Sources of Fecal Indicator Bacteria in Urban Streams and Ocean Beaches, Santa Barbara, California

Fecal indicator bacteria (FIB) indicative of fecal contamination in urban streams and recreational ocean beaches in Santa Barbara, California often exceed recreational water-quality standards. During low flow, FIB and human-specific Bacteroides concentrations in urban streams were associated with point discharges. FIB concentrations varied three-fold during diurnal sampling as a result of small variations in these discharges. During stormflow, FIB concentrations were higher than during low flow and varied over three orders of magnitude. FIB in stormflow were associated with non-point sources, and concentrations decreased as fecal contamination was washed from the urban watershed. Sources of fecal contamination to near-shore ocean water included surface discharges * Corresponding author: Phone: +619-225-6131, FAX +619225-6101, e-mail: from urban streams, and fecal material from birds associated with sand, and to a lesser degree kelp, along the beachfront. FIB concentrations varied over three orders of magnitude during daily tidal cycles. Concentrations were higher during ebb tides and decreased to less than the detection limit during low tide when seepmeter and Rn data show groundwater discharge to the ocean was greatest. Groundwater discharge and leakage from a sewer line buried in the sand were not large sources of FIB contamination to near-shore waters. Interpretations of the sources of FIB from Principal Component Analysis (PCA) of genetic (Terminal-Restriction Fragment Length Polymorphism, T-RFLP, data), molecular (PhosphoLipid Fatty Acid, PLFA, data), and chemical data (such as caffeine, fecal sterols, and detergent metabolites) were similar and consistent with interpretations supported by physical measures of water flow. The most robust PCA results were from PLFA data which explained 97 percent of the total variance within the first and second principal components. In contrast PCA analysis of chemical and T-RFLP data, explained 34 and 32 percent of the total variance, respectively. However, T-RFLP and chemical tracers captured relations not apparent in PLFA data, and certain compounds, especially the fecal sterols, lent themselves to specific interpretations of the origin of fecal contamination.