Use of multivariate analysis to identify phytoplankton bioindicators of stream water quality in the mono-modal equatorial agro-ecological zone of Cameroon

Abstract

Abstract The aquatic ecosystem is compromised by many contaminants that may lead to reduced ecosystem functions and severe consequences on human health. This study aimed at determining suitable bioindicators of water quality among the phytoplankton community for the biomonitoring of freshwater streams in the mono-modal agroecological zone of Cameroon. For this purpose, water physicochemical and hydrological parameters, together with the phytoplankton abundance and diversity were measured from June 2016 to May 2017 along the Benoe stream (South-West Region). The Shannon–Wiener diversity and Pielou’s evenness indices indicated a clean to mildly polluted stream with a diverse phytoplankton community which consisted of 84 species belonging to 51 families. The community was dominated by the Bacillariophyta (64%), followed by Chlorophyta (13%) and Cyanophyta (10%). Multivariate statistical analysis revealed that the total dissolved solids (TDS), electrical conductivity (EC), stream water velocity and discharge were the most important stream characteristics affecting the abundance of the dominant phytoplankton genera. These analyses unveiled seasonal variations in the stream characteristics as well as spatial community distribution along an urban - small-scale farming – large-scale farming gradient and their influence on the phytoplankton relative abundances. Consequently, phytoplankton indicator species were identified with increased abundance of Synedra ulna being indicative of low TDS and EC, while Gyrosigma baltium dominance was connected with increased TDS and EC. High Pleurosira laevis abundance was associated with the urban zone while high Diatoma sp. and Oscillatoria sp. abundances were related to large-scale farming zone of the stream. These phytoplankton species have good potential for use as bioindicators for monitoring water quality in the Benoe stream and other streams in the monomodal agroecological zone of Cameroon.