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.

A study aimed to determine the level of water pollution and phytoplankton diversity of two dam ponds (Ngaikada and Kpokolota) in Bertoua city was conducted from March 2016 to April 2017 using a monthly sampling frequency. Water samples were collected at surface directly using a 1L polyethylene vials and at 1.5 m depth using a 6L Van Dorn bottle. Physicochemicals analyzes were carried out according to the standard methods of APHA and Rodier, while the harvesting of phytoplankton organisms was done by direct sampling and analyzed by the Utermôhl method. The results of the physicochemicals analyzes reveal no significant difference (