The occurrence of cyanobacteria blooms in freshwater ecosystems and their link with hydro-meteorological and environmental variations in Tanzania

Abstract

Cyanobacteria (blue-green algae) are photosynthetic bacteria that under favorable environmental conditions produce secondary metabolites (cyanotoxins) which are harmful to the environment, including humans. The mass proliferation of harmful cyanobacteria is termed CyanoHABs. CyanoHABs can adapt to different climatic fluctuations, therefore, understanding their dynamics in freshwater systems is crucial. Variation in climatic and hydrological processes, changing land use and economic growth all influence the occurrence and distribution of CyanoHABs. There have been inadequate CyanoHAB studies at local scales, therefore their occurrence and dynamics cannot be generalized. This study reviews and synthesizes cases of CysnoHAB occurrence, magnitude, and timing and how these are linked with climatic and hydrological variations in the United Republic of Tanzania. In this study, a scoping review approach was adopted. Research articles, reports, and databases were consulted. The most common species of toxin-producing cyanobacteria were identified in different water bodies in Tanzania, as well as the record of mass fatality of birds (Lesser Flamingo) in Lake Manyara, which in almost all cases occurred during dry years. While previous studies on CyanoHAB dynamics and their links to climate, hydrological, and environmental changes have not been undertaken in Tanzania, there are studies in Lake Victoria and Tanganyika. Therefore, there should be an immediate response from water users, managers, researchers, and water authorities to address and actively engage in monitoring and managing the risks associated with CyanoHABs in Tanzania.

Understanding the Effects of Changing Weather: A Case of Flash Flood in Morogoro on January 11, 2018

“…is was also reported by Kimambo et al [34] on the standardized precipitation and evapotranspiration index (SPEI) with alteration of positive (positive 2 for wet conditions) and negative (negative 2 for severe drought condition). A comparison for the extreme (per year and for the month of January) rainfall for the period (1971-2012) is demonstrated in Figure 10.…”

“…Heisler et al [37] also highlight the relationship between nutrients transfer in rivers as a result heavy rainfall (for example, an observation made by the author just a month after a rainy season in Figure 11(c)) algal blooms tend to proliferate. Algal blooms are also common in the study area and they have been associated with variations of both climate and hydrological changes [34]. Normally in risk assessment, three elements are involved, i.e., vulnerability, exposure, and threats.…”

Cyanobacterial Blooms in Lake Varese: Analysis and Characterization over Ten Years of Observations

“…Furthermore, the biovolume measurements require less time for the microscopic analysis than cell identification and enumeration providing data with lower uncertainties. The parameters selected in this work such as the water temperature, DO, nutrient availability, and the water transparency measured as SD, play a key role in the occurrence of cyanobacterial blooms [19,20,22,23,26,27,[52][53][54]. In addition to these factors known to be good predictors for cyanobacteria abundance, we tried to evaluate whether the air temperature could be considered as parameter.…”

The Diversity of Cyanobacterial Toxins on Structural Characterization, Distribution and Identification: A Systematic Review

“…South Africa and Nigeria have also been threatened by cyanobacterial toxins. MCs were reported in Ethiopia [158], Algeria [159], Tanzania [160], Kenya [161], South Africa [162], Tunisia [163], Zimbabwe [164], Morocco [165], Uganda [166], Egypt [167], Nigeria [168] and Ghana [169]. CYNs were found in Egypt [170] and Nigeria [171].…”