Assessment of the ecological status of the rivers of the city of Douala from Macrophyte communities: Case of Kondi and Tongo Bassa

Observations made in rivers of Douala showed that aquatic ecosystems receive little attention in terms of their environmental monitoring. The aim of this study was to assess the ecological status of Kondi and Tongo Bassa rivers at from their communities of macrophytes. Specifically, it was question to evaluate the physicochemestry environment of these rivers as well as the diversity of the macrophyte species. Then, the physicochemestry parameters were measured (about 50cm deep) between 08am and 11am. Concerning characterization of macrophytes, 03 transects of 400m length each were materialized. Then, 201 quadrats of 1m2 were realised to make a specific and quantitative inventory. The listed species were assigned an Abundance-dominance coefficient. Then, the diversity and resemblance indices, the abundance index, the average recovery, the Shannon index and the Piélou equitability index, the Sorensen similarity coefficient, the Shannon index and the Piélou equitability index were analysed. According to results, ammonia, orthophosphates and nitrates particularly influence the distribution of macrophytes in the Kondi and the Tongo Bassa rivers. These parameters show that the water include high organic matter loads indicating organic pollution. In addition, the plant communities encountered in these rivers were relatively rich, diversify and distributed according to a decreasing gradation of mineralization and trophy. Also, the Piélou index in these rivers was generally below 0.55 reflecting poorly diversified waters. Finally, the structure of the macrophyte reveals that it was generally dominated by a few species, including the Poaceae particulary Pennisetum purpureum species, characteristic of eutrophic environments.