Abstract

An understanding of the annual variations in the phytoplankton community in freshwater lakes, and of the drivers responsible for these variations, is essential for lake management. In this study we collected and analyzed seasonal samples of phytoplankton and assessed environmental variables in Nansi Lake from 2011 to 2015, in order to identify the seasonal dynamics of the phytoplankton community and the main drivers in each phylum. The results showed that phytoplankton diversity in Nansi Lake followed annual cycles, which were interrupted by a water diversion in 2013. The disruption of equilibrium was clearly demonstrated by the Shannon–Wiener diversity index, Pielou’s evenness index, and Simpson’s dominance index, whereas the species richness and abundance showed resilience, maintaining regular annual cycles. The dominant species were frequently Synedra acus Kütz (Bacillariophyta), Closterium gracile Bréb (Chlorophyta), and Scenedesmus quadricauda Bréb (Chlorophyta) in summer and autumn. Non-metric multidimensional scaling (NMDS) analysis suggested that the phytoplankton was most widely distributed in summer, when conditions were more conducive to phytoplankton growth and reproduction. Redundancy analysis (RDA) indicated that the main drivers for the phytoplankton community varied in different taxonomic units. Specifically, the NP ratio and permanganate index (COD_Mn) had significant effects on Chlorophyta, whereas pH, dissolved oxygen (DO), and transparency significantly influenced Bacillariophyta. This study highlights the importance of seasonal phytoplankton succession and the need for identification of the main drivers in each phylum in order to achieve more effective control of phytoplankton blooms in freshwater lakes.

摘要

了解淡水湖泊中浮游植物群落的年度变化以及造成这些变化的驱动因素，对于湖泊管理至关重要。在这项研究中，我们收集并分析了2011年至2015年南四湖浮游植物的季节性样本，并评估了环境变量，以便确定浮游植物群落的季节动态以及每个门的主要驱动因素。结果表明，南四湖浮游植物的多样性遵循年度周期，并在2013年被引水中断。香农-维纳多样性指数，Pielou均匀度指数和Simpson优势度指数清楚地表明了平衡的破坏，而该物种丰富度和丰度显示出韧性，保持定期的年度周期。优势种经常出现夏秋季有Synedra acusKütz（芽孢杆菌），Closterium gracileBréb（芽孢杆菌）和Scenedesmus quadricaudaBréb（芽孢杆菌）。非度量多维标度（NMDS）分析表明，当条件更有利于浮游植物生长和繁殖时，浮游植物在夏季分布最广。冗余分析（RDA）表明，浮游植物群落的主要驱动因素在不同的生物分类单位中有所不同。具体来说，NP比和高锰酸盐指数（COD _Mn）对绿藻有显着影响，而pH，溶解氧（DO）和透明度对蓝藻有显着影响。这项研究强调了季节性浮游植物演替的重要性以及确定每个门的主要驱动因素的必要性，以便更有效地控制淡水湖中的浮游植物水华。