Lower Cypress Creek Pilot Project: Concurrent Assessment of E. coli Bacteria and Optical Brighteners

A thirteen-week Texas Stream Team study in lower Cypress Creek is currently underway to sample for the presence of optical brighteners and E. coli bacteria. Optical brighteners are additives found in laundry detergents and paper products including toilet paper and have been used as an indicator of potential sewage contamination in surface water. Optical brighteners adsorb to cotton and fluoresce under ultraviolet light when present. E. coli is a species of fecal coliform bacteria used as indicators of possible sewage contamination. They are commonly found in human and animal feces and are an indicator of presence of pathogens that can be a health risk if consumed. Concurrent sampling of optical brighteners and E. coli bacteria can assist in pollution screening and source identification of fecal contamination.

Six sites in the lower reach of Cypress Creek are being monitored for E. coli bacteria and optical brighteners twice a week. One weekly sample is collected on Sunday and designed to target weekend activities, while the other sample is collected on Thursday and targets weekday activities. The sites are also located upstream and downstream of the Ranch Road 12 bridge near the Wimberley Town Square to target the bat colony that migrates to the bridge annually as a potential source of bacteria. The methods employed include Texas Stream Team’s Probe Core kit and E. coli bacteria monitoring protocols. The optical brightener pilot study is a modified method previously used by Dr. Kelly Albus of the University of North Texas.

The Cypress Creek watershed has experienced rapid growth and development and historical water quality monitoring has resulted in increasing E. coli bacteria concentrations. Some sources of fecal contamination in surface waters include discharge from wastewater treatment plants, malfunctioning on-site septic systems, domestic and wild animal feces, and stormwater runoff. Results of this study will help identify potential sources of fecal contamination along the lower reach of Cypress Creek. The study will conclude in late September, so stay tuned for the findings!