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This study presents the analysis of the seismic records of eight underwater explosions triggered by the French Navy Mine Warfare Office in December 2018 in the Bay of Hyères, southeast France. The explosions (charges of 80-680 kg TNT-equivalent) were recorded by 17 temporary stations composed of medium-to-broadband velocimeters and accelerometers and of microelectromechanical systems accelerometers with sampling rates of 250 or 500 samples per second, installed at less than 10 km from the sources. The relatively high sampling rates used in this study allow us to observe, at the same time, seismic, hydroacoustic, and acoustic signals at the shore. This experiment offers a unique opportunity to investigate the impact at the shore, and in the water, of relatively large-charge weight detonations as well as of the amplification effects of the sedimentary cover. We notably see that the hydroacoustic signal is, at the rocky sites, the most energetic wavepacket recorded, and that its observation seems to be conditioned by the bathymetry and the seabed sedimentary cover. We also show that the hydroacoustic phase can be advantageously used to precisely estimate the location and origin time of the explosions. Finally, analyses of the spectrum and site response along the shore and at a bell tower on the Porquerolles Island provide interesting insights on the mitigation of the possible nuisance caused at the shore by the disposal of unexploded historical ordnance. [ABSTRACT FROM AUTHOR]

A traditional taxonomic approach coupled to a biological traits analysis was conducted in order to provide a new insight into macrobenthic communities associated with subtidal sandy environments. Results suggest that the macro-scale distribution of benthic communities is mainly driven by the migration rate of bedforms (sandbank, barchan dune and transversal dune) which changes the sediment grain size and reduces macrobenthic diversity. A classic scheme of species/traits succession was also observed from less to more physically disturbed areas. Finally, the high frequency of migration events homogenized macrobenthic communities between the troughs to the crest of bedforms. As bedforms areas are targeted for the commissioning of offshore windfarms the information provided by the present paper will be particularly useful to implement the environmental impact assessment required for such activities at sea. • Macrobenthic communities vary with the kind of bedforms because of the discrepancy in the intensity of sediment movements; • Massive recruitment by juveniles change the structural diversity in spring but not the macrobenthic ecosystem functioning; • Frequent sediment movements homogenize the macrobenthic communities between the troughs to the crest of bedforms. [ABSTRACT FROM AUTHOR]