Sponge inventory of the French Mediterranean waters, with an emphasis on cave-dwelling species.

Mediterranean sponges represent about 10 % of the world sponge biodiversity, with these sessile organisms dominating in terms of diversity and biomass in most of the rocky bottoms shaded from light. After 60 years of intensive study of the sponge diversity along the French coast, we present the first comprehensive reference-list for this biogeographic area. A total of 389 sponge species was recorded, of which 222 known in the Marseille region. In this area, special attention was paid to species from underwater caves. Although this particular habitat appeared as one of the richest, a wealth of hidden diversity still requires description. About 37 % of the sponge diversity can be found in underwater caves, most of these species being also distributed in other habitats. However, 23 % of this sponge diversity is cave-exclusive. An easy and rapid assessment method was developed with a selection of 65 representative sponge species, for the monitoring of semi-dark cave communities. This method, based on data acquisition with photoquadrats and their processing using a DataBase built with ACCESS, was deployed in 13 studied sites. Altogether, this study represents a useful contribution for marine environment managers who might refer to this French reference list and apply the rapid and easy assessment method in the framework of several European Directives and international Conventions.

New hexactinellid sponges from deep Mediterranean canyons.

During the exploration of the NW Mediterranean deep-sea canyons (MedSeaCan and CorSeaCan cruises), several hexactinellid sponges were observed and collected by ROV and manned submersible. Two of them appeared to be new species of Farrea and Tretodictyum. The genus Farrea had so far been reported with doubt from the Mediterranean and was listed as "taxa inquirenda" for two undescribed species. We here provide a proper description for the specimens encountered and sampled. The genus Tretodictyum had been recorded several times in the Mediterranean and in the near Atlantic as T. tubulosum Schulze, 1866, again with doubt, since the type locality is the Japan Sea. We here confirm that the Mediterranean specimens are a distinct new species which we describe. We also provide18S rDNA sequences of the two new species and include them in a phylogenetic tree of related hexactinellids.

Rapid biodiversity assessment and monitoring method for highly diverse benthic communities: a case study of mediterranean coralligenous outcrops.

Increasing anthropogenic pressures urge enhanced knowledge and understanding of the current state of marine biodiversity. This baseline information is pivotal to explore present trends, detect future modifications and propose adequate management actions for marine ecosystems. Coralligenous outcrops are a highly diverse and structurally complex deep-water habitat faced with major threats in the Mediterranean Sea. Despite its ecological, aesthetic and economic value, coralligenous biodiversity patterns are still poorly understood. There is currently no single sampling method that has been demonstrated to be sufficiently representative to ensure adequate community assessment and monitoring in this habitat. Therefore, we propose a rapid non-destructive protocol for biodiversity assessment and monitoring of coralligenous outcrops providing good estimates of its structure and species composition, based on photographic sampling and the determination of presence/absence of macrobenthic species. We used an extensive photographic survey, covering several spatial scales (100s of m to 100s of km) within the NW Mediterranean and including 2 different coralligenous assemblages: Paramuricea clavata (PCA) and Corallium rubrum assemblage (CRA). This approach allowed us to determine the minimal sampling area for each assemblage (5000 cm(2) for PCA and 2500 cm(2) for CRA). In addition, we conclude that 3 replicates provide an optimal sampling effort in order to maximize the species number and to assess the main biodiversity patterns of studied assemblages in variability studies requiring replicates. We contend that the proposed sampling approach provides a valuable tool for management and conservation planning, monitoring and research programs focused on coralligenous outcrops, potentially also applicable in other benthic ecosystems.

Marine sponges as biomonitor of polychlorobiphenyl contamination: concentration and fate of 24 congeners.

The aim of this study was first to assess the relevance of a marine sponge, Spongia officinalis, as a biomonitor of PCB. Twenty-four chlorobiphenyl congeners have been measured along a pollution gradient both in sponges and seawater. S. officinalis displays a capacity to accumulate all types of congeners. The highest concentration factors were found for hexa- and heptachlorobiphenyls. Concentrations recorded in sponges agreed quite well with the PCB concentrations of study sites. The prevalence of CB138 and CB153 definitely demonstrated the urban origin of the PCB detected, despite the ban on their production and the existence of a wastewater treatment plant since 1987. The CB138/CB153 ratio is approximately 1.2 in commercial mixtures as well as in seawater. In sponges, this ratio varies strongly in space and time, from 1 in sponges at the most polluted site to 0.3 at the reference site. This change in the ratio of these two very persistent congeners, which is not observed in seawater, indicates a metabolism of CB138 in sponges. As it was recently demonstrated for nonpersistent organic contaminants, sponges might well be able to degrade PCB, but further work is needed to identify the processes involved.