基于环境DNA宏条形码技术的秦淮河生物多样性研究

Abstract

秦淮河是南京的母亲河, 其生物多样性受城市化进程影响面临严重威胁, 而物种资源调研是生物多样性保护的基础。环境DNA宏条形码技术较形态学监测是一种简单高效、灵敏度高的新型监测技术。为探究秦淮河浮游生物、底栖动物及鱼类的生物多样性, 于2019年7月, 采用环境DNA宏条形码技术对其进行了探究, 并分析了秦淮河上下游间的差异及环境因子对其群落结构的影响。结果表明: 秦淮河共监测到浮游动物13属22种407个操作分类单元(Operational Taxonomic Units, OTUs), 浮游植物85属60种4445个OTUs, 底栖动物16属17种212个OTUs, 鱼类53属44种1663个OTUs。其中浮游动物以游泳轮虫目(Ploima)和双甲目(Diplostraca)为主, 共占浮游动物63.37%, 浮游植物以隐藻门(Cryptomonas)和褐藻门(Ochrophyta)为主, 共占浮游植物88.11%, 底栖动物中节肢动物门(Arthropoda)占比最高, 达91.67%, 鱼类中鲤形目(Cypriniformes)占比最高, 达69.99%。与秦淮河历史形态学监测数据相比, 环境DNA宏条形码技术在物种丰度鉴定方面显著高于传统形态学鉴定的物种丰度。通过主坐标分析和PERMANOVA检验, 发现秦淮河下游、上游南支和上游北支间有极显著差异(P < 0.001)。其中浮游动物、浮游植物和底栖动物受分组影响更大, 分组对鱼类的影响相对较小。下游α多样性较上游更为贫乏, 上游南支(南京)α多样性较上游北支(句容)更丰富。浮游生物和底栖动物均表现出了明显的随距离增加而衰减的趋势。冗余分析表明, 较低营养级的生物对环境因子的变化更为敏感, 浮游生物和底栖动物的主要影响因子为总氮、总有机碳、总磷、氨氮、化学需氧量和溶解氧。鱼类的影响因子为溶解氧、总有机碳、总氮、总磷和化学需氧量。研究通过对秦淮河生物多样性的调研, 可为秦淮河的生物多样性保护提供理论参考。;Qinhuai River is the mother river of Nanjing, and its biodiversity is seriously threatened by the process of urbanization. The survey of species resources is the basis of biodiversity protection. Compared with morphological monitoring, the environmental DNA metabacroding is a simple, efficient and sensitive new monitoring technology. In order to explore the biodiversity of plankton, zoobenthos and fish in Qinhuai River, the environmental DNA metabacroding was used to explore it in July 2019, the differences between upstream and downstream of Qinhuai River were analyzed, and the relationship between the community composition of Qinhuai River and environmental variables was evaluated. The results showed that a total of 13 genus, 22 species and 407 operational taxonomic units (OTUs) of zooplankton, 85 gennus, 60 species and 4445 OTUs of phytoplankton, 16 genus, 17 species and 212 OTUs of zoobenthos, 53 genus, 44 species and 1663 OTUs were detected through the environmental DNA metabacroding. Among them, Ploima and Diplostraca, accounting for 63.37%, were dominant species in zooplankton community at the order level. The most abundant species in phytoplankton community at the phylum level were Cryptomonas and Ochrophyta, accounting for 88.11%. The zoobenthos were dominated by Arthropoda at the phylum level, which accounted for 91.67%. The Cypriniformes accounting for 69.99%, were dominants in fish of different samples at the order level. Compared with the historically morphological monitoring data of Qinhuai River, the environmental DNA metabarcoding technique was more powerful than the morphological method in assessment of species richness. Through the principal coordinate analysis (PCoA) and PERMANOVA test, a significant difference (P < 0.001) was found among downstream, the south branch of upstream and the north branch of upstream of Qinhuai River. Zooplankton, phytoplankton and zoobenthos were more affected by the group of sites than fish. Alpha(α) diversity of downstream in Qinhuai River was poorer than that of upstream, and Alpha(α) diversity of the south branch of upstream (Nanjing) was richer than that of the north branch (Jurong). All of the taxa of Qinhuai River except fish showed strong relationship between geographical distance (km) and biotic community similarity based on Bray-Curtis distance. Redundancy analysis (RDA) showed that organisms with lower trophic levels were more sensitive to changes in the environmental factors. The main influencing factors in plankton and zoobenthos community distribution were total nitrogen (TN), total organic carbon (TOC), total phosphorus (TP), ammonia nitrogen (NH₃-N), chemical oxygen demand (COD) and dissolved oxygen (DO). While the key factors in fish community distribution were DO, TOC, TN, TP and COD. Our results can provide a theoretical reference for the protection of the biodiversity of Qinhuai River.