The presence and abundance of Escherichia coli in beach sediment following a coastal renourishment project

Erosion poses a major threat to oceanic beaches worldwide. To combat this
threat, management agencies often utilize renourishment, which supplements
eroded beaches with offsite sand. This process alters the physical
characteristics of the beach and can subsequently influence the presence
and abundance of microbes. In this study, we examined how a renourishment
project impacted sand grain size and the presence and abundance
of Escherichia coli (E. coli), a common bacteria species. Using
an observational field approach, we compared abundances of E.
coli and sand grain sizes between non-renourished and renourished
sections of Folly Beach, South Carolina, USA in 2014 and 2015. We found
that E. coli was prevalent in every zone of the beach in both years of
sampling. Additionally, we found that in comparison to non-renourished
areas, renourished areas had significantly higher abundances
of E. coli and coarser sand grains in the intertidal zone.
However, these differences were temporary and
only present following the initial renourishment event.
Collectively, our findings raise concerns about how physical changes in
sand grain size, and the introduction of offsite sand to a
beach, could alter bacterial presence and growth. However, more
work is needed to fully understand the timescales these effects operate
upon.

海岸侵蚀对全球范围内的海洋海滩构成重大威胁。为应对这一威胁，管理机构通常采用海滩养滩手段，即通过引入异地砂土补充受侵蚀海滩的砂量。该过程会改变海滩的物理特性，进而影响微生物的存在与丰度。
本研究探究了海滩养滩工程对砂粒粒径以及常见细菌物种大肠杆菌（Escherichia coli, E. coli）的存在与丰度的影响。研究采用野外观测法，于2014年与2015年对比了美国南卡罗来纳州福利海滩（Folly Beach）未养滩区域与养滩区域的大肠杆菌丰度及砂粒粒径。
研究发现，在两年的采样周期内，海滩所有区域均普遍存在大肠杆菌。此外，相较于未养滩区域，养滩区域的潮间带内大肠杆菌丰度与砂粒粒径均显著更高。但这些差异仅为暂时性的，仅在初次养滩工程完成后存在。
综合来看，本研究结果引发了相关担忧：砂粒粒径的物理变化以及向海滩引入异地砂土，可能会改变细菌的存在与生长状态。但仍需开展更多研究，以充分明确这些效应发挥作用的时间尺度。