Data from: Residual eDNA detection sensitivity assessed by quantitative real-time PCR in a river ecosystem

Several studies have demonstrated that environmental DNA (eDNA) can be used to detect the presence of aquatic species, days to weeks after the target species has been removed. However, most studies used eDNA analysis in lentic systems (ponds or lakes), or in controlled laboratory experiments. While eDNA degrades rapidly in all aquatic systems, it also undergoes dilution effects and physical destruction in flowing systems, complicating detection in rivers. However, some eDNA (i.e. residual eDNA) can be retained in aquatic systems, even those subject to high flow regimes. Our goal was to determine residual eDNA detection sensitivity using quantitative real-time polymerase chain reaction (qRT-PCR), in a flowing, uncontrolled river after the eDNA source was removed from the system; we repeated the experiment over two years. Residual eDNA had the strongest signal strength at the original source site and was detectable there up to 11.5 hours after eDNA source removal. Residual eDNA signal strength decreased as sampling distance downstream from the eDNA source site increased, and was no longer detectable at the source site 48 hours after the eDNA source water was exhausted in both experiments. This experiment shows that residual eDNA sampled in surface water can be mapped quantitatively using qRT-PCR, which allows a more accurate spatial identification of the target species location in lotic systems, and relative residual eDNA signal strength may allow the determination of the timing of the presence of target species.多项研究已证实，环境DNA（environmental DNA, eDNA）可在目标物种被移除后的数天至数周内，用于检测水生生物的存在。然而，绝大多数相关研究均针对静水环境系统（池塘或湖泊）开展，或是在受控实验室条件下进行eDNA分析。尽管eDNA在所有水生系统中均会快速降解，但在流水系统中还会受到稀释效应与物理破坏的双重影响，这进一步加大了河流环境中eDNA的检测难度。不过，仍有部分eDNA（即残留eDNA）可在水生系统中留存，即便在高流量的河流系统中亦是如此。本研究的目标在于：在未受人为干预的流水河流中，当eDNA来源被移除出系统后，采用定量实时聚合酶链式反应（quantitative real-time polymerase chain reaction, qRT-PCR）检测残留eDNA的灵敏度；我们连续两年重复开展了该实验。实验结果显示：残留eDNA在原始来源位点的信号强度最高，且可在eDNA来源移除后的11.5小时内于该位点被检测到。随着采样点与eDNA来源位点的下游距离增加，残留eDNA的信号强度逐渐减弱；在两次实验中，当eDNA来源水体耗尽后的48小时，原始来源位点便无法再检测到残留eDNA。本实验表明，借助qRT-PCR可对地表水中采集到的残留eDNA进行定量分析，这能够实现流水生态系统中目标物种位置的精准空间定位；同时，相对残留eDNA信号强度或可用于推断目标物种的存在时间。