长江下游江段秋季浮游植物生态指标与理化指标评价

采用种类相似性指数、多样性指数等多项生物学指标分析2009年秋季长江下游段的浮游植物群落特征，并结合理化指标评价其水质营养状态。结果表明：2009年秋季，长江下游段共检出绿藻(Chlorophyta)、硅藻(Bacillariophyta)、蓝藻(Cyanophyta)、裸藻(Euglenophyta)、隐藻(Cryptophyta)5门27种，浮游植物细胞丰度变化在5.68×104～7.08×104 cells/L，平均为6.01×104 cells/L，浮游植物生物量变化在30.43～34.73 μg/L，平均为32.46 μg/L；各采样站位之间的浮游植物相似性指数变化在0.30～0.63，介于轻度相似至中度相似之间；多样性指数变化在2.38～2.73，多样性较好或丰富，显示出长江下游段的浮游植物群落处于较稳定的状态；水质CODMn、TN、TP和TLI（∑）分别变化在2.71～3.23 mg/L、1.24～1.35 mg/L、0.058～0.072 mg/L和44.87～45.96；综合水质生物学和化学评价结果可知2009年秋季长江下游段的水质较好；但从水质评定级别来看，化学评价得出的水质等级与生物学评价得出的水质等级有所不同，显示出两种方法的差异性，因此，生物监测应与理化监测相结合，以提高监测结果的准确性和可靠性。〖

WATER QUALITY EVALUATION BY PHYTOPLANKTON COMMUNITYSTRUCTURE INDICES AND PHYSICAL CHEMICAL INDICES IN THELOWER REACH OF THE YANGTZE RIVER IN AUTUMN

Biological indices such as similarity index,diversity index were used to analyze the community structure characteristics of phytoplankton,and both biological indices and physical chemical indices were used to evaluate the water quality in the lower reach of the Yangtze River in Autumn.Results showed that there were 5 phyla including 27 species of phytoplankton in the lower reach of the Yangtze River in Autumn.The abundance of phytoplankton ranged from 5.68×104 to 7.08×104 cells/L,with the average of 6.01×104 cells/L,and the biomass of phytoplankton ranged from 30.43 to 34.73 μg/L,with the average of 32.46 μg/L. The similarity indices ranged from 0.30 to 0.63,indicating that the phytoplankton similarity was between mild similarity and middle similarity.The phytoplankton diversity indices ranged from 2.38 to 2.73,which meant that both phytoplankton diversity and phytoplankton evenness were good and the phytoplankton community structure was in a stable level in the lower reach of the Yangtze River in Autumn.The permanganate (CODMn),total nitrogen (TN),total phosphorus (TP) and Comprehensive Trophic State Index (TLI(∑)) ranged form 2.71 to 3.23 mg/L,1.24 to 1.35 mg/L,0.058 to 0.072 mg/L and 44.87 to 45.96 respectively.It could be concluded that the water quality of the lower reach of the Yangtze River in Autumn was good.However,the pollution degrees evaluated by physical chemical method was more sensitive than that evaluated by biological method,which revealed the difference between the two evaluation methods.Therefore,in order to improve the veracity and reliability of the monitoring result,the biological monitoring methods should be coupled with the physical chemical monitoring as well.〖