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）可用于在目标水生物种被移除后的数天至数周内检测其存在。然而，绝大多数现有研究均针对静水环境系统（池塘或湖泊）或受控实验室实验中的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影响，这使得河流中的eDNA检测更为复杂。不过，仍有部分eDNA（即残留eDNA）可在水生系统中留存，即便在高流量的流水系统亦是如此。本研究旨在借助实时定量聚合酶链式反应（quantitative real-time polymerase chain reaction，qRT-PCR），在移除系统内eDNA来源后，于不受人为干预的流动河流中测定残留eDNA的检出灵敏度；本实验连续开展了两年。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出。随着采样点距离eDNA来源位点下游越远，残留eDNA的信号强度便随之降低；且在两项实验中，当eDNA来源水体耗尽后的48小时，便无法在来源位点检出残留eDNA。本实验证实，可通过qRT-PCR对地表水采样得到的残留eDNA进行定量分析，从而更精准地在流水生境中定位目标物种的分布区域；且残留eDNA的相对信号强度或可用于推断目标物种在该区域的出现时间。