California Water Science Center

Sources of Microbial Contamination at Public Beaches, Santa Barbara

Streams and ocean beaches in Santa Barbara, California, have concentrations of fecal indicator bacteria that exceed public health standards for recreational water. The City of Santa Barbara has been collecting fecal indicator bacteria data from streams and near shore ocean water weekly since June 2001. Concentrations of fecal indicator bacteria in urbanized reaches of Mission Creek, Arroyo Burro, and other urban streams, and in near shore ocean water at recreational beaches can exceed public health standards for recreational water. The sources of the fecal indicator bacteria in streams and near shore ocean water are not known in the Santa Barbara area. Possible sources of fecal bacteria contamination to Arroyo Burro and Mission Creek include direct contamination from animals and transient human populations residing in the area, contamination from leaking sewer lines, or from leaking household connections to sewer lines. Contamination may enter the streams directly or be transmitted short distances through shallow ground water before discharging to the stream. Similar sources also may contaminate recreational beaches and fecal bacteria contributions from resident bird populations also may be large source of bacteria along the oceanfront. Fecal bacteria contamination in near shore ocean water may be associated with tidal extremes that allow increased flux of contaminated ground water from beach sediments.

The purpose of this study is to evaluate the sources of fecal contamination to streams and ocean beaches in Santa Barbara, California. The scope of the study includes: (1) an analysis of existing fecal bacteria data; (2) hydrologic analysis of surface-water/ground-water interactions along urban streams, primarily Mission Creek; (3) hydrologic analysis of ground-water discharge along ocean beaches; and (4) genetic and molecular analysis of bacterial populations in water samples and fecal indicator bacteria cultured from fecal source material, urban streams, and ocean beaches. Because of the association of fecal bacteria with organic carbon, the scope of the study also includes characterization of the composition of dissolved organic carbon in shallow ground water, streamflow, and near-shore ocean water. Specific organic compounds will be measured as tracers in municipal wastewater.

The focus of this study is on analysis of existing hydrologic, chemical, and microbiological data; collection of surface-water and shallow ground-water hydrologic, chemical, and microbiological data; and characterization of dissolved organic carbon composition. Existing fecal bacteria data from streams are linked to continuous-record streamflow data for calculation of bacterial loads and statistical analysis of seasonal trends. Hydrologic data collected for this study define the interaction between streams and the local ground water and evaluate the potential for fecal bacteria to be transported through ground water to surface water. Radium isotopic data with traditional hydrologic data evaluate ground-water discharge along the beach. Genetic and molecular microbiological data are tracers of the sources of bacterial contamination. These data are supplemented with optical property data on the composition of dissolved organic carbon associated with different sources of fecal bacteria and chemical tracers of municipal wastewater to help identify the source of fecal bacteria contamination.

Project Chief:John Izbicki
Phone: 619-225-6100

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Page Last Modified: Thursday, 29-Dec-2016 23:06:29 EST