Impact of Rainfall and Some Water Abiotic Factors on the Abundance Dynamic of Vibrio and Aeromonas Adhered to Copepods Surface in Some Coastal Streams and Rivers in Cameroon (Central Africa)
Résumé
A study was carried out on the tributaries draining into Rivers in the coastal region of Cameroon
(Central Africa). It aimed at assessing the abundance of Vibrio and Aeromonas cells adhered to copepods with
respect to some considered abiotic factors. It has been noted that the tributaries are substantially concentrated
in organic matter and these fluctuated, depending on the amount of rainfall received by the rivers throughout
the period of the study. The abundance of Aeromonas cells adhered to copepod fraction ranged from 38
CFU.Ind-1 to 8×103 CFU.Ind-1
. That of Vibrio cells ranged from 75×102 CFU.Ind-1 to 42.4×103 CFU.Ind-1
. Of
the total bacteria identified in this study, V. cholerae relatively dominated the bacterial community (38%),
followed by A. sobria (30%), A. hydrophila (27%) and other species namely V. alginoticus, V.
parahaemolyticus, V. mimicus, V. vulnificus, A. cavia, Aeromonas sp. represented 5%. From the Principal
Component Analysis (PCA) assessing the influence of abiotic factors in the abundance changes of bacteria
attached to copepods, it appears that the first cloud of points includes the rainfall, pH, Aeromonas and Vibrio
while the second cloud on the left pole groups namely water temperature, salinity, carbon dioxide and
oxydability. Vibrio and Aeromonas cells preferentially colonized copious quantities of copepods during the
period of excess flood when the concentration of nutrients in the water column regressed. A complex network of
abiotic factors thus acts in synergy to influence the attachment of Aeromonas and Vibrio cells to copepods. To
prevent the risk of cholera outbreaks and non-cholera infections, ecological monitoring should be further
enhanced during the period of excess rainfall.
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