Mika Kathryn B, Chavarria Karina A, Imamura Greg, Tang Chay, Torres Robert, Jay Jennifer A
Department of Civil and Environmental Engineering, University of California Los Angeles, Los Angeles, CA 90095.
Water Air Soil Pollut. 2017 Apr;228. doi: 10.1007/s11270-017-3291-y. Epub 2017 Mar 6.
This study investigated causes of persistent fecal indicator bacteria (FIB) in beach sand under the pier in Santa Monica, CA. FIB levels were up to 1,000 times higher in sand underneath the pier than that collected from adjacent to the pier, with the highest concentrations under the pier in spring and fall. (EC) and enterococci (ENT) under the pier were significantly positively correlated with moisture (ρ = 0.61, p < 0.001, n = 59; ρ = 0.43, p < 0.001, n = 59, respectively), and ENT levels measured by qPCR (qENT) were much higher than those measured by membrane filtration (cENT). Microcosm experiments tested the ability of EC, qENT, cENT, and general (GenBac) to persist under in-situ moisture conditions (10% and 0.1%). Decay rates of qENT, cENT, and GenBac were not significantly different from zero at either moisture level, while decay rates for EC were relatively rapid during the microcosm at 10% moisture (k = 0.7 days). Gull/pelican marker was detected at eight of 12 sites and no human-associated markers (TaqHF183 and HumM2) were detected at any site during a one-day site survey. Results from this study indicate that the high levels of FIB observed likely stem from environmental sources combined with high persistence of FIB under the pier.
本研究调查了加利福尼亚州圣莫尼卡码头下方沙滩中持续性粪便指示菌（FIB）的成因。码头下方沙滩中的FIB水平比从码头附近采集的样本高出多达1000倍，春季和秋季码头下方的浓度最高。码头下方的大肠杆菌（EC）和肠球菌（ENT）与湿度显著正相关（相关系数分别为ρ = 0.61，p < 0.001，n = 59；ρ = 0.43，p < 0.001，n = 59），并且通过定量聚合酶链反应（qPCR）测量的ENT水平（qENT）远高于通过膜过滤法测量的水平（cENT）。微观实验测试了EC、qENT、cENT和总细菌（GenBac）在原位湿度条件（10%和0.1%）下的持续生存能力。在两种湿度水平下，qENT、cENT和GenBac的衰减率与零无显著差异，而在微观实验中，当湿度为10%时，EC的衰减率相对较快（k = 0.7天）。在为期一天的现场调查中，在12个地点中的8个检测到海鸥/鹈鹕标志物，在任何地点均未检测到与人类相关的标志物（TaqHF183和HumM2）。本研究结果表明，观察到的高FIB水平可能源于环境来源以及码头下方FIB的高持久性。
