密闭培养对纤细角毛藻稳定同位素组成的影响

Effects of Closed Culture on the Stable Isotopic Composition of Chaetoