a number of laboratory and in situ experiments seem to indicate that the levels of contaminants that are accumulated are a good reflection of environmental contamination. Recent studies offer new research outlooks with the possibility of (i) using biochemical parameter measurements as a means of early detection and estimation of metal contaminant levels, and (ii) evaluating the current and past contamination levels for a given site by making use of the dating and memorization capacities that are characteristic of certain phanerogam species .
Aquatic ecosystems are increasingly subject to human-induced pressures, which significantly jeopa... more Aquatic ecosystems are increasingly subject to human-induced pressures, which significantly jeopardise ecosystem conservation. The use of ecological indicators is considered at present the most adequate tool to assess water status, as they supply information about the state of the ecosystem and, if chosen accurately, reflect changes in environmental quality (Blandin, 1986; Dauer, 1993). The main criteria that should be considered when selecting an ecological indicator are its sensitivity to disturbance, its ability to synthesise complex information in a reliable way, its easiness and simplicity of application, its applicability in extensive geographical areas, and its relevance to policy and management requirements (Blandin, 1986; Dale and Beyeler, 2001; Salas et al., 2006). Seagrass are increasingly used as ecological indicators, because of their wide distribution, their ecological role, and their sensitivity to disturbance (Pergent et al., 1995; Short and Wyllie-Echeverria, 1996; Krause-Jensen et al., 2005). The seagrass P. oceanica is widely distributed in Mediterranean coastal waters (Procaccini et al., 2003) and its specific responses to anthropogenic disturbance are acknowledged (Balestri et al., 2004; Ruiz and Romero, 2003; Leoni et al., 2006). However information and data remain heterogeneous, and are rarely synthesised or associated with a meadow quality assessment (Lopez y Royo et al., 2007). The use of seagrass as tool for an ecological evaluation of coastal waters has recently been highlighted in European legislation by the Water Framework Directive (WFD) (EC, 2000). The Directive establishes the basis for monitoring, protection and enhancement of all aquatic ecosystems in European Member States (MS), by setting ecological quality objectives (i.e. ''good water status'' for all European waters by 2015) which require to assess water quality status using a combination of ecological indicators in priority. Angiosperms are one of the four biological quality elements required for the evaluation of ecological status. Given its policy relevance, it is therefore essential, for seagrass in Europe, to consider WFD requirements when developing an ecological index. The WFD requires the establishment of assessment systems, based on pressures and impacts on the ecosystems and their relevant components, and sets precise criteria and a stepwise procedure for their development (EC, 2000). The main requirements being: (i) the use of specific biological elements (BQE) supported by physico-chemical elements, (ii) the development of the classification on the basis of the relationship between BQE and disturbance, (iii) the quantification of ecological status on the basis Ecological Indicators 10 (2010) 380-389
The location and dynamics of Posidonia oceanica beds were studied in the marine natural reserve o... more The location and dynamics of Posidonia oceanica beds were studied in the marine natural reserve of Cerbère-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 'matter' 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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Papers by Gerard Pergent