From In Situ to satellite observations of pelagic Sargassum distribution and aggregation in the Tropical North Atlantic Ocean

International audienceThe present study reports on observations carried out in the Tropical North Atlantic in summer and autumn 2017, documenting Sargassum aggregations using both ship-deck observations and satellite sensor observations at three resolutions (MSI-10 m, OLCI-300 m, VIIRS-750 m and MODIS-1 km). Both datasets reported that in summer, Sargassum aggre-gations were mainly observed off Brazil and near the Caribbean Islands, while they accumulated near the African coast in autumn. Based on in situ observations, we propose a five-class typology allowing standardisation of the description of in situ Sargassum raft shapes and sizes. The most commonly observed Sargassum raft type was windrows, but large rafts composed of a quasi-circular patch hundreds of meters wide were also observed. Satellite imagery showed that these rafts formed larger Sargassum aggregations over a wide range of scales, with smaller aggregations (of tens of m 2 area) nested within larger ones (of hundreds of km 2). Match-ups between different satellite sensors and in situ observations were limited for this dataset, mainly because of high cloud cover during the periods of observation. Nevertheless, comparisons between the two datasets showed that satellite sensors successfully detected Sargassum abundance and aggregation patterns consistent with in situ observations. MODIS and VIIRS sensors were better suited to describing the Sargas-sum aggregation distribution and dynamics at Atlantic scale, while the new sensors, OLCI and MSI, proved their ability to detect Sargassum aggregations and to describe their (sub-) mesoscale nested structure. The high variability in raft shape, size, thickness, depth and biomass density observed in situ means that caution is called for when using satellite maps of Sargassum distribution and biomass estimation. Improvements would require additional in situ and airborne observations or very high-resolution satellite imagery

Mapping human impacts to support sustainable uses of marine ecosystems in the Mediterranean sea

European Geosciences Union (EGU) General Assembly, 23-27 May 2022, Vienna, AustriaLocal and global anthropogenic pressures due to climate change and to local uses and activities are exerting significant cumulative impacts to greater extents of the oceans and seas. Coastal ecosystems are particularly threatened by the intensity and coexistence of several marine uses and pressures, including sewage and urban constructions, tourism, ship traffic, fisheries and aquaculture. Assessment of pressures and the identification of mitigation measures are key urgent actions, as already highlighted by the EU Marine Strategy Framework Directive and the United Nations Sustainable Development Goal 14. The aim of this work, developed within the Interreg-Med project SHAREMED, is to systematize existing knowledge on threats and pollution, including those of transboundary origin, for long term strategies and common action marine spatial planning, jointly developed with stakeholders. The quest is to assess coexisting environmental threats, and their propagation in space and time, at proper spatial and temporal scales, according to the type and action of each stressor (i.e. global vs. local). Cumulative pressures are tackled within a dedicated Atlas comprising three sub-basinsins of the Mediterranean Sea: the North Adriatic Sea, the Sicilian Channel and the North-Western region. The Atlas integrates information generated at the best available resolutions by 1) in-situ sampling, 2) remote observations, 3) numerical models, and 4) focusing on target ecosystems and habitat forming species. These sub-basins are subjected to multiple local and larger scale (e.g. climate) pressures that propagate in space and time, and across political boundaries, that need to be addressed through coordinated actions, based on evidence-rooted common understanding. Interactions with relevant Stakeholders, solicited through an online survey, and meetings, were used to select target ecosystems and to identify the key relevant pressures. The Atlas is based on open-access databases and portals, literature reviews and from ad-hoc model simulations concerning marine heatwaves, ship traffic, oil pollution, marine litter and fishing efforts. We will present the main preliminary results and needs and gaps in observations related to marine ecosystems threatsPeer reviewe

