富营养化浅水湖泊生态修复中背角无齿蚌(Anodonta woodiana)对水质改善的影响

Effects of Anodonta woodiana on water quality improvement in restoration of eutrophic shallow lakes

滤水速率的快慢是决定滤食性河蚌对水质改善与否的关键,但受蚌龄大小、食物多少和季节变化的影响.以背角无齿蚌(Anodonta woodiana)为研究对象,设置幼龄蚌组、成年蚌组和无蚌对照组,在惠州西湖生态修复后的清水态和未修复的富营养化水体同时进行中型系统原位实验,测定了各处理组水层中氮、磷、总悬浮物(TSS)浓度和浮游藻类生物量(用叶绿素a(Chl.a)浓度表示)的季节变化,以研究蚌龄、食物和季节变化对背角无齿蚌水质改善的影响.结果表明,与对照组相比,背角无齿蚌提高了清水态水体总磷(TP)和铵态氮浓度,但对总氮(TN)、TSS和浮游藻类Chl.a浓度的影响不显著,表明其不能有效改善清水态水体水质;富营养化水体中,背角无齿蚌虽对水中TN浓度影响不显著,但显著降低了TP浓度、浮游藻类Chl.a浓度和TSS浓度;表明背角无齿蚌可改善富营养化水体水质;且富营养化水体中幼龄蚌的滤水速率显著高于成年蚌;幼龄蚌的滤水速率春季最大(0.132±0.018 L/(g·h)),夏季最小.因此,在富营养化水体修复前期,可通过放养本地滤食性河蚌,如背角无齿蚌,以改善水质,春季放养幼龄蚌更佳,为接下来的修复创造有利条件;而在生态修复后期的清水态水体中,单独的河蚌对水质改善效果不明显.本研究可为水生态系统保护和富营养化水体生态修复提供参考.

The filtration rate of filter-feeding mussels is crucial in improving the water quality.However,it is affected by mussel age,food concentration and season.A situ mesocosm experiment with young and adult mussels of Anodonta woodiana was set up in restored clear and eutrophic sub-lakes of Huizhou West Lake.Nutrients,total suspended solids(TSS)and biomass of phytoplankton as chlorophyll-a(Chl.a)were measured and their filtration rates were calculated in different treatments with seasons to study the effect of filter-feeding mussels on water quality in the restoration of eutrophic shallow lakes.Results showed that in clear water,the mussels increased the ammonium nitrogen and total phosphorus(TP),but did not change the concentrations of total nitrogen(TN),TSS,and Chl.a,which indicated that the mussels cannot improve the water quality in the clear water conditions.In eutrophic water conditions,though the mussels did not change the concentrations of TN,they decreased the concentrations of TSS,Chl.a and TP,which indicated that they can improve the water quality in eutrophic conditions.The filtration rate of young mussels was generally higher than that of adults.In addition,the filtration rate of the young mussels was the highest(0.132±0.018 L/(g·h)in spring,and lowest in summer.Thus,local mussels,such as Anodonta woodiana,can be set to improve water quality at early stages in restoring the degraded ecosystem due to eutrophication,especially in spring.However,mussels alone cannot improve water quality in clear water conditions during the late stages of restoration.The results of this study are important for management of aquatic ecosystems and restoration of eutrophic shallow lakes.