凡纳滨对虾盐碱水养殖池塘沉积物-水界面氮元素交换通量的研究

NITROGEN EXCHANGE FLUX OF SEDIMENT-WATER INTERFACE IN LITOPENAEUS VANNAMEI SALT ALKALI POND

  • 摘要: 为探究凡纳滨对虾(Litopenaeus vannamei)盐碱水养殖池塘沉积物-水界面中氮元素的转化规律, 于2019年5—7月测定了山东省滨州市3个不同盐度(28、45和55)的池塘上覆水和沉积物间隙水中各种形态氮的含量。利用Fick第一定律估算了池塘沉积物-水界面氮元素交换通量, 分析了环境因素与交换通量的相关性。结果表明: (1)总体来讲, DIN、DON、TN由沉积物向水体扩散, 即沉积物为DIN、DON和TN的源; \rmNO^-_3 -N由水体向沉积物扩散, 沉积物为 \rmNO^-_3-N的汇。在养殖期间, 盐度28、45和55组, DIN总交换通量分别为 1.69、23.07和19.36 mg/m2, DON总交换通量分别为36.60、27.90和19.98 mg/m2, TN总交换通量分别为38.09、43.66和32.56 mg/m2。(2)从季节变化来看, DIN、DON、TN在养殖初期(5月)的交换通量显著高于养殖末期(7月); 从盐度组来看, 在5月, 盐度28、45和55组, DIN平均交换通量分别为2.08、6.37和12.47 mg/(m2·d), 7月分别为–0.48、0.06和1.47 mg/(m2·d), 盐度55组显著大于其他两组(P<0.05); DON交换通量5月分别为13.91、5.32和6.79 mg/(m2·d), 盐度28组显著大于其他两组(P<0.05), 7月分别为5.82、10.94和5 mg/(m2·d), 盐度45组显著大于其他两组(P<0.05); 5月TN平均交换通量分别为15.9、8.79和19.16 mg/(m2·d), 盐度45组显著小于其他两组(P<0.05), 7月分别为5.31、9.1和3.28 mg/(m2·d), 盐度45组显著大于盐度55组(P<0.05)。(3)冗余分析结果显示, 盐度与\rmNO^-_2 -N、\rmNO^-_3 -N、\rmNH^+_4 -N交换通量显著正相关; 有机质与\rmNH^+_4 -N、TN通量显著正相关; 温度与\rmNH^+_4 -N交换通量显著负相关; 含水率、孔隙度与\rmNO^-_3 -N、DON交换通量显著正相关。综上所述, 沉积物是氮的潜在污染源, 此污染潜力在养殖末期显著小于养殖初期; 高盐度组有利于释放DIN, 中低盐度组有利于释放DON。研究结果将有助于认识盐碱水养殖池塘的氮交换通量, 为该种养殖模式的科学管理提供数据支撑。

     

    Abstract: Coastal saline-alkali land aquaculture is increasingly rising, with the nutrient exchange at the sediment-water interface playing an important role in the ecosystem. It serves as an indicator of endogenous pollution levels in pond sediments. In order to explore the nitrogen transformation dynamics at the sediment-water interface in Litopenaeus vannamei culture ponds. Measurements were taken from May to July 2019, analyzing various nitrogen forms in overlying water and sediment interstitial water across three ponds in Binzhou City, Shandong Province, with different salinity (28, 45, 55). Using Fick’s first law, nitrogen exchange fluxes at the sediment-water interface were estimated, and correlations between environmental factors and exchange fluxes were examined. The results show that, (1) Nitrogen forms, including DIN, DON, and TN, predominantly diffuse from sediment to water, indicating sediment as the source. Conversely, \rmNO^-_3 -N moves from water to sediment, with sediment acting as the sink. During the breeding period, total exchange fluxes of DIN were 1.69, 23.07, and 19.36 mg/m2, DON were 36.60, 27.90, and 19.98 mg/m2, and TN were 38.09, 43.66, and 32.56 mg/m2, respectively, for salinity levels of 28, 45, and 55. (2) Seasonally, exchange fluxes of DIN, DON, and TN were significantly higher in May compared to July. For instance, the average DIN exchange fluxes for salinity levels 28, 45, and 55 were 2.08, 6.37, and 12.47 mg/(m2·d) in May respectively, decreasing to –0.48, 0.06, and 1.47 mg/(m2·d) in July respectively. Notably, the DIN exchange flux in salinity 55 group was significantly higher than that in the other two groups (P<0.05). In May, the DON exchange fluxes were 13.91, 5.32, and 6.79 mg/(m2·d), respectively. Salinity 28 group exhibited significantly higher values compared to the other two groups (P<0.05). Conversely, in July, the fluxes were 5.82, 10.94, and 5 mg/(m2·d), respectively, with the salinity 45 group significantly surpassing the others (P<0.05). Additionally, in May, the average TN exchange fluxes were 15.9, 8.79, and 19.16 mg/(m2·d) respectively. Significantly, the salinity 45 group exhibited lower fluxes than that in the other two groups (P<0.05). However, in July, the fluxes were 5.31, 9.1, and 3.28 mg/(m2·d) respectively, with the salinity 45 group significantly surpassing the salinity 55 group (P<0.05). (3) Redundancy analysis showed positively correlations between salinity and exchange fluxes of \rmNO^-_2 -N, \rmNO^-_3 -N, and \rmNH^+_4 -N. Organic matter exhibited positive correlations with \rmNH^+_4 -N and TN fluxes. There was a significant negative correlation between temperature and \rmNH^+_4 -N exchange flux, moreover, water content and porosity demonstrated positive correlations with \rmNO^-_3 -N and DON exchange fluxes. In conclusion, sediments act as potential sources of nitrogen, with pollution potential significantly reduced towards the end of aquaculture compared to the early stage. The salinity 55 group facilitates DIN release, while the salinity 28 and 45 groups facilitates promote DON release. The results enhance understanding of nitrogen exchange fluxes in large surface aquaculture ponds and provide valuable data to support the scientific management of this aquaculture model.

     

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