滇池入湖河流大清河河口段浮游藻类格局研究

2006年7月至2007年12月对大清河3个样点的浮游藻类组成及密度、浮游叶绿素a浓度等指标进行逐月监测.共观察到浮游藻类65个分类单元,计53个属.所有样点的平均藻类密度是1.23×10⁸ ind·L^-1,最高密度为1.39×10⁹ ind·L^-1,最低密度为3.21×10⁵ ind·L^-1.铜绿微囊藻(Microcystis aeruginosa)为绝对优势种,监测期间其平均相对丰度为92.23%.随着离湖距离的增加,浮游藻类总密度、铜绿微囊藻的百分含量明显降低,而香农-威纳(Shannon-Wiener)、辛普森(Simpson 1/Dominance)多样性指数和均匀度(Evenness)则呈现升高趋势.同时,样点2、3的铜绿微囊藻百分含量与滇池的极为相似,而样点1则距离滇池较远,其铜绿微囊藻的百分含量及生物多样性指数方面均不同于样点2、3,说明滇池水的倒灌已显著影响到样点2、3的藻类组成.通过比较各样点间的群落相似性指数发现:样点1、3间的相似性指数显著低于样点1、2和样点2、3间的相似性指数.样点2、3间的相似性指数除2007年4、5及7月外,均超过60%.通过对样点1、2和3的浮游藻类群落在工程运行前后进行"非度量多维标度"(NMS)分析,发现示范工程运行后的1年内还未对大清河监测河段水生生物群落的恢复有显著作用.

Spatio-temporal pattern of phytoplankton in estuarial reach of Daqinghe river-inflow river of Dianchi Lake

From June 2006 to December 2007,monthly samplings of 3 sites were carried out for measuring chlorophyll a concentration,composition and density of phytoplankton.Phytoplankton sampling yielded 65 taxonomic units(mostly to genus levels) in 53 genera.Microcystis aeruginosa was predominant with 92.23% of the total taxa.The average algal density for all the sites was 1.23×10⁸ ind·L^-1 and the maximum was 1.39×10⁹ ind·L^-1,while the minimum was 3.21×10⁵ ind·L^-1.With the increased distance between Dianchi Lake and the sampling sites(from site 3 to 1),total density of phytoplankton and Microcystis aeruginosa decreased dramatically,while the Shannon-Wiener,Simpson(1/Dominance) diversity and evenness went up significantly.Besides,Microcystis aeruginosa of site 2 and 3 was similar with that of Dianchi Lake,while site 1 was different from site 2 and 3 due to its long distance away from Dianchi Lake,indicating significant impacts of Dianchi Lake water on taxonomic composition of site 2 and 3.From the percentage similarity index of community(PSc) among 3 sites,we found that PSc index between site 1 and 3 was significantly lower than that of site 1&2 and site 2&3.Except for April,May and July 2007,the PSc index between site 2 and 3 was higher than 60%.After the project operation,Microcystis aeruginosa of site 1 and 2 showed decreasing trend.Nevertheless,Microcystis aeruginosa of site 3 increased.At the same time,species richness of the 3 sites increased dramatically after the project.Changes in algal community structure(i.e.,the species present and their relative abundances) following project operation were evaluated by non-metric multi-dimensional scaling(NMS) ordinations.The results showed that overall algal assemblage structure of the 3 sites remained similar throughout the study period(MRPP,p>0.05),indicating no significant impacts on phytoplankton community 1-year after project operation.