金潮原因种铜藻外源无机碳利用特征初步研究

为揭示铜藻(Sargassum horneri)对无机碳利用的基本特性及铜藻在漂浮过程中生物量迅速累积并最终发展为金潮的生理生态学机理,以我国近海金潮原因种铜藻为研究对象,在不同pH (6.5、8.0和9.5)条件下研究了添加TRIS缓冲剂、碳酸酐酶抑制剂(AZ、EZ)和阴离子交换蛋白抑制剂(DIDS)后藻体的固碳速率、光合作用-无机碳响应曲线(P-C曲线)及pH漂移曲线。结果显示,TRIS缓冲剂对铜藻的固碳速率无显著影响(P>0.05),而3种抑制剂均显著(P<0. 05)抑制铜藻的固碳速率且抑制效率从大至小依次为DIDS> EZ>AZ。藻体的固碳速率随着外源无机碳浓度的增加而增加,并渐趋饱和。此外,藻体的最大固碳速率(V_max)随着pH的升高而降低,而半饱和常数(K_0.5)则随着pH的升高而升高,藻体的pH补偿点为9.0左右。结果表明,铜藻既可以利用海水中的CO_2也可以利用HCO_3^-进行光合作用;并且铜藻对HCO_3^-的吸收存在通过阴离子交换蛋白直接转运吸收和利用碳酸酐酶将HCO_3^-转化为CO_2后再吸收两种方式。对HCO_3^-的高效吸收利用能力可能是铜藻保证维持较高光合作用、快速积累生物量并最终演变为金潮的重要因素之一。

Preliminary studies on the utilization characteristics of exogenous inorganic carbon in Sargassum horneri,a gloden tide causative species

To reveal the basic characteristics of inorganic carbon utilization and ecophysiological mechanism of the rapid biomass accumulation of S. horneri during the floating process and eventually developing into the golden tide,the photosynthetic carbon fixation rates,P-C curves and pH drift curves of S. horneri,the golden tide causative species in China,were determined in the presence of TRIS buffer,carbonic anhydrase inhibitors(AZ,EZ) and anion exchanger inhibitors(DIDS) at different pH levels(6.5,8.0 and 9.5). The results showed that the photosynthetic carbon sequestration rates in the control group were(59.62 ± 2.35),(33.70 ± 1.51),(12.48 ± 0.32)μmol O2· h^-1·g^-1 FW,at p H values of 6.5,8.0 and 9.5,respectively. The photosynthetic carbon sequestration rates of the TRIS buffer treatment group were(58.66 ± 1.87),(33.38 ± 1.76),(12.26 ± 0.18)μmol O2·h^-1·g^-1 FW,at pH values of 6.5,8.0 and 9.5,respectively. The TRIS buffer had no significant(P > 0.05) effect on the photosynthetic carbon fixation rates of S. horneri. But the three inhibitors significantly(P < 0.05) suppressed them,with the inhibition ratios of 7.25%,52.03% and 60.65% for AZ,EZ and DIDS,respectively. The photosynthetic carbon fixation rates of S. horneri increased with enhanced exogenous inorganic carbon concentration until arrived at the carbon dioxide saturation point. At the pH value of 6.5,the photosynthetic oxygen release rate reached saturation under the inorganic carbon concentration of 2.2 mmol·L^-1,while at both pH values of 8.0 and 9.5,the photosynthetic oxygen release rate reached saturation under the inorganic carbon concentration of 8.8 mmol·L^-1. The maximum photosynthetic carbon fixation rates(Vmax) of algae decreased while the half-saturation constant(K0.5) increased with the increased pH,the pH compensation point of S. horneri was about 9.0.These results indicated that S. horneri could utilize both CO2 and HCO3^- in seawater for photosynthesis.Furthermore,the absorption of HCO3^- included the direct absorption through the anion-exchange protein and indirect absorption by transforming HCO3^- into CO2 through carbonic anhydrase outside of the cell membrane.The efficient absorption and utilization of HCO3^- in S. horneri may be one of the important factors to ensure the high photosynthesis and rapid biomass accumulation of its floating thalli,and ensure its eventually developing into the golden tide.