太湖介形虫分布与水环境因子间关系的典范对应分析

CCA OF OSTRACOD DISTRIBUTION AND ENVIRONMENTAL FACTORS IN THE TAIHU LAKE

2004年9月至2005年8月间对太湖介形虫分布状况进行了季节性的调查,共获得介形虫15种,其中克氏瘤丽星介Physocypria kraepelini,豆形豆形玻璃介(比较种)Fabaeformiscandona cf.fabaeformis和塔尔薄丽星介Dolerocypria taalensis的出现频度分别达71.05%、44.74%和42.11%,为太湖水体中的常见种。相似性分析(UPGMA)结果表明太湖介形虫可分为四个不同的类型,即终年出现物种、仅秋季出现物种、夏秋季出现物种和仅春季不出现的物种。应用典范对应分析(Canonical Correspondence Analysis,CCA)对太湖38个样点的15种介形虫与9个环境因子关系研究的结果是介形虫与环境因子间的相关性高达100%,提示太湖水体环境因子变化影响了介形虫的分布和季节性变化;水体的9个环境因子中的pH值、植被密度、总磷和总氮对介形虫的分布影响最大;而化学需氧量和溶氧量对其也有一定的影响。从物种分布状况看,稳定湖花介Limnocythere stationis对水体中环境因子的敏感性明显高于其它物种,其高分布频度对高总磷和高叶绿素具指示作用;太湖中的三种常见种介形虫(克氏瘤丽星介、豆形豆形玻璃介(比较种)和塔尔薄丽星介)的分布主要受总磷和化学需氧量的影响,其高分布频度是水体高化学需氧量的良好指标种;在高总氮和高化学需氧量的春季水体中无角尾狭星介Stenocyprisderupta,近球形金星介Cyprissubglobosa,上野湖湾介Strandesiauenoi,绿色湖湾介S.viridis,条纹湖湾介S.vittata,环星介(未定种)Zonocypris sp.和史氏达尔文介Darwinula stevensoni的出现,暗示这些物种的高分布频度可以指示水体中的低总氮和低化学需氧量。

Fifteen ostracod species were recorded from the Taihu Lake during the period from September 2004 to August 2005. Among them, Ph ysoc y pria kraepelini , Fabae f ormiscandona cf. f abae f ormis and Doleroc ypria taalensis were common species with high occurrence frequency in the Taihu Lake. UPGMA clustering of species based on their occurrence frequency in different ecological conditions revealed four main species assemblages. Canonical Correspondence Analysis （CCA） explained 100% of the correlation between species and environmental variables, suggesting that the occurrence of many species was related to seasonal changes in ecological conditions. Among nine environmental factors, pH value, plant density （Pd）, total phosphorus （Tp） and total nitrogen （Tn） were the most affective variables on the species occurrence. Because of its sensibility to high total phosphorus （Tp） and chlorophyll, Limnocythere stationis may be used as a good indicator of them. For the same reason, Physocypria kraepelini, Fabaeformiscandona cf fabaeformis and Dolerocypria taalensis may serve as nice indicators of high chemical oxygen demand （COD） ; and the high occurrence frequency of Stenocypris derupta , Cypris subglobosa , Strandesia uenoi , S. viridis, S. vittata, Zonocypris sp. and Darwinula stevensoni indicated low total nitrogen （Tn） and chemical oxygen demand （COD） in water.