Microcystins in groundwater wells and their accumulation in vegetable plants irrigated with contaminated waters in Saudi Arabia.

The present study describes the presence of toxic cyanobacteria and microcystin (MCYST) concentrations in groundwater wells and tissues of vegetable plants irrigated with well waters in Asir region, southwest of Saudi Arabia. The results revealed the presence of cyanobacteria in all groundwater wells with a dominance of Oscillatoria limentica. This species was found to produce MCYSTs at a concentration of 336 microg g(-1) as determined by enzyme-linked immunosorbent assay (ELISA). HPLC chromatogram for the methanolic extract of this species showed one main peak corresponding to MCYST-YR. MCYSTs were also detected in well waters at concentrations (0.3-1.8 microg L(-1)), exceeding the WHO guideline level (1 microg L(-1)) in some wells. All vegetable plants collected during the present study were found to accumulate MCYSTs in their leaves and roots at concentrations ranged from 0.07 to 1.2 microg g(-1) fresh weight. The study suggests that ground waters and vegetable plants should be continuously monitored for the presence of MCYSTs to protect the public against the exposure to such potent hepatotoxins.