Biodiversité en environnement marin

Les océans couvrent plus de 70 % de notre planète. Ils hébergent une biodiversité d'une extraordinaire richesse, dont beaucoup reste à découvrir. Préserver cette biodiversité marine nécessite de mieux la connaître dans toutes ses dimensions, du gène à l'écosystème. Comprendre sa dynamique et ses usages est un véritable défi scientifique. La protection de ce patrimoine est désormais une priorité mondiale inscrite dans plusieurs conventions internationales et un objectif affirmé des politiques européennes et des stratégies nationales. Un livre sans parti pris, pour tous les citoyens curieux de leur environnement, qui cherchent à se construire une opinion sans oublier que la préservation de ces richesses naturelles est entre leurs mains

Clarifying marine invasions with molecular markers: an illustration based on mtDNA from mistaken calyptraeid gastropod identifications

Species invasions are occurring at an increasing rate in coastal environments. Accurately identifying introductions is a critical issue to take full advantage of the new invasion databases. Further, life history differences between morphologically comparable species may require that different management strategies be instigated to effectively control different species. Facing this problem, we used molecular approaches and documented a case of mistaken identification in a group of marine invertebrates, the calyptraeid gastropods. Members of this group have repeatedly and successfully invaded new habitats after anthropogenic introduction, especially in estuaries and bays on the west coast of the United States of America. For example, Crepidula fornicata, native to the east coast of the USA, has been reported from at least five USA west coast estuaries. We sequenced a fragment of the COI gene of a sample of putative C. fornicata from Humboldt Bay, California. By constructing a phylogeny of these and other calpytraeid gastropod sequences, we discovered that the individuals were C. convexa, the convex slippershell. In contrast to C. fornicata, C. convexa has large, demersal eggs and larvae are well developed at hatching. Its potential for dispersal is therefore lower as compared to C. fornicata and therefore any strategy to manage the invasion should take this into account. In the present study, we demonstrated the utility of molecular tools that can be used by non-taxonomic experts, to quickly and accurately identify alien species – an important first step in any study of invasion biology.Dugald J. McGlashan, Mark Ponniah, Phillip Cassey, Frédérique Viar

Speaking their language – Development of a multilingual decision-support tool for communicating invasive species risks to decision makers and stakeholders

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A global-scale screening of non-native aquatic organisms to identify potentially invasive species under current and future climate conditions

The threat posed by invasive non-native species worldwide requires a global approach to identify which introduced species are likely to pose an elevated risk of impact to native species and ecosystems. To inform policy, stakeholders and management decisions on global threats to aquatic ecosystems, 195 assessors representing 120 risk assessment areas across all six inhabited continents screened 819 non-native species from 15 groups of aquatic organisms (freshwater, brackish, marine plants and animals) using the Aquatic Species Invasiveness Screening Kit. This multi-lingual decision-support tool for the risk screening of aquatic organisms provides assessors with risk scores for a species under current and future climate change conditions that, following a statistically based calibration, permits the accurate classification of species into high-, medium- and low-risk categories under current and predicted climate conditions. The 1730 screenings undertaken encompassed wide geographical areas (regions, political entities, parts thereof, water bodies, river basins, lake drainage basins, and marine regions), which permitted thresholds to be identified for almost all aquatic organismal groups screened as well as for tropical, temperate and continental climate classes, and for tropical and temperate marine ecoregions. In total, 33 species were identified as posing a ‘very high risk’ of being or becoming invasive, and the scores of several of these species under current climate increased under future climate conditions, primarily due to their wide thermal tolerances. The risk thresholds determined for taxonomic groups and climate zones provide a basis against which area-specific or climate-based calibrated thresholds may be interpreted. In turn, the risk rankings help decision-makers identify which species require an immediate ‘rapid’ management action (e.g. eradication, control) to avoid or mitigate adverse impacts, which require a full risk assessment, and which are to be restricted or banned with regard to importation and/or sale as ornamental or aquarium/fishery enhancement