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Climate variability, anthropogenic activities, and hydrological shifts are fueling the nuisance of harmful algal
blooms in water bodies. Unfortunately, cyanobacterial harmful algal blooms (CyanoHABs) dynamics have not
received much attention in Tanzania. The study aimed to identify and characterize common species of cyano
bacteria and examine their possible change in composition and succession in the Ngerengere catchment,
Morogoro, Tanzania. Water samples from the selected reservoirs were collected quarterly between October 2017
and September 2018 for physico-chemical parameters in situ and in the laboratory. A benchtop FlowCAM was
used for the identification of cyanobacteria and compared with the literature and available online databases.
Principal component analysis (PCA) was used to examine the association between the physico-chemical variables
and meteorological patterns. The study found common CyanoHABs such as Microcystis, Cylindrospermopsis,
Anabaena (Dolichospermum), Lyngbya as well as other species such as diatoms and Euglena which are also
considered nuisance. Virtually, a colonial cyanobacteria species dominated the fishponds, while Mindu Dam was
more of filamentous species. The study suggest that Mindu dam, based on Carlson’s Trophic State Index (TSI),
falls under eutrophic while the fishponds were hypereutrophic. Associated physico-chemical conditions, heavy
rainfall and prolonged dry conditions influenced cyanobacteria bloom dynamics. The hydrological connectivity
between the fishponds and the Mindu Dam poses a threat to public health because a significant population in
Morogoro depends on Mindu Dam for domestic water supply. There is a need for the development of a frame
work for mitigative and adaptive measures in the catchment, especially during pre-and post-occurrence of
blooms. |
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