我国东部浅水湖泊水生态效应特征

为探究我国东部浅水湖泊生态系统的时空异质性及其演替的响应指标，基于东部浅水湖泊长时间序列（1986-2014年）的监测数据，分析了不同湖泊类型的水质和浮游植物群落分布特征，并综合运用稳态转换理论和典范对应分析方法（CCA），研究了富营养化湖泊浮游植物群落的演替特征以及响应因子.结果表明:①从水系上看，太湖水系湖泊的水质最差，ρ（TP）、ρ（TN）和ρ（Chla）最高，分别为（0.276±0.606）（3.563±1.430）mg/L和（14.801±10.117）μg/L，SD（透明度）为（0.486±0.272）m；从水文连通性上看，湖泊的水质为通江湖泊>非通江湖泊>阻隔湖泊.②空间分布上，湖口以下干流浮游植物密度最高，为2.674×107 L-1.蓝藻门为东部浅水湖泊的优势种群，密度最高达1.897×107 L-1，绿藻门和硅藻门次之，黄藻门最少，仅为3.951×103 L-1.③东部浅水湖泊生态系统演替发生在ρ（Chla）为5.21~10.57 μg/L阈值范围内.④以东部典型湖泊-太湖为例，浮游植物群落分别在1997-1998年和2000-2001年两个时间梯度达到最大值.EC（电导率）和ρ（TN）是影响太湖浮游植物群落分布的显著因子.研究显示，随着东部浅水湖泊水质恶化，浮游植物群落结构特征发生突变，导致其生态系统发生演替，预防东部浅水湖泊生态系统演变应严控EC和ρ（TN）. 

Characteristics of Ecological Effects in the Eastern Shallow Lakes, China

This study investigates the spatial and temporal heterogeneity and response indicators of ecosystem succession in the eastern shallow lakes. The monitoring data from 1986-2014 were collected to qualify the distribution characteristics of water quality and phytoplankton community of different lake types. The succession feature and its response indicators of phytoplankton community in eutrophic lakes were explored by using regime shift theory and canonical correspondence analysis (CCA). The results show that:(1) From the perspective of water systems, Taihu Lake had the highest concentrations of TP (0.276±0.606 mg/L), TN (3.563±1.430 mg/L) and, Chla(14.801±10.117 μg/L), while the value of Secci-depth (SD) was (0.486±0.272)m. In terms of hydrological connectivity, Yangtze River-connected lakes had the best water quality, followed by non-river-connected lakes, and river-isolated lakes. (2) The spatial distribution of phytoplankton varied with the highest density of 2.674×107 L-1. Cyanophyta was the predominant alga in the eastern shallow lakes with the density of up to 1.897×107 L-1, followed by Chlorophyta and Bacillariophyta, while the lowest density was only 3.951×103 L-1 for Xanthophyta. (3) The ecosystem succession in the eastern shallow lakes occurred at Chla concentration threshold of 5.21-10.57 μg/L. (4)For example, in Taihu Lake, the density of phytoplankton community reached the maximum in 1997-1998 and 2000-2001. In addition, conductivity and TN concentration were significant factors affecting the distribution of phytoplankton communities in Taihu Lake. The results indicate that the change points of phytoplankton community structure were detected along with the deterioration of water quality in the eastern shallow lakes, thus attributing to the ecosystem succession. The key to prevent the degradation of shallow lake ecosystems in the Eastern Plain is to strictly control the conductivity and TN concentration.