添加氮磷对龙须菜光合固碳能力影响的现场研究

Field study on photosynthetic carbon acquisition of Gracilaria lemaneifomis after adding nitrogen and phosphorus

采用碘量法和碱度法,通过测定密闭容器中溶解氧和无机碳浓度的变化,从产氧和固碳两个方面研究添加氮、磷对龙须菜光合作用速率的影响。实验设置为加氮(ADDN,10μmol/LNH4Cl)、加磷(ADDP,1.0μmol/LKH2PO4)、同时加氮磷(ADDNP,10μmol/LNH4Cl+1.0μmol/LKH2PO4)、不加氮磷(NONP)4个处理,不加龙须菜的海水作为对照。根据实验前后光合作用瓶内各参数的变化,计算了龙须菜光合产氧速率(RO,mg/gDW.h),固碳速率(RDIC,μmol/gDW.h),HCO3-吸收速率(RHCO-3,μmol/gDW.h)、CO2吸收速率(RCO2,μmol/gDW.h)以及光合熵(PQ)和二氧化碳分压(pCO2)的变化,探讨了氮磷营养盐对龙须菜光合作用固碳速率的影响,为提高龙须菜的碳汇功能提供理论参考。结果表明,8～11月添加氮磷对龙须菜RO的影响差异不显著,12月加氮和加磷能显著提高龙须菜RO,RO存在明显的季节变化;添加氮磷对RDIC的影响差异不显著,存在明显的季节变化,与RO相同,9月最高(287.3μmol/gDW.h),12月最低位(134.8μmol/gDW.h);RCO2除12月外,不同处理差异不显著,季节变化明显,平均RCO28月最高,11月最低;RHCO-3不同处理差异不显著,季节变化明显,9月最高,12月最低;实验结束后容器内pCO2范围为82.7～238.7μatm(平均152.1μatm),双因素方差分析表明不同处理pCO2差异不显著,不同月份差异显著;不同处理和不同月份PQ值均有显著差异,加氮组平均PQ值最高(1.23),不同月份平均值为0.59～1.50。

Effects of ammonia and phosphorus addition on Gracilarial emaneifomis photosynthetic rate were evaluated in terms of oxygen production and carbon acquisition,and the carbon sink function of this cultured seaweed was discussed.Iodimetry measurement for dissolved oxygen and total alkalinity（TA）determination for dissolved inorganic carbon（DIC）were taken to measure the rates of O 2 production and DIC acquisition of G.lemaneifomis.During the experiment period,seaweed G.lemaneifomis was cultured in sealed synthetic glass containers under 4different nutrient conditions（ADDN,10 μ mol/LNH 4 Cl ;ADDP,1.0 μ mol/LKH2PO4;ADDNP,10 μ mol/LNH 4 Cl＋1.0 μ mol/LKH2PO4;NONP,without addition of nitrogen or phosphorus）,in situ seawater as control.The results showed that from August to November,the added ammonia and phosphorus had no significant effect on R O（photosynthetic rate in oxygen production）of G.lemaneifomis ;in November,the added ammonia and phosphorus significantly increased the R O of the seaweed.The added ammonia and phosphorus had no significant impact on R DIC.R CO 2 ranged from 6.9to 18.4 μ mol/gDW.h（average 11.3 μ mol/gDW.h）.No significant difference in each condition but obvious seasonal variations were observed.R HCO 3 ranged from 117.1to 487.1 μ mol/gDW.h.ANOVA analysis revealed no significant difference in pCO 2 for each treatment,but there were obvious seasonal variations in pCO 2.Significant difference in photosynthetic quotient（PQ）was found among treatments and months ;PQ（average）maximized（1.23）when ammonia was added,and the monthly average PQ was in the range of 0.59～1.50.