A new morphospecies of Microcystis sp. forming bloom in the Cheffia dam (Algeria): Seasonal variation of microcystin concentrations in raw water and their removal in a full‐scale treatment plant

Abstract

Toxic cyanobacterial blooms are an increasing problem in Algeria. The production of cyanotoxins (microcystins) and their presence in drinking water represent growing hazards to human health. In this study, seasonal variations in the concentrations of total microcystins and physicochemical parameters (pH, temperature, dissolved oxygen, nitrate, orthophosphate, and chlorophyll-a) were analyzed in the Cheffia dam (Algeria), mainly used to supply drinking water. The removal of cyanobacterial cells and microcystins was also evaluated in full-scale plant associated with the Cheffia reservoir. The levels of microcystins (MCYSTs) in both raw and drinking water were evaluated using the protein phosphatase type 2A (PP2A) inhibition test as MCYST-LR equivalents. Identification of microcystin variants was achieved by LC/MS/MS. During the period of study (March-December 2004), microscopic observation showed the dominance in the autumn months (September-November) of a new morphospecies of Microcystis sp. The MCYST-LR equivalent concentrations in raw water varied between 50.8 and 28,886 ng L(-1). The highest level of toxins was observed in October 2004 and was significantly correlated with the chlorophyll-a. Three variants of microcystins assigned as microcystin-YR (MCYST-YR), microcystin-LR (MCYST-LR), and 6Z-Adda stereoisomer of MCYST-LR were observed in the crude extract of the Microcystis sp. bloom sample. During the bloom period, total elimination of Microcystis sp. and toxins were achieved through a classical treatment plant comprised of coagulation and flocculation, powdered activated carbon at 15 mg L(-1), slow sand filtration and chlorination before storage.

Blooms of Toxic Cyanobacteria in Freshwater in Algeria

“…In the surface waters of the northeast Algerian, several studies have shown that cyanobacterial blooms containing microcyst ins were dominated by the genus Microcystic [4,5,6,7,8,9]. Our investigation in the Cheffia dam has shown that this reservoir has seasonal cyanobacterial blooms that start in summer and last into autumn, however Lake Oubeira has persistent blooms that encompass all seasons.…”

“…Maximum growth rates are attained by most cyanobacteria at temperatures above 25°C. For example, within these two surface waters cyanobacterial blooms have been observed during the warmest months particularly in summer and in early autumn waters [5].…”

“…The LC/MS/MS analysis of cyanobacterial extract prepared from the raw water sample, in which the highest microcyst in concentration is observed, revealed the presence of two microcyst in variants: microcyst in-YR (MCYSTYR) and microcyst in-LR (MCYST-LR), [5]. However, in the lake Oubeirathe high concentration of microcyst ins was detected in autumn 2004 at 29 mg equivalent MC-LR/l [4].…”

Morphological characteristics and phylogenetic analyses of unusual morphospecies of Microcystis novacekii forming bloom in the Cheffia Dam (Algeria)

“…Three species, Microcystis aeruginosa, M. wesenbergii and M. ichthyoblabe are often found in North African freshwater bodies (Oudra et al 2001, Nasri et al 2004, however, this unusual Microcystis morphospecies was reported for the first time by Nasri et al (2007) as the dominant Microcystis sp. forming bloom in the Cheffia Dam (Algeria).…”

Cyanotoxins in Serbia and water treatment procedures for their elimination

“…PAC was successfully used to treat high MC levels in a drinking water treatment process (Nasri, et al, 2007). For effective toxin removal very high doses of PAC are required, and very important parameter is contact time (Chorus, Bartram, 1999;Song, et al, 2005).…”