2018年春夏季苏北浅滩生物可利用氮分析

根据2018年4、5和6月份苏北浅滩海域的调查数据，分析了该海区生物可利用氮NO₃^--N、NO₂^--N、NH₄⁺-N、尿素和溶解游离氨基酸（DFAA）的浓度及其分布特征，并探讨了早期浒苔绿潮与生物可利用氮的关系.结果表明，NO₃^--N是该海域5种生物可利用氮组分的主体，其浓度为（17.51±10.25）μmol/L，占生物可利用氮组分80%以上，其它依次是尿素、NH₄⁺-N、DFAA和NO₂^--N，浓度分别为（1.54±0.81），（1.17±0.63），（0.43±0.15），（0.27±0.15）μmol/L，浒苔绿潮暴发初期生物可利用氮的平面分布特征整体呈现出明显的近岸高，外海低的趋势，高值区主要集中在近岸养殖业发达海域及河口地区.在浒苔快速增殖阶段，各生物可利用氮组分含量变化幅度较大，其中NO₃^--N含量降低最为明显，浒苔快速增长期的6月份较4月份降幅约40%，NO₃^--N是浒苔绿潮形成和发展的主要氮源.此外，尿素及DFAA浓度也明显降低，也可以作为营养物质被浒苔吸收利用.

Analysis of bioavailable bitrogen in Subei Shoal in Spring and Summer 2018

The concentrations of bioavailable nitrogen including NO₃^--N, NO₂^--N, NH₄⁺-N, urea-N and DFAA were analyzed during the three cruises in Jiangsu shoal from Apr. to Jun. 2018, and the roles of different nutrients in the development of early green tides are discussed. In this area, the NO₃-N with a concentration of about (17.51±10.25) μmol/L was the dominant bioavailable nitrogen component, accounting for more than 80% of the bioavailable nitrogen, followed by urea-N (1.54±0.81)μmol/L, NH₄⁺-N (1.17±0.63)μmol/L, DFAA (0.43±0.15)μmol/L and NO₂^--N (0.27±0.15)μmol/L. The concentrations of those nutrients generally decreased from inshore to offshore. The high-nutrient areas are mainly located in the coastal aquaculture areas and estuaries. After the outbreak of the green tide, the concentrations of bioavailable nitrogen greatly decreased, among which the NO₃^--N concentration decreased by about 40% in June compared with that in April. The NO₃^--N might be the main nutrient source to support the initiation of the green tides. In addition, the concentrations of urea-N and DFAA which could be directly absorbed and utilized by Ulva prolifera were also significantly reduced during the green tides.