Distribution of cyanotoxins in aquatic environments in the Niger Delta
Keywords: Cyanotoxins, cyanobacteria, pathology, cytotoxic, hepatoxin, biomass, nutrients.
AbstractThe presence and types of cyanotoxins in some aquatic environments in the Niger Delta were investigated. Water samples surveyed in the study were surface water of Sombreiro, Nun and New Calabar Rivers. Others were groundwater from Abonnema and Kiama and pond water from Ogboro. Sampling locations of Sombreiro and the New Calabar rivers and the groundwater at Abonnema are all in the Rivers State while other locations were in Bayelsa State all in Nigeria. Cyanotoxins were
extracted using the rotary evaporator procedure. The toxins were intraperitoneally administered to mice. Pathological studies revealed that the extracts contained hepatotoxic peptides (microcystin and
nodularin), cytotoxic alkaloids (cylindrospermopsin) and neurotoxic alkaloids (anatoxin-a, anatoxin-a(s) and saxitoxin). Cyanobacterial examination of the water samples revealed that Anabena was the most
predominant cyanobacterium. Anabena and Microcystis were more predominant in the river and pond water while Anabena and Cylindrospermopsis were more predominant in the ground water. The nutrient load of water bodies influenced biomass (weight) of cyanobacteria. High nutrient load (BOD, COD, nitrates, sulphate, etc) produced high cyanobacterial biomass while low nutrient load produced
correspondingly low cyanobacterial biomass. Nutrient load of river water were significantly higher than groundwater samples. The pond water produced intermediate values of most physicochemical parameters. The percentage hydrocarbon utilizing fungal counts (6.6 - 10.0%), total coliform (240 MPN/100 ml) and fecal coliform (92 to 160 MPN/100 ml) counts were greater than ground water samples (0%, 7.9 to 24 MPN/100 ml and 0.18 to 0.93 MPN/100 ml) respectively. These results suggested that though the conventional bacterial indicators were high, the presence of cyanobacteria and cyanotoxins
in these aquatic systems may also contribute to rendering these drinking water sources unfit for domestic consumption.
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