The Effects Of The Artificial Floating Bets On The Community Structure Of Plankton And Fish In The Yangtze Estuary

An artificial floating bets experimental project which reeds was served as the floatingbets plants and was made of bamboo was carried out on the adjacent water ofQingcaosha Reservoir in the Yangtze estuary from2013.5to2013.7to study its growingstate and nutrient uptake ability, the effects on the community structure of plankton andfish. It aimed to provide reference for the application of the floating bets on the waterecological restoration in the Yangtze estuary.1. The growing state and nutrient uptake ability of the common reedThe common reed rhizomes were fixed on the floating bet frames, and after2months’experiments, the results showed that the average density of reeds increased graduallyduring the experiment with the lowest value of25.6±2.5ind/m2in May and highest100.7±15.3ind/m2in July, and the difference between months was significant （P＜0.05）. The plant height increased from2.6±1.4cm in May to55±15.5cm in July withsignificant difference between months （P＜0.05）.The average density of reeds washighly correlated with the plant height（r=0.904）.The fresh weight of reeds per unit area was0.212±0.045Kg/m2, the dry weight ofreeds per unit area was0.063±0.013Kg/m2, the TN concentration of reeds was1.33±0.03mg/g, the TP concentration of reeds was0.27±0.01mg/g, TN fixed amountper square meter was84.1mg/m2, TP fixed amount per square meter was17.3mg/m2.2. The effects on the community structure of planktonThe effects of the floating bets on the community structure of plankton was studiedafter two months running, and the results shows that there were16speciesphytoplankton were found in the experiment site, mainly belonged to Bacillariophyceae,Chlorophyta, Cyanophyta and Pyrrophyta.6species phytoplankton were found in thecontrol site belonged to Bacillariophyceae. The density of the Bacillariophyceae in theexperiment site was98.65ind./L, and it was4.6times of that in the control site. Thedensity of the phytoplankton in the experiment site was109.6ind./L, and it was5.1 times of that in the control site. The number of the phytoplankton species andbiodiversity index were higher than that in the control site.There were3species of zooplankton were found in the experiment site whichbelonged to Copepods, and3species of zooplankton were found in the control sitewhich belonged to Copepods and Cladocera, the density of zooplankton in theexperiment site was220.81ind./m3, which was3.7times of it in the control site, Thebiodiversity index D、H，、J of the experiment site were higher than they were in thecontrol site, but the biodiversity index D1was lower than it in the control site.3. The effects on the community structure of fishThe community structure changes of fish in the experiment site were studied duringthe experiment, and the results show that there were27species of catches were found inthe experiment site, in which22species of fish belonged to7orders, and the proportionof cypriniformes was37.04%, and was higher than other orders. The second part wasPerciformes, its proportion was22.22%, the proportion of siluriformes was7.41%, andthere were only one specie in Clupeiformes, mullet,pleuronectiformes and filefishorders,5species of arthropod were found, and its proportion was18.52%, Eriocheirsinensis was in the absolute advantage in early June, its IRI%was30.36%, butLateolabrax became the first dominant species since the mid-June, the average bodylength of Lateolabrax catch in the experiment site was5.56cm, and all of them were theyoung fish born in2013.The biodiversity indexes of fish: Margalef index（d）was2.32; Simpson index（C）was0.30; Pielou index（J′）was0.60; Shannon—Wiener index（H′）was1.62; Wilhmindex（H″）was1.81. There were no significant difference between the biodiversityindexes, d was above2.00, H′and H″were above1.5, C was below0.3, only J′waslower than normal, it means that the biodiversity index was high overall, and the speciesbiodiversity was better. The differences between catch community in mid to late Junewas the lowest, but the differences between early June and early July of catchcommunity was the highest, and the Lateolabrax was the main reason, this furtherconfirmed that Lateolabrax was the dominant factor lead to the community changes inexperiment site.