Decay Rate of Escherichia coli in a Mountainous Tropical Headwater Wetland

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....

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Published in:Water (Basel) Vol. 13; no. 15; p. 2068
Main Authors: Nakhle, Paty, Boithias, Laurie, Pando-Bahuon, Anne, Thammahacksa, Chanthamousone, Gallion, Nicolas, Sounyafong, Phabvilay, Silvera, Norbert, Latsachack, Keooudone, Soulileuth, Bounsamay, Rochelle-Newall, Emma J., Marcangeli, Yoan, Pierret, Alain, Ribolzi, Olivier
Format: Journal Article
Language:English
Published: Basel MDPI AG 01.08.2021
MDPI
Subjects:
Bacteria
Developing countries
E coli
Ecosystems
Environmental Sciences
Escherichia coli
Feces
Flow velocity
Hypotheses
Laos
LDCs
Metabolism
mountains
Pathogens
Public health
Radiation
Seasons
sediment deposition
Sediments
solar radiation
streams
Surface water
Vegetation
water pollution
water purification
Water quality
watersheds
Wetlands
East Asia
Laos
ISSN:2073-4441, 2073-4441
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Summary: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.
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ISSN:2073-4441
2073-4441
DOI:10.3390/w13152068