Study On NDistributiono Of Carbon, Nitrogen And Phosprus In Sediment-water In Grapss Carp (Ctenopharygodonidellus Polyculute System)

Spatial distribution and change of nutrient in overlying water and pore water was studied in grass carp polyculture ponds. The main results are detailed as follows:1. Spatial distribution of NH₄⁺-N, NO₃^--N, NO₂^--N and PO₄^3--P in overlying water, pore water and the change of TN, TP and TC concentration in sediments was studied in grass carp polyculture ponds by means of land-based enclosure from June to October, 2009. The results showed that: (1) the concentration of NH₄⁺-N NO₃^--N, NO₂^--N, PO₄^3--P was 0.056¹.499,0.022⁰.228,0.049³.903 and 0.003¹.882 mg.L^-1, respectively. The proportion of NH₄⁺-N in the DIN increased over time. Different systems showed different distribution of nutrients. (2) During the experiment, the concentration of TN and TP doesn't change significantly, however, the concentration of TC reduced significantly, especially in GSC. It is suggested that the accumulation of organic matter and potential release of NH₄⁺-N in underlying water can reduced effectively in GSC polyculture system, therefore, this system might be legitimately applied in aquaculture.2. Spatial distribution of NH₄⁺-N, NO₃^--N, NO₂^--N and PO₄^3--P in overlying water, pore water and the change of TN, TP, TC and Eh in sediments was researched in grass carp polyculture ponds by means of land-based enclosure from June to October, 2010. The results showed that: (1) the concentration of NH₄⁺-N, NO₃^--N, NO₂^--N, PO₄^3--P in overlying water was 0.068¹.249, 0.002⁰.294, 0.001⁰.130 and 0.005⁰.481mg.L^-1 ,respectively. The concentration of NH₄⁺-N, NO₃^--N+NO₂^--N and PO₄^3--P in pore water ranged from 0.095 to 2.859, 0.004 to 1.099, 0.010 to 0.249 mg.L^-1,respectively. (2)Different systems showed different distribution of nutrients. But no obvious correlation between the depth and vertical distribution of nutrients was found. (3) During the experiment, the concentration of TC and TN increased slightly, but TP declined. (4) Eh in sediment decreased to reduction state in culture medium. (5) In Grass carp monoculture model, the concentration of nutrients in overlying water and pore water changed significantly, among which the NH₄⁺-N concentration showed the highest value; but in 3-species polyculture model(GSL2), the change was not obvious with NH₄⁺-N the lowest and NO₃^--N+NO₂^--N the highest . The impact of vannamei on sediment disturbance is not effecient, but with proper proportion silver carp, the polyculture could reduce the accumulation of benthic organic matter and change nutrient components effectively .3. The study on spatial distribution of organic carbon in overlying water, pore water sediment was investigated in grass carp polyculture system from Jun 2009 to Oct. The results showed that: the concentrations of DOC, POC and TOC in overlaying water ranged from 2.581 to 5.861, 4.701to 27.710, 7.907 to 31.256mg.L^-1,respectively.(2)the concentrations of DOC in surface pore water ranged from 2.337 to 55.14 mg.L^-1.DOC from surface pore water in monoculture model (G) was lowest in Sep. (3)The vertical distribution of DOC in pore water range from 2.336 to 69.05, and its content has no significant correlation with the depth(p≤0.05). DOC in G model was lower than that in other models. (4)The vertical distribution of TOC% in sediment floated between 2.762⁵.684% and decreased as the depth increased . TOC% in GSC model decreased fastest at different depths of sediment. The main component of organic carbon in the overlying water is POC; In Overlying water and pore water in GSC model, zhe concentration of DOC changed less than that in G model, but the concentration of TOC in sediment changed more comparatively.