Julien GOURAND

Over the past decade, the mobilization of tools based on biological effect measurement in support of environmental quality monitoring has largely demonstrated its interest. Indeed, these tools allow a better consideration of the toxic effects of contaminants on organisms and thus specify the causal links between pressure and impacts. Among the biological responses of interest, modulation of feeding behavior often emerges as one of the first responses observed in aquatic invertebrates exposed to chemical or environmental stressors (Macedo-Sousa et al., 2007). Thus, feeding behavior, due to its sensitive and discriminating nature, represents a particularly relevant tool, both for the evaluation of the quality of environmental matrices (Maltby, 1999), and for the evaluation of the toxicity of chemical compounds (Xuereb et al., 2009). In-situ monitoring of the feeding rate in caged gammarids, in particular, is recognized as a reliable tool for monitoring inland water bodies (Coulaud et al., 2011; Mathiron et al., 2025). On the other hand, to date, there is no equivalent approach for the evaluation of the quality of coastal water bodies, despite the strong anthropogenic pressures weighting on these environments. In this context, this thesis aims to develop a methodology for the quantification of the feeding rate, adapted to the common prawn Palaemon serratus, for the evaluation of the quality of marine water bodies. Thus, this work was structured around the following objectives:

i) Definition of the composition of a feeding substrate suitable for the quantification of the feeding rate of the common prawn.

ii) Studying the inter-individual variability of the basal response under the influence of abiotic factors (i.e., temperature and salinity).

iii) Evaluate the sensitivity of the bioassay during exposure to an insecticide known to alter the feeding behavior.

iv) Testing the applicability in-situ as part of an enclosing bioassay on constrasted stations stations along the Normand coast (see : BIOSURVEILLANCE and EVALL projects).