Spatio-temporal variations in pathogenic bacteria in the surface sediments of the Zuari estuary, Goa, India
Abstract
Estuaries are hotspots of anthropogenic activities. The deposition of pathogenic bacteria in the sediment and their re-suspension into the water column are influ-enced by riverine discharge and tides. The abundance of Escherichia coli O157:H7, Shigella spp., Salmonella spp., total coliforms (TC) and Vibrio spp. (Vibrio chol-erae (VC), Vibrio parahaemolyticus (VP), Vibrio algi-nolyticus (VA)) was assessed along with the total bacterial count (TBC) and total viable count (TVC) in surface sediments along the banks of the Zuari estu-ary, Goa, India. The study was carried out fortnightly for a period of 17 months covering three seasons, i.e. pre-monsoon (PreM), monsoon (MON) and post-monsoon (POM). The spatial and temporal changes in the quality of organic matter were also assessed. The organic matter content was high and rich in carbohy-drates and proteins towards upstream sites. The qual-ity of organic matter was influenced by the seasons. E. coli O157:H7 was detected only during MON towards the upstream stations. A negative correlation between TC and TBC with salinity was evident indicating the influence of land run-off. The Shigella spp. and VA were high towards the mouth of the estuary during PreM. However, during POM, the TVC, TC and VP were abundant towards the upstream and VC were abundant at the mouth of the estuary. Among the Vib-rios, VP and VA were the most frequently occurring bacteria whereas TC and Shigella spp. were dominant among allochthonous pathogens in the sediments irre-spective of space and time. In addition to influence of seasons, the sampling time influenced by tidal condi-tion also played an important role in the population dynamics of pathogenic bacteria in the sediments. Future studies should address the interaction of pathogenic bacteria with suspended particles, their transport and survival in the sediments.
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