The implementation of the biological effects monitoring in fish and bivalves is required under descriptor 8 (chemical contaminants) of the Marine Strategy Framework Directive (MSFD) monitoring program (2008/56 / EC). At the French level, this directive was transposed by decrees concerning the Good Environmental Status (GEnS) and the Monitoring Program (MP) in 2012 and 2015, respectively.

Monitoring effects in gastropods (common Ospar Imposex indicator) is already in course and assured by the ROCCH at Ifremer, however it concerns only one type of contamination, TBT, and a single organism, the dogwhelk (Nucella lapillus). In the English Channel, the monitoring of pollutant biological effects in fish and molluscs is based exclusively on the SeliSeine oceanographic campaign, in the Bay of Seine. This campaign is actually the only way to acquire data on the biological effects of chemical contamination in marine organisms (fish and bivalves) for both the MSFD and CEMP Ospar monitoring programs. Two other seaboards are concerned by this monitoring: the western Mediterranean coast (Fos-Marseille) and the north of Biscay Bay (estuaries of the Loire and the Vilaine). Thus, a "Seli" campaign is proposed every year since 2015 (Selimed-1 on NO Europe from September 6 to 14, 2016, Seliloire-1 on NO Thalia from August 16 to 23, 2017).

As part of the Seliseine campaign, the main objective will be to sample:

• Common sole, Solea solea, a species of scientific and economic interest, already studied in several programs at Ifremer. There are many research and monitoring programs - past or current - estimating stocks, studying life traits, migration, trophic network trophic, and contamination level.
• Flounder (Platichthys flesus) which is one of the sentinel species recommended by Ospar and in Southern Europe for the biomonitoring of the marine environment (Cuevas et al., 2015).

Adult sole is a species fished in areas further offshore than the more estuarine flounder. Selection of these two species will provide information on the health of adult flatfish along the estuary - bay continuum.

In Seliseine, the aim is to assess the relationship between the level of chemical contamination and the health of soles and flounders from Seine Bay by the measurement of a panel of biological markers of exposure and effects, as well as by the analysis of several organic and metallic contaminants. The indicators that will be calculated on the basis of these markers will allow, via an integrated chemistry-biology approach, to participate in the evaluation of the distance to good ecological status.