Studies On The Aquatic Plant Community Structure Of Ditches And Water Purification Effect Of Some Living Organismsin The Fisheries

As our country aquaculture has depended quickly, Chinese aquaculture production has beenthe first in the world.however, industrial effluent, domestic waste water, agricultural pollution and the bait remained, metabolites and fecal,cause serious environment pollution; additive added into feed illegally, metal harmful to health and drugs residues threaten the safe and health of aquaculture animals or plants, which have a bearing on aquaculture sustainable development in our country. The purpose of this research topic is to explore a suitable and effective technology to solve the eutrophication of water body by combiningthe ecological restoration, aquaculture restructuring and theculture model. The main reseach contens and main results are summarized as follow:1.Through field investigating, the community structure and biomass of aquatic plant and the effect of Natural Ditch(ND) and Cement Ditch(CD) on water quality were studied to improve basis for building ecological ditch in the aquaculture farm. Studies showed:it comprised17families23genus24species and consisted of Alternanthera philoxeroides-Zizania latifolia community, Alternanthera philoxeroide-Nelumbo nucifera community in ND, where the basal coverage of aquatic plant is more than50%and the average of biomass is2633.85g/m2; it comprised7families7genus7species and composed of Valisneria batanscommunity, Ceratophyllum demersum community in CD, where the basal coverage is less than20%and the biodiversity is greater than CD. The concentration of TN in ND and CD are0.97±0.32mg/L,1.48±0.61mg/L respectively; the concentration of TP is0.13±0.06mg/L,0.16±0.07mg/L respectively; the concentration of Chl-a is35.12±17.73μg/L,69.24±17.31μg/L respectively; the concentration of DO is3.67±2.17mg/L,6.12±1.95mg/L respectively. The aquatic plant is rich and the effect of water quality purification is obvious in ND, but DO is substantially lower than CD. Considering system stability, cost of building and effect of water quality purification, suggest toemploy ND.2. Compare ofwater purification effect in various density Hyriopsis cumingii (0ind/pool,36ind/pool,48ind/pool,60ind/pool)in40m2cement ponls. The result reveals, the water purification effect in the ponds with Hyriopsis cuningiiare all better than the control ponds.Based on careful comparison, when the breeding density is48unit/pool (1.Oind/m3), it is the best and its removal rate of TN, TP, Chl-a respectively are48.51%,44.93%,65.10%.3. Studied on water purification effect of Hyriopsis cumingii, Vallisneria Nutans and the combination of both. DO,9.44mg/L in the Hyriopsis cumingii ponds, are obviously lower than the others(Vallisneria Nutansponds,10.91mg/L; the combination of both,10.77mg/L). The removal effect of nitrogen in ponds of Vallisneria Nutans and the combination,whose long removal rate respectively is78.18±5.08%,72.41±4.31%, are obviously more stable and better than the control and Hyriopsis cumingii.To TP and SRP, water purification effect of Hyriopsis cumingii, Vallisneria Nutans, andthe combination are all stronger the control, but it is no difference between each other.Hyriopsis cumingii shows a very strong ability to removal Chl-a in a short time, but its long effect is not as good as Vallisneria Nutans, and the combination. Compare ofcomprehensivewater purification effect:Vallisneria Nutans and the combination are stronger than the control and Hyriopsis cumingii, and consider stability of water environment:the combination group>Vallisneria Nutansgroup> the control group> Hyriopsis cumingii group, therefore the combination is the most suitable forwater purification and environmental enhancement.