Ciliates community distribution and saprobic evaluation of an urban hydrosystem: The Biyeme stream Cameroon

Objective: This work aims to evaluate the pollution status of the Biyeme stream using ciliates community, in order to determine the influence of organic pollution on their composition , distribution and their use as water quality indicators. Methodology and results: Thirty-four genera and 49 species were identified using classical methods, among which 14 species are bioindicators of saprobity with 6 (4 or 4-5 mesosaprobic species) having high frequencies at stations Biyeme 1, 2, and 3. The similarity coefficient of Sorensen showed a close resemblance among the ciliates fauna of station Biyeme 1 and 2 (67.69%) with low similarity between stations 1 (36.4%), 2 (44.0%) and 3 (48.8%) with station 4. At stations Biyeme 1, 2, and 3, low values of Shannon and Weaver, Pielou index and dissolved oxygen were observed, while the values of chemical indicators of organic pollution (PO 4 3- COD, BOD 5, N0 3 - ) were high. The combination of physico-chemical parameters and ciliates communities have enabled to evaluate the pollution level of an urban hydrosystem in Cameroon. These results show that the Biyeme stream could be classified as alpha to betamesosaprobic (stations Biyeme 1, 2 and 3) and oligosaprobic (station Biyeme 4) following the importance of anthropic action exerted along the stream. Conclusion and application : Appropriate disposal of organic waste substances is a primordial sanitary measure to maintain the stream in its natural state therefore rendering it available for human use.