Effet de la fertilisation organique à base de fientes de poules sur la diversité et l’abondance de la flore algale dans un étang piscicole à Kinshasa, République Démocratique du Congo

Algae (phytoplankton) are considered an essential food source for fish, especially in aquaculture. This study examines the effect of using chicken manure as an organic fertilizer on the diversity and density of algae in a fish pond in the city of Kinshasa, Democratic Republic of the Congo. The experiment spanned eight months in a 10 m² pond stocked with Oreochromis niloticus fish, which was fertilized weekly with 25 kg of chicken manure (for a total of 24 bags). Water samples collected each month facilitated the microscopic identification of algae and the calculation of diversity indices. The results show that, prior to fertilization, only a single species of algae was present : Oscillatoria sp. During the fertilization process, four species of algae were identified, followed by seven species (Cymbella sp, Pinularia sp, Scenedesmus sp, Spirogyra sp, Oscillatoria sp, Pleurocapsa sp, and Pseudopolyedriopsis sp) after fertilization. The identified algal flora was classified into four phyla and seven distinct genera. The Shannon index ranged from 0 before fertilization to 1.386 during fertilization, then reached 1.946 afterward, indicating high diversity during and after organic fertilization. Furthermore, the Berger-Parker index decreased, indicating a more diverse and less dominated community. The species Oscillatoria sp remained the most frequently identified. These results clearly demonstrate that enriching the water with nutrients using chicken manure stimulates phytoplankton growth and promotes biodiversity in the pond. It therefore appears that this technique is one of the solutions for boosting the primary production needed to feed the fish and increasing the profitability of fish farming.