Physical-chemical water parameters structuring phytoplankton assemblages in endorheic and alkaline lentic system, Lake Rukwa in the Western Rift Valley, Southern Highlands of Tanzania
Lake Rukwa is the only endorheic and alkaline lentic system in the Western Rift Valley, in the Southern Highlands of Tanzania. Due to anthropogenic impacts threatening this system, there is a need to understand various factors and processes affecting its phytoplankton community. Phytoplankton were studied in three locations, one offshore (zone 1) and two near river Luika (zone 2) and Songwe (zone 3) in the dry and wet seasons (October 2016 and May 2017), respectively. The study examined the composition, distribution and assemblage structure of phytoplankton in relation to physical water parameters. A total of 19 species belonging to four classes were recorded. These included nine species of Bacillariophyceae (Diatoms), four species of Dinoflagellates, three species of Cyanobacteria and three species of Chlorophytes. The sampling zones differed significantly in phytoplankton composition and richness, with richness being high in offshore open waters than in the river mouths. Spearman’s rank correlation between water parameters and phytoplankton community attributes indicated the influence of physical parameters on phytoplankton distribution.