Understanding the potential impacts of agricultural contaminant flows on aquatic fauna in constructed wetlands (CWs) – SYNBIOTOX

Alexandre Martin defended his doctoral thesis on 25/3/2025

Some of the agricultural contaminants (pesticides, nitrogen) spread on cultivated soils reach the hydrosphere through agricultural drainage (1) with proven consequences on aquatic ecosystems and their functions. Constructed wetlands are designed to break down nitrates and certain pesticides through natural purification features. Nevertheless, they constitute potential reservoirs of contaminants likely to impact the wild species they shelter by acting as ecological traps.

Summary

Agrochemicals, including pesticides and nitrates, can be transferred to the hydrosphere, with adverse effects on organisms and aquatic ecosystems. Constructed wetlands (CWs) can be implemented in the agricultural landscape to reduce the transfer of agrochemicals to the hydrosphere through their natural purification properties. However, although their primary aim is to reduce pollution of the aquatic environment, paradoxically, CWs can act as interceptors and concentrators of pesticides and nitrates, with the negative repercussions that these contaminants can have on aquatic organisms, making CWs potential ecological traps for aquatic fauna.

By studying a pilot site located in Seine-et-Marne (France) and subject to water quality monitoring since 2012, the present thesis aims to assess the potential for an agricultural CW to act as an ecological trap for amphibians and aquatic invertebrates. Through a series of multi-level, in situ ecological and ecotoxicological monitoring studies, the results obtained tend to show that the risk induced by agrochemical fluxes in the CW is notable for amphibians, and that negative sub-cellular, behavioral, and ecological effects are exerted on aquatic fauna. This work provides a better understanding of the potential impacts of agricultural contaminant fluxes on aquatic fauna in CWs.