Environmental DNA (eDNA) metabarcoding can rapidly characterize the composition and diversity of benthic communities, thus it has high potential utility for routine assessments of benthic impacts of marine finfish farming. In this study, 126 sediment grab samples from 42 stations were collected at six salmon farms in British Columbia, Canada. Benthic community changes were assessed by both eDNA metabarcoding of metazoans and macrofaunal polychaete surveys. The latter was done by analysing 11,466 individuals using a combination of morphology-based taxonomy and DNA barcoding. Study objectives were to: (i) compare biotic signals associated with benthic impacts of salmon farming in the two data sources, and (ii) identify potential eDNA indicators to facilitate monitoring in Canada. Alpha diversity parameters were consistently reduced near fish cage edge and negatively correlated with pore-water sulphide concentration, with coefficients ranging from −0.62 to −0.48. Although Polychaeta are a common indicator group, the negative correlation with pore-water sulphide concentration was much stronger for Nematoda OTU richness (correlation coefficient: −0.86) than for Polychaeta (correlation coefficient: −0.38). Presence/absence of Capitella generally agreed well between the two methods despite that they differed in the volume of sediments sampled and the molecular marker used. Multiple approaches were used to identify OTUs related to organic enrichment statuses. We demonstrate that eDNA metabarcoding generates biotic signals that could be leveraged for environmental assessment of benthic impacts of fish farms in multiple ways: both alpha diversity and Nematoda OTU richness could be used to assess the spatial extent of impact, and OTUs related to organic enrichment could be used to develop local biotic indices.

中文翻译：

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与鲑鱼养殖场底栖影响相关的生物信号来自沉积物的 eDNA 元条形码

环境 DNA (eDNA) 元条形码可以快速表征底栖群落的组成和多样性，因此它对于海洋有鳍鱼类养殖的底栖影响的常规评估具有很高的潜在效用。在这项研究中，在加拿大不列颠哥伦比亚省的六个鲑鱼养殖场收集了来自 42 个站点的 126 个沉积物抓取样本。底栖群落变化通过后生动物的 eDNA 元条形码和大型多毛类动物调查进行评估。后者是通过使用基于形态学的分类法和 DNA 条形码的组合分析 11,466 个人来完成的。研究目标是：(i) 比较两个数据源中与鲑鱼养殖底栖影响相关的生物信号，以及 (ii) 确定潜在的 eDNA 指标，以促进加拿大的监测。Alpha 多样性参数在鱼笼边缘附近持续降低，并与孔隙水硫化物浓度呈负相关，系数范围为 -0.62 至 -0.48。尽管多毛纲是一个常见的指标组，但线虫 OTU 丰富度（相关系数：-0.86）与孔隙水硫化物浓度的负相关性（相关系数：-0.86）比多毛纲（相关系数：-0.38）强得多。存在/不存在Capitella普遍认同这两种方法，尽管它们在采样的沉积物体积和使用的分子标记方面有所不同。使用多种方法来识别与有机富集状态相关的 OTU。我们证明 eDNA 元条形码产生的生物信号可用于以多种方式对养鱼场的底栖影响进行环境评估：α 多样性和线虫 OTU 丰富度均可用于评估影响的空间范围，与有机富集相关的 OTU 可用于评估用于开发当地生物指数。