喀斯特湿地空心莲子草入侵迹地水质时空变化特征

为了解威宁草海湿地空心莲子草入侵迹地水质时空变化特征，于2018年1月(冬)、2018年4月(春)、2018年7月(夏)及2018年10月(秋)，在草海湿地空心莲子草入侵迹地，根据空心莲子草入侵状态分别采集水体样品，测定pH值、总氮(TN)、氨氮(NH4+-N) 、总磷(TP)、高锰酸盐指数(CODMn )和叶绿素a(Chl.a)等水质指标，对空心莲子草入侵迹地水体富营养化状态及水质时空变化特征进行分析。结果表明：（1）草海湿地空心莲子草入侵迹地水质pH、TN、NH4+-N、TP、CODMn、Chl.a季节性差异显著（p<0.05），TN、NH4+-N、TP、CODMn和Chl.a随水域变化从上游至下游呈降低趋势。TN、NH4+-N、TP、Chl.a随入侵程度的增加呈显著降低趋势（p<0.05）；（2）空心莲子草入侵迹地水体综合营养指数随季节变化呈下降趋势，春季水质最差。随水域变化综合营养指数沿上游到下游呈降低趋势，上游水质最差。草海湿地空心莲子草入侵迹地水体总体处于中度富营养化状态；（3）草海湿地空心莲子草入侵迹地属于磷限制型，通过限制磷元素的输入可有效降低水体富营养化程度。

Temporal and spatial changes of water quality in the invasion site of Alternanthera philoxeroides in Karst wetland

In order to understand the temporal and spatial changes of the water quality of Alternanthera philoxeroides invaded the Caohai Wetland in Weining, in January 2018 (winter), April 2018 (spring), July 2018 (summer) and October 2018 (autumn), In the Caohai Wetland Alternanthera philoxeroides invasion site, water samples were collected according to the invasion status of Alternanthera philoxeroides to determine pH, total nitrogen (TN), ammonia nitrogen (NH4+-N), total phosphorus (TP), and permanganate index ( CODMn) and chlorophyll a (Chl.a) and other water quality indicators, to analyze the eutrophication status of the water body in the invasion site of Alternanthera philoxeroides and the temporal and spatial changes of water quality. The results showed that: (1) The water quality of Alternanthera philoxeroides in the Caohai Wetland had significant seasonal differences in pH, TN, NH4+-N, TP, CODMn, and Chl.a (p<0.05); TN, NH4+-N, TP, CODMn and Chl.a showed a decreasing trend from upstream to downstream with the changes of waters. TN, NH4+-N, TP, Chl.a showed a significant decreasing trend with the increase of invasion degree (p<0.05); (2)Seasonal changes showed a downward trend, with the worst water quality in spring; the comprehensive nutrient index showed a downward trend along the upstream to downstream with the changes in the water area, and the upstream water quality was the worst; the Caohai Wetland Alternanthera philoxeroides invaded the site water body in an overall moderate eutrophication state; (3) The Caohai Wetland Alternanthera philoxeroides is a phosphorus-restricted area, and restricting the input of phosphorus can effectively reduce the eutrophication of the water body.