Abstract
Invasive rats are known threaten vulnerable native bird species in Western Indian Ocean islands. Brodifacoum (BDF), used to eradicate them, disrupts the vitamin K cycle, causing hemorrhages in target mammals. This study aimed to assess environmental contamination and BDF transfer to non-target marine species after a rodent eradication initiative in a pristine environment. Rodent eradication was conducted in a small mangrove forest (17 ha) on Europa Island using broadcasted BDF pellets. This work focused on intertidal and coastal food web contamination, involving two sampling sites and three field campaigns. Sampling encompassed water and non-target organisms (4 invertebrates and 2 fishes).No BDF traces were detected in water samples. However, BDF was detected in 100% of biological samples from the exposed site, 4 months after spreading, with concentrations ranging from <1 to 165.2 ng.g-1 dw. Primary exposure was observed for crabs and hermit crabs by camera traps, and likely linked to the highest concentrations quantified in the hepatopancreas of crabs (Scylla serrata). BDF levels in fishes, Gerres longirostris and Lutjanus argentimaculatus, suggested secondary exposure via the marine food chain and/or the environment. Sessile oysters from the control site exhibited BDF traces, sing of potential contamination via tidal currents. Temporal trends were studied by comparing concentrations found in the two post-campaigns. This comprehensive investigation of punctual contamination in a pristine environment would support modeling of pollutant transfer mechanisms.