Abstract：
The present study was designed to assess the effectiveness of the eDNA metabarcoding approach to determine the phytoplankton composition in the marine environment with a special focus on mucilage episodes in the Sea of Marmara. For this purpose, the samples were collected from 5 different sites located in the Sea of Marmara and the northern Aegean Sea during the mucilage episode in June 2021. The phytoplankton diversity was analyzed morphologically and by 18S rRNA gene amplicon sequencing, and the dataset of both methods was compared, accordingly. The results showed significant differences between methods in terms of composition and the abundance of the phytoplankton groups. While Miozoa was the most abundant group by metabarcoding, light microscopy (LM) indicated a dominance of Bacillariophyta. Katablepharidophyta was found at lower abundances by the metabarcoding (representing < 1% of the community); the members of this phylum were not observed by a microscope. At the lower taxonomic levels, Chaetoceros was the only genus detected in all samples by both methods. Additionally, while mucilage-forming Gonyaulax fragilis, Cylindrotheca closterium, and Thalassiosira rotula were detected to species-level by LM, metabarcoding was able to determine these organisms at the genus level. On the other hand, the genus Arcocellulus was found in all metabarcoding datasets and not detected by microscopy. The results indicated that metabarcoding can detect a greater number of genera and reveal taxa that were overlooked by light microscopy but to develop a complete picture of phytoplankton diversity in the sample, microscopical observations still are in need.
摘要：
本研究旨在评估eDNA元编码方法确定海洋环境中浮游植物组成的有效性，并特别关注马尔马拉海的粘液事件。为此,这些样本是在2021年6月的黏液事件期间从马尔马拉海和爱琴海北部的5个不同地点收集的.通过18SrRNA基因扩增子测序和形态学分析浮游植物多样性,并比较了两种方法的数据集，因此。结果表明，方法之间在浮游植物群的组成和丰度方面存在显着差异。虽然Miozoa是最丰富的组，光学显微镜（LM）显示芽孢杆菌占优势。通过metabarcoding发现Katablephidophyta的丰度较低（占群落的<1％）；显微镜未观察到该门的成员。在较低的分类水平，Chaetoceros是通过两种方法在所有样品中检测到的唯一属。此外,而形成粘液的Gonyaulaxfragilis，cyclodrothecaclosterium,和轮藻被LM检测到物种水平，代谢编码能够在属水平上确定这些生物。另一方面,Arcocellulus属在所有的元编码数据集中被发现，并且没有被显微镜检测到。结果表明，元编码可以检测到更多的属，并揭示被光学显微镜忽略的分类单元，但可以完整地了解样品中的浮游植物多样性，微观观察仍然需要。
