不同类型水生植物群落对蓝绿藻类的抑制作用

Inhibitory effects of different types aquatic macrophyte communities on blue-green algae

选择2种常见水生植物荇菜(Nymphoides peltatum)和黑藻(Hydrilla verticillata),构建了荇菜群落(浮叶植物群落)、黑藻群落(沉水植物群落)和荇菜-黑藻群落(复合群落)等3种不同类型水生植物群落,在模拟富营养化水体环境条件下与自然水体中藻类共培养,研究了不同类型水生植物群落对藻类的抑制作用。结果表明:1)3种群落对水体中藻类的抑制作用顺序为荇菜群落>复合群落>黑藻群落,实验结束时水体叶绿素a分别减少了63.1%、44.7%、3.3%。2)荇菜群落中蓝藻受到了较强抑制作用,其总藻细胞密度比初始减少了99.5%;而绿藻总藻细胞密度则比初始增加了31.6%;黑藻群落中蓝藻仍保持较高生物量,绿藻藻细胞密度一直处于较低水平;复合群落对蓝绿藻均有很好的抑制效果,蓝藻藻细胞密度比初始下降了95.9%,绿藻藻细胞密度始终保持在较低水平。3)3种群落中藻类组成变化不同:荇菜群落中初始以微囊藻、色球藻等蓝藻门植物为优势种,逐渐转变为以小球藻、栅藻、四角藻等绿藻门植物为优势种;黑藻群落中藻类一直以微囊藻为优势种,伴生有少量的小球藻属、栅藻属、隐藻属藻种;复合群落水体中藻类组成与荇菜群落中藻类变化相似,实验期间微囊藻数量逐渐减少,而栅藻数量逐渐升高。4)不同群落中植物生物量增加明显,荇菜和黑藻的鲜重在单种群落和复合群落中均具有较高的增长率,分别为129.8%、63.6%和108.8%、66.5%;植物生长对光照、温度、pH等环境因子具有明显的调节作用,荇菜群落中水下20cm处光衰减率与水体叶绿素a显著相关,说明荇菜的遮光作用是其产生显著抑藻作用的重要原因。

Two common macrophytes Nymphoides peltatum and Hydrilla verticillata were chosen to construct three types of aquatic microphyte communities,i.e.,N.peltatum community（floating-leaved）,H.verticillata community（submerged）,and N.peltatum ＋ H.verticillata compound community,which were respectively cultivated in a simulated eutrophic aquatic environment with the blue-green algae introduced from natural water body,aimed to study the inhibitory effects of these macrophyte communities on algal growth.All the test communities showed an evident inhibitory effect,with the sequence of N.peltatum community compound community H.verticillata community.By the end of the experiment,the chl-a concentration was decreased by 63.1%,44.7% and 3.3%,respectively.N.peltatum community had an intensive inhibitory effect on Cyanophyta,whose total cell density was decreased by 99.5%,but the total cell density of Chlorophyta was increased by 31.6%.H.verticillata community showed more inhibition on Chlorophyta,but less impact on Cyanophyta.In N.peltatum ＋ H.verticillata compound community,the total cell density of Cyanophyta decreased by 95.9%,and that of Chlorophyta remained at a lower level.The composition of algae varied with macrophyte communities.In N.peltatum community,the dominant algae changed gradually from Cyanophyta such as Microcystis and Chroococcoid to Chlorophyta such as Chlorella,Tetraedron,and Scenedesmus;in H.verticillata community,Cyanophyta remained dominant,and companied with less species such as Chlorella,Tetraedron,and Cryptomonas;and in the compound community,the variation of algal composition was similar to that in N.peltatum community.During the experiment,the total cell density of Cyanophyta decreased gradually,while Chlorophyta increased.Macrophyte biomass increased markedly,with the wet weight of N.peltatum and H.verticillata in their single and compound communities increased by 129.8% and 63.6%,and 108.8% and 66.5%,respectively.The macrophyte growth showed a distinct influence on the aquatic environment factors such as illumination,temperature and pH.In N.peltatum community,the reduction rate of illumination at water depth 20 cm had a significant correlation with the chl-a concentration in water body,suggesting that N.peltatum＇s shading effect was the main cause of algal inhibition.