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In managing for marine biodiversity, it is worth recognising that, whilst every species contributes to biodiversity, each contribution is not of equal importance. Some have important effects and interactions, both primary and secondary, on other components in the community and therefore by their presence or absence directly affect the biodiversity of the community as a whole. Keystone species have been defined as species that have a disproportionate effect on their environment relative to their abundance. As such, keystone species might be of particular relevance for the marine biodiversity characterisation within the assessment of Good Environmental Status (GEnS), for the Marine Strategy Framework Directive (MSFD).The DEVOTES Keystone Catalogue and associated deliverable document is a review of potential keystone species of the different European marine habitats. The catalogue has 844 individual entries, which includes 210 distinct species and 19 groups classified by major habitat in the Baltic Sea, North East Atlantic, Mediterranean, Black Sea (EU Regional Seas) and Norwegian Sea (Non-­‐EU Sea). The catalogue and the report make use/cite 164 and 204 sources respectively. The keystones in the catalogue are indicated by models, by use as indicators, by published work (e.g. on traits and interactions with other species), and by expert opinion based on understanding of systems and roles of species/groups. A total of 74 species were considered to act as keystone predators, 79 as keystone engineers, 66 as keystone habitat forming species, while a few were thought of having multiple roles in their marine ecosystems. Benthic invertebrates accounted for 50% of the reported keystone species/groups, while macroalgae contributed 17% and fish12%. Angiosperms were consistently put forward as keystone habitat forming and engineering species in all areas. A significant number of keystones were invasive alien species.Only one keystone, the bivalve Mya arenaria, was common to all four EU regional seas. The Mediterranean Sea had the largest number of potential keystones (56% of the entries) with the least in the Norwegian Sea. There were very few keystones in deep waters (Bathyal-­‐Abyssal, 200+ m), with most reported in sublittoral shallow and shelf seabeds or for pelagic species in marine waters with few in reduced/variable salinity waters. The gaps in coverage and expertise in the catalogue are analysed at the habitat and sea level, within the MSFD biodiversity component groups and in light of knowledge and outputs from ecosystem models (Ecopath with Ecosim).The understanding of keystones is discussed as to when a species may be a dominant or keystone with respect to the definition term concerning ‘disproportionate abundance’, how important are the ‘disproportionate effects’ in relation to habitat formers and engineers, what separates a key predator and key prey for mid-­‐trophic range species and how context dependency makes a species a keystone. Keystone alien invasive species are reviewed and the use of keystone species model outputs investigated. In the penultimate sections of the review the current level of protection on keystone species and the possibilities for a keystone operational metric and their use in management and in GEnS assessments for the MSFD are discussed. The final section highlights the one keystone species and its interactions not covered in the catalogue but with the greatest impact on almost all marine ecosystems, Homo sapiens. WP6, Deliverable 6.1, DEVOTES Project

In the Vaccares lagoon (Rhône delta, Camargue, France), mullets of the species Liza ramada (Pisces, Teleostei) are parasitized by seven metazoan species, ectoparasites of gills : six Monogenea and one Copepoda. The spatial and temporal structures of this parasite community were analysed. The host migrates within this delta in the course of the seasons, and its parasites are potentially affected by the fluctuating environmental constraints. The crossed effects between the structure of the parasite infrapopulations and some environmental characteristics were studied with a co-inertia analysis. This study emphasizes the interactions between the populations structures and the environment, and their consequences on local biodiversity. Open access 17 p.

This article deals with a performant parallel solution for a host-macroparasite model, both deterministic and stochastic, in a marine environment. Detailed biological phenomena are reproduced, such as spatial and temporal heterogeneities in these populations. A new version of the simulator and a new parallel algorithmic solution are presented. The interdisciplinary work presented here is at the interface of ecology, mathematics and computer science. International audience Open access