Patrick Bonhomme

An ecosystem-based approach to assess the status of a Mediterranean ecosystem, the Posidonia oceanica seagrass meadow.

Biotic indices, which reflect the quality of the environment, are widely used in the marine realm. Sometimes, key species or ecosystem engineers are selected for this purpose. This is the case of the Mediterranean seagrass Posidonia oceanica, widely used as a biological quality element in the context of the European Union Water Framework Directive (WFD). The good quality of a water body and the apparent health of a species, whether or not an ecosystem engineer such as P. oceanica, is not always indicative of the good structure and functioning of the whole ecosystem. A key point of the recent Marine Strategy Framework Directive (MSFD) is the ecosystem-based approach. Here, on the basis of a simplified conceptual model of the P. oceanica ecosystem, we have proposed an ecosystem-based index of the quality of its functioning, compliant with the MSFD requirements. This index (EBQI) is based upon a set of representative functional compartments, the weighting of these compartments and the assessment of the quality of each compartment by comparison of a supposed baseline. The index well discriminated 17 sites in the north-western Mediterranean (French Riviera, Provence, Corsica, Catalonia and Balearic Islands) covering a wide range of human pressure levels. The strong points of the EBQI are that it is easy to implement, non-destructive, relatively robust, according to the selection of the compartments and to their weighting, and associated with confidence indices that indicate possible weakness and biases and therefore the need for further field data acquisition.

Recovery of the seagrass Zostera marina in a disturbed Mediterranean lagoon (Etang de Berre, Bouches-du-Rhône, Southern France)

Until 1966, Berre lagoon (Provence, southern France) was a salty lagoon with a highly diversified marine fauna and flora. Increased inputs of freshwater from a hydroelectric plant led to the desalination and stratification of the lagoon. Following these changes, a wide diversity of species disappeared, including the eelgrass Zostera marina, a keystone species which previously constituted extensive meadows in the lagoon. After almost three decades of absence, patches of eelgrass were observed in 2001 and 2002 but the success of future recolonization by this community is uncertain.

Spatial patterns and GIS habitat modelling of fish in two French Mediterranean coastal areas

The spring and summer distribution of adults and larval fish stages of Sparids and Scorpaenids was studied in two sites in the western Mediterranean. Fish adults and larvae of those two taxa were identified and sorted according to their life stages in order to study their distribution and develop suitable habitat maps. Study areas were located on French coastal waters, the “Côte Bleue” Marine Park (CBMP) has an east-west orientation with substratum dominated by Posidonia beds and the Marine Reserve of Cerbère-Banyuls (MRCB) runs north–south and is dominated by rocky substrates. Generalised Additive Models (GAM) combined with Geographic Information System (GIS), were used to model the suitable habitats for fish larvae and adults. During spring months, waters exhibit low Sea Surface Temperatures (SST), low Photosynthetically Active Radiation (PAR), high values of Sea Surface Chlorophyll-a concentration (Chl-a), and mostly negative values of Sea Level Anomaly (SLA) indicating anticyclonic eddies. During summer months, waters have higher values of SST, lower values of Chl-a and positive values of SLA indicating cyclonic eddies. The results revealed different environmental responses in the distribution of fish adults and larvae in the CBMP and MRCB. Suitable habitats for adult were mainly dependent on the substrate types (Posidonia meadows and sand) and they were found close to the coast, whereas fish larvae were dependent on environmental cues (Chl-a, SLA, SST) with a sparse spatial distribution.

Protected Areas and Overuse in the Context of Socio-Natural Changes: An Interdisciplinary French Case Study

Abstract: This article provides an interdisciplinary analysis of the notion of overuse in natural areas. Based on the case of the French Calanques massif (located along the Mediterranean coast between Marseilles and Cassis), sociology and biology combine their analyses to examine the social processes behind the increasingly widespread use of natural areas and the ecological consequences thereof. The data are comprised of interdisciplinary research based on eighty semi-structured interviews conducted on-site and 330 telephone survey questionnaires. We critically analyse of the notion of overuse and underscore the socio-economic, cultural and ideological weight it carries in the context of socio-natural change; this calls into question the relevance of the ancient nature/culture dichotomy. Drawing on theoretical tools from environmental sociology, this article also provides some perspectives for natural area managers.

Application of ordinal correspondence analysis for submerged aquatic vegetation monitoring

The European Water Framework states that macrophyte communities (seaweeds and seagrass) are key indicators of the ecological health of lagoons. Furthermore, the restoration of these communities, especially the Zostera meadows, is one of the main objectives of the Berre lagoon restoration plan. Consequently, a monitoring programme of the main macrophyte species still present in the lagoon was initiated in 1996. This monitoring resulted in a sequence of 11 spatially structured annual tables consisting of the observed density of these species. These tables are processed in this study. First, we specify the principles of Behs ordinal correspondence analysis (OCA), designed for ordered row/column categories, and compare this method to classical correspondence analysis (CA). Then, we show that OCA is straightforwardly adaptable for processing a sequence of ordered contingency tables like ours. Both OCA and CA are afterwards used to reveal and test the main patterns of spatio-temporal changes of two macrophyte species in the Berre lagoon: Ulva and Zostera. The results we obtained are compared and discussed.

Ecosystem-Based Versus Species-Based Approach for Assessment of the Human Impact on the Mediterranean Seagrass Posidonia oceanica

Biotic indices, which reflect the quality of the environment, are widely used in the marine realm. The Posidonia oceanica seagrass meadow is a benthic sublittoral habitat characteristic of the Mediterranean Sea. The Ecosystem-Based Quality Index (EBQI) is based upon the overall functioning of the Posidonia oceanica ecosystem, from primary producers and the litter to top predators. It is compliant with the Marine Strategy Framework Directive (MSFD) of the European Union (EU). It provides managers with a response that is very different from that of the indices only based upon the key species P. oceanica and a few affiliate species. While the species-based indices are mainly designed for assessing the water quality of a waterbody (e.g. pollution), the EBQI provides a picture of the actual status of the ecosystem functioning, including not only pollution but also the whole range of human impacts, from anchoring to overfishing.