杭州西湖浮游植物群落对沉水植物恢复的响应

Response of Phytoplankton Community to Restoration of Submerged Macrophytes in West Lake,Hangzhou

为评价杭州西湖沉水植物恢复对浮游植物群落的影响,以西湖湖西水域(茅家埠、乌龟潭、浴鹄湾)为代表,通过5年连续采样监测数据,研究了该区域沉水植物恢复前后浮游植物物种组成、生物量、多样性指数及其与水质理化参数的动态变化关系。结果表明,2009-2013年共检出浮游植物156种,隶属8门、78属,其群落结构在3个湖区间不存在显著差异(P>0.05),藻类优势种的年际变化呈现由绿藻门(Chlorophyta)的球衣藻(Chlamydomonas globosa)、小球衣藻(Chlamydomonas microsphaera)和蓝藻门(Cyanophyta)的铜绿微囊藻(Microcystis aeruginosa)、不定微囊藻(Microcystis incerta)逐渐向绿藻门的蛋白核小球藻(Chlorella pyrenoidosa)、细丝藻(Ulothrix teneriima)、多形丝藻(Ulothrix variabilis)和硅藻门(Bacillariophyta)的颗粒直链藻(Melosira granulata)、具星小环藻(Cyclotella stelligera)转变。浮游植物群落的Margalef和Shannon-Weiner多样性指数分别在0.632~3.396和0.581~4.438之间变化,指示水体处于中度富营养状态且有转好趋势。调查期间水体总氮和总磷浓度分别在0.92~5.26 mg/L和0.005~0.108 mg/L。水质理化参数分析表明,茅家埠和乌龟潭浮游植物生物量与水体总氮的变化呈显著正相关(P<0.05)。研究表明,相比工程实施前,西湖湖西水质有明显好转,沉水植被恢复是富营养化水体治理的有效措施之一。

Eutrophication of water bodies has been attracting attention globally. Phytoplankton is affected by the degree of eutrophication and phytoplankton community structure is affected by submerged macrophytes. This study evaluated the effect of restoring submerged macrophytes on the phytoplankton community in West Lake,Hangzhou.Variations in phytoplankton community species composition,biomass,biodiversity indices,and changes in the physicochemical parameters of the water body were investigated before and after restoration of submerged macrophytes in the western lake district,including Maojiabu Lake,Wuguitan Lake and Yuhuwan Lake,during five-years of monitoring from 2009 to 2013. Samples were collected at three sites located near the centers of the three lakes.The Margalef diversity index and Shannon-Weiner diversity index were used to assess the trophic status,and total nitrogen（ TN） and total phosphorus（ TP） concentrations were measured to indicate the nutrient level. A total of156 phytoplankton species,belonging to 8 phyla and 78 genera,were recorded during the study and no significant differences in phytoplankton community structure were observed among the three lake districts（ P〉0. 05）. The dominant species of phytoplankton gradually shifted from Chlamydomonas globosa and Chlamydomonas microsphaera（ Chlorophyta）,and Microcystis aeruginosa and Microcystis incerta（ Cyanophyta） to Chlorella pyrenoidosa,Ulothrix teneriima and Ulothrix variabilis（ Chlorophyta） and Melosira granulata and Cyclotella stelliger（ Bacillariophyta）.The Margalef and Shannon-Weiner diversity indices fluctuated from 0. 632 to 3. 396 and from 0. 581 to 4. 438,respectively,indicating that water quality in the western area of West Lake was moderately eutrophic and that it improved significantly（ P〈0. 05） after the demonstration project. TN and TP concentration ranges were,respectively,0. 92-5. 26 mg/L and 0. 005-0. 108 mg/L. Analysis of water quality parameters indicates that the annual variation of phytoplankton density in Maojiabu Lake and Wuguitan Lake was positively correlated with TN（ P〈0. 05）. Our findings prove that water quality in West Lake improved after submerged vegetation was restored and demonstrate that macrophyte restoration is an effective means of managing eutrophication.