Phytoplankton Dynamics of Mokolo and Mopa Ponds in Bertoua City (East-Cameroon)

Abstract

This study aims to improve the understanding of algal community's dynamics in response to different environmental factors in two dam ponds (Mokolo and Mopa) in the city of Bertoua (East-Cameroon). Physicochemical and biological analyzes were carried out monthly by direct sampling at the surface and using Van Dorn bottle at 1 m depth. The organisms were collected using transparent glass vials of about 500 ml and fixed with 2.5 ml of a lugol solution, then analyzed using the Utermôhl method. Physicochemical analyzes show low transparency (<75 cm) of the ponds despite their shallow depth (≤150 cm), high levels of dissolved oxygen (>60%), BOD 5 (>30 mg/L) and chlorophyll "a" (>30 µg/L). These data made it possible to categorize the Mokolo and Mopa ponds as hypereutrophic with nitrogen as the limiting factor for eutrophication. Biological data show quite diversified ponds with 138 species identified in Mokolo Pond and strongly dominated by Diatoms with 2951 ind. representing 46% of the total abundance. In Mopa Pond, 147 species were identified, mainly represented by Chlorophyceae with 3629 ind. representing 52% of the total abundance. Azpeitia africana (Mokolo) and Eresmophaera gigas (Mopa) were the most represented taxa during the study. This study will have deduced that the structure and dynamics of algal communities are under the control of different factors or processes that interact simultaneously, namely ascending factors or bottom-up corresponding to nutrient resources and sunlight and descending factors or top-down that are exerted by grazing and active physiological substances produced by other algae that are known to influence phytoplankton.

Spatio-Temporal Distribution of Phytoplankton and Water Quality of Some Rivers of Haute Sanaga Department (Central Africa)

“…Aboim et al (2019) also claim that the low water volume associated with high nutrient levels inputs, from urban or agricultural effluents, result in a great biological diversity and abundance of phytoplankton in some waterbodies. The correlations observed between some taxa and nutrients support the idea that the latter are responsible for phytoplankton densities (Kegne Tenkeu et al 2020).…”

“…The overall taxonomic richness of phytoplankton (63 taxa) observed in all 12 stations is low compared to that (300 taxa) obtained by Kengne Tenkeu et al (2020) in ponds (Eastern region of Cameroon). This huge discrepancy is likely a consequence of the different types of sampling environments: rivers in Mbandjock and Nkoteng versus lakes in the Easter region of Cameroon.…”

“…The concentration of oxygen in LDS (65.5 ± 11.64 %) and SDS (68 ± 0.70 %) could reflect biological processes such as photosynthesis (Brönmark & Hansson, 2000). In this respect, Kengne Tenkeu et al (2020) argue that dissolved oxygen levels can affect algal blooms through phytoplankton photosynthesis.…”

Trophic status and phytoplankton diversity of two dam ponds in Eastern Cameroon (Central Africa)

“…Al-Aubadiet al (2019) point out that rainfall favors the erosion of mineral and organic particles from the catchment area, which are transported by runoff water to the ponds where they cause the mix of water, increasing the suspended solids content of the environment and consequently its transparency and turbidity. The electrical conductivity and Total Dissolved Solids have been elevated in ponds, reflecting high anthropogenic activity and high organic pollution (Kengne Tenkeu et al, 2020). The high average of electrical conductivity values in ponds would be justified by leaching from agricultural land and the input of domestic wastewater into the ponds.…”

“…These anthropogenic pressures lead from year to year to an increase in the emission of pollutants of all kinds, most of which reach the aquatic ecosystems that constitute the major biospher receptacle (Colas et al, 2014). Eutrophication has become a growing phenomenon in most developing countries due to the excess of nutrients (nitrogen and phosphorus) released into the environment that are transported to hydrosystems without prior treatment (Kengne Tenkeu et al, 2020). This eutrophication phenomenon undermines the ecological integrity of ponds making fish farming difficult, or even impossible, yet it covers huge animal protein needs by reducing the massive outflow of foreign exchange (Agadjihouèdé et al, 2011).…”