Journal of Applied Biosciences (J. Appl. Biosci.) [ISSN 1997 - 5902]
Volume 23: 1422 - 1435. Published November 10, 2009.
Spatial and temporal variation of fecal contamination indicators in Grand-Lahou lagoon, Côte d’Ivoire
K.S. KONAN*,**, A. M. KOUASSI**, A.A. ADINGRA**, D. GNAKRI*
*Université d’Abobo-Adjamé 02 BP 801 Abidjan, Côte d’Ivoire ; 2Centre de Recherches Océanologiques, BP V18 Abidjan, Côte d’Ivoire
Corresponding author: konandks@yahoo.fr
ABSTRACT
Objective: To determine the level of bacterial pollution of the surface waters of the Grand Lahou lagoon using the fecal contamination indicators (thermotolerant coliforms, Enterococci and sulphite-reducing anaerobes).
Methodology and results: Thirty six (36) samplings were carried out during three annual cycles (May 2003 to April 2006) in ten (10) stations spread throughout the Grand-Lahou lagoon. Bacterial counts of thermotolerant coliforms, Enterococcus and sulphite reducing anaerobic bacteria were made together with the determination of physical and chemical parameters (temperature, salinity, pH, oxygen, turbidity, water transparency, NO2-, NH4+ and PO43-). Temperature, salinity, pH, turbidity and transparency were characterized by a seasonal rhythm depending on oceanic and continental inputs. Water in the Grand-Lahou lagoon is turbid, and nutrients and hydrogen sulphide concentrations show that the milieu is eutrophic. The mean annual bacteria counts were between 1 and 5 log (CFU/ml) for thermotolerant coliforms, from 0 log to 4 log (CFU/100 ml) for Enterococcus and between 0 and 4 log (CFU/100 ml) forsulphite reducing anaerobic bacteria.
Conclusion and application of findings: In the study area the fecal bacterial loads are more abundant during the rainy season and least during the dry season. The area of the lagoon under continental influence and more subject to anthropogenic inputs and to more important hydrodynamic effects presents higher bacteria density than the area under oceanic influence. Further studies should be undertaken in order to compare these strains with those isolated in hospitals. Thus, it will be possible to determine the actual involvement of the lagoon waters in diarrheal epidemics that periodically appear in the city of Grand-Lahou and villages located on its bank. Meanwhile, some measures should be taken by the City of Grand-Lahou to take steps towards the building of some latrines in the villages and to educate the riverine population in order to minimize the fecal contamination.
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