碳源和氮源加富对脆江蓠生长及生化组分的影响

摘要

在实验室条件下研究了碳源(添加 CO2)和氮源(添加 NaNO3)加富对大型海藻脆江蓠(Gracilaria chouae)生长及其生化组成的影响。设置碳源加富(800µL/L CO2)和对照(400µL/L CO2)2个碳源处理组,氮源加富(100µmol/L、300µmol/L 和500µmol/L 3NO--N)和对照(10µmol/L 3NO--N)4个氮源处理组,每个处理3个重复。实验共进行10 d,测定不同处理组藻体的生长及可溶性总糖(SS)、可溶性蛋白质(SP)、藻红蛋白(PE)、叶绿素a(Chla)、总碳(TC)和总氮(TN)含量的变化。结果表明,碳源和氮源加富都会促进脆江蓠的生长,在800µL/L CO2和100µmol/L 3NO--N处理组,脆江蓠的瞬时生长率(SGR)最大(11.70%/d)；高浓度CO2会降低藻体SP、PE和Chla的含量,但提高了SS的含量；随着硝态氮浓度的增大, PE和SP含量逐渐增加,而SS含量逐渐降低, Chla含量没有明显变化。藻体的TN含量随着硝态氮浓度的增加而逐渐提高,而TC和C/N比值则呈现逐渐降低的趋势,并且藻体的TN和TC含量呈现出显著的负相关关系(P<0.05)。本实验证实添加碳、氮会引起脆江蓠生长和生化组成的变化,但其能耐受较高的CO2浓度和氮浓度。%Ocean acidification and eutrophication are two prominent problems that affect marine ecosystems in many aspects. Ocean acidification affects a series of physiological activities of macroalgae, which serve as important primary producers in marine ecosystems with regard to growth, photosynthetic carbon, and nutrient absorption. Moreover, it is globally acknowledged that seaweed cultivation is an effective way to ease the pressure of offshore eutrophication. Gracilaria chouae (Rhodophyta, Rhodophyceae, Florideophycidae, Gigartinales, Gracilariaceae) is distributed in warm water along the coast of Zhejiang and Fujian Provinces. It grows in stone bogs in the intertidal zone, and sandstone and shells in the subtidal zone. Gracilaria chouae is approximately 20–40 cm long with a rufous color and cylindrical fronds. The ecological effects of G. chouae are remarkable; for example, G. chouae has been used to improve pond water quality, because it absorbs N and P when it is growing. Moreover, it shows high economic value as both raw agar material and abalone feed. The majority of research on G. chouae has been about pond cultivation techniques, growth, uptake of nutrient and biochemical composition, and ultrastructure of vegetative cells. However, there are few reports on the interaction effects of C and N on its eco-physiological characteristics. This study investigated the growth and biochemical composition of G. chouae in response to different C sources (a model of ocean acidification) and N sources (a model of eutrophication). Gracilaria chouae was exposed to two C concentrations of 800 µL/L CO2 (enhanced) and 400 µL/L CO2 (as con-trol), and four N concentrations of 100 µmol/L, 300 µmol/L, and 500 µmol/L 3NO- -N (enhanced), and 10 µmol/L 3NO--N (as the control), with three replicates for each group. The culture density of G. chouae was 1 g/L. The algae were cultured under 100 µmol (photons)/(m·s) illuminated by incandescent tubes for 12L:12D photoperiod at 20℃. The culture seawater was continuously aerated and renewed every 2 days. Differences in seaweed growth, soluble sugar (SS), soluble protein (SP), phycoerythrin (PE), chlorophyll a (Chla), total nitrogen (TC), and total carbon (TN) were measured 10 days after being exposure to different conditions. The results indicated that enhanced C and N were proposed to increase seaweed growth, and the special growth rate reached its peak (11.70%/d) in the 800 µL/L CO2 and 100 µmol/L 3NO--N treatments. Moreover, high CO2 levels induced decrease of SP, PE, and Chla contents, whereas SS content increased. With density increase of NaNO3, PE and SP gradually increased, SS gradually reduced, and Chla had no significant change (P>0.05). TN increased, but TC and C/N decreased with increasing NaNO3. TN and TC had significant negative correlations in G. chouae (P<0.05). These results showed that ocean acidification promotes G. chouae growth and directly affects its physiological and biochemical characteristics. The growth rate of G. chouae stayed high under high N and P conditions. Therefore, G. chouae can be considered a suitable bioremediation species for artificial culture in regions that experience eutrophication.