硅酸盐影响浮游藻类群落结构的围隔试验研究

在新开湖设置浮式围隔,通过调控围隔水体硅酸盐含量,研究了硅对富营养化水体浮游藻类群落生长及演替的影响.结果表明,随着硅酸盐浓度的增加,硅藻的生物量提高,其种类所占比例明显增加,由10.2%上升到22.1%;蓝藻和绿藻的种类比例则下降,由76.8%下降到61.5%.加硅处理中,硅藻虽然没有完全取代蓝、绿藻的绝对优势地位,但是出现了尺骨针杆藻(Synedra ulna)、细齿菱形藻(Nitzschia denticula)、针状拟菱形藻(Nitzschia acicularis)、缢缩异极藻头状变种(Gomphonema constrictum var. capitata)、橄榄形异极藻 (Gomphonema olivaceum)等在对照处理中并未检出的藻种.中硅(原子比N∶Si∶P=16∶8∶1)和高硅(N∶Si∶P=16∶16∶1)处理中,Shannon多样性指数分别为2.17±0.40和2.12±0.21,而对照组为1.89±0.55.试验末期,对照围隔的水体表面出现铜绿微囊藻(Microcystis aeruginosa)水华,而硅酸盐含量高的围隔中,同期没有水华出现.硅酸盐的增加能够促进硅藻及其它藻类生长,改变少数几种蓝、绿藻占据优势的状态,提升水生生态系统的多样性水平,并对淡水蓝藻水华的产生起到一定削弱作用.

Effects of Silicate on the Community Structure of Phytoplankton in Enclosures

Controlling the concentrations of silicate, enclosure experiments were conducted in Xinkai Lake to investigate the influence of Si concentration on the growth and succession of phytoplankton communities in a eutrophic freshwater. With the addition of silicate, the biomass of diatoms increased and the ratio of diatom species to the total significantly increased from 10.2% to 22.1%. While the species percent of Cyanobacteria and Chlorophyta decreased to 61.5%, as compared with 76.8% in control. Several diatom species, such as Synedra ulna, Nitzschia denticula, Nitzschia acicularis, Gomphonema constrictum var. capitata, Gomphonema olivaceum, which were not found in control, were observed in the silicate-enriched treatments. The Shannon indices of 2.17±0.40 and 2.12±0.21 were obtained from the medium-Si (atomic ratio N:Si:P=16:8:1)and high-Si (N:Si:P=16:16:1) treatments, which were higher than that of the control enclosure (1.89±0.55, without silicate addition). At the late phase of the experiments, algal blooms mainly composed of Microcystis aeruginosa appeared in control but not in the silicate-enriched enclosures. The results show that the enrichment of silicate can promote the growth of diatoms and the other algal species and change the dominance of few Cyanobacteria and Chlorophyte species. Therefore, it can elevate the algal biodiversity of an aquatic ecosystem and weaken the cyanobacterial blooms to a certain degree.