Studies focusing on marine macrophyte metabarcoding from environmental samples are scarce, due to the lack of a universal barcode for these taxa, and to their poor representation in DNA databases. Here, we searched for a short barcode able to identify marine macrophytes from tissue samples; then, we created a DNA reference library which was used to identify macrophytes in eDNA from coastal sediments. Barcoding of seagrasses, mangroves and marine macroalgae (Chlorophyta, Rhodophyta and Phaeophyceae) was tested using 18 primer pairs from six barcoding genes: the plant barcodes rbcL, matK and trnL, plus the genes ITS2, COI and 18S. The 18S gene showed the highest universality among marine macrophytes, amplifying 95%–100% of samples; amplification performance of the other barcodes was limited. Taxonomy was assigned using a phylogeny‐based approach to create an 18S DNA reference library. Macrophyte tissue sequences were accurately identified within their phyla (88%), order (76%), genus (71%) and species (23%). Nevertheless, out of 86 macrophytes tested, only 48% and 15% had a reference sequence at genus and at species level, respectively. Identification at these levels can be improved by more inclusive reference libraries. Using the 18S mini‐barcode and the reference library, we recovered eDNA from 21 marine macrophytes in sediments, demonstrating the barcode's ability to trace primary producers that contribute to blue carbon. We expect this barcode to also be useful for other ecological questions, such as tracing macro primary producers in marine food webs.

中文翻译：

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海洋大型植物的 DNA 迷你条形码。


由于缺乏这些类群的通用条形码，并且它们在 DNA 数据库中的代表性较差，因此针对环境样本中海洋大型植物元条形码的研究很少。在这里，我们搜索了一个能够从组织样本中识别海洋大型植物的短条形码；然后，我们创建了一个 DNA 参考库，用于识别沿海沉积物 eDNA 中的大型植物。使用来自 6 个条形码基因的 18 个引物对测试了海草、红树林和海洋大型藻类（绿藻门、红藻门和褐藻门）的条形码：植物条形码 rbcL、matK 和 trnL，以及基因 ITS2、COI 和 18S。 18S基因在海洋大型植物中表现出最高的通用性，扩增了95%–100%的样本；其他条码的扩增性能有限。使用基于系统发育的方法分配分类学，以创建 18S DNA 参考库。大型植物的组织序列在门（88%）、目（76%）、属（71%）和种（23%）中被准确识别。然而，在测试的 86 种大型植物中，只有 48% 和 15% 分别拥有属和种水平的参考序列。通过更具包容性的参考库可以改进这些级别的识别。使用 18S 迷你条形码和参考库，我们从沉积物中的 21 种海洋大型植物中回收了 eDNA，证明条形码能够追踪对蓝碳有贡献的初级生产者。我们预计该条形码对于其他生态问题也很有用，例如追踪海洋食物网中的宏观初级生产者。