Spatiotemporal pattern of phytoplankton community structure and its determining factors in the channel of the middle route of South-to-North Water Diversion Project
Zhang Chunmei, Zhu Yuxuan, Song Gaofei, Wujuan Mi, Bi Yonghong, Wang Shulei, Liang Jiankui, Shang Mingyu
Abstract
为了解南水北调中线干渠浮游植物群落的时空格局，自2018年8月开始分4个季度对干渠沿程的11个样点进行采样调查，同步开展水环境调查；共检出浮游植物7门83属145种，物种丰富度上，硅藻种类数最多，绿藻和蓝藻分别占第2和第3位，且春季>秋季>冬季>夏季；优势种包括极小曲丝藻（Achnanthidum minutissimum）、桥弯藻（Cymbella sp.）、空星藻（Coelastrum sphaericum）、衣藻（Chlamydomonas sp.）等（优势度Y>0.02）；全年叶绿素a浓度为（4.09±2.89）μg/L，细胞密度为（6.79±7.15）×10<sup>6</sup> cells/L，夏季细胞密度显著高于其他季节，以绿藻、蓝藻为主，其他季节以硅藻、绿藻为主；空间上，细胞密度从南到北呈递增趋势，穿黄工程后显著高于穿黄工程前；RDA与多元线性回归分析显示：水温和营养盐是影响群落结构的关键因素，其次是流量和流速，这些因子成为群落时空格局的决定因子；NMDS与聚类分析显示：时间变化对于群落结构产生的影响比空间变化更为显著.本研究确认了跨流域长距离输水的中线干渠中浮游植物群落的显著时空异质性；鉴于流速、流量对群落的决定作用，建议在输水管理中加强生态调度技术研究，以调控浮游植物群落，保障水质稳定.;In order to investigate the spatiotemporal pattern of phytoplankton communities and the determining factors in the channel of the Middle Route of South-to-North Water Diversion Project, seasonal samples of phytoplankton and aquatic from 11 different sample stations were collected and analyzed from 2018 to 2019. Phytoplankton species were detected as 7 Phylum, 145 species, with the largest number of taxa belonging to Bacillariophyta. The dominant taxa were Achnanthidum minutissimum, Cymbella sp., Coelastrum sphaericum, Chlamydomonas sp., etc. (Y>0.02). The chlorophyll-a concentration was (4.09 ±2.89) μg/L, and the cell density was (6.79±7.15)×10<sup>6</sup> cells/L, with the maximum cell density in summer. Chlorophyta was dominant in summer, but Bacillariophyta were prevalent in other seasons. There existed a gradually increase in chlorophyll-a concentration and cell density along the channel, and there were significant differences before and after the Yellow River Tunnel Project; Meanwhile, the results of redundancy and multiple linear regression analysis for the relationship between the phytoplankton and environment showed that water temperature and nutrient were the key factors, and the second was water flow and water velocity; NMDS and cluster analysis indicated the phytoplankton community-owned obvious spatiotemporal heterogeneity in the long-distance water transportation, and the seasonal changes showed much more pronounced effect on the phytoplankton community compositions than spatial variation. In view of the determining role of flow rate and flow velocity on phytoplankton structure, more attention should be paid to the ecological scheduling regulation of phytoplankton community in the management of water quality safety and stability.