Collaborative Database to Track Mass Mortality Events in the Mediterranean Sea

Anthropogenic climate change, and global warming in particular, has strong and increasing impacts on marine ecosystems (Poloczanska et al., 2013; Halpern et al., 2015; Smale et al., 2019). The Mediterranean Sea is considered a marine biodiversity hot-spot contributing to more than 7% of world's marine biodiversity including a high percentage of endemic species (Coll et al., 2010). The Mediterranean region is a climate change hotspot, where the respective impacts of warming are very pronounced and relatively well documented (Cramer et al., 2018). One of the major impacts of sea surface temperature rise in the marine coastal ecosystems is the occurrence of mass mortality events (MMEs). The first evidences of this phenomenon dated from the first half of'80 years affecting the Western Mediterranean and the Aegean Sea (Harmelin, 1984; Bavestrello and Boero, 1986; Gaino and Pronzato, 1989; Voultsiadou et al., 2011). The most impressive phenomenon happened in 1999 when an unprecedented large scale MME impacted populations of more than 30 species from different phyla along the French and Italian coasts (Cerrano et al., 2000; Perez et al., 2000). Following this event, several other large scale MMEs have been reported, along with numerous other minor ones, which are usually more restricted in geographic extend and/or number of affected species (Garrabou et al., 2009; Rivetti et al., 2014; Marbà et al., 2015; Rubio-Portillo et al., 2016, authors' personal observations). These events have generally been associated with strong and recurrent marine heat waves (Crisci et al., 2011; Kersting et al., 2013; Turicchia et al., 2018; Bensoussan et al., 2019) which are becoming more frequent globally (Smale et al., 2019). Both field observations and future projections using Regional Coupled Models (Adloff et al., 2015; Darmaraki et al., 2019) show the increase in Mediterranean sea surface temperature, with more frequent occurrence of extreme ocean warming events. As a result, new MMEs are expected during the coming years. To date, despite the efforts, neither updated nor comprehensive information can support scientific analysis of mortality events at a Mediterranean regional scale. Such information is vital to guide management and conservation strategies that can then inform adaptive management schemes that aim to face the impacts of climate change.MV-L was supported by a postdoctoral contract Juan de la Cierva-Incorporación (IJCI-2016-29329) of Ministerio de Ciencia, Innovación y Universidades. AI was supported by a Technical staff contract (PTA2015-10829-I) Ayudas Personal Técnico de Apoyo of Ministerio de Economía y Competitividad (2015). Interreg Med Programme (grant number Project MPA-Adapt 1MED15_3.2_M2_337) 85% cofunded by the European Regional Development Fund, the MIMOSA project funded by the Foundation Prince Albert II Monaco and the European Union's Horizon 2020 research and innovation programme under grant agreement no 689518 (MERCES). DG-G was supported by an FPU grant (FPU15/05457) from the Spanish Ministry of Education. J-BL was partially supported by the Strategic Funding UID/Multi/04423/2013 through national funds provided by FCT - Foundation for Science and Technology and European Regional Development Fund (ERDF), in the framework of the programme PT2020

Vers une reconstitution des populations de grande nacre Pinna nobilis en Méditerranée française ?

International audienceAs a result of the massive mortality event impacting Pinna nobilis populations throughout the Mediterranean since 2016, with a mortality rate estimated at as much as 100 % in the waters of the Port-Cros Archipelago Marine Protected Area (Port-Cros National Park, eastern Provence, France), living pen shell were found in August 2020 on the south side of the island. Initial monitoring identified 8 living young individuals in November 2020. These individuals were still alive in March 2021.Keywords: PinnaVers une reconstitution des populations de grande nacre Pinna nobilis en Méditerranée française ? À la suite d'une mortalité massive des populations de grande nacre Pinna nobilis à travers toute la Méditerranée depuis l'automne 2016, et une estimation de leur mortalité dans les eaux de l'aire marine protégée de l'archipel de Port-Cros (Parc national de Port-Cros, Provence orientale, France) proche de 100 %, des grandes nacres vivantes ont été trouvées en août 2020 sur la face sud de l'île. Les premiers suivis ont permis d'identifier 8 jeunes individus vivants en novembre 2020. Ces individus étaient toujours vivants en mars 2021

Un jeu de territoire pour la planification de l'espace maritime du littoral marseillais

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Un jeu de territoire pour la planification de l'espace maritime du littoral marseillais

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The use of citizen science for marine biodiversity surveys : from species identification to ecologically relevant observations

International audienceThe current development of citizen science is an opportunity for marine biodiversity surveys to use recreational SCUBA diver data. In France, the DORIS project is extensively used for marine species identification, while many initiatives offer volunteer divers the means to record their observations. Thanks to the scientific synergy generated by the flagship project of the artificial reefs (ARs) of Prado Bay, located off the coast of Marseille (France), a multi-annual biodiversity survey was performed by a team of recreational divers certified by the French Federation for Submarine Sports and Education (FFESSM). The analysis of their observations with other citizen science data showed a good taxonomic coverage for fishes and mollusks. These observations also allowed (1) to follow AR colonization over the study period, with the increasing number of taxa and the growing occurrence of large fishes, and (2) to characterize taxa distribution between the different AR types, revealing the inefficiency of one type of AR which failed to provide the results expected from its design. This example demonstrates that the transition from species identification to ecologically relevant observation is perfectly feasible using volunteer naturalist SCUBA divers, on condition that both the protocols and the data are validated by professional scientists

Planifier l'espace maritime au large d'une grande ville : comment intégrer les dimensions sociale et écologique au service d'un véritable objectif de durabilité ?

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Un jeu de territoire pour la planification de l'espace maritime du littoral marseillais

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