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International audience; The COZOMED-MERMEX project aims at understanding how hydrodynamic forcing (currents, tides, winds)combine with anthropogenic forcing and climate to affect the variability of coastal Mediterranean zooplanktoncommunities under contrasting tidal influence. This study includes (i) a zero state of knowledge via a literaturereview of existing data and (ii) a case study on the system Boughrara lagoon - Gulf of Gabes. This ecosystemgives major services for Tunisia (about 65% of national fish production) but is weakened by its situation in aheavily anthropized area and under influence of urban, industrial and agricultural inputs. Besides this regionis subject to specific climate forcing (Sahelian winds, scorching heat, intense evaporation, flooding) whichpossible changes will be considered. The expected issues are (i) to improve our knowledge of hydrodynamicforcing on zooplankton and ultimately on the functioning of coastal Mediterranean ecosystems impacted byanthropogenic and climatic effects and (ii) to elaborate management tools to help preserving good ecologicalstatus of these ecosystems: hydrodynamic circulation model, mapping of isochrones of residence times, mappingof the areas of highest zooplankton abundances (swarms), and sensitive areas, etc. This project strengthensexisting scientific collaborations within the MERMEX program (The MerMex Group, 2011) and in the frameof an international joint laboratory (COSYS-Med) created in 2014. A first field mulidisciplinary campaign wasperformed in October 2016. The strategy combined measurements of sea level and currents (mooring of ADCP,Argonaute and tidal gauges), hydrological description of water masses (horizontal and vertical transect with aMinibat equipped with CTD, fluorescence and turbidity sensors) and discrete sampling of nutrients, DOC, POC,pico, nano, microphytoplankton and mesozooplankton. The first results allow a description of water currents andshows a good coupling between tidal cycles (ebb-flood and spring tide neap tide) and the dynamics of planktoniccompartments in the lagoon.

International audience; The COZOMED-MERMEX project aims at understanding how hydrodynamic forcing (currents, tides, winds)combine with anthropogenic forcing and climate to affect the variability of coastal Mediterranean zooplanktoncommunities under contrasting tidal influence. This study includes (i) a zero state of knowledge via a literaturereview of existing data and (ii) a case study on the system Boughrara lagoon - Gulf of Gabes. This ecosystemgives major services for Tunisia (about 65% of national fish production) but is weakened by its situation in aheavily anthropized area and under influence of urban, industrial and agricultural inputs. Besides this regionis subject to specific climate forcing (Sahelian winds, scorching heat, intense evaporation, flooding) whichpossible changes will be considered. The expected issues are (i) to improve our knowledge of hydrodynamicforcing on zooplankton and ultimately on the functioning of coastal Mediterranean ecosystems impacted byanthropogenic and climatic effects and (ii) to elaborate management tools to help preserving good ecologicalstatus of these ecosystems: hydrodynamic circulation model, mapping of isochrones of residence times, mappingof the areas of highest zooplankton abundances (swarms), and sensitive areas, etc. This project strengthensexisting scientific collaborations within the MERMEX program (The MerMex Group, 2011) and in the frameof an international joint laboratory (COSYS-Med) created in 2014. A first field mulidisciplinary campaign wasperformed in October 2016. The strategy combined measurements of sea level and currents (mooring of ADCP,Argonaute and tidal gauges), hydrological description of water masses (horizontal and vertical transect with aMinibat equipped with CTD, fluorescence and turbidity sensors) and discrete sampling of nutrients, DOC, POC,pico, nano, microphytoplankton and mesozooplankton. The first results allow a description of water currents andshows a good coupling between tidal cycles (ebb-flood and spring tide neap tide) and the dynamics of planktoniccompartments in the lagoon.

International audience; The Gulf of Lion in northwestern Mediterranean Sea is characterized by a large continental shelf reaching up 40 miles width. Several hydroclimatic processes such as river discharges, strong winds and permanent current induce a complex hydrodynamics resulting in several habitats for plankton communities. The whole French continental shelf of the Gulf of Lion was sampled with a LOPC at two periods (May 2010 and January 2011). Zooplankton community’s characteristics and environmental parameters were investigated to describe biophysical interactions. Statistical tests allowed us to define 3 coherent ecoregions representing different types of habitat: (1) the coastal area, (2) the Rhône plume influence and (3) the continental shelf area. The zooplankton size distribution was investigated within the three areas using the normalized biomass size spectrum (NBSS). The size structure of zooplankton community differs following the areas and their environmental conditions. The coastal area was characterized by the steepest NBSS and highest chla concentrations, the upwelling and the formation of deep water participated to keep the water mixed. The Rhône plume showed the lowest NBSS slopes associated with strong water stratification. These waters were rich in nutrient promoted high chlorophyll a concentrations in the surface water layer and carried on the continental shelf a lot of organic matter. The continental shelf showed the lowest abundances and was hit by the Northern Current depending on the season.Defining habitats provides a firm basis to develop efficient sampling strategies for studying zooplankton dynamics, to validate zooplankton distribution models and to improve coastal management programs.

International audience; Environmental conditions and zooplankton size structure and taxonomic diversity were investigated in the Gulf of Lion in May 2010 and January 2011. The integrated physical and biological measurements provided a 3D view with high spatial resolution of the physical and biological variables and their correlations over the whole gulf. The effects of physical processes such as freshwater input, coastal upwelling, and water column mixing by winds on phytoplankton and zooplankton distributions were analyzed using these data. Several analytic tests were performed in order to define several ecoregions representing different habitats of plankton communities.Three habitats were distinguished based on statistical analysis performed on biological and physical variables: (1) the coastal area characterized by shallow waters, high chl a concentrations, and a steep slope of the normalized biomass size spectrum (NBSS); (2) the area affected by the Rhône with high stratification and flat NBSS slope; and (3) the continental shelf with a deep mixed layer, relatively low particle concentrations, and moderate NBSS slope. The zooplankton diversity was characterized by spatial differences in community composition among the Rhône plume area, the coastal shelf, and shelf break waters. Defining habitat is a relevant approach to designing new zooplankton sampling strategies, validating distribution models and including the zooplankton compartment in trophodynamic studies.

International audience; In meso-tidal lagoons the coral reef barrier can be temporarily covered by water at high tide and emerged at low tide, inducing particular cross-reef dynamics. In order to understand the importance of crossreef fluxes on lagoon dynamics a field survey had been conducted on Ouano Lagoon (New Caledonia). The lagoon water dynamics were analyzed and compared to a numerical model output. The main current was found to be northward during the flood, with inward flows through the ocean passes and through the south passage and outward flows through the north passage. During the ebb, currents are usually reversed. Concerning tidally averaged fluxes, they are mainly inward at the ocean passes and southward in passages. Finally, numerical tests were performed to evaluate the impact of cross-reef fluxes on this circulation. The results of this study are, then, discussed.