DOCTORAT H/F CONTEPAV Impact environnemental des épaves de navires dans la Manche: caractérisation des relargages de contaminants et de leurs variations spatio-temporelles

The PhD will take place within the UMR 6566 CReAAH-LARA which is a highly multidisciplinary laboratory (archaeology, archaeosciences, history) and the Institut des Substances et Organismes de la Mer (ISOMER) which analyzes the diversity, the functioning and the disturbances of marine ecosystems, both hosted by Nantes University. The processing and analysis of the samples will be done mainly at ISOMER, but also in partnership with IFREMER and the ECOCHEM-ODNature laboratory of the Royal Belgian Institute of Natural Sciences.

Title : Environmental impact of shipwrecks in the English Channel: characterization of contaminant releases and their spatio-temporal variations
Key words : maritime heritage, shipwrecks, contaminants, PAHs, pollution.
This research aims to assess the environmental impact of a series of wrecks from the Second World War located in the Bay of Seine and off Dieppe. This is a new study in France, which has one of the largest concentrations of wrecks from major conflicts in the world. It will combine an approach that meets the expectations of the assessment of Descriptor 8 "Contaminants in the environment" of the Marine Strategy Framework Directive 2008/56/EC (MSFD), with innovative research to analyze the spatio-temporal effects of shipwrecks on the chemical and biological components of marine ecosystems. The study area will be the Channel-North Sea sub-region (SRM MMN), which appears to be the most contaminated of the 4 maritime sub-regions. In the sediments of the coastal water body, metals are the most problematic contaminants, mainly nickel, lead, zinc, chromium and mercury. Contamination with polycyclic aromatic hydrocarbons (PAHs) is mostly localized between Dieppe and the eastern part of the Seine Bay. In bivalves, no exceedance of the health threshold was observed for metals. Exceedances of PAHs, fluoranthene and benzo(a)pyrene, were found in the Seine Bay. This project, which brings together environmental sciences and humanities, will find its place in Axis 2 of the GdR OMER, Characterization and diagnosis of marine systems. It should provide new knowledge on additional anthropic pressures on ecosystems, and will also lead to further reflection on the management of this heritage. If until now the dialogue on the protection and enhancement of historic wrecks has focused on cultural and heritage enhancement (UNESCO Convention, 2001), it will be addressed from an ecological and environmental perspective. The data obtained will lead to a new dialogue between the public authorities and the actors of the maritime world on the management and protection of this heritage; a dialogue that will feed the working group of the GdR OMER "Oceans & heritage processes". To meet the challenge of this project, it will characterize the release of contaminants and their spatio-temporal variations using a combination of different monitoring methods (direct analysis by sampling, passive sensors) and matrices (sediment, water, biota). The objectives are: 1) To highlight the diffusion of contaminants by sampling at different distances from the wreck; 2) To determine the historical pollution related to wrecks by sampling sediments at depth; 3) To measure the short-term release of contaminants by sampling biota and installing passive samplers; 4) To identify wrecks as a source of historical, diffuse, or point source pollution; 5) To compare the measured values with the measurements of the ROCCH stations in order to correlate the observed threshold exceedances and the problematic substances. The results will also be compared with the OSPAR guidelines to determine the good ecological status of nearby ecosystems; 6) Relate the historical data of the wrecks, in relation to the shipwreck and post-sinking events (scraping, counter-mining) and the levels of contaminants measured, and demonstrate the influence of the state of conservation of the ship on the pollution levels.