澜沧江梯级水库浮游植物群落结构特征及其关键驱动因子

Characteristic of phytoplankton community structure and its driving factors along the cascade reservoirs in the Lancang River

筑坝改变河流生源要素迁移转化过程及浮游植物群落分布特征,影响河流生态系统结构与功能。为探究梯级筑坝河流浮游植物群落结构特征及其关键驱动因子,2016年丰水期、2018和2021年丰、枯水期在澜沧江开展了浮游植物群落及相关环境要素的调研。本文重点对比分析了丰水期自然河道段和水库浮游植物间的差异,基于广义相加模型(GAM)建立浮游植物与环境要素间的关系,研究发现:丰水期浮游植物生物量显著高于枯水期,丰、枯水期浮游植物群落结构均呈现上游以硅藻门为主,中下游以绿藻门、蓝藻门为主的变化特征。营养盐和水库的水力停留时间(HRT)是导致上、下游浮游植物生物量差异的关键环境要素;总磷、水温和HRT是影响浮游植物群落多样性指数的主要环境要素;总磷、氨氮是影响丰富度指数的关键环境要素。本研究结果有助于深化理解梯级筑坝河流生态环境效应。

Dam construction changes the migration and transformation of biogenic elements and inevitably affecting the structure and function of river ecosystem.To explore the phytoplankton community characteristic and its driving factors along cascade reservoirs,we investigated the phytoplankton communities and environmental factors in wet seasons of 2016,2018 and 2021,and dry seasons of 2018 and 2021 respectively,in a cascade river,the Lancang River.This study focused on the comparison of phytoplankton communities between natural riverine and reservoirs in wet seasons.The widely used generalized additive model(GAM) was applied to analyzed the complex relationships between phytoplankton and key environmental factors.The results showed that phytoplankton biomass in wet seasons was significantly higher than that in dry seasons.Phytoplankton community was dominated by diatoms in the upper reaches,and chlorophyta and cyanobacteria in the middle and lower reaches.Based on the GAM model,nutrients and hydraulic retention time(HRT) were the dominant environmental factors which contributed to phytoplankton biomass differences between upstream and downstream.Total phosphorus(TP),water temperature and HRT were the key environmental factors affecting the Shannon-Wiener diversity index.TP and ammonia nitrogen were the crucial environmental factors affecting the Margalef species richness index.These findings can help to deepen our understanding about the water ecological environment effects of cascade reservoirs.