Fecal Indicator Sources in Small Creeks.

Rural stream catchments in the Mid-Atlantic drain a mixture of fecal indicator organism (FIO) sources including septic treatment, vegetable and cereal farms, wildlife areas, and varied concentrations of animal farming.

Many Mid-Atlantic stream reaches do not meet state agencies’ clean water designation for microbial impacts due to inputs from untraceable sources.

A creek that flows through varied land uses and riparian zones was sampled weekly for 65 weeks in 2015-16 to discover dynamics of microbial water quality based on FIO colony counts.

FIO concentrations across varied land uses during base flow periods were compared. The range of E. coli concentrations was between 1.5 and 2 orders of magnitude. The mean relative difference of FIO colony counts was a stable, narrow range of relative deviation from the means of base flow E. coli counts at each of five monitoring sites.

One site that was geographically central in the measured stream reach showed low deviation , close to the geometric mean for the all E. coli counts

This indicates a temporally stable downstream increase in fecal indicator abundance. This relationship may be tied to increasingly favorable in-stream habitat (if base flow populations remain stable over years) or a downstream increase of FIO inputs.