基于环境DNA metabarcoding的西轩岛近海鱼类多样性研究

Diversity of fish species in Xixuan Island coastal waters based on environmental DNA metabarcoding

中文关键词: 环境DNA metabarcoding  高通量测序  西轩岛近海  渔业资源  鱼类多样性

英文关键词: Environmental DNA metabarcoding  High throughput sequencing  Xixuan Island coastal waters  Fishery resources  Fish diversity

中文摘要:

      鱼类多样性的保护对于生态系统的科学管理和资源的可持续利用至关重要。环境DNA metabarcoding技术的出现和应用为水生生物的调查与监测带来了强有力的技术革新。本研究以浙江舟山近海岛屿——西轩岛为例，设计了4个不同采样站位，先后于2019年2月(冬季)、5月(春季)和11月(秋季)共采集水样12个，通过环境DNA提取、扩增、高通量测序以及生物信息学分析，对西轩岛近海鱼类多样性进行了分析，同时评估了鱼类多样性的时空差异。结果显示，共监测到鱼类33种，隶属于12目26科32属，其中，鲈形目(Perciformes)种类最多，共19种，约占所有种类的57.6%。不同采样季节的多样性指数和均匀度指数均存在显著差异，表明季节可能是影响西轩岛近海鱼类多样性的因素之一。综合时间和空间分析的结果显示，在繁殖季节且远离舟山本岛一侧的采样点监测到的鱼种数量更多。通过比对之前传统渔业资源调查的结果发现，不同季节优势种存在较大变化，可能与采样点数量较少且集中有关。进化树富集结果显示，各季节的优势鱼种与传统调查手段的结果有较大差异，表明目前环境DNA仍不能完全替代传统调查方法，但可以将环境DNA方法与传统的调查方法相结合，以确保监测结果的准确性和可靠性。

英文摘要:

      Global biodiversity loss is one of the most serious environmental crises of the 20th and 21st centuries. Fish diversity, an important component of biodiversity, is also in decline. The conservation of fish diversity is therefore essential for ecosystem management and the sustainable use of resources. Most current aquatic biodiversity surveys rely on conventional methods. The emergence and application of environmental DNA (eDNA) technology has triggered unprecedented innovations in aquatic organism investigation and monitoring. eDNA metabarcoding refers to the selection of appropriate universal primers for different target taxa and the identification of multiple target species in environmental samples via PCR amplification combined with high-throughput sequencing. The Zhoushan Archipelago, located in the northeastern waters of Zhejiang Province, consists of 2 085 islands with a total area of 22 216 square kilometers. Located at the confluence of the Yangtze River, the Qiantang River, the Yongjiang River, and the Taiwan Warm Current, the Zhoushan Archipelago forms a unique and complex hydrological environment, which provides a rich source of nutrients and a suitable habitat for fish. In recent years, the large-scale exploitation of marine resources and marine pollution have led to a serious loss of fish diversity near the Zhoushan Archipelago. To restore fish diversity, conservation efforts have been implemented by the government and researchers, including stricter fishing bans and ecological fish stock enhancement and release. However, the lack of reliable tools to understand the species and assess biodiversity is the most critical issue in conservation efforts. Trawl sampling and morphological identification are the primary fish diversity assessment methods. However, these conventional methods are often inefficient, time-consuming, selective, and destructive. The extensive rocky reefs in the Zhoushan Archipelago make it difficult to use conventional fishery resource survey methods efficiently. Therefore, simple and accurate methods for species diversity monitoring are needed. In this study, Xixuan Island, an offshore island in Zhoushan, was taken as a reference. Four different sampling stations were designed, and a total of 12 water samples were collected in February, May, and November 2019. The species composition and diversity characteristics of offshore fish communities around Xixuan Island were described, and the spatial and temporal differences in fish diversity were evaluated. A total of 33 fish species belonging to 12 orders, 26 families, and 32 genera were detected. Among them, Perciformes has the most abundant species, with 19 species, accounting for approximately 57.6% of all species detected. The diversity and evenness indices of the different sampling seasons were significantly different (P<0.05), indicating that season may be one of the factors affecting the diversity of offshore fish around Xixuan Island. The results of the combined temporal and spatial analysis showed that more fish species were detected during the breeding season at sampling sites far from the main island side of Zhoushan. By comparing the results with the conventional fishery resources survey, we found a large variation in the dominant species in different seasons, which may be related to the limited sampling site numbers. Temperature and longitude may be important factors affecting the fish diversity around Xixuan Island. The result of enriching the dominant species in each season by heat trees differed significantly from those of traditional surveys, indicating that eDNA cannot completely substitute the conventional survey methods; however, it can be applied as an auxiliary method to monitor fishery resources, improve detection efficiency, and reduce interference to ecosystems. This study not only provides novel methods for the fishery resources survey in offshore Zhoushan but also provides technical support for the subsequent investigation and evaluation of fish diversity and its protection and management.