Effects of low pH on zooplankton in some suburban waterbodies of Chongqing City

Samples of zooplankton were collected for 4 times from May,1989 to May,1992 in some subur- ban waterbedies of Chongqing City, a heavy acid rain area in the southwest China. The qualitative and quanti- tative analysis results indicated that the species of zooplankton(y)were found to decIine gradually with a re- duction of pH value(x)ranging from 4.01 to 8.80. The regression equation of relation between them may be expressed as: y=1.520x-2.488(r=0.61, P<0.01,n=22)with respect to abundance of zooplankton,the mean density was abundant(3609. 23 ind./L)at pH ranging from 5.0 to 8.8,but was lower(151.50 ind./L)at pH ranging from 4.0 to 5.0. The evidence presented suggests that effects of low pH on zooplank- ton is the greatest below pH 5.0.