不同扰动强度对浮游藻类群落结构演替的影响

Effect of Different Disturbance Strength on Succession of Phytoplankton Community

三峡水库蓄水后,库区支流水华频发。为研究水华生消机理,以中度扰动理论为指导,在神农溪支流水库敏感区域设立围隔实验系统,研究不同扰动强度对浮游藻类群落结构演替的影响。设置不同扰动强度,对围隔水体叶绿素a浓度(ρ(Chl-a))、浮游藻类细胞密度进行跟踪监测。结果表明,无扰动的围隔浮游藻类生长最迅速,并暴发水华,ρ(Chl-a)最高值达到53.725 mg/m3,浮游藻类细胞密度最高值达到111.42×106cells/L,而有扰动的围隔浮游藻类则生长缓慢,扰动越强ρ(Chl-a)及藻细胞密度越低,它们与扰动强度呈显著负相关(r1=-0.918,r2=-0.845)。中度扰动理论适合本实验,存在一个临界扰动强度,浮游藻类多样性水平最高,多样性指数最高值为3.329;低于临界值时优势藻种生长较快抑制其他藻种的生长,高于临界值时不利浮游藻类生长,藻类生物量及生物多样性水平降低。

Algae blooms have been observed frequently in tributary bays of the Three Gorges Reservoir since impounding. In order to study the mechanism of algae blooms, some experiments were conducted based on the intermediate disturbance hypothesis. The enclosures experimental system was built to investigate the effect of different disturbance strength on succession of phytoplankton community in sensitive areas of the reservoir tributaries of Shennong River. Different disturbance strength was set up, and the concentration of chlorophyll-a（p（Chl-a）） and density of phytoplankton ceils were tracked and monitored. Results showed that the algae grew quic.kly in the enclosures with no disturbance, with the maximum of p（Chl-a） as 53.725 mg/m3, the maximum density of phytoplankton cells as 111.42×106 cells/L. However, the algae grew slowly in the enclosures with disturbance, the stronger the disturbance, the lower the p（Chl-a） and ceils density, both p（Chl-a） and cells density showed significant negative correlation （r1 =-0.918,r2 =-0.845） with the disturbance strength. The intermediate disturbance hypothesis was appropriate for the experiment, and there was a critical value of disturbance strength in which the phytoplankton diversity is the highest, and the maximum of diversity index reached 3.329. With the disturbance strength below the critical value, the dominant species of phytoplankton grew quickly and restrained other algae＇ growth, while with the disturbance strength above critical value, the changed habitat was conducive to the growth of algae, resulting in reduction of the phytoplankton biomass and the diversity.