溶解无机氮加富对海带养殖水体无机碳体系的影响

通过室内模拟实验,研究了在海带养殖水体中添加不同浓度的无机氮(NO-3-N和NH+4-N)对海水无机碳体系的影响。结果表明,无机碳体系各组分的变化趋势与无机氮添加浓度和无机氮形态有关。当NO-3-N和NH+4-N浓度范围分别在(4.73~52.78)μmol/L和(2.56~34.66)μmol/L时,DIC、HCO-3和pCO2均随着营养盐浓度的增加呈下降趋势,其中以NO-3-3和NH+4-3组变化最为明显,均达到最低值,分别为2 054、2 112μmol/L,1 776、1 869μmol/L,86、114μatm;而当NO-3-N和NH+4-N浓度范围分别为(52.78~427.29)μmol/L、(34.66~268.33)μmol/L时,DIC、HCO-3和pCO2随着营养盐浓度的增加,其下降幅度逐渐减弱,但实验结束时DIC、HCO-3和pCO2仍低于对照组。NO-3-N对海带养殖水体无机碳体系的影响较NH+4-N明显,加NO-3-N组对水体的固碳能力显著高于加NH+4-N组。当NO-3-N和NH+4-N浓度分别为52.78μmol/L、34.66μmol/L时,海带的光合固碳能力达到最大,过高或者过低均会降低海带对水体无机碳的吸收固定。

Effects of DIN enrichment on inorganic carbon system of Saccharina japonica culture water

Effects of dissolved inorganic nitrogen （NO3--N and NH4＋-N） addition on the dissolved inorganic carbon （DIC） system of Saccharina japonica culture water were studied. The results indicated that the inorganic carbon system was correlated with the concentrations and forms of DIN. The concentrations of DIC, HCO3- and pCO2 decreased with the increase ni- trogen concentration in the range of 4.73-52.78 μmol/L （NO3-N） and 2.56-34.66 μmol/L （NH4＋-N）, and they were most remarkably affected by the NO3--3 and NH＋-3 treatments, cor- responding with the lowest values of 2054 and 2112 μmol/L, 1776 and 1869 μmol/L, 86 and 114 μatm, respectively. However, when the concentration of nitrogen was in the range of 52.78-427.29 μmol/L （NO3-N） and 34.66-268.33 μmol/L （NH4＋-N）, the falling trends of DIC, HCO3- and pCO2 were weakened with the increasing nitrogen, but the concentrations of DIC, HCO3- and pCO2 were still lower than the control. Influence of NO3-N addition on inor- ganic carbon system of seawater was larger than NH4＋-N addition, and the ability of carbon fix- ation in NO3--N treatment was significantly higher than that in NH4＋-N treatment. The highest capability of photosynthetic carbon fixation by S. japonica appeared in 52.78 μmol/L NO3-N and 34. 66 μmol/L NH＋-N. The DIC assimilation ability by S. japonica would decrease when NO2-N and NH4＋-N deviated from the optimum values.