*Result*: Relationship between REE signatures and biological traits of marine benthic fauna in a temperate mud patch: Application of multivariate analyses.

*The increasing contamination of coastal environments by Rare Earth Elements (REEs) necessitates a thorough understanding of the dynamics of these elements in ecosystems under anthropogenic pressure. Sedimentary bodies influenced by large rivers, such as the West Gironde Mud Patch (WGMP), are among these pressured ecosystems. REE analyses in seven benthic marine species and ambient media (i.e., dissolved fraction of bottom water, sediments) of this mud patch has provided REE signatures (i.e., REE concentrations and shape of normalized patterns) using one concentration descriptor (i.e., ∑REE) and six descriptors of pattern shapes (i.e., La/La*; Ce/Ce*; Eu/Eu*; Pr/Lu; Pr/Gd; Gd/Lu). A robust procedure of multivariate analyses (i.e., PERMDISP, PERMANOVAs, PCO) was applied to study the controlling factors of REE signatures in these species. Assessment of the within- and between-species variability suggests that differences in REE concentrations and shapes of normalized patterns between species were related to the ambient media's geochemical processes and the fauna's ecological and biological traits. REE concentrations in the fauna document trophic dilution, reflected by elevated concentrations in pure microphages and reduced concentrations in pure carnivores. The predominance of calcareous skeletons in bivalves and brittle stars results in a dilution effect on REE concentrations at the whole-organism level. The chitinous exoskeleton of crabs and shrimps is subject to adsorption processes for REEs present in the sediment.
(Copyright © 2025 The Authors. Published by Elsevier Ltd.. All rights reserved.)*

*Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.*