Influence of Some Abiotic Factors on the Diatom Densities in the Mezam River (Bamenda, North-West Cameroon)

Abstract

Wetlands of the city of Bamenda are characterized by intense agricultural activities. The resulting consequences are aquatic pollution. The management of these wetlands requires the study of the animal and plant communities found there. Diatoms are known to be good markers of environmental change. The aim of the study was to determine the influence of some abiotic parameters on the diatom densities of the Mezam river. The study was conducted from January to December 2022. Some physicochemical parameters were measured in situ. Water samples were collected and transported to the laboratory for the measurement of nitrates, total phosphorus, carbon dioxide and biological oxygen demand. The diatoms were sampled and analyzed in the laboratory. Factorial axis 2 (0.47%) of correspondence factor analysis opposed the positive variables (conductivity, total dissolved solids and salinity) to the negative variables (water temperature, pH, nitrates, total phosphorus, oxidability, carbon dioxide and alkalinity). Study sites showed a mineralization gradient going from upstream (Site 1) to downstream (Site 3). Total species richness amounted to 4 classes divided in 18 families, 21 genera and 43 species. The most dominating family was Naviculaceae with 10 species. Multiple component analysis showed, in different study sites, the correlation between chemical parameters and density of different genera. The more the site was polluted, the more the density of Navicula, Tabellaria, Melosira and Coscinodiscus increased. On the contrary, the less the site was polluted, the more the density of Cyclotella, Gomphonema, Cocconeis, Gyrosigma, Synedra increased. These results showed that the distribution of diatoms in the different study sites was influenced by a set of conditions related to physicochemical parameters, but more on their densities.