Physicochemical characterization, dynamics abundance bacteriological and aquatic fauna of groundwater in the City of Mbalmayo (Cameroon)
In order to understand the potential impact of abiotic factors on the dynamics of bacterial abundance and diversity of the groundwater fauna in Cameroon, a study was carried out in 10 wells in the town of Mbalmayo. In each well, twelve samples were taken at monthly intervals. Analyses were carried out according to standard protocols. The results of the abiotic parameters show significant seasonal variations from one station to another. The principal component analysis (PCA) based on the mean values of the physicochemical and microbiological parameters groups the stations studied into 3 categories according to the chemical facies of the water. The first category includes wells with water of good physicochemical and microbiological quality, characterized in particular by low mineralization, low levels of nitrogen and phosphorus ions indicative of pollution, and concentrations of coliforms and streptococci below the WHO acceptable value for drinking water. From a faunistic point of view, the species richness is relatively high and is dominated by arthropods. It remains generally poorly correlated with water quality, but the species richness of the stygobite fauna, and even more so the abundance of stygobite species, decreases when water quality deteriorates. The Stygobite fauna, here the peracarid crustaceans, appear to be good indicators of groundwater quality.
In order to understand the potential impact of abiotic factors on the dynamics of bacterial abundance and diversity of the groundwater fauna in Cameroon, a study was carried out in 10 wells in the town of Mbalmayo. In each well, twelve samples were taken at monthly intervals. Analyses were carried out according to standard protocols. The results of the abiotic parameters show significant seasonal variations from one station to another. The principal component analysis (PCA) based on the mean values of the physicochemical and microbiological parameters groups the stations studied into 3 categories according to the chemical facies of the water. The first category includes wells with water of good physicochemical and microbiological quality, characterized in particular by low mineralization, low levels of nitrogen and phosphorus ions indicative of pollution, and concentrations of coliforms and streptococci below the WHO acceptable value for drinking water. From a faunistic point of view, the species richness is relatively high and is dominated by arthropods. It remains generally poorly correlated with water quality, but the species richness of the stygobite fauna, and even more so the abundance of stygobite species, decreases when water quality deteriorates. The Stygobite fauna, here the peracarid crustaceans, appear to be good indicators of groundwater quality.
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Fecal Streptococci (UFC/100 mL)
J. Bio. & Env. Sci. 2021
A
B
1.0
0.5
0.0
-0.5
1.0
0.5
0.0
.
DBO5
Ca
NO3-
Mg
Temp.
HCO3-.
PO43-
.
O2 Cond. .
MES
NO2
NH4+
.
pH
.
.
-0.5 0.0 0.5 1.0
PB6
PB3 PB5
Grp. I
PB1
PB7 .
Grp. III
PB8
PB4
.
.
and long dry season (P= 0.045; P= 0.031) and the
short wet season (P= 0.021), respectively.
Faecal coliforms (UFC/100 mL)
A
Small dry season Great rainy season
Great dry season Small rainy season
160
140
120
100
80
60
40
20
0
PB1 PB2 PB3 PB4 PB5 PB6 PB7 PB8 PB9 PB10
Stations
B
Small dry season Great rainy season
Great dry season Small rainy season
250
200
150
100
-0.5
.
Grp. II PB2
. PB10 PB9 .
-0.5 0.0 0.5 1.0
50
0
PB1 PB2 PB3 PB4 PB5 PB6 PB7 PB8 PB9 PB10
Stations
Fig. 7. Projection of the mean values of the
physicochemical parameters of water (A) and stations
(B) on the plane of the first two axes of the principal
component analysis of the wells studied in the city of
Mbalmayo (Grp. Group; Cond: Electric conductivity; O2:
Dissolved oxygen; NO3 - : Nitrate; NO2 - : Nitrite; NH4 + :
Ammoniacal nitrogen; PO4 - : Orthophosphate; HCO3:
Alkalinity; Ca: Calcium hardness; MES: Suspended
Solids; BOD5: Biochemical Oxygen Demand; pH:
Hydrogen potential; Temp: Temperature).
Wells diversity
Bacterial Abundance
Overall, the seasonal mean concentrations of fecal
coliforms and fecal streptococci were variable in the
groundwater of Mbalmayo. Fecal coliform
concentrations ranged from 12 to 148 CFU/100 mL
(Fig. 8.A), and fecal streptococci concentrations
ranged from 3 to 232CFU/100mL (Fig. 8.B).
However, fecal coliform and fecal streptococcal
concentrations remained below 20CFU/100mL at
stations PB1, PB6 and PB7 during all seasons.
Significant differences were obtained during the short
Fig. 8. Variation in mean seasonal abundance of
fecal coliforms (A) and fecal streptococci (B) over the
course of the study.
Faunal inventory
A total of 80 morphotypes belonging to 5 branches
were harvested (Table 1). These were Arthropods
(58.88%), Annelids (40.66%), Nemathelminths
(0.08%), Plathelminths (0.05%) and Molluscs
(0.03%). These taxa are divided into 6 classes, 16
orders, 46 families and more than 71 genera. The
Hexapoda class predominates with 34.89% of the
total abundance (Fig. 9.) with 9 orders, 24 families
and 30 genus; it is followed by the Crustacea class
(23.99%) with 4 orders, 9 families and 22 genus.
Of the 46 families collected, the Naididae class is the
most represented with 7 genus: Dero, Chaetogaster,
Nais, Amplichaeta, Stylaria, Pristina and
Aulophorus. It is followed by the family Cyclopidae
represented by 6 genus: Tropocyclops, Ectocyclops,
Mesocyclops, Afrocyclops, Allocyclops and
Thermocyclops.
98 | Polycarpe et al.
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