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The measurement of Chlorophyll-a in aquatic systems has usually correlated to harmful algae in water bodies.
Harmful algal blooms (HABs) are as a result of massive proliferation of blue-green algae (Cyanobacteria). Harmful
algal blooms (HABs) pose threats to both the environment as well as human health, and despite this well-known
fact, their monitoring and management are still challenging. Climate change, extreme weather events, and hy-
drological changes are the main drivers and predicted to benefits HABs dynamics in most parts of the world. In
Tanzania, studies of HABs proliferation and their possible correlation with variability in climate and hydrology
still lag behind despite high demand for developing predicting tools and prevention of HABs proliferation. The
present study reports on the retrospective analysis of HABs variation in Mindu Dam located in Morogoro,
Tanzania using remote sensing techniques. In the present study comparison between in situ measurement and
ocean color (OC2) Chlorophyll-a with the surface reflectance's (band and band combinations) of Landsat 7 and
Landsat 8 Operational Land Imager (OLI), was performed. Another approach involved searching for patterns and
trends, and teleconnection between Chlorophyll-a index (best band ration) and the climate and hydrological
variations in the catchment. The findings demonstrated that minimum and maximum temperatures, solar radi-
ation, Chlorophyll-a concentration registered significant increasing trends. Wind speed and directions, water
levels for Mindu Dam showed a significant decreasing trend. On the other hand, rainfall showed no trend. The
patterns suggest that there are link and causality between the HABs variations and meteorological parameters
such as temperatures, solar radiations, and water levels. The study, therefore, contributes to the application of
recent advances in remote sensing and retrospectively analysis of bloom dynamics and search for their link with
climate and hydrological changes. |
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