漓江桂林市区段夏季浮游植物群落特征与水质评价

Phytoplankton community and water quality in guilin city section of Lijiang River in summer,China

浮游植物是水生态系统的重要组成部分，其群落结构变化与水体环境条件密切相关，能直接影响水生态系统的功能，是水环境质量优劣的重要指示因子之一。为揭示漓江流域浮游植物群落结构特征及其与水质的相互关系，2012年8月对漓江桂林市区段干流（桂林赵家桥村至桂林王家村）的理化指标及浮游植物的群落组成分布进行了分析研究，并结合水体理化指标和生物指数对漓江水质进行了评价。结果表明，漓江水体高锰酸盐指数、总氮、总磷、氨氮的变化范围依次为1.80-6.20、1.12-2.68、0.022-0.282、0.34-1.73 mg·L-1，其含量在上游变化平稳，到三条支流汇入处大幅增高，最高值均出现在南溪河入口处。共调查到浮游植物7门60属128种，其中硅藻50种（占种类组成的39.06%），绿藻52种（占40.63%），蓝藻16种（占12.50%），裸藻7种（占5.47%），黄藻、金藻和甲藻各1种（分别占0.78%）。优势种依次为冠盘藻（S. tephanodiscus）、蛋白核小球藻（C. pyrenoidosa）、喙头舟形藻（N.rhynchocephala）、短小舟形藻（N.exigua）、广缘小环藻（C.Bodanica）、四尾栅藻（S.quadricanda）和肘状针杆藻（S. ulna）。浮游植物密度为10.3×10^4-1047.0×10^4ind.·L^-1，平均密度为474.7×10^4 ind.·L^-1，其中密度最小的是赵家桥村，密度最大的是南溪河入口；种类上绿藻门占据多数，密度和优势种分布上以硅藻居多，总体上属于硅藻-绿藻型水体。浮游植物多样性指数Shannon-Wiener指数（H）在1.60-4.27之间，Simpson指数（D）在2.24-12.74之间，水质总体上为清洁-轻度污染。Margalef指数（d）在1.85-4.23之间，Pielou指数（J）在0.40-0.83之间，指数值总体较高，漓江水体中浮游植物群落结构比较稳定，受外界环境的影响较小。漓江干流水质总体上属于Ⅱ-Ⅲ类水体，在支流汇入处理化指标浓度增加，浮游植物多样性指数急剧降低，种类数减少，耐污品种大量繁殖，水质恶化。因此，有必要加大支流流经地区面源污染控制和治理力度，加强对市区下游断面浮游植物群落结构的监测，有效避免水质恶化。

Phytoplankton plays a crucial role for primary productivity in aquatic ecosystems. The changes in community structure are related to the environmental conditions of water and directly affect the function of aquatic ecosystems; it is one of the important indicating factors of the quality of the water environment. In order to reveal the relationship between the structure of the phytoplankton community and the water quality of Lijiang River, the physical and chemical indicators and Phytoplankton community characteristics in the Guilin city section of Lijiang River （from Zhaojiaqiao village to Wangjia village） were investigated in August, 2012. The results showed that the contents of permanganate index （CODMn）, total nitrogen （TN）, total phosphorus （TP）, ammonia （NH4＋-N） were from 1.80 to 6.20, 1.12 to 2.68, 0.022 to 0.282 and 0.34 to 1.73 mg·L-1, respectively, which smoothly changed in the upstream and significantly increased in tributaries. A total of 128 species which belong to 60 genera of 7 phyla were identified in Lijiang River, including 50 species of Bacillariophyta （39.06%）, 52 species of Chlorophyta （40.63%）, 16 species of Cyanophyta （12.5%）, 7 species of Euglenophyta （5.47%）, 1 species of Pyrrophyta （0.78%）, 1 species of Chrysophyta （0.78%） and 1 species of Xanthophyta （0.78%）. The dominant species were S. tephanodiscus,C. pyrenoidosa, N.rhynchocephal, N.exigua,C.Bodanica,S.quadricandaandS. ulna. The cell abundance of phytoplankton ranged from 10.3×104 to 1047.0×104 ind.·L-1 and the average cell abundance was 474.7×104 ind.·L-1, which was the smallest in Zhaojiaqiao village and the largest in Nanxihe entrance; green algae was major on species and diatom was major on cell abundance and distribution of dominant species. Thus, Lijiang River could be classified as the diatom-green algae river. Shannon-Wiener and Simpson indexes of phytoplankton were from 1.60 to 4.27 and 2.24 to 12.74, indicating that the water quality of Lijiang River was cleaning-light pollution. Margalef and Pielouin indexes were from 1.85 to 4.23 and 0.40 to 0.83, indicating that the plankton community structures of this river were stable and unsusceptible to the outside interference. However, the biodiversity index was drastically reduced, the number of phytoplankton species was decreased, and the stain species bloomed in the tributaries, suggesting that the tributaries area was polluted. On the whole, the water quality of Lijiang River wasⅡ-Ⅲ water bodies, but tributaries were seriously contaminated. Therefore, in order to avoid the deterioration of water quality, it is necessary to increase control on non-point source pollution and strengthen monitoring on phytoplankton community structure in the downstream section of the Guilin.