紫外辐射对两种海洋微藻生长及培养体系碳流的影响

The effects of UVR on the growth of two marine microalgae and the carbon flow in the culture system

以硅藻威氏海链藻(Thalassiosira weissflogii)和甲藻锥状斯氏藻(Scrippsiella trochoidea)为实验材料,通过室内模拟华南地区秋季晴天紫外辐照强度,研究两种不同波段的紫外辐射(Ultraviolet radiation,UVR)对两种微藻生长以及培养体系碳流的影响。结果表明:UV-A对两种微藻的生长有显著的促进作用,而UV-B则表现为抑制作用。锥状斯氏藻对UV-B的耐受性更强。在UV-A的作用下,培养体系中溶解无机碳(Dissolved inorganic carbon,DIC)的净消耗量低于对照组,但释放出更多的溶解有机碳(Dissolved organic carbon,DOC)。对照组的有色溶解有机物(Chromophoric dissolved organic matter,CDOM)含量显著升高,表明浮游植物生长过程是CDOM的来源之一。然而,在UV-A的作用下,两种微藻培养体系的CDOM浓度变化呈现相反趋势,说明不同藻种的CDOM产物受光漂白和光腐殖化的影响不同。在UV-B的作用下,微藻碎屑的分解使水体DIC和DOC浓度轻微升高。总体上,锥状斯氏藻比威氏海链藻净释放出更多的DOC和CDOM。

The effects of two different wavelengths of ultraviolet radiation(UVR)on the growth of two species of marine microalgae,i.e.Thalassiosira weissflogii(diatom)and Scrippsiella trochoidea(dinoflagellate),and the carbon flow in their culture systems were examined.The intensity of simulated UVR in this study was set according to sunny doses in fine day of autumn in southern China.The results showed that UV-A caused a positive effect on the growth of T.weissflogii and S.trochoidea,while UV-B obtained an opposite pattern.In general,S.trochoidea was much tolerant to UV-B than T.weissflogii.Compared to the control,net consumption of dissolved inorganic carbon(DIC)decreased under UV-A exposure.In addition,more dissolved organic carbon(DOC)was released in the culture media under UV-A exposure.The level of chromophoric dissolved organic matter(CDOM)was significantly higher in the control,indicating that microalgae could be an important source for CDOM.However,the change of CDOM level during the experiment also showed an opposite pattern between these two microalgae culture media under UV-A,indicating different processes of photobleaching and photohumification.Under the UV-B exposure,DIC and DOC increased slightly due to the degradation of microalgae detritus.In summary,S.trochoidea might release more DOC and CDOM than T.weissflogii.