Persistence and growth of faecal culturable bacterial indicators in watercolumn and sediments of Vidy Bay, Lake Geneva, Switzerland
POTE John , HALLER Laurence , KOTTELAT R′egis , SASTRE Vincent , ARPAGAUS Philippe , WILDI Walter
DOI:
Received January 23, 2008,Revised April 29, 2008, Accepted , Available online
Volume 21,2009,Pages 62-69
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The aims of this study was to investigate the persistence and the growth of culturable bacterial indicators (CBI) including total
coliforms (TC) and faecal coliforms represented by Escherichia coli, enterococcus (ENT), and aerobic mesophilic bacteria (AMB) in
the surface sediments and the water column of Vidy Bay (Lake Geneva, City of Lausanne, Switzerland). The study was carried out for
60 d using microcosms containing Sewage Treatment Plant (STP) e uent and nonsterile water without CBI, as well as contaminated
and non-contaminated sediments. The e ects of water temperature and of organic matter associated with sediments on the survival of
CBI in the sediments and the water column were observed. The number of CBI colonies in the contaminated sediments of Vidy Bay and
in the STP e uent was almost identical in the order of 105–107, 104–106, 103–105, and 104–107 CFU/100 g sediment or /100 mL water
for TC, E. coli, ENT, and AMB respectively. A degradation of CBI was observed in the sediments where organic mater content was
low and in the water column at a temperature of 10°C after 5 d of experimentation. In addition, a growth of CBI was observed in the
sediment which is rich in organic matter at 20°C. The results of this study indicate: (1) the higher concentrations of the CBI observed
in di erent points in the water column of Vidy Bay may not be explained only by the recent contribution of the three potential sources
of the Bay contamination including STP and the Chamberonne and Flon Rivers, but also by the persistence, removal from sediment
and multiplication of CBI in the sediment and water column; (2) the sediment of Vidy Bay constitute a reservoir of CBI and can even
support their growth; and (3) the CBI not only survive in sediments, but also can be remobilized and increased in the water column,
therefore, it become a permanent microbiological pollution in Vidy Bay.
