温度和无机碳浓度对龙须眼子菜(Potamogeton pectinatus)碳同位素分馏的影响

Effects of temperature and dissolved inorganic carbon concentration on the carbon isotopic fractionation of Potamogeton pectinatus

温度和无机碳浓度是沉水植物碳同位素分馏的重要影响因素。通过在16、19、22、25、28、31℃6个温度条件和溶解无机碳浓度(DIC)为0.0001mol.L-1和0.0001mol.L-1两种条件下培养沉水植物——龙须眼子菜(Potamogeton pectinatus),获得了不同条件下生长的龙须眼子菜植物样品,随后进行了定量和碳同位素组成(δ13CP)分析。分析结果表明,随生长温度的升高,龙须眼子菜碳δ13CP均升高,具有明显的温度相关性(R2>0.90)。在DIC浓度为0.0001mol.L-1时,随着生长温度的升高,δ13CP从-14.83‰增加至-13.47‰;而在DIC浓度为0.001mol.L-1时,δ13CP从-18.56‰增加至-15.15‰。同一生长温度条件下,DIC浓度对δ13CP也有明显影响,δ13CP随DIC浓度增高而降低。在不同生长温度条件下,DIC浓度对δ13CP的影响大小随生长温度的增高而降低,在温度为16℃时,两个DIC浓度下的δ13CP相差3.73‰;而在温度为31℃时,这一差值减少为1.68‰。同时,通过建模进行计算,获得了不同温度下龙须眼子菜(P.pectinatus)碳同位素分馏与初始DIC浓度的关系,并对有关的参数的意义进行了探讨。

Many factors including internal and external variables are responsible for the carbon isotopic composition （δ^13C） of submersed plants and make it complex to interpret and apply in ecological studies. In order to assess the effects of temperature and dissolved inorganic carbon （DIC） concentration on the carbon isotopic fractionation in the growth of submersed plants, Potamogeton pectinatus was cultivated with tubers at sixtemperatures from 16℃ to 31℃ with a increment of 3 ℃ and two DIC concentrations, 0. 0001 mol· L^-1 and 0. 0001 mol· L^- 1. Plant materials were collected and weighed after they were cultured for 50 days in illumination incubator lighting with 16 ： 8 （ Day ： Dark ）. And their carbon isotopic compositions were analyzed. In general, temperature and inorganic carbon concentration exerts a stronger influence on the growth and carbon isotopic fractionation of P. pectinatus. Net growth rates of P. pectinatus had a high positive correlation with temperature （ R^2 〉0.9）. At high DIC concentration （0. 001mol· L^-1 ）, net growth rates of P. pectinatus ranged from 0.64mg·min^-1to 0. 91mg·min^-1 with the average Q10 of 1.3, where at low DIC concentration （0. 0001mol· L^-1）, they varied from 0.38 mg·min^-1 to 0.75mg·min^-1 with the average Q10 of 1.9. In the same time, with the increase of temperature from 16℃ to 31℃, the δ^13Cvalues of P. pectinatus increase from -14.83‰ to -13.47‰ at DIC of 0. 0001molL^-1, where the values increase from - 18.56‰ to - 15.15‰ at DIC of 0. 001 molL^-1. The difference of δ^13C between the two DIC concentrations is 3.73‰ at the temperature of 16℃, and is 1.68‰ at the temperature of 31℃. The results implied that the DIC concentration has larger effects on carbon fractionation of this plant at low temperature than that at high temperature. Carbon isotopic fractionation of P. pectinatus was modeled by using a diffusio werecalculated by using the δ^13C values at two DIC concentrationsof the same parameters all have highly corrective coefficients with temperatureand might be fractionation of P. pectinatus. used to predict the carbon isotopic