太湖流域直湖港水系不同水质状况的河道水体对麦穗鱼卵孵化的影响

Effects of different water quality condition on the hatching efficiency of Pseudorasbora parva eggs in Zhihugang river system,Taihu Lake Basin

以麦穗鱼(Pseudorasbora parva)为研究对象,分析了4种河道水体的水质参数与麦穗鱼苗孵化率、浮游动物密度的关系。直湖港水体的总氮(TN)含量最高,总磷(TP)、氨氮(NH3-N)含量较高,pH、溶解氧(DO)较低,具有最高的鱼苗孵化率,而轮虫数量为0,剑水蚤数量居中。人工湿地水体的pH、化学需氧量(CODMn)、DO含量、电导率(EC)较高,TN、TP含量、氧化还原电位(ORP)较低,具有最低的鱼苗孵化率,轮虫数量和剑水蚤数量最高。RDA分析前4轴共解释水生类群结构总变异的91.44%,相对重要的6个环境因子是TN、pH、EC、TP、COD_(Mn)、DO,分别解释了结构变异的22%、18%、15%、11%、11%、8%。与鱼苗孵化率正相关性较高的指标为TN(r=0.62)、TP(r=0.40),而负相关性较高为EC(r=-0.47)、DO(r=-0.42)、pH(r=-0.47)。与轮虫密度正相关性较高指标为pH(r=0.49)、EC(r=0.36),负相关性较高为TN(r=-0.54)、TP(r=-0.32)。与剑水蚤密度正相关性较高指标为NH_(3)-N(r=0.31),负相关性较高为TN(r=-0.28)、ORP(r=-0.27)。可见含氮量决定了鱼苗的孵化率,水体营养盐含量高时鱼苗的孵化率就会相应提高。

Pseudorasbora parva was selected as the study object,the relationships of water quality indices from four river channels with fish egg hatching rate and zooplankton density were analyzed.The Zhihugang(ZHG)water quality was characterized by the highest TN,higher TP and NH3-N,lower pH and DO,and had the highest fish egg hatching rate,but the zero-density of rotifers and the middle density of cyclops.The constructed wetlands(RGSD)water quality was characterized by higher pH,CODMn,DO and EC,lower TN,TP and ORP,and showed the lowest fish egg hatching rate while the highest densities of rotifers and cyclops.The first four axes of RDA analysis explained 91.44%of the total structural variation of aquatic groups.The most important six environmental factors were TN,pH,EC,TP,COD_(Mn) and DO,which explained 22%,18%,15%,11%,11%and 8%of the variation,respectively.Water quality indices with higher positive correlation for egg hatching rate were TN(r=0.62)and TP(r=0.40),those with higher negative correlation were EC(r=-0.47),DO(r=-0.42)and pH(r=-0.47).Water quality indices with higher positive correlation for rotifer density were pH(r=0.49)and EC(r=0.36),those with higher negative correlation were TN(r=-0.54)and TP(r=-0.32).Water quality indices with higher positive correlation for cyclops density was NH_(3)-N(r=0.31),and the higher negative correlation indices were TN(r=-0.28)and ORP(r=-0.27).In a word,the water nitrogen content determines the egg hatching rate,and the hatching rate was the highest in eutrophic water.