沉水植物化感作用对西湖湿地浮游植物群落的影响

通过微宇宙实验,在控制光照和营养盐浓度的条件下分别研究了苦草(Vallisneria spiralis)、金鱼藻(Ceratophyllum demersum)和穗花狐尾藻(Myriophyllum spicatum)的化感作用对采集于杭州西湖湖西湿地的藻类密度、叶绿素a浓度、群落结构、多样性指数等的影响。其结果表明,3种沉水植物对微宇宙系统中的藻类都具有明显影响,藻类密度与叶绿素a浓度受到显著抑制,3个草-藻研究系统中藻类群落结构都发生了变化。在实验末期苦草组、金鱼藻组和穗花狐尾藻组中藻类总生物量(以细胞密度计)分别较初始值降低了37.06%、78.37%和83.40%。栅藻对3种沉水植物的化感作用敏感性较弱。藻类生物多样性方面,穗花狐尾藻系统中最高,其次是金鱼藻组,最后是苦草组,其Shannon-Wiener指数(H)分别为2.76、2.06和0.72,穗花狐尾藻组中H的显著高于苦草组(P0.05)。

Effects of allelopathy of submerged macrophytes on the phytoplankton community collected from the west part of the West Lake wetland in Hangzhou, China

Submerged macrophytes play an important role in maintaining clear water in shallow eutrophic lakes. The submerged macrophytes exert strong influence on the phytoplankton by several mechanisms, including the excretion of allelopathic substances. However, the allelopathic substances from various submerged macrophytes are not completely the same. Allelopathy of different submerged macrophytes may have various effects on the biomass and community structure of natural plankton. This paper investigated the allelopathic effects of three species of submerged macrophytes, Vallisneria spiralis, Ceratophyllum demersum, and Myriophyllum spicatum, on the biomass and community structure of the phytoplankton collected from the west part of Hangzhou West Lake wetland, using mesocosms under controlled environmental factors, such as light and nutrients. The changes in the phytoplankton density, chlorophyll-a content, phytoplankton community composition, and Shannon-Weiner Index (H) were monitored. The results showed that the total phytoplankton density and chlorophyll-a content were significantly reduced, and that the phytoplankton community structure also changed in all three co-culture systems. At the end of the experiment, the total biomass of algae (cell density) was 37.06%, 78.37%, and 83.40% lower than the initial values of each system. However, the phytoplantkton-inhibitory ratios were not significantly different among the three species of submerged marcophytes (P > 0.05). The dominant algal genera in the control group were Pediastrum and Crucigenia; in the V. Spiralis group were Chlorococcum and Volvox; in the C. demersum group were Chlorella and Pediastrum; in the M. spicatum groups was Chlorococcum. Scenedesmus exhibited less sensitivity to the allelopathic substances from the three submerged macrophytes. The highest phytoplankton species richness was observed in the M. spicatum group. The Shannon-Weiner Index (H) was 2.76, 2.06, and 0.72 for the V. spiralis, C. demersum, and M. spicatum groups, respectively. Furthermore, the phytoplankton biodiversity index (H) of the M. spicatum group is significantly higher than that of the V. spiralis group (P < 0.05).