Cyanobacterial harmful algal blooms (CyanoHABs) have become a worldwide concern for freshwater environments. The development of CyanoHABs has been frequently attributed to eutrophication and climate change. However, the potential roles of microbial community in regulating CyanoHABs are unclear. To investigate the inter-correlations among organisms of different trophic levels with in the microbial loop, weekly water samples were taken from Barberton Reservoir from Apr-Oct 2017. Community structures of bacterioplankton, phytoplankton and zooplankton were examined microscopically or by 16S rRNA gene sequencing. Environmental conditions, such as temperature, pH, conductivity, organic and inorganic nutrient concentrations, were also measured.
Results/Conclusions
Initial results from the microscopic analysis showed dynamic distributions of cyanobacterial and algal taxa based on time and space. A total 34 distinct cyanobacteria taxa mainly within 9 genera, including Aphanocapsa, Chroococcus, Pseudanabaena, Planktolyngbya, Snowella, Dolichospermum, Cylindrospermopsis, Planktothrix, Merismopedia and Anabaena. Phytoplankton community also included algal phyla of Bacillariophyta, Chlorophyta, Chrysophyta and Cryptophyta. Redundancy analysis (RDA) identified temperature, dissolved oxygen (DO), turbidity, total phosphate (TP), Ca, Na concentrations as predictor variables for the cyanobacterial community; these variables together accounted for 66% of the observed cyanobacterial variation. RDA also identified temperature, DO, turbidity, TP, Cu and bicarbonate concentrations as predictor variables for the algal community; the above variables together accounted for 79% of the observed variation. 16S rRNA genes of heterotrophic bacterioplankton are under sequence service. The potential relationship between CyanoHAB species and community structures of heterotrophic bacteria, algae and zooplankton and their interactions with environmental variables will be further examined.