底泥营养物质释放对围隔水生生态系统的影响

采用围隔研究了底泥对湖泊生态系统的影响.试验用的8个围隔设置于武汉东湖,其中E1～E4围隔采用富营养的东湖Ⅰ站底泥,E5～E8围隔采用相对贫营养东湖Ⅲ站底泥;E1、E2及E5、E6围隔中注入湖水,其余围隔注入自来水.试验持续2个半月.研究结果表明,加入I站底泥的围隔中pH、总氮(TN)、总磷(TP)平均值显著高于加入Ⅲ站底泥的围隔.E1～E4围隔中自8月初形成持续的微囊藻水华,其生物量显著高于没有微囊藻水华的E7、E8围隔,E5、E6围隔则形成短期微囊藻水华.E1～E4围隔浮游植物多样性指数远低于没有微囊藻水华的E7、E8围隔.上述结果表明,在浅水水体中,底泥对水质的影响要远远大于湖水,围隔中蓝藻水华发生的磷域值介于E5、E6和E7、E8围隔中磷含量之间,为0.06～0.10 mg/L.

Effects of Sediment Nutrients Release on Enclosure Ecosystems

Effects of sediment on lake ecosystem were studied by using enclosures.Eight enclosures were set up in Lake Donghu.Enclosure E1-E4 used sediment from eutrophic station I and enclosure E5-E8 used sediment from oligotrophic station Ⅲ.Lake water was pumped into enclosures E1,E2 and E5,E6,tap water was added into other four enclosures.The experiments lasted for about two and a half months.The results showed that pH,TN and TP were significantly higher in E1-E4 than those in E5-E8.Microsytis bloomed continuously in enclosures E1-E4 since August E1-E4 had much higher phytoplankton biomass than enclosures E7,E8 where no blooms were formed.E5,E6 had Microsystis blooms only for a short period of time.The index of ploytoplankton biodiversity was much lower in E1-E4 enclosure than that of E7,E8 enclosure.The above results indicated that the effect of sediments on shallow water ecosystem was much higher than water column,and the threshold TP value for Microsytis blooms was probably between 0.06-0.10 mg/L,i.e.between the average TP contents in E5,E6 and E7,E8.