Motile Aeromonas: which spatial and temporal evolution in an urban effluent and in coastal marine environment?
Bacteriological analyse of surface water in an urban effluent and in coastal marine environment showed a seasonal contamination of this water by motile Aeromonas. Spatial and seasonal changes of Aeromonas abundances were studied, in relation to several environmental factors, in the purified effluent and in seawater. The motile Aeromonas spp. and the fecal coliform distributions in the sewage treatment effluent showed the same seasonal cycles with a maximum occuring in winter (mean: 29·106 UFC/100 ml) and a minimum in summer (mean of 6·106 UFC/100 mL). The abatement of Aeromonas abundances was correlated with a strong irradiation and a low turbidity. In the coastal marine water, there was an inversion of the motile Aeromonas spp. cycle in comparison with that of fecal coliforms, with high levels in hot periods (mean: 56 CFU/100 mL for S3) and low levels in cold periods (mean of 5 CFU/100 mL for S3). Salinity appeared responsible for the destabilisation of the seasonal sequences of Aeromonas and their reduction with non detectable concentrations in water analysed volumes. The presence of these bacteria in the purified effluent, sometimes with concentrations higher than those of the fecal coliforms, poses a problem of health hazard and clearly show that fecal contamination bacteria cannot be predictive for the presence or the absence of Aeromonas and, consequently, cannot be considered as good indicators of pollution.