具有短水力滞留的小型富营养化水库浮游植物群落结构与动态

Structure and dynamics of phytoplankton assemblage in a small eutrophic reservoir with a short residence time

竹仙洞水库是珠海市对澳门直接供水的水库,也是拱北水厂的重要的水源地。于2006年4月到12月,每2月一次调查了竹仙洞水库水文、水质和浮游植物分布,分析了浮游植物群落季节动态特征。浮游植种类不多,5次采样共检到61种。在丰度上,浮游植物主要以衣藻(Chlamydomonas sp.)、小环藻(Cyclotella meneghiniana)、游丝藻(Planktonema sp.)和隐藻(Cryptomonas sp.)等优势种为主,在生物量上以绿藻和硅藻为优势类群。蓝藻在竹仙洞水库的相对优势并不明显。应用典范对应分析(CCA)对竹仙洞水库浮游植物与环境因子关系分析,环境因子中的pH值、水位、正磷和水力滞留时间对浮游植物的分布影响最大;而透明度和降雨量对其也有一定的影响。从种类分布状况看,衣藻、游丝藻、隐藻对水体中环境因子的敏感性明显高于其它种类,这些种类的相对丰度在低温、低水位和较长水力滞留时间的4月份较高;硅藻门的直链藻(Melosira spp.)、菱形藻(Nitzchia sp.)和裸藻门的梭裸藻(Euglena acus)3种细胞体积较大的种类分布主要受降雨量和透明度的影响,在6月、8月和12月具有较高的相对丰度。与其它热带-亚热带富营养型水库相比,竹仙洞水库的浮游植物群落具有种类相对较少、以绿藻丰度较大的特点;直径在20μm以上的鞭毛绿藻和丝状绿藻以及细胞较小的硅藻门的小环藻是生物量的主要贡献者,短水力滞留时间是浮游植物群落结构与动态变化的关键控制因子。

Zhuxiangdong reservoir supplies drinking water to Macao, and also plays an important role in water supply to Gongbei water plant in Zhuhai city. Phytoplankton and environmental variables were monitored in a two-month interval in 2006 from April to December. 61 species of phytoplankton in total were observed in this eutrophic reservoir. The phytoplankton abundance was dominated by Chlamydomonas sp., Cyclotella meneghiniana, Planctonema lauterbornii and Cryptomonas sp., while the phytoplankton biomass was dominated by Chlamydomonas sp., Pandorina morum and Planctonema lauterbornii in green algae and Cyclotella meneghiniana in diatoms. In contrast to most eutrophic water bodies, the relative abundance of Cyanophyta was low in the Zhuxiandong Reservoir. Canonical Correspondence Analysis （CCA） was applied to explore the relationship between phytoplankton species and environmental parameters using CANOCO 4.5. pH, water level, phosphate and water retention time were the major environmental factors influencing the composition of phytoplankton species while Secchi disk depth and precipitation affects on the quantitative structure of phytoplankton community. The dominant phytoplankton species： Chlamydomonas sp., Planctonema lauterbornii and Cryptomonas sp. were more vulnerable to the variation of environmental factors than the other species. Their relative abundance were high in April characterized with low temperature, low water level and longer water retention time. The large sized species such as Melosira spp., Nitzschia spp. and Euglena acus prefer high Secchi depth and precipitation. They have high relative abundance in June, August and December. The phytoplankton in Zhuxiandong reservoir were characterized by fewer phytoplankton species and relatively high abundance for green algae, being different from most of eutrophic reservoirs in the same region. Flagellated green algae, filamentous green algae and Cyclotella meneghiniana （diatom） were the major contributors for phytoplankton biomass. The structure and dynamics of phytoplankton community was primarily controlled by short water retention time in the small reservoir.