Notes on Homalopoma sanguineum (Linnaeus, 1758) (Gastropoda, Archaeogastropoda, Turbinidae)

Volume: 12Start Page: 77End Page: 8

Molluscs from coralline algae aggreggates of the Catalan littoral shores

12 páginas, 3 tablas, 1 figura.The present work includes a study on the species of Mollusca from the calcareous algae concretions prospecte in the catalan coast (NE Spain). Moreover, it is characterized the Mollusca community from the substract and the studied area, having been used the Shannon Weaver diversity index to study them. Using the mathematic index of "Medium General Dominance" and "Frequency" (SOYER, 1970), it has determined the importance of the presence of the species in the studied concretions.Peer reviewe

Immediate and delayed effects of a mass mortality event on gorgonian population dynamics and benthic community structure in the NW Mediterranean Sea

11 pages, 8 figures, 1 tableIn the boreal summer of 1999, many invertebrates of hard-bottom communities in the NW Mediterranean Sea suffered mass mortality. Our study assessed the population of the temperate octocoral Paramuricea clavata before the event and monitored the population over the following 4 yr. Spatial patterns showed decreasing mortality with increasing depth between 0 and 50 m, as well as high local variability. The temporal pattern was characterized by a sharp decrease in biomass (58%) shortly after the event caused by the combined effect of colony death (9% of the population) and an increase in the extent of colony injury (from 9% before the event to 52% shortly after it). After 4 yr of monitoring, our results indicated a large delayed effect of the event. Population density decreased continuously after November 1999, and by the completion of the study in November 2003 the accumulated density decrease was 48% of the initial population. This decrease was mainly due to the death of colonies subjected to extensive injury, and because recruitment did not offset mortality. After November 1999, biomass continued to decrease at a slow rate, becoming almost constant after November 2001. Overall, the delayed effect of the event accounted for a 70% loss in P. clavata biomass. The fact that a stabilization of the density and biomass of this species was observed during the last year of our study suggests that the delayed impact of the 1999 mass mortality event may be nearing its end. Nevertheless, given the low dynamics of P. clavata and its role as a habitat former, the delayed effect of the mass mortality event indicates the relevant role that disturbance can play on the population dynamics of this species and as a community structuring force on the coralligenous community. © Inter-Research 2005Financial support for this work was provided by the Port-Cros National Park, the Total Foundation and by research grants REN2002-01631/MAR and CTM2004-03120/MAR from the ‘Ministerio de Educación y Ciencia’, SpainPeer Reviewe

Spatio-temporal variations of biomass and abundance in bathyal non-crustacean megafauna in the Catalan Sea (North-western Mediterranean)

13 pages, 5 figures, 2 tablesThe spatio-temporal variations in diversity, biomass and abundance of bathyal invertebrates (excluding decapod crustaceans, which have been analysed elsewhere)from the North-western Mediterranean margin are described. The upper canyon (~450 m), middle slope (~650 m) and lower slope (~1,200 m) habitats were investigated throughout the year. The first two sites are visited daily by a specialised commercial fisheries’ fleet, while the deeper site has not been impacted by fishing activities. A total of 140 species from 12 phyla were collected from the 3 study areas. Of these, the Mollusca, Echinodermata, Polychaeta and Cnidaria were the most speciose groups. The patterns of species diversity (H') and evenness (E) were similar in time and space. The upper canyon and middle-slope sites were dominated by echinoderms and molluscs, while the lowerslope site was dominated by cnidarians and sponges. Multifactorial ANOVA showed significant spatio-temporal differences in the biomass and/or abundance only in echinoderms, molluscs, cnidarians and polychaetes. The faunal diVerences observed were explained by habitat type, but not by season. The role of submarine canyons and commercial fishing on shaping the diversity and biomass of bathyal Mediterranean invertebrates is discussed.The data presented here is a result of the RETRO project (CICYT MAR90-757 to FS).Peer reviewe

Évaluation de l’impact de la plongée dans le coralligène : L’utilité des études démographiques des populations de Paramuricea clavata

24 pages, 9 figures, 2 tables[EN] Coralligenous communities are an important “hot spot” of Mediterranean biodiversity. These communities are presently threatened by a combination of anthropogenic impacts partly related to global change. Managers of MPAs are increasingly concerned about the capacity of coralligenous communities to endure crowds of divers, and there is a call for descriptors and for quantitative methods for estimating this capacity. A good indicator to detect the impacts on coralligenous communities should gather the following essential traits: to be a long-lived, clonal, engineering species displaying an erect shape and a large size in order to facilitate the monitoring. Among the main taxonomic groups of the coralligenous, gorgonians display several advantages and, in this study, the red gorgonian Paramuricea clavata was selected as a model species to evaluate the effects of diving impact and climate change on coralligenous communities. We present three cases of study about the demographic monitoring of red gorgonian populations affected by the 1999 mass mortality event (Port-Cros) and subjected to high diving activity (Medes Islands and Cap de Creus). Finally, combining all these data we simulate the interacting effects of divers damage and mass mortality events on the persistence of gorgonian populations. The results of long-term monitoring of permanent plots allowed showing that although diving activity affects significantly the red gorgonian populations, the effect of climate change has more significant effects on the populations. Port-Cros populations affected by the 1999 mass mortality suffered a 60% biomass loss that has not been recovered in the following eight years. Simulations showed that the combination of both disturbances can have large and lasting effects on the future viability of red gorgonian populations. As gorgonian assemblages are only one facies of the coralligenous communities, other species should be selected for detecting the impact on these communities. Nevertheless, the development of similar demographic approaches for other species would be more difficult than for gorgoniansFinancial support was provided by the Port-Cros National Park through the Total FoundationPeer Reviewe