Ecological Ｒestoration Technology Applied in the Lakeside zone Demonstration Project of Gehu Lake

27 Mar Ecological Ｒestoration Technology Applied in the Lakeside zone Demonstration Project of Gehu Lake

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Abstract

在滆湖湖滨带进行生态修复试验，为湖滨带修复技术的进一步完善和滆湖水环境治理提供参考， 也为太湖 流域湖滨带生态功能恢复提供实用示范技术。在太滆运河滆湖河口 28． 67 hm2 试验区内设置围隔， 放养鲢鳙、 细鳞鲴、三角帆蚌，保护和栽培水生植物等， 对比分析各种工程技术措施及水生生物群落结构对营养盐削减效 果，监测和评价水质。2008 － 2009 年试验期间的水质监测结果表明， 试验区综合污染指数 1． 76 ～ 1． 79， 为重污 染水平; 对照点( 滆湖大湖区) 为 2． 03 ～ 2． 09， 属严重污染水平， 试验区污染程度较对照点降低了一个等级。以 漂浮植物为主的湖滨带湖湾湿地生物群落发育良好， 与对照点相比， 试验区 TN 去除率达 26． 52% ， TP 为 27. 92% ， 而 NH3 -N 为 46． 15% ～ 68． 12% ， 但 chl-a 及 CODMn则高于对照点。在试验区内的围隔试验中， 以沉水 植物为主的除磷效果最好，达 37． 06% 。放养的鲢鳙有效控制了蓝藻暴发。

English Abstract

Gehu Lake， located upstream of Taihu Lake， is the second largest lake in southern Jiangsu Province．
Historically， it was a typical shallow macrophytic lake and played an important role in protecting water quality in
Taihu Lake． However， large scale reclamation in the littoral zone beginning in the 1970＇s and the hardening of levees in the 1990＇s has seriously damaged the biological resources of the lake． Since 2008， Gehu Lake has been a turbid algae-dominated lake and large scale cyanobacterial blooms occur every year． The lakeside zone is a natural
barrier， intercepting exogenous terrestrial pollutants and providing valuable habitat． In 2008 and 2009， we established an ecological restoration demonstration project in the riparian zone along the mouth of Tai-Ge canal， connecting Gehu Lake to Taihu Lake． This article is a detailed introduction to the demonstration project and the goal is to
provide a useful reference for remediating littoral ecology and improving water quality in shallow lakes． The demonstration area， enclosed by netting， was 28． 67 hm2 and ten sampling stations ( Stations A-J) were monitored． There
were no macrophytes in the demonstration area and herbivorous fish were removed by gill net before the investigation
began． In March of 2008， three experimental areas ( Station A， B and C) were established in the eastern section of
the project area and floating plants， macrophytes and emergent aquatic plants were introduced． In February of
2009， another three experimental areas ( Station F， G and H) were established in the northern section of the project area and submerged plants and a smaller number of floating plants were introduced． During the investigation，
silver carp ( Hypophthalmichthys molitrix) ， bighead carp ( Aristichthys nobilis) ， Xenocypris microlepis and triangle
sail mussel ( Hyriopsis cumingii) were released to the project area． To evaluate the effect of the ecological restoration project and analyze the nutrient reduction efficiency of different bioremediation techniques， we investigated the
change in the phytoplankton and zooplankton communities and monitored water quality parameters． Water quality at
Station A， B， C， D ( central demonstration area) and E ( control station， 1 500 m from the demonstration project)
was monitored monthly in 2008 and then at Station F， G， H， I and J ( the same locations as Station D and E) in
2009． Water quality monitoring results show that the comprehensive pollution indices in the demonstration project
area ranged from 1． 76 to 1． 79 in 2008 － 2009， while the comprehensive pollution indices at the control station
ranged from 2． 03 to 2． 09． The higher pollution indices at the control site indicates the ecological remediation project did improve water quality， although it remained heavily polluted． The floating plant-dominated wetland community developed well and played an important role in nutrient reduction． The average removal rates of total nitrogen
( TN) ， total phosphorus ( TP) and ammonia nitrogen ( NH3-N) in the trial zone were， respectively， 26． 52% ， 27．
92% ， and ( 46． 15 － 68． 12) % compared with the control station． However， chlorophyll-a and the potassium permanganate index ( CODMn) in the demonstration area were higher than at the control station． The enclosures within
the demonstration project area removed TP most effectively ( 37． 06% ) ． Stocking silver carp and bighead carp effectively suppressed cyanobacterial blooms in the demonstration project area