Microbiological Quality of a Prohibited Bathing Coastal Ecosystem: Aytré Bay (Charente-Maritime, France) - Archive ouverte HAL Accéder directement au contenu
Poster De Conférence Année : 2021

Microbiological Quality of a Prohibited Bathing Coastal Ecosystem: Aytré Bay (Charente-Maritime, France)

Résumé

Background: Aytré Bay is one of the largest beaches and popular coastal ecosystems in Charente Maritime(France). It is a sandy-muddy cove with a gentle slope and a length of 1.8 km. Its foreshore covers an area of 2.5 km2, which can be uncovered at low tide up to 1.5 km. This beach has been characterized by persistent fecal contamination for more than 20 years with very marked peaks of Escherichia coli and intestinal enterococci (Fecal Indicators Bacteria: FIBs). The studies conducted on the two bathing sites of this bay and the development projects around the beach have not improved the microbiological quality. The sources of this regular fecal contamination remain undetermined. Following the European directive (2006/7/EC), this beach is prohibited for bathing since the summer of 2018. Objectives: To understand the determinism of this fecal contamination, it is essential to characterize the temporal dynamics of fecal bacteria in this microbial ecosystem. Method: To study the microbial ecology of this beach, two to eight water and sediment samples were taken each month over one year at the two bathing sites. FIBs abundance was quantified following the standard microplate methods recommended by the European directive. Chemo-physical and climatic parameters such as salinity, pH, dissolved oxygen, total organic carbon, chlorophyll, dissolved nutrients, water temperature, and rainfall were measured to analyze the effect of these environmental factors on FIBs abundance. Moreover, an analysis of total and active bacteria diversity by the metabarcoding of the 16S rRNA genes and their transcripts was performed to evaluate the richness of this environment and to analyze FIBs and bacterial communities’ relationship. Results: The analysis of microbiological water quality in both bathing areas showed that intestinal enterococci abundance was more regularly exceeded the regulatory thresholds than E. coli abundance. Both FIBs abundances were lower in sediment than in water samples. Metabarcoding approaches showed that bacterial diversity was not the same for the two sampling sites and specific bacterial populations present the same patterns as intestinal enterococci. Environmental parameters such as water temperature, salinity, rainfall were correlated with FIBs and some active bacterial communities. Conclusion: The abundance of FIBs, diversity of total and active bacteria, and environmental parameters were analyzed to determine the seasonal dynamics of FIBs that will allow finding hypotheses on fecal contamination origin of this bathing area.
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Dates et versions

hal-03612545 , version 1 (17-03-2022)

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  • HAL Id : hal-03612545 , version 1

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Méry Ndione, Pascaline Ory, Hélène Montanié, Tony Agion, Michael Treilles, et al.. Microbiological Quality of a Prohibited Bathing Coastal Ecosystem: Aytré Bay (Charente-Maritime, France). World Microbe Forum, American Society for Microbiology (ASM), Federation of European Microbiological Societies (FEMS), Online Worldwide., Jun 2021, Cambridge, United Kingdom. ⟨hal-03612545⟩

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