【文章內(nèi)容簡介】 lgae appears6．在東湖里進行的圍隔實驗．在東湖里進行的圍隔實驗Enclosure experiments inside the lake 什么導(dǎo)致了東湖藍藻 “ 水華” 的消失？?營養(yǎng)鹽的變化？?牧食浮游動物的變化？?濾食性魚類的變化？自自 1985年夏季，藍藻水華消失年夏季，藍藻水華消失The diappearance of Microcystis bloom from Lake Donghu in 1985What is the cause of the disappearance of waterbloom? ?Nutrients？?Predator？?Filtering fishes？Enclosure experiment in the summer of 1989 ?Eight cubiform enclosures were installed within the lake?The enclosures with bottom and sides were made of impermeable polyethylene cloth, each measuring m square at the four vertical sides and at the bottom.?The enclosures are filled with lakewater to the depth of 2 m。 thus each enclosure held m3 of lakewater. ?The lakewater was filtered through a plankton before being introduced into the enclosures in order to prevent the unintended introduction of fish fry. 1989年夏季的實驗?zāi)晗募镜膶嶒瀲粲貌煌杆木垡蚁┎牧现瞥蓢粲貌煌杆木垡蚁┎牧现瞥? m見方見方上面敞開、下面有底的水箱，上面敞開、下面有底的水箱，湖水湖水 m深（湖水容積深（湖水容積 m3））湖水用浮游生物網(wǎng)濾過，以避免把小魚苗帶進圍隔。湖水用浮游生物網(wǎng)濾過，以避免把小魚苗帶進圍隔。 Purpose:1) How does the stocking of silver carp and bighead carp influence the munity structure of phytoplankton in the enclosure? 2) Can the dense stocking of fish eliminate water bloom? 目的：目的：1）鰱和鳙的放養(yǎng)如何影響圍隔內(nèi)浮游植物的群）鰱和鳙的放養(yǎng)如何影響圍隔內(nèi)浮游植物的群落結(jié)構(gòu)？落結(jié)構(gòu)？2）魚的密集放養(yǎng)能否消滅水華？）魚的密集放養(yǎng)能否消滅水華？Fig.藻類體積 (Algal volume (mm3 L1)1989年 510月各圍隔中和周圍湖水中浮游植物總量、藍藻生物量和鞭毛藻生物量變動情況Changes in the biomass of total phytoplankton, cyanobacteria and flagellates in the enclosures and the surrounding lake water in the Donghu Lake during MayOct. 1989 (after Shei and Liu, 1991)E3E5E7Lake water1989年 510月各圍隔中和周圍湖水中浮游植物總量、藍藻生物量和鞭毛藻生物量變動情況Changes in the biomass of total phytoplankton, cyanobacteria and flagellates in the enclosures and the surrounding lake water in the Donghu Lake during MayOct. 1989 (after Shei and Liu, 1991)The fluctuation of chlorophylla content and the biovolume of the total phytoplankton in the three enclosures was similar in pattern, but in the fishfree 7, the values were much higher than in the enclosures stocked with fish and in the ambient lakewater. The introduction of fish brought about marked changes not only in the biovolume of total phytoplankton, but also in the position of the dominant group. In the enclosures stocked with fish, the proportion of Cyanophyceae was meager. In the enclosures without fish, large colonyforming Microcystis was predominant (Shei and Liu, 1991). 三個圍隔中葉綠素三個圍隔中葉綠素 a的含量和浮游植物總體積的波動情況相似，的含量和浮游植物總體積的波動情況相似，但在無魚的但在無魚的 7中，數(shù)值要比有魚的圍隔和周圍湖水中高的多，中，數(shù)值要比有魚的圍隔和周圍湖水中高的多，魚的引入，不僅給浮游植物的總體積而且對優(yōu)勢類群的組成帶魚的引入，不僅給浮游植物的總體積而且對優(yōu)勢類群的組成帶來了明顯的改變。養(yǎng)了魚的圍隔中，藍藻的比例很小，沒有魚來了明顯的改變。養(yǎng)了魚的圍隔中，藍藻的比例很小，沒有魚的圍隔，微囊藻屬（的圍隔，微囊藻屬（ Microcystis）的大型群體獨占優(yōu)勢）的大型群體獨占優(yōu)勢（（ Shei and Liu,1991）） Experiment in the summer of 1990 The purpose of this experiment was:1) to restore waterbloom in more of the enclosures。 2) to introduce silver carp and bighead carp into those enclosures covered already with waterbloom, to see if the bloom can be consumed by the fish。 3) to monitor the change in the size structure of phytoplankton munity in enclosures after the introduction of fish. 1990年夏季的實驗?zāi)晗募镜膶嶒災(zāi)康模耗康模?）使更多的圍隔里重現(xiàn)水華；）使更多的圍隔里重現(xiàn)水華；2）在水華已覆蓋水面的圍隔里引進鰱和鳙，看水華能）在水華已覆蓋水面的圍隔里引進鰱和鳙，看水華能否被魚吃掉；否被魚吃掉；3）監(jiān)測圍隔中引入魚以后浮游植物群落在大小結(jié)構(gòu)方）監(jiān)測圍隔中引入魚以后浮游植物群落在大小結(jié)構(gòu)方面的變化。面的變化。 1 Silver carp, 6 (average body weight 148 g), total stocking density 71 g/m3 2 Bighead carp, 6 (average weight 176 g), total stocking density g/m33 Silver carp, 4 (average 21g), bighead carp, 2 (average weight 32 g), total stocking density 12 g/m34 Silver carp, 4 (average 23 g), bighead carp 2 (average weight 32 g). total stocking density 13 g/m35 Silver carp, 3 (average 152 g), bighead carp,3 (average weight 172g), total stocking density 78 g/m36 No fish 用了用了 6個圍隔，圍隔的位置和大小與個圍隔，圍隔的位置和大小與 1989年相同，各圍年相同，各圍隔放養(yǎng)魚類的情況如下：隔放養(yǎng)魚類的情況如下： 1 鰱魚鰱魚 6尾（平均體重尾（平均體重 148 g）） 2 鳙魚鳙魚 6尾（平均尾（平均 176 g）） 3 鰱魚鰱魚 4尾（平均尾（平均 21g）） 4 鰱魚鰱魚 4尾（平均尾（平均 23 g）） 5 鰱魚鰱魚 3尾（平均不尾（平均不 152 g）） 6 不放魚不放魚 216。Luxuriant Microcystis bloom occurred in enclosures l, 2, 5 and 6. 216。In enclosures 1, 2 and 5, the biomass of phytoplankton was substantially reduced. 216。In the enclosures without fish (6), the bloom, once formed, persisted to the end of the experiment. 216。In enclosures 3 and 4,total chlorophylla amount remained low throughout the experiment, and on the average, more than 80% of the total phytoplankton was