Variation Characteristics Of Nutrients In Surface Sediment And Cultivate Effect Of Bait Organisms In Pond Which Buried Culture Medium

The seasonal variation of different forms of nitrogen and phosphorus in the surface sediment of the pond,relationship between nitrogen and phosphorus and food organism,and the variation of nutrients in interstitial water was studied in this experiment.And then the effects of adding molasses and humic acid on benthic food organisms,water quality and different organic matter in surface sediment were studied.It provides a theoretical basis for the scientific and rational use of culture medium and culture medium's recipe optimization.The main results were as follows:1.Characteristics and correlation of different forms nitrogenIn this experiment,the changes of different forms of nitrogen in the surface sediment were measured after culture medium was put into the pond.The results showed that:the content of nitrogen in ion exchangeable form(IEF-N),nitrogen in weak acid extractable form(WAEF-N),nitrogen in strong alkali extractable form(SAEF-N)and nitrogen in strong oxidation extractable form(SOEF-N)of transferable total nitrogen increases as the amount of the culture medium was increased in treatment group;in the control group,the content of IEF-N was higher than that of the treatment group,and other forms of nitrogen were basically less than the treatment group.The contents of IEF-N,SAEF-N and SOEF-N were gradually decreased from spring to autumn.In addition,the correlation analysis found that:WAEF-N and SAEF-N was conducive to the cultivation of benthic bait organisms,but SOEF-N was contrary.The content of ammonia nitrogen(NH4+-N)was highest,followed by nitrate nitrogen(NO3--N),and nitrite nitrogen(NO2--N)content was the least in all forms of nitrogen.2.Characteristics and correlation of different forms phosphorusThe changes of different forms of nitrogen in the surface sediment were measured after culture medium was put into the pond.The results showed that: the contents of phosphorus forms were as follows:Al-bound phosphorus(Al-P)>Ca-bound phosphorus(Ca-P)>Fe-bound phosphorus(Fe-P)>Labile-phosphorus(Labile-P)in each groups of inorganic phosphorus(IP),and Labile-P,Al-P and Ca-P increases as the amount of the culture medium was increased.The contribution of culture medium to pond phosphorus was mainly due to the increase of Labile-P and Fe-P.Correlation analysis found there was a relationship between Fe-P and Ca-P,Fe-P and Chironomid larvae also have a certain correlation.3.Variation characteristics of nutrients in interstitial waterAfter culture medium was put into the pond,collected the interstitial water with Peeper device,determination the concentration change of ferrous ion(Fe2+),phosphate(PO43--P),nitrate nitrogen(NO3--N)and ammonia nitrogen(NH4+-N).The results showed that: the contents of Fe2+ and NH4+-N in the interstitial water increased gradually from top to bottom,appeared to stabilize in the depths of 5cm,there was little change in the vertical trend between different seasons;the content of NO3--N decreased gradually from top to bottom in spring,and there was an increasing trend from autumn to autumn,the longitudinal seasonal variation of PO43--P was opposite to NO3--N.Compared with the control group,the treatment groups content of nutrition was found to be higher than the control group,and the treatment group2(1.35×104 kg/ha)was the highest.In addition,studied the effects of planting Elodea nuttallii on nutrition in interstitial water,showed that the contents of Fe2+,PO43--P and NH4+-N in the interstitial water can be significantly decreased in spring,summer and autumn,while NO3--N removal effect was only obvious in summer.4?Study on optimization effect of culture mediumIn order to enhance the breeding effect of bait organisms,on the basis of the original medium,we added some molasses and humic acid,observe the effect of cultivation,and monitor the change of conventional water quality.The results showed that:the addition of molasses and humus acid helps to enhance the breeding of bait organisms,and the molasses addition group was significantly higher than the original medium group(p<0.05).Dissolved oxygen(DO)showed that the molasses group was higher than the humic acid group,and the humic acid group was higher than the original medium group;conductivity(EC)and dissolved total solids(TDS)were the highest in the original culture medium,and lowest in the molasses added group?On the influence of nitrogen and phosphorus in water,the contents of nitrite nitrogen(NO2--N),phosphate(PO43--P)and total phosphorus(TP)in the humic acid adding group were higher than that in the molasses added group and the original medium group,nitrate nitrogen(NO3--N),ammonia nitrogen(NH4+-N)and total nitrogen(TN)were slightly higher in the original culture group than those in the other two groups.The total organic matter(TOM)and dissolved organic matter(DOM)in the surface sediment were highest in the humic acid adding group,and lowest in the original medium group,the difference was not significant(P>0.05),the content of three active organic matter(active organic matter(LOM),middle active organic matter(MLOM)and highly active organic matter(HLOM))was highest in molasses added group,and lowest in the original medium group,but the difference was not significant(P>0.05).