In this study the plankton diversity in 13 environmental samples from Varna Bay (in the western Black Sea) was analyzed using massively parallel sequencing (MPS). This preliminary study was undertaken to assess the potential of this technology for future implementation in monitoring programs in the Black Sea. Amplicon sequences of the 18S rRNA gene (V4-5 regions) were obtained using the Illumina MiSeq 250PE platform. A total of 1137 operational taxonomic units (OTUs) were obtained among which 242 OTUs with >0.990 BLAST top hit similarity (21.3% of all detected OTUs) closely related to sequences belonging to −protists. A large portion (175 OTUs = 72.3%) was identified at the species levels, including species typical for the Bulgarian Black Sea plankton community, as well as many that haven’t been reported earlier in the Bulgarian Black Sea coast (124 OTUs = 51.2%). Dinoflagellates were represented by the highest species number (77 OTUs comprising 31.8% of protist species), with dominant genera Gyrodinium and Heterocapsa. The present survey revealed the presence of 12 species listed as harmful, some of which have been previously overlooked, such as Cochlodinium polykrikoides, Karenia bicuneiformis, and Karlodinium veneficum. Species identification was possible for 10.3–36.0% of the detected OTUs in the six major supergroups. The frequency in Rhizaria was significantly lower than that in other major groups (p < 0.05–0.01), implying difficulties in the classification from morphology-based observations. The metagenetic data had an insufficient resolution of the 18S rRNA gene for species identification in many genera. These issues may hamper the implementation of MPS-based surveys for plankton monitoring, especially for detecting harmful algal blooms (HAB). The sequencing technology is steadily improving and it is expected that sequence length and quality issues will be resolved in the near future. The ongoing efforts to register taxonomic information and quality controls in the international nucleotide sequence databases (INSDs) will be essential for improving taxonomic identification power.

在这项研究中，使用大规模并行测序（MPS）分析了来自瓦尔纳湾（位于黑海西部）的13个环境样品中的浮游生物多样性。进行了这项初步研究，以评估该技术在黑海监测计划中未来实施的潜力。使用Illumina MiSeq 250PE平台获得18S rRNA基因（V4-5区域）的扩增子序列。总共获得1137个操作生物分类单位（OTU），其中242个具有> 0.990 BLAST最高命中相似度的OTU（占所有检测到的OTU的21.3％）与属于-protists的序列密切相关。在物种水平上确定了很大一部分（175 OTU = 72.3％），包括保加利亚黑海浮游生物群落的典型物种，以及保加利亚黑海沿岸尚未有的许多报告（124 OTU = 51.2％）。鞭毛藻以最高的种数代表（77个OTU，占原种的31.8％），且属优势种。Gyrodinium和Heterocapsa。本次调查显示存在12种被列为有害物种，其中一些以前被忽略，如Cochlodinium polykrikoides，Karenia bicuneiformis和Karlodinium v​​eneficum。在六个主要超群中，有可能为检测到的OTU中的10.3–36.0％进行物种鉴定。根瘤菌的发生率明显低于其他主要群体（p < 0.05-0.01），这意味着基于形态学观察的分类存在困难。对于许多属中的物种鉴定，该后生数据对18S rRNA基因的分辨率不足。这些问题可能会妨碍基于MPS的浮游生物监测调查的实施，尤其是对于检测有害藻华（HAB）而言。测序技术正在稳步提高，预计序列长度和质量问题将在不久的将来得到解决。在国际核苷酸序列数据库（INSD）中注册分类信息和质量控制的持续努力对于提高分类识别能力至关重要。