Fluorometry as a bacterial source tracking tool in coastal watersheds, Trinidad, California

Bacterial counts have long been used as indicators of water pollution that may affect public health. There are currently four bacterial groups that are used by public health agencies to monitor public beaches and to post health warnings if a state standard is exceeded. By themselves, bacteria are indicators only and do not differentiate the source or location of the pollutant that would allow remediation. Various methods of microbial source tracking have been investigated. Unfortunately, these methods are generally time consuming, labor intensive and expensive. While a variety of methods are under development, there is no generally accepted method proven to be accurate and cost efficient. In this study, a fluorometer was used to measure fluorescence in natural creeks as an indicator of concentrations of optical brighteners found in laundry detergent. Fluorescence can be used as a tool for source tracking failing or malfunctioning onsite wastewater treatment systems. Fluorometry was used in Trinidad area watersheds in conjunction with bacterial sampling and measurement of other water quality data for correlation and comparison. Results showed that optical brighteners, when coupled with other information such as rainfall and turbidity, may be able to accurately predict whether bacterial standards will be exceeded within individual watersheds. Fluorescence of optical brighteners was also shown to be a useful tool for prioritizing watersheds and tributaries for more detailed investigation of bacterial pollution sources.