Periphytic algal community structure and their relation with abiotic parameters

The periphytic algae on natural substrate and the environmental variables were investigated during dry and rainy season in seven rivers of three mining areas at Tortiya in north, Hiré and Lauzoua in the south of Côte d'Ivoire from November 2017 to January 2019. The environmental and periphytic algae data collected were subjected to a multivariate analysis. A non-metric multidimensional scaling of periphytic algae taxa and a principal component analysis of abiotic parameters were used. The relationship between biodiversity with physical and chemical parameters was determined. The Algal Generic Pollution Index was employed to study the water quality of these rivers. Two hundred and twenty five (225) taxa belonging to seven phyla were recorded. Regarding algal groups, green algae (Chlorophyta) were most diverse (69 taxa) followed by Euglenophyta, Bacillariophyta (Diatoms), Cyanobacteria with respectively 60, 54 and 44 taxa. Other groups consisted of at least 2 taxa from Dinophyta, 4 and 3 taxa respectivily of Ocrophyta and Rhodophyta. Manganese mining area (Lauzoua) recorded highest diversity with 216 taxa. It is followed by Tortiya with 202 taxa. Gold mining area (Hiré) recorded lowest diversity with 195 taxa. The stations from gold mining had lowers values of biotic index and biovolume but highest values of Palmer's index than stations from diamond and manganese mining areas. This would therefore be the environment most disturbed by gold mining activity. Manganese and diamond mining at Lauzoua and Tortiya respectively have a lesser effect on the organisation of the periphytic algal community.