围隔中鲢和菹草控藻效果及其生态学意义

在滇池沿岸的池塘中 ,构建了面积为 10 0m2 ,水深为 85cm ,底质均为淤泥的四个围隔 ,其中在三个围隔内分别放养密度为 10 0g/m3 、75g/m3 、5 0g/m3 的鲢。它们均在一定程度上控制浮游植物的生物量并改善水体透明度 ,其中初始放养鲢 75g/m3 的围隔控制效果最明显。放养三种密度的鲢在有效控制微囊藻水华的同时 ,原先水体的优势种类发生质的变化 ,水体中浮游植物的多样性也明显增加。放鱼 2个月后 ,在生物操纵的围隔中同时种入菹草 ,在75g/m3 的鲢控藻的围隔中 ,菹草长势良好 ,浮游动物大量出现 ,透明度进一步增加

ECOLOGICAL MEANING AND BLOOM CONTROLLING OF DIFFERENT DENSITY OF SILVER CARP FOLLOWED WITH POTAMOGETON CRISPUS IN ENCLOSURES

As we know,Silver carp (Hypophthalmichthys molitrlx) could decrease the biomass of the blue-green algae and have effect on species composition of phytoplankton,but different environment needs different density of Silver carp to control the cyanobacterial bloom. Dianchi lake is situated at Yungui Plateau,and the environment of it is different from other lakes. So the experiment was carried out. In this study, four enclosures in the same size,with an area of 100m 2 and a depth of 85cm,and sediment inside,were constructed near Dianchi Lake. And the water inside the enclosures came from the surface of Dianchi lake. Three enclosures were cultured with 100g/m 3,75g/m 3and 50g/m 3 of biomass of Silver carp respectively,and the left one was as control.During two months,the Chla. of phytoplankton were decreasing and the SD of the water were improving in enclosures cultured with Silver carp.The enclosure with 75g/m 3 of Silver carp improved the ecology well.Through putting the fish into the enclosures,the outbreaking of the cyanobacterial bloom was controlled,the dominant species of algae changed,and the biodiversity of phytoplankton increased. In order to study the effects of the Potamogeton crispus L. followed with Silver carp on the ecology of the enclosures. Continual experiment was done. After culturing the fish for two months,the enclosures which had been cultured with Silver carp were planted with Potamogeton crispus L.,and the aquatic plants in enclosure with 75g/m 3 of Silver carp grew better than in others,the zooplankton appeared with large amounts,and the SD of the water increased more.