Seasonal occurrence and toxicity of Microcystis spp. and Oscillatoria tenuis in the Lebna Dam, Tunisia.
Physicochemical and biological water quality, including the total microcystin concentrations, was investigated for the first time from January to December 2005 in the Lebna Dam, Tunisia. Microcystin levels and characterization of the different microcystin variants present were measured by protein phosphatase (PP2A) inhibition assays and by LC/MS/MS, respectively. Nutrient values were high, with total inorganic nitrogen and phosphorus concentrations ranging from 0.05 to 8.4 mg L(-1) and from 0.03 to 1.37 mg L(-1), respectively. However, the chlorophyll-a concentrations were very low with a peak (5.32 microg L(-1)) on 20 September 2005 at 9 m depth water samples. Microscopic examination of the phytoplankton samples showed the dominance in the autumn of three morphospecies of the genus Microcystis and the species Oscillatoria tenuis. The total (particulate and dissolved) microcystin concentrations at the surface and at 9 m depth water samples ranged between 0.008 and 1.73, and 0.005 and 5.57 microg microcystin (MC)-LR equivalent L(-1), respectively, with a peak on 20 September. The presence of the microcystin synthetase genes (mcyA, -B, and -C) in the lysates of the three morphospecies of the genus Microcystis and the species O. tenuis indicated that these species were responsible for the microcystin production in this system. The analysis of the field cyanobacterial sample extract containing these species by LC/MS/MS revealed the presence of two microcystin variants: microcystin-LR (MC-LR) and microcystin-YR (MC-YR).
El Herry
Soumaya
S
Laboratoire Santé Publique-Environnement, 5, Rue J.B. Clément, Université Paris-Sud 11, UFR de Pharmacie, 92296 Châtenay-Malabry, France.
Fathalli
Afef
A
Rejeb
Amel Jenhani-Ben
AJ
Bouaïcha
Noureddine
N
D001426:Bacterial Proteins / Q000235:genetics; D001427:Bacterial Toxins / Q000032:analysis* / Q000235:genetics; D004784:Environmental Monitoring; D005618:Fresh Water; D052998:Microcystins / Q000032:analysis* / Q000235:genetics; D046931:Microcystis / Q000737:chemistry / Q000235:genetics / Q000302:isolation & purification*; D054300:Oscillatoria / Q000737:chemistry / Q000235:genetics / Q000302:isolation & purification*; D010453:Peptide Synthases / Q000235:genetics; D010839:Phytoplankton / Q000737:chemistry / Q000235:genetics / Q000302:isolation & purification; D054648:Protein Phosphatase 2 / Q000037:antagonists & inhibitors; D012621:Seasons; D014416:Tunisia; D014874:Water Pollutants, Chemical / Q000032:analysis*; D014881:Water Supply
D001426:Bacterial Proteins; D001427:Bacterial Toxins; D052998:Microcystins; D014874:Water Pollutants, Chemical; D054648:Protein Phosphatase 2; D010453:Peptide Synthases