Physical properties of epilithic river biofilm as a new lead to perform pollution bioassessments in overseas territories

Béatrice Lauga,Pascal-Jean Lopez,Farid Begarin,Alexandre Haouisée,Dominique Monti,Cedric Hubas,Hélène Budzinski,Olivier Gros,Nathalie Tapie,Xavier Lourenço,Philippe Keith,Laurence Romana,Théo Risser,Jean-Louis Mansot,Alexandra Jestin,Estelle Lefrançois

doi:10.1038/s41598-020-73948-7

Abstract

Chlordecone (CLD) levels measured in the rivers of the French West Indies were among the highest values detected worldwide in freshwater ecosystems, and its contamination is recognised as a severe health, environmental, agricultural, economic, and social issue. In these tropical volcanic islands, rivers show strong originalities as simplified food webs, or numerous amphidromous migrating species, making the bioindication of contaminations a difficult issue. The objective of this study was to search for biological responses to CLD pollution in a spatially fixed and long-lasting component of the rivers in the West Indies: the epilithic biofilm. Physical properties were investigated through complementary analyses: friction, viscosity as well as surface adhesion were analyzed and coupled with measures of biofilm carbon content and exopolymeric substance (EPS) production. Our results have pointed out a mesoscale chemical and physical reactivity of the biofilm that can be correlated with CLD contamination. We were able to demonstrate that epilithic biofilm physical properties can effectively be used to infer freshwater environmental quality of French Antilles rivers. The friction coefficient is reactive to contamination and well correlated to carbon content and EPS production. Monitoring biofilm physical properties could offer many advantages to potential users in terms of effectiveness and ease of use, rather than more complex or time-consuming analyses.

Highlights

Chlordecone (CLD) levels measured in the rivers of the French West Indies were among the highest values detected worldwide in freshwater ecosystems, and its contamination is recognised as a severe health, environmental, agricultural, economic, and social issue
All stations downstream from the banana plantations were polluted by CLD, except for the Grande Goyaves River (GRGdo)
Epilithic diatom assemblages in mature biofilm did not reveal CLD contamination

Summary

Introduction

Chlordecone (CLD) levels measured in the rivers of the French West Indies were among the highest values detected worldwide in freshwater ecosystems, and its contamination is recognised as a severe health, environmental, agricultural, economic, and social issue. In these tropical volcanic islands, rivers show strong originalities as simplified food webs, or numerous amphidromous migrating species, making the bioindication of contaminations a difficult issue. Chlordecone (CLD, Kepone®, Curlone®)[11], the main pollutant of concern, was formerly used in banana tree plantations and remains strongly persistent This molecule, banned from use in the 1990s, continues to be present in aquatic ecosystems and contaminates fish and crustaceans consumed by local populations with health-endangering consequences[12]. One of the most important aspects of the relationship between bacteria and subsequent colonisers occurs through the production of EPS that plays a protective key role for b acteria[19,20], and in the attachment of colonies to the s ubstrate[21,22,23,24] with compounds that can either be activators or inhibitors of subsequent microalgal fixation[25,26]

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