| Along with the advance of Marine environment supervision,coastal aquaculture met important transformation of the crisis.Shrimp cultivation is the main component of marine culture.With the increasing of high-density farming,shrimp pond waste water eutrophication became more and more severe.It leads to ecological imbalances,lower economic efficiency,which severely limits the development of aquaculture.In this situation,we established a series of sustainable model for treating shrimp pond waste water,which can reduce waste water emission and environment affect.The results are as follows:Screening of large seaweed and determination of densityIn this experiment,two large seaweed species,Gracilaria lichevoides and Ulva lactuca,were selected to set four breeding densities of 0.5 g/L,2 g/L,4 g/L and a blank control group,respectively.It was carried out in 100 L white polyethylene tub,and the tail water of shrimp culture was 50 L in a barrel.After 5 days,the results showed that the nutrient absorption rates of the two seaweeds were directly proportional to the density.There was no significant difference in NH4-N removal rates between G.lichevoides and U.lactuca(P>0.05).Among them,the NH4-N removal rate of the latter was higher.The removal rates of NO3-N,TN and TP in G.lichevoides were significantly higher than those in U.lactuca(P<0.05).when the two kinds of seaweed in the breeding density of 2 g/L and 4 g/L,the nutrient removal rate did not increase significantly,taking into account the actual production of seaweed farming density should not be too high,so the breeding density of 2 g/L is the best.In addition,the specific growth rate of seaweeds was negatively correlated with theirstocking densities.The specific growth rates of G.lichevoides were 5.73%1.65%and 0.48%,respectively,those of Ulva lactuca were 2.01%、1.187%and 0.138%,when the stocking density was 0.5 g/L,2 g/L and 4 g/L.Two-factor analysis of variance showed that the former was significantly higher than the latter,when the two species of seaweed breeding density of 0.5 g/L(P<0.05).Therefore,regardless of the removal rate of nutrients,or specific growth rate,G.lichevoides are the best candidates for water purification.Screening and Density Determination of Three Benthic ShellfishThe experiment used three species of common bivalve,Potamocorbula laevis,Sinonovacula constricta and Tegillarca granosa to purify the shrimp farming tail water in Zhejiang Province.Each shellfish was provided with three farming density groups and a group of blank groups of three replicates.The breeding density of P.laevis is 100 ind,200 ind and 400 ind,and those of T.granosa is 20 ind,30 ind and 50 ind,repectively.The breeding density of S.constricta is 13 ind,20 ind and 32 ind.The results showed that the removal efficiency of nutrients is the best which the NH4-N,NO3-N,TN,TP removal rates were 50.98%,48.31%,57.49%,77.62%;when the culture density of P.laevis was 200ind,and those of S.constricta is 20 ind,the nutrients removal rates were 45.56%,-28.45%,50.96%,53.69%,repectively.When the breeding density of 30ind in T.granosa,aquaculture water purification efficiency is the highest,the nutrient removal rates were 38.85%,47.49%,36.1%,26.04%,repectively.Based on the above results,we can see that the removal efficiency of P.laevis is higher than T.granosa and S.constricta,P.laevis also has the advantages of strong tolerance,fast growth and short reproductive cycle.It is the best candidate for Integrated Multi-trophic Aquaculture.Preliminary study on polyculture of Potamocorbula laevis and Gracilaria lichevoidesBased on the results above,we chose P.a laevis and G.lichevoides for polyculture with different densities to treat tail water of shrimp aquaculture.2 g/L G.lichevoides with 2 ind/L,4 ind/L,8 ind/L P.laevis Hybrid breeding,respectively,another group.The results showed that the optimal mix ratio was 8 ind/L P.laevis and 2 g/L G.lichevoides and the nutrient removal rate was the highest.the NH4-N,NO3-N,TN,TP removal rates were 90.67%,51.85%,72.66%,86.18%,respectively.the specific growth rate of G.lichevoides also showed a gradual upward trend with the increasing density of P.laevis.Compared with the previous same density,the specific growth rate of G.lichevoides have a remarkable elevation.Therefore,to make full use of complementarity of the two ecosystems can not only remove toxic substances in the water environment of NH4-N,to create a good environment for aquaculture,but also can greatly improve the specific growth rate of algae,and solve the contradiction between aquaculture and environmental pollution.The study of biological purification of aquaculture effluent with the Tegillarca granosa and different levels of probioticsThis article mainly deals that biological purification of greenhouses prawn effluent with the blood clam(T.granosa)and different levels of Effective Microorganisms(EM),in order to build a new and efficient integrated farming structure,reduce the marine sewage discharge.Five groups with three replications each were set up for 7 days.Group 1-4 had 33 blood clams and 390μl,510μl,720μl and Oμl EM bacteria,respectively.Group 5 used as control with no blood clam and EM bacteria.The results showed that the purification efficiency of group 1-4 was higher than that of the control group.The nutrient removal efficiency of group 2 was the highest,which can remove 68.61%±0.25%of nitrate,85.34%±2.94%of phosphate,72.85%±3.62%of ammonia nitrogen,59.24%±3.16%of total nitrogen and 79.82%±2.15%of totalphosphorus.Synthesizes the above analysis,The combination of the suitable concentration of EM bacteria and the T.granosa can significantly improve the purification efficiency of water quality,reduce the discharge of the tail water effectively and provide the basic data for the realization of ecological comprehensive breeding.We can be concluded from the above studies that the mixed cultivation of Potamocorbula laevis Gracilaria lichevoides can effectively reduce the nutrients and suspended particles of shrimptail water and increase the specific growth rate of seaweed to achieve rapid energy flow and material recycling within the system.Compared with the separate cultivation of Tegillarca granosa,the combination of appropriate concentration of EM bacteria and Tegillarca granosa can significantly improve the purification efficiency and increase the beneficial bacteria in water however,EM concentration should be considered to avoid excessive or insufficient addition of water negatively affected.In addition,we initially designed a set of recirculating breeding system for shrimp culture-natural sedimentation-biological purification-natural sedimentation,and prospects of its application prospects. |
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