Impact of altitude and physicochemical parameters on groundwater quality and biodiversity in Fako Division, South West Region, Cameroon

Abstract

In order to bring more light on the aquatic fauna of groundwater and its emergence, a study on the impact of altitude and physicochemical parameters on the biodiversity in some groundwater points in Fako division, South West Region of Cameroon was investigated. For this study, a total of 33 sampling points was investigated in the towns of Muyuka (average elevation 70 m), Limbe (33 m), Tiko (64), Owe (74 m), Ekona-Mautu (372 m) and Buea (900 m). The physico-chemical parameters of water were analysed using standard methods. Fauna was collected in wells using a phreatobiological net and in the springs by filtration. The physicochemical analyses showed that, the sampling points found at lower altitudes in Fako had high water temperatures (26.68 ± 1.32°C) slightly acidic pH (6.06 ± 0.76 CU), high level of turbidity (16.41 ± 9.80 FTU), high orthophosphate levels (1.18 ± 3.28 mg/L), good dissolved oxygen level (58.77 %), weakly mineralized (385.2 ± 313.7 μS/ cm). The sampling points found at high altitudes had very good oxygenation (67.05 ± 7.09 %), were highly turbid (13.96 ± 6.14 FTU), low temperatures (19.94 ± 14.00 °C), almost neutral pH (6.93 ± 0.52 CU), lowly mineralized (313.74 ± 344.25 μS/cm), higher levels of orthophosphates (8.23 ± 36.96 mg/L). The taxonomic richness was relatively higher at lower altitudes (10265 individuals (inds)) than at high altitudes (10749 inds). A total of 21014 organisms were collected during the study period, belonging to 04 phyla, 12 classes and 58 families and 62 genera/or sub families, dominated by insects (25 %) followed by arachnids (17.7 %) and the fewest families were the classes Hirudinea (0.3 %), Collembola (0.4 %) and Gastropoda (0.5 %). Groundwater was rich and diversified, made up abundantly of epigean families due to the poor management of the water points and their nearness to agricultural areas and also due to the relationship between ground-surface water. A positive correlation was observed between altitude and salinity (p = 0.372) and dissolved oxygen (p = 0.580). while a negative correlation was obtained between altitude and nitrate (p = -0.525), temperature (p = -0.708) and pH (p = -0.266). The stygobites collected belonged to the families Asellidae, Stenasellidae, Darwinulidae and Cirolanidae. No significant difference as observed between stygobites during the seasons, but a significant difference was observed between stygobites and sampling points (Asellidae p = 0.002, Stenasellidae p= 0.006, Cirolanidae p= 0.002 and Darwinulidae p = 0.004) and between stygobites and sampling sites (p ˂ 0.05 for Asellidae, Stenasellidae, Cirolanidae and Darwinulidae).