摘要：
Identifying the factors affecting thc variations of chlorophyll-a concentration is very important in assessment and management of water quality in lakes.Most of previous studies focused on the relationships between chlorophyll-a concentration and abiotic factors,while paid little attention on the effects of biotic ones.To examine the relative importance of the abiotic and biotic factors on seasonal variation of chlorophyll-a in shallow lakes,water samples were collected semimonthly from February 2009 to January 2010 in Lake Tingtang,and four-day or one-week intervals from May 2008 to April 2009 in Lake Jinghu,respectively.Simultaneously,the abiotic factors including water temperature,pH,dissoloved oxygen,Secchi depth,total nitrogen (TN) and total phosphorus (TP) as well as the densities of rotifers and ciadocerans were analyzed.The chlorophyll-a concentration in each water body was measured in two fractions:one filtered through a 25 μm plankton net (Chl.a＜25 μm) and another unfiltered (Chl.a).During the monitoring period,the two fractions of chlorophyll-a in two lakes were both positively correlated with water temperature and negatively associated with secchi depth,and they did not show reverse relationship with the densities of rotifers and cladocerans in both lakes.Chl.a and Chl.a＜25 μm increased significantly with TP but decreased with TN/TP ratio in Lake Jinghu,while they showed reducing trends with TN and TN/TP ratio in Lake Tingtang.During winter,the rotifer density was negatively associated with Chl.a and Chl.a＜25 μm in Lake Jinghu,and the similar relationships between them were found in Lake Tingtang,indicating that the low cblorophyll-a concentration in winter might be partly due to the prey effect of rotifers on phytoplankton.Based on the relative weight of the effect intensity of each correlated factor on the variation of chlorophyll-a concentration,Chl.a and Chl.a＜25 μm were both affected mostly by secchi depth.Additionally,the two fractions of chlorophyll-a decreased with an increase in secchi depth.Taken together,the results in this paper implied that Secchi depth might be a simple and convenient index for predicting chlorophyll-a concentration in the small enclosed lakes.%为探讨非生物因子和生物因子对水体叶绿素a(Chl.a)浓度变动的相对重要性,对芜湖市内的汀棠湖(每半月1次)和镜湖(每4天或7天1次)进行高频采样,分析理化因子及浮游动物密度与Chl.a浓度间的关系.结果表明,从全年来看,2个湖泊的Chl.a浓度均与水温和透明度间分别呈现显著的正相关性和负相关性,与浮游动物密度均无显著相关性;镜湖Chl.a浓度随着总磷浓度和氮磷比的增加分别呈上升和降低趋势.从季节来看,冬季两湖中的Chl.a浓度最低,轮虫密度与此阶段镜湖中藻类Chl.a总浓度和小型藻类的Chl.a浓度间均呈显著负相关,且其对上述两类Chl.a浓度变动的影响程度最大,表明轮虫对藻类的牧食效应降低了冬季镜湖中的Chl.a浓度.从各环境因子对Chl.a浓度变动影响的相对权重来看,除了冬季的镜湖外,2个湖泊中的两类Chl.a浓度均与透明度的关系最密切,且均随着透明度的上升而降低,暗示了透明度可作为预测小型封闭性浅水湖泊中Chl.a浓度的简便指标.
