Effect of sediment particle size and temperature on fecal bacteria mortality rates and the fecal coliform/fecal streptococci ratio

Fecal coliform (FC) and fecal streptococci (FS) mortality rates were measured at three different temperatures an in three feces-amended sediments with different particle size in a laboratory study. In controlled conditions, using physiological saline to reduce cell death by osmotic shock, FC mortality rates exceeded FS mortality rates. These rates declined as sediment particle-size shrank and as temperature decreased. There was no interaction between these two factors in determining fecal bacteria persistence. The apparent half-lives of FC exceeded those of FS, even though mortality rates were higher. The FC/FS ratio was found to be influenced by temperature, the presence of sediment, and sediment particle size.