Assessment of cylindrospermopsin toxin in an arid Saudi lake containing dense cyanobacterial bloom.

This study reports the presence of the cyanobacterial toxin cylindrospermopisn (CYN) and its producer Cylindrospermopsis raciborskii for the first time in Saudi freshwater sources. C. raciborskii was found in Gazan Dam Lake water with two morphotypes (coiled and straight). The appearance and cell density of this species was significantly positively related to high temperature and high ammonium concentrations, and negatively with nitrate and phosphate concentrations in the lake. Intracellular concentrations of CYN (4-173 µg L(-1)) were associated with C. raciborskii rather than other cyanobacteria with a maximal value obtained in June 2011, coinciding with the highest bloom of this species (19 × 10(7) trichome L(-1)). CYN cell quotas (0.6-14.6 pg cell(-1)) varied significantly along the study period and correlated with most environmental factors. The results of ELISA and liquid chromatography-mass spectrometry proved that the CYN production by strains of this species was isolated from this lake during the present study, with an amount reaching 568 µg g(-1). Extracellular CYN was also detected in cell-free lake water at concentrations 0.03-23.3 µg L(-1), exceeding the drinking water guideline value of 1 µg L(-1) during the Apr-Jul period. As this lake is an important source for drinking and irrigation waters, CYN monitoring should be included in the environmental and health risk assessment plans of these water bodies.

Microcystin production in epiphytic cyanobacteria on submerged macrophytes.

Cyanotoxins have been largely studied in planktonic and benthic cyanobacteria, but microcystin (MCYST) production in epiphytic cyanobacteria has not been reported yet. The present study reports for the first time the MCYST production in epiphytic cyanobacteria on submerged macrophytes. During this study, four common submerged macrophytes in eutrophic pond in Saudi Arabia were surveyed for the presence of toxic epiphytic cyanobacteria. The results showed that chlorophyll-a and total biovolume of epiphytic cyanobacteria differed significantly among submerged plants with highest values obtained in Stratiotes aloides and lowest in Elodea canadensis. Epiphytic materials collected from Ceratophyllum demersum and S. aloides had higher species diversities than materials collected from E. canadensis and Myriophyllum verticillatum. The cyanobacteria, Merismopedia tenuissima and Leptolyngbya boryana were recorded with a high abundance in epiphytic materials collected from all submerged macrohpytes. Based on Enzyme-linked immunosorbent assay (ELISA), these two species were found to produce MCYSTs (MCYSTs) with concentrations of 1438 and 630 microg g(-1) dry weight, respectively. HPLC analysis of the methanolic extracts of the two species showed that M. tenuissima extract contained MCYST-RR and -LR/demethyl LR plus 3 minor unidentified MCYSTs, while L. boryana extract contained MCYST-YR, -LR/demethyl LR, and 2 minor unidentified MCYSTs. This study suggests that epiphytic species should be considered during monitoring of toxic cyanobacteria in water sources.

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.

Microcystin-producing blooms of Anabaenopsis arnoldi in a potable mountain lake in Saudi Arabia.

This study reports for the first time the presence of Anabaenopsis arnoldi blooms in Saudi freshwaters. This species has been investigated with high cell densities (3.8 x 10(3)-264 x 10(3) cells mL(-1)) during June-November 2007 in Tendaha Lake, one of the major freshwater sources in Saudi Arabia. High temperature and conductivity, and a high concentration of phosphate, and low nitrate concentrations may have contributed to the formation of these blooms. The blooms were found to produce microcystins (MCYSTs) at concentrations up to 364 microg g(-1) dry weight as detected by an enzyme-linked immunosorbent assay. MCYSTs were also detected in the raw and treated water of the lake at concentrations (1.6-8.3 and 0.33-1.6 microg L(-1), respectively) exceeding the World Health Organization guideline level of 1 microg L(-1) for these toxins. HPLC analysis revealed that the extracts of A. arnoldi blooms contained MCYST-RR, -YR and two unidentified MCYSTs, but a pure culture of A. arnoldi isolated from Tendaha Lake during the present study produced MCYST-RR and -YR only. This is the first study to report MCYST production by A. arnoldi. Therefore, this cyanobacterium should be taken into consideration during monitoring of toxic cyanobacterial blooms in drinking and recreational water sources in the world, particularly arid and semi-arid countries including Saudi Arabia.

Cyanobacteria and their toxins in treated-water storage reservoirs in Abha city, Saudi Arabia.

Occurrence of toxic cyanobacteria in drinking and recreational waters poses human health at risk as they can release potent toxins into the water. In the present study, open and covered treated-water storage reservoirs as well as their relevant tap waters in Abha city, Saudi Arabia, were surveyed for the presence of cyanobacteria and their toxins. The results revealed the contamination of most open reservoir and tap waters by algae and cyanobacteria, with an abundance of toxigenic species of cyanobacteria. Depending on the results of the Limulus amebocyte lysate (LAL) assay and enzyme linked immunosorbent assay (ELISA), endotoxins and microcystins (MCYSTs) were found in most open reservoir and tap waters at concentrations up to 32 EU ml(-1) and 0.3 microg ml(-1), respectively. The extracts of axenic cultures of most cyanobacterial species isolated from these reservoirs showed activity to LAL assay, with large endotoxin amounts obtained in Calothrix parietina (490 EU g(-1)) and Phormidium tenue (210 EU g(-1)). Based on ELISA and HPLC analysis for these extracts, only C. parietina can produce MCYSTs (202 microg g(-1)) with a profile consisting of MCYST-RR and -LR. This study suggests that open treated-water storage reservoirs should be covered to prevent the presence of cyanobacteria and their toxins in such drinking and recreational waters.