| The research was measured and analyzed on enzyme activities in sediment and nutrient dynamics in three polyculture models in mainly cultural grass carp pond (model I, grass carp, silver carp, bighead crap, crucian carp of250,35,40,15. Model Ⅱ, grass carp, silver carp, bighead crap, paddlefish, crucian carp of250,35,20,20,15. model Ⅲ, grass carp, silver carp, crucian carp of250,35,15).1. Results show that the mean contents of total nitrogen in waters in model Ⅰ, model Ⅱ, model Ⅲ were1.251mg/L,1.001mg/L and1.228mg/L, respectively, and the mean ammonium nitrogen content,0.391mg/L,0.345mg/L and0.319mg/L, respectively. The content of nitrate showed a decreasing order of model Ⅰ>model Ⅱ> model Ⅲ, and content of nitrite were model Ⅱ, model Ⅰ, model Ⅲ. The mean content of total phosphorus in model Ⅰ, model Ⅱ and model Ⅲ were0.087mg/L,0.070mg/L and0.092mg/L, respectively. The content of phosphate decrease in order:model Ⅰ> model Ⅲ> model Ⅱ. There were significant differences between model Ⅰ and model Ⅱ, model Ⅱ and model Ⅲ of total nitrogen content and total phosphorus content in waters (P<0.05). The three indexes—ammonium nitrogen, nitrate concentration, nitrite concentration were all no significant difference among these three models(P>0.()5).The phosphate content was no significant difference among these three models (P>0.05).2. Results show that the mean contents of total nitrogen in sediments in model Ⅰ model Ⅱ, model Ⅲ were0.793mg/g,0.910mg/g and0.963mg/g, respectively. The mean ammonium nitrogen content in model Ⅰ, model Ⅱ, model Ⅲ were0.005mg/g,0.006mg/g and0.004mg/g, respectively. The mean total phosphorus in model Ⅰ, model Ⅱ, model Ⅲ were0.394mg/g,0.459mg/g and0.393mg/g, respectively. The mean content of phosphate in model Ⅰ, model Ⅱ, model Ⅲ were0.0050mg/g,0.0045mg/g and0.0047mg/g, respectively. The content of total nitrogen in model Ⅰ had significant difference compared with model Ⅲ (P<0.05). The ammonium nitrogen content and phosphate content were no significant difference among these three models (P>0.05). The transformation of nitrogen and phosphorus nutrients in the sediment was quicker, too. Obviously, model Ⅱ is the most conducive to transformation and utilization of nitrogen and phosphorus nutrients in the waterbody.3. During the production cycle, the alkaline phosphatese activities and oxidoreductases activities in model Ⅱ were more volatile than model Ⅰ and model Ⅲ, the mean contents of alkaline phosphatase in model Ⅰ, model Ⅱ, model Ⅲ were526.53μg/g,705.75μg/g and774.62μg/g, respectively, it was significant difference between model Ⅰ and model Ⅲ (P<0.05). In three polyculture models, polyphenol oxidase contents in model Ⅱ was higher than model Ⅰ and model Ⅲ, the mean of model Ⅱ was100.01mg/100g. The mean peroxidase content of model Ⅰ, model Ⅱ, model Ⅲ were1.28mg/g,1.34mg/g and1.29mg/g, respectively. The mean content of catalase in model Ⅰ, model Ⅱ, model Ⅲ were2.73mL/g,2.74mL/g and2.97mL/g, respectively, the highest of oxidase activity and LOI were found in June and August, LOI content in three polyculture models had no bigger difference during the production cycle. it was significant correlation between peroxidase and LOI (P<0.05). The mean content of urease in model Ⅰ, model Ⅱ, model Ⅲ were0.130mg/g,0.206mg/g and0.250mg/g, respectively, there were significant correlation between urease and TN in sediment, urease and ammonium nitrogen in sediment (P<0.05). The mean protease content of model Ⅰ. model Ⅱ. model Ⅲ were274.70μg/g.242.79ug/g and345.89μg/g, respectively, it was very significant correlation between protease and TN in sediment (P<0.01), protease and urease played important roles in nitrogen cycling.Alkaline phosphatase, oxidizing enzyme, urease and protease all had important roles in nitrogen and phosphorus cycle. Model influenced the nutrients content in the waters and sediment, indirect effect on the enzyme content. According to the dynamics of the six enzyme activities and accumulation of N and P, model Ⅱ is the optimal culture method. |
PDF Full Text Request