Abstract：
Environmental impact assessments of marine aggregate extraction are traditionally conducted based on morphological characteristics of macrobenthos, which is time-consuming, labour-intensive and requires specific taxonomic expert knowledge. Bulk DNA metabarcoding is suggested as a promising alternative. This study compares the traditional morphological and the bulk DNA metabarcoding method to assess the impact of sand extraction activities on three sandbanks in the Belgian North Sea. Substantial differences in the detected species were observed between methods: Abundant and/or large macrobenthos species were detected by both methods, while small species or species with an exoskeleton were usually only detected by the morphological method. Taxa uniquely detected by bulk DNA metabarcoding could be explained by specimens identified at a higher taxonomic level by morphology, or by specimens with very low read numbers, probably representing species missed in the morphological sorting process, DNA traces on the specimens or false positives during PCR amplification efficiency. Despite the difference in detected species, comparable alpha and beta diversity patterns were observed by both methods, indicating that bulk DNA metabarcoding can effectively detect the overall ecological changes associated with sand extraction. We further demonstrate that bulk DNA metabarcoding reduces sample processing both in time (44 % faster) and cost (26 % cheaper) compared to the morphology-based identification. However, biomass quantification remains challenging for bulk DNA metabarcoding since of the ten most abundant genera, only two genera (Echinocardium and Ophelia) showed a significant positive correlation between biomass and read numbers. Additionally, bulk DNA metabarcoding does not provide information on life stages or size of the identified specimens. As such, our results underpin the complementary nature of both methods, wherein DNA-based analyses allow for rapid detection of community changes (as similar patterns in alpha and beta diversity and biotic index were observed), while morphology-based analyses provide additional information on e.g. secondary production (biomass) and size composition. We show how the strengths of both methods can be combined to assess the impact of sand extraction.
摘要：
传统上，海洋骨料提取的环境影响评估是根据大型底栖动物的形态特征进行的，这很耗时，劳动密集型，需要特定的分类学专业知识。建议将大容量DNA元转录编码作为一种有前途的替代方法。这项研究比较了传统的形态学和散装DNA元编码方法，以评估沙子提取活动对比利时北海三个沙洲的影响。在方法之间观察到检测到的物种的实质性差异：两种方法都检测到丰富和/或大型底栖动物物种，而小物种或具有外骨骼的物种通常只能通过形态学方法检测到。可以通过形态学在更高的分类学水平上鉴定出的标本来解释通过大量DNA代谢编码唯一检测到的分类群，或者读数很低的标本，可能代表形态分类过程中遗漏的物种，PCR扩增效率过程中标本上的DNA痕迹或假阳性。尽管检测到的物种不同，两种方法都观察到了可比的α和β多样性模式，这表明大量的DNA元编码可以有效地检测与沙子提取相关的整体生态变化。我们进一步证明，与基于形态学的鉴定相比，批量DNA元编码减少了样品处理的时间（快44％）和成本（便宜26％）。然而,生物质定量仍然是具有挑战性的散装DNA元碳编码，因为十个最丰富的属，只有两个属（Echinocardium和Ophelia）在生物量和阅读数之间显示出显着的正相关。此外,大量的DNA元编码不能提供有关已识别标本的生命阶段或大小的信息。因此，我们的结果支持了两种方法的互补性，其中基于DNA的分析允许快速检测群落变化（因为观察到α和β多样性和生物指数的相似模式），而基于形态学的分析提供了关于例如次级生产(生物质)和尺寸组成的额外信息。我们展示了如何结合两种方法的优势来评估砂提取的影响。
