Diversity and dynamics of potentially toxic cyanobacteria and their public health significance in lake Koto Barombi, Cameroon
Bloom–forming freshwater cyanobacteria pose human and livestock health problems due to their ability to produce toxins and other bioactive compounds. Some non-toxic cyanobacteria accumulate as buoyant surface dwelling scums and thick mats which affect the benthic fauna by degrading aquatic habitats and giving negative aesthetic values to the water body. They cause taste and odour problems by producing bioactive compounds. The diversity and succession of bloom-forming nostocales in surface waters were determined monthly in Lake Koto Barombi in Cameroon using light microscopy. Physico-chemical analyses of the water were also carried out. Three prominent genera encountered were Cylindrospermopsis, Anabaena, and Aphanizomenon. Microcystis flos-aquae were also found in high numbers. There was a positive correlation between potentially toxic and bloom-forming nostocales and a negative correlation between potentially toxic nostocales and nitrates. Water temperature was an important driving force for their succession. Potentially toxic nostocales and ‘other potentially toxic cyanobacteria’ accounted for 54% of the phytoplankton population in August and 57% in October in some stations but the general concentration of phytoplankton was low. The concentration of nostocales present in January and November 2013 were higher than the WHO guidelines for safe water for recreation. The results of semi-structured questionnaires revealed high prevalence of gastrointestinal disease during periods of algal blooms.
Key words: Cyanobacteria, cyanoHAB, potentially toxic nostocales, dynamics, harmful, algae, public health, scums