主养草鱼与主养黄颡鱼池塘沉积物—水界面氮磷营养盐通量变化及与环境因子的关系

为了探讨不同主养模式池塘养殖期间沉积物—水界面氮磷营养盐通量变化特征以及与环境因子之间的相互关系,利用沉积物—水界面营养盐扩散通量的原位观测装置,分析了2013年4—10月主养草鱼和主养黄颡鱼池塘沉积物—水界面营养盐交换通量,并探讨了影响营养盐交换通量的因素。结果发现:(1)在养殖初期,各种形态氮磷在养殖池塘沉积物—水界面主要表现为从上覆水向沉积物的沉积,养殖中后期,由于温度升高以及池塘沉积物中营养物质的大量累积,各种形态氮磷表现为以沉积物向上覆水扩散为主,表明池塘沉积物是氮磷营养盐的源与汇;(2)两种不同主养模式池塘氮磷通量的统计结果表明,沉积物—水界面-N、-N和-P通量变化无显著差异,而-N、TN和TP通量有显著差异;(3)上覆水中DO含量的升高显著促进界面间-N和-N释放通量,而-N和-P释放通量与上覆水DO浓度成显著负相关;温度的升高对各种无机形态的氮磷通量有显著的促进作用。

Diffusion fluxes of nitrogen and phosphorus across sediment-water interface in different aquaculture model ponds

Ctenopharyngodon idella and Pelteobagrus fulvidraco are considered as two economically important aquaculture species in China with the largest production. The sediment-water interface in aquatic systems is a bridge connecting bottom sediments with the overlying water column. The transition zone between oxygenated overlying water and anoxic, or anaerobic, sediments forms over a gradient of just a few millimeter sand and can easily be disturbed by mechanical mixing (bioturbation). To determine the seasonal variance of nitrogen and phosphorus exchange in different aquaculture model ponds and explore the relationship between nitrogen and phosphorus fluxes and environment factors of overlying water in two polyculture systems, C. idella and P. fulvidraco aquaculture models ponds, we studied by in situ Observation device of nutrient flux in sediment-water interface from April to October of 2013. In situ experiments, benthic fluxes of nutrients at the sediment-water interface were measured, and its related factors were analyzed. During our experiment, nitrate, nitrite and TN were taken up by sediment in the beginning of the culture period (from Apr. to Jun.), while it changed to release from sediments to water in the middle and later stages of the culture period. Meanwhile, fluxes of PO₄^3- and TP presented the similar trends. Results also showed that the differences of concentration variation range of NO₂^--N, NO₃^--N and PO₄^3--P were not significant between the two aquaculture models, however there were significant differences of NH₄⁺-N, TN and TP fluxes at sediment-water interface. Otherwise, there was significantly positive relationship between nitrite and nitrate fluxes and DO concentration, while there was negative relationship between NH₄⁺-N and PO₄^3--P fluxes and DO concentration. Elevated temperature can promote different forms of nitrogen and phosphorus fluxes in aquacultural ponds.