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Article

Decay Rate of Escherichia coli in a Mountainous Tropical Headwater Wetland

1
Géosciences Environnement Toulouse (GET), Université de Toulouse, CNRS, IRD, UPS, 31400 Toulouse, France
2
c/o Department of Agricultural Land Management (DALaM), Institut de Recherche Pour le Développement (IRD), IEES-Paris UMR 242, Sorbonne Université, Vientiane 01000, Laos
3
Institute of Ecology and Environmental Sciences of Paris (iEES-Paris), Sorbonne Université, University Paris Est Creteil, IRD, CNRS, INRA, 75005 Paris, France
*
Author to whom correspondence should be addressed.
Academic Editor: Stefano Amalfitano
Water 2021, 13(15), 2068; https://doi.org/10.3390/w13152068
Received: 18 May 2021 / Revised: 23 July 2021 / Accepted: 24 July 2021 / Published: 29 July 2021
(This article belongs to the Section Water Quality and Contamination)
Surface water contamination by pathogen bacteria remains a threat to public health in the rural areas of developing countries. Fecal indicator bacteria (FIB) like Escherichia coli (E. coli) are widely used to assess water contamination, but their behavior in tropical ecosystems is poorly documented. Our study focused on headwater wetlands which are likely to play a key role in stream water purification of fecal pollutants. Our main objectives were to: (i) evaluate decay rates (k) of the total, particle-attached and free-living E. coli; (ii) quantify the relative importance of solar radiation exposition and suspended particles deposition on k; and (iii) investigate E. coli survival in the deposited sediment. We installed and monitored 12 mesocosms, 4500 mL each, across the main headwater wetland of the Houay Pano catchment, northern Lao People’s Democratic Republic (Lao PDR), for 8 days. The four treatments with triplicates were: sediment deposition-light (DL); sediment deposition-dark (DD); sediment resuspension-light (RL); and sediment resuspension-dark (RD). Particle-attached bacteria predominated in all mesocosms (97 ± 6%). Decay rates ranged from 1.43 ± 0.15 to 1.17 ± 0.13 day−1 for DL and DD treatments, and from 0.50 ± 0.15 to −0.14 ± 0.37 day−1 for RL and RD treatments. Deposition processes accounted for an average of 92% of E. coli stock reduction, while solar radiation accounted for around 2% over the experiment duration. The sampling of E. coli by temporary resuspension of the deposited sediment showed k values close to zero, suggesting potential survival or even growth of bacteria in the sediment. The present findings may help parameterizing hydrological and water quality models in a tropical context. View Full-Text
Keywords: fecal indicator bacteria; Lao PDR; Mekong basin; water purification; survival rates; mesocosms; solar radiation; sedimentation; particle deposition; particle resuspension fecal indicator bacteria; Lao PDR; Mekong basin; water purification; survival rates; mesocosms; solar radiation; sedimentation; particle deposition; particle resuspension
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MDPI and ACS Style

Nakhle, P.; Boithias, L.; Pando-Bahuon, A.; Thammahacksa, C.; Gallion, N.; Sounyafong, P.; Silvera, N.; Latsachack, K.; Soulileuth, B.; Rochelle-Newall, E.J.; Marcangeli, Y.; Pierret, A.; Ribolzi, O. Decay Rate of Escherichia coli in a Mountainous Tropical Headwater Wetland. Water 2021, 13, 2068. https://doi.org/10.3390/w13152068

AMA Style

Nakhle P, Boithias L, Pando-Bahuon A, Thammahacksa C, Gallion N, Sounyafong P, Silvera N, Latsachack K, Soulileuth B, Rochelle-Newall EJ, Marcangeli Y, Pierret A, Ribolzi O. Decay Rate of Escherichia coli in a Mountainous Tropical Headwater Wetland. Water. 2021; 13(15):2068. https://doi.org/10.3390/w13152068

Chicago/Turabian Style

Nakhle, Paty, Laurie Boithias, Anne Pando-Bahuon, Chanthamousone Thammahacksa, Nicolas Gallion, Phabvilay Sounyafong, Norbert Silvera, Keooudone Latsachack, Bounsamay Soulileuth, Emma J. Rochelle-Newall, Yoan Marcangeli, Alain Pierret, and Olivier Ribolzi. 2021. "Decay Rate of Escherichia coli in a Mountainous Tropical Headwater Wetland" Water 13, no. 15: 2068. https://doi.org/10.3390/w13152068

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