水体叶绿素a和硅藻群落时空分布及影响因子的对比分析——以云贵高原异龙湖为例

藻类是湖泊生态系统中重要的初级生产者,物种多样性高且对水环境变化敏感,其生产力水平与群落构建模式是反映湖泊环境梯度和生态系统特征的可靠指标。其中硅藻优势属种的演替模式及其环境条件识别,是开展湖泊生态健康和环境质量评价的重要内容。本文选择亚热带地区浅水湖泊异龙湖开展季节调查,对20个采样点的叶绿素a和硅藻群落组成等指标开展分布特征及其驱动因子的定量评价,系统分析藻类变化的时空模式、驱动因子及其指标异同。2020年12月一2021年9月,异龙湖水环境特征的季节波动明显,综合营养指数TSI平均为74.76,总体处于富营养水平。在80个水体样品中共发现硅藻21属68种,群落结构以浮游类型(平均占比79.33%±20.69%)的耐中富营养种为主;在4个季节的调查中,膜糊直链藻Aulacoseira ambigua(61.62%±20.26%)为优势种。主成分分析显示,硅藻群落组成存在明显的空间差异和季节变化。冗余分析和方差分解等结果表明,水体营养因子(TN、TP和N:P)是影响叶绿素a浓度空间变化的重要因子(解释方差为19.08%±11.4%),水温和水深梯度的影响较小(9.63%±11.31%...

A comparative study on spatio-temporal variations and environmental drivers of lake-water chlorophyll-a and diatom communities in Lake Yilong

Algae are important primary producers in lake ecosystems, with high species diversity and sensitivity to changes in water environment. Algal productivity and community structure can serve as reliable indicators for tracking the lake environmental gradient and ecosystem features. The succession of dominant diatom species and the identification of environmental gradients are important in evaluating lake ecological health and environmental quality. In order to quantify the spatio-temporal variations in lake-water chlorophyll-a(Chl.a) and diatom communities, a seasonal survey of diatom composition and limnological characteristics was carried out at 20 sampling sites of Lake Yilong for assessing the driving factors of algal distribution and the degree of similarity between both indicators. From December 2020 to September 2021, the water environment displayed strongly seasonal fluctuations, and the trophic state index (TSI) varied with a mean of 74.76, suggesting the persistence of a eutrophic level across seasons. A total of 68 diatoms species belonging to 21 genera were identified in 80 water samples, mainly comprising planktonic species (relative abundance, mean±SD: 79.33%±20.69%). Specifically, Aulacoseira ambigua (61.62%±20.26%) was found to be the dominant species across seasons. Principal components analysis (PCA) showed that there were significant spatial heterogeneity and seasonal variations in diatom communities. The results of redundancy analysis and variance partitioning showed that nutrient variables (e.g., TN, TP and N:P) were the important factors causing spatial variation of lake-water chlorophyll-a concentration (an explained variance of 19.08%±11.4%), while the gradients of water temperature and depth played a secondary and moderate role (9.63%±11.31%). Similarly, nutrition variables (e.g., TN, TP, N:P and SiO^2-₃) were identified as key factors in structuring diatom communities, accounting for 27.55%±15.83% of the community variances. While water temperature and depth were insignificant in influencing the spatial variation of diatom community structure (2.53%±3.78%), however, their interaction with nutrient level played a much stronger role (15.95%±11.45%). The results of multiple regression analysis further showed that water temperature had predominant impacts on the seasonal variation in both algae biomass and diatom community distribution (56.4% and 20.1%), while the role of nutrient factors (TN, TP, N:P and SiO^2-₃ etc.) was relatively small (6.5% and 19.2%). In conclusion, the nutrient served as a key factor in causing spatial heterogeneity of algal distribution, while water temperature was an important driver of seasonal changes in phytoplankton in Lake Yilong. Meanwhile, there existed significant differences in the driving processes for seasonal and spatial distribution of lake-water algae as indicated by diatom community structure and primary productivity. This study provides empirical evidence on the strongly seasonal fluctuation and spatial heterogeneity in the limnological property and ecological processes in subtropical shallow lakes, and implies that it is imperative to combine multiple indicators of algae for an integrated assessment of lake environment quality and ecological health.