Indicator organisms associated with stormwater suspended particles and estuarine sediment.

This study examined the fate of indicator organisms (fecal coliform, E. coli, and enterococci) from urban stormwater runoff associated with estuarine sediments and stormwater suspended particles. The research found a significant increase of fecal coliform, E. coli, and enterococci in the estuarine sediments at study sites following a given stormwater event. The sedimentation mechanism was linked to an increase in indicator organisms in the estuarine sediments. These indicator organisms attached to stormwater suspended particles, which then settled to the bottom sediment. A higher percentage of attachment onto stormwater suspended particles was observed for E. coli as compared to enterococci and fecal coliform. Among the three organisms, enterococci preferentially attached to the particles with diameters from 10 microm to 30 microm, while fecal coliform and E. coli had a broader distribution. Estuarine sediments were found to prolong survival of indicator organisms for at least seven days prior to reduction to background levels.