A coccoid picocyanobacterium Synechocystis sp. (0.6-2 μm of cell diameter) was found to be dominant during summer period in the experimental wastewater stabilisation pond of Marrakesh. The taxonomy of this isolated strain was confirmed by electron microscope study. The general patterns of ultrastructure and the mode of cell division resemble Chroococcales. The cyanobacterium strain was axenic and cultured on both inorganic Z8 and BG13 media. Mammalian toxicity was confirmed by mice bioassay. The major sympton of poisoning was severe diarrhoea. Histopathological study shows a slight hepatotoxicosis associated with a pronounced change in the intestinal mucosa which shows swelling and destruction of villi epithelium and shedding of enterocytes into the lumen. Although slow, these kinds of poisoning are comparable to those induced by okadiac acid intraperitoneal mice injection (diarrhetic shellfish poisoning “DSP” toxins). By using the enzyme-linked immunosorbent assay (ELISA), the amount ofhepatotoxins “microcystins” was determined. The result shows that Synechocystis can produce a small amount of total microcystine [an average of 15 μg−1 dry weight corresponding to 20 ng(109cell)−1]. These findings lead us to consider Synechocystis as both a potent neurotoxin and hepatotoxin producer. Because of the confirmed cyanobacterium toxicity, an eventual ecological implication should be considered. However, a toxic chronic test experiment on Daphnia was simultaneously carried out. Juvenile D. magna (less than 24 hours old), were fed three concentrations (104, 106, 108 cells / ml) of Synechocystis. A group of organisms fed with Chlorella vulgaris (3. 105 cells/ml) and another group without food, were studied as control treatments. Only animals cultured with 104 cells/ml of cyanobacterium survived at 80% until the end of the test (21 days). Reproduction and normal growth occurred in control treatments fed with Chlorella vulgaris and the group fed with the lowest concentration of Synechocystis. One-way ANOVA statistical analyses show significant differences in Daphnia survival and growth, between treatments with and without Synechocystis and between treatments with and without food. In terms of this study, there is evidence that toxic picocyanobacteria blooms occurring in wastewater stabilization ponds of Marrakesh, could have harmful repercussions on zooplanktonic, bacteria and other algae communities. Consequently, this will constitute a possible hindrance for sewage self-purification process and system treatment performance. In addition, the reuse of such treated wastewater effluent for irrigation will constitute an additional, potent, health hazard for animals and human's.
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Research Article|
November 01 2000
Harmful cyanobacterial toxic blooms in waste stabilisation ponds
B. Oudra;
B. Oudra
1Lab. d'Algologie, Faculté des Sciences-Semlalia-Marrakech, Département de Biologie, Marrakech, Maroc
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M. El Andaloussi;
M. El Andaloussi
2Laboratoire de pathologie Tensift 186, Bd. Mohamed -V-Marrakech, 40 000 Maroc
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S. Franca;
S. Franca
3Lab. Microbiologia Exp., Instituto Nacional de Saude Ricardo Jorge, Av. Padre Cruz 1699 Lisboa, Portugal
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P. Barros;
P. Barros
4Lab. Ecotoxicologia, Departemento de Zoologia e Antropologia, Faculdade de Ciências, Universidade do Porto, 4050 Porto Portugal
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R. Martins;
R. Martins
4Lab. Ecotoxicologia, Departemento de Zoologia e Antropologia, Faculdade de Ciências, Universidade do Porto, 4050 Porto Portugal
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K. Oufdou;
K. Oufdou
5Lab. de Microbiologie, Faculté des Sciences-Semlalia-Marrakech, Département de Biologie, Marrakech Morocco
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B. Sbiyyaa;
B. Sbiyyaa
1Lab. d'Algologie, Faculté des Sciences-Semlalia-Marrakech, Département de Biologie, Marrakech, Maroc
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M. Loudiki;
M. Loudiki
1Lab. d'Algologie, Faculté des Sciences-Semlalia-Marrakech, Département de Biologie, Marrakech, Maroc
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N. Mezrioui;
N. Mezrioui
5Lab. de Microbiologie, Faculté des Sciences-Semlalia-Marrakech, Département de Biologie, Marrakech Morocco
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V. Vasconcelos
V. Vasconcelos
4Lab. Ecotoxicologia, Departemento de Zoologia e Antropologia, Faculdade de Ciências, Universidade do Porto, 4050 Porto Portugal
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Water Sci Technol (2000) 42 (10-11): 179–186.
Citation
B. Oudra, M. El Andaloussi, S. Franca, P. Barros, R. Martins, K. Oufdou, B. Sbiyyaa, M. Loudiki, N. Mezrioui, V. Vasconcelos; Harmful cyanobacterial toxic blooms in waste stabilisation ponds. Water Sci Technol 1 November 2000; 42 (10-11): 179–186. doi: https://doi.org/10.2166/wst.2000.0637
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