According to his international commitments for the Oslo and Paris convention (OSPAR) and for the European framework directives (waterframework directive -WFD- and marine strategy framework directive -MSFD-), France implements a water quality monitoring and sends the results to the international databases. The ROCCH network (French chemical monitoring network) as a part of the French water quality monitoring network, collects the chemical contamination data in the coastal mollusks flesh and in the marine sediment. Sediment monitoring is carried out during annual cruises in different façade each year, over the duration of a 6 years WFD or MSFD cycle.

ROCCH monitoring in sediments enables assessing chemical quality of the near-continental shelf, and its temporal evolution with comparison with the results obtained in previous cruises. The results of the 2020 - 2022 cruise will be compared with those of the RNOSED 99, ROCCHSED 08 and ROCCHSED14 cruises in the Bay of Biscay. Part of the samples collected will be kept in the ROCCH bank for eventual further scientific work (Ifremer or other research teams).

During 2022 cruise, two other operations will also be undertaken : one aimed at the knowledge of regional chemical backgrounds (realization of long cores to identify contamination levels of the pre-industrial period and to evaluate temporal trends up to present time) and the second for studying metallic contamination around Capbreton canyon.

For chemical quality evaluation, the 1^st superficial centimeter of the sediment core will be sampled for chemical analyses. The list of studied chemical contaminants in a sample depends on the monitoring program (OSPAR or WFD ¿ MSFD) and includes normalizing parameters like grain size or total organic carbon concentration. The complete list includes up to 45 substances or families of substances, with metals, organic components like hydrocarbons, chlorinated, brominated and fluorinated components, pesticides and biocides (TBT). Data will be stored in the marine environmental database Quadrige and available via SURVAL tool (Ifremer website). Use of stored samples can be asked to the ROCCH coordination.

For pre-industrial chemical contamination determination, specific corer has to be used for long cores (several tens of centimeters long), at sites with low energy deposition, stable sedimentation and well-preserved stratification.