Sources of Low Level Human Fecal Markers in Recreational Waters of Two Santa Barbara, CA Beaches: Roles of WWTP Outfalls and Swimmers
•Dogs and seabirds were sources of fecal indicator bacteria in surf zone water.•HF183 human markers were low but chronic in surf zone water over three study years.•Watersheds did not supply HF183 to surf zone water.•Higher levels of HF183 occurred in afternoons than in mornings.•WWTPs possibly contr...
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| Published in: | Water research (Oxford) Vol. 202; p. 117378 |
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| Main Authors: | , , , , , , , |
| Format: | Journal Article |
| Language: | English |
| Published: |
Elsevier Ltd
01-09-2021
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| Subjects: | |
| Online Access: | Get full text |
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| Summary: | •Dogs and seabirds were sources of fecal indicator bacteria in surf zone water.•HF183 human markers were low but chronic in surf zone water over three study years.•Watersheds did not supply HF183 to surf zone water.•Higher levels of HF183 occurred in afternoons than in mornings.•WWTPs possibly contributed, but swimmers correlated to HF183 markers directly.
Worldwide, fecal indicator bacteria (FIB) evidence coastal water contamination for which sources are unknown. Here, for two FIB-impacted Santa Barbara recreational beaches, hypothesized fecal sources were investigated over three dry seasons (summers) using nearly 2000 field samples of water (ocean, creek, groundwater), sand, sediments, effluent and fecal sources. In years 1 and 2, gull and dog feces were identified as the probable main FIB sources to surf zone waters, yet HF183 human fecal markers were consistently detected. Determining HF183 sources was therefore prioritized, via year 3 sub-studies. In lower watersheds, human and dog wastes were mobilized by small storms into creeks, but no storm drain outfalls or creeks discharged into surf zones. Beach area bathrooms, sewers, and a septic system were not sources: dye tracing discounted hydraulic connections, and shallow groundwater was uncontaminated. Sediments from coastal creeks and downstream scour ponds, nearshore marine sediments, and sands from inter- and supratidal zones contained neither HF183 nor pathogens. Two nearby wastewater treatment plant (WWTP) outfalls discharged HF183 into plumes that were either deep or distant with uncertain onshore transport. Regardless, local sources were evidenced, as surf zone HF183 detection rates mostly exceeded those offshore and nearshore (around boat anchorages). The presence of swimmers was associated with surf zone HF183, as swimmer counts (on weekdays, holidays, weekends, and during races) significantly correlated (p<0.05, n = 196) to HF183 detections. Besides comprehensively assessing all possible fecal sources, this study provides new explanations of chronic low-level human markers in recreational beach surf zones, suggesting likely lowest achievable HF183 thresholds.
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| Bibliography: | ObjectType-Article-1 SourceType-Scholarly Journals-1 ObjectType-Feature-2 content type line 23 |
| ISSN: | 0043-1354 1879-2448 |
| DOI: | 10.1016/j.watres.2021.117378 |