Retrospective analysis of Chlorophyll-a and its correlation with climate and hydrological variations in Mindu Dam, Morogoro, Tanzania

Offoro N Kimambo; Hector Chikoore; Jabulani R Gumbo; Titus A M Msagati

doi:10.1016/j.heliyon.2019.e02834

Retrospective analysis of Chlorophyll-a and its correlation with climate and hydrological variations in Mindu Dam, Morogoro, Tanzania

Heliyon. 2019 Nov 14;5(11):e02834. doi: 10.1016/j.heliyon.2019.e02834. eCollection 2019 Nov.

Authors

Offoro N Kimambo^{1

2}, Hector Chikoore³, Jabulani R Gumbo⁴, Titus A M Msagati⁵

Affiliations

¹ Department of Geography & Environmental Studies, Solomon Mahlangu College of Science & Education, Sokoine University of Agriculture, Morogoro, Tanzania.
² Department of Ecology & Resource Management, School of Environmental Sciences, University of Venda, Thohoyandou, South Africa.
³ Department of Geography & Geo-Information Sciences, School of Environmental Sciences, University of Venda, South Africa.
⁴ Department of Hydrology & Water Resources, School of Environmental Sciences, University of Venda, South Africa.
⁵ College of Science, Engineering & Technology, University of South Africa, South Africa.

Abstract

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 hydrological 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 radiation, 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.

Keywords: Atmospheric science; Chlorophyll-a; Climate engine tool; Climatology; Cyanobacteria; Earth sciences; Ecology; Environmental science; Harmful algal blooms; Hydrology; Remote sensing.