Trophic status of some waterfalls in Sudano - Guinean highland zones (Cameroon)

Trophic status of different waterfalls in the highlands of west and northwest regions of Cameroon was assessed by using diatomic index. Ten waterfalls were sampled, in the rainy season (August, September and October 2008) and dry season (January, February and March 2009). Diatomic index and species dominance were calculated. Diatom samples were collected upstream and downstream of each waterfall by scraping the rocks. Samples were treated with oxygenated water to destroy organic matter. Two to three drops of prepared sample were used to mount permanent slides. Identification was made using a light microscope. Diatoms species were observed at 1000x. The state of poor ecological status and moderate ecological status were the most observed respectively during rainy and dry season. The Balatchi waterfall was the most degraded and was characterized by the absence of aquatic plant called Podostemceae. Diatomic index varying between 2.27 and 3.76. Dominant species were Gomphonema parvulumand Navicula leptostriata (upstream), Cymbella amphicephala and Gomphonema parvulum var. lagermanii (downstream). The less degraded non Podostemaceae waterfall was Metchie and index values varied between 2.99 and 4.23. The most degraded Podostemaceae waterfalls was Anyajua.