Ecophysiological and Anthropogenic Determinants of Phytoplankton Community Structure in Streams Receiving Effluents from the Douala-Bassa Industrial Zone

Abstract

Physicochemical parameters and plankton community structure of streams flowing through the Douala-Bassa Industrial zone were assessed in seven different sites. Anthropogenic activities, water accessibility and the different industries located along the watercourse were considered in selecting the sites. Four sets of water samples were collected from each site and analysed for phytoplankton community structure, nutrient, Chl a and bacteria. Physicochemical parameters were measured insitu using a multi parameter equipment (HANNA 8289). Water temperature ranged from 25.27 - 26.840 C. The pH of the water samples ranged from 6.33 – 7.50 while Turbidity ranging from zero - 1000 NTU. The Electrical Conductivity was 495.33 - 261.67 µS/cm and Dissolved Oxygen was zero - 1.11 ppm. Chlorophyll a concentration ranged from 1.2 – 48.96µg/l. Total Suspended Solids ranged from 0.15 – 0.88. Phosphate and ammonium concentrations ranged from 1.22 – 12.81µM and 4.29 – 136.48 µM respectively nitrates concentration was 1.15 – 217.09 µM. The number of phytoplankton species varied between the sites with a total of 68 species belonging to 11 Divisions. The Bacillariophytas were the most abundant with 27 species. The Chlorophyta followed with 12 species. The most dominant phytoplankton species were Microcystis sp, Pinnularia gibba and Nitzschia palea. Site 7 was the most diverse site with 70 species. High concentrations of nutrients and the presence of eutrophic species such as the Bacillariophytas and Microcystis suggests pollution and a need to monitor activities carried out along the water course with respect to quantity and quality of wastewater discharged into the stream. The ecosystem was in a eutrophic state with variations in the water quality parameters. This could be attributed to possible untreated effluents incorporated in the ecosystem. It can be concluded from the study that phytoplankton dynamics in the Douala-Bassa Industrial Zone are directly related to ecophysiological and anthropogenic drivers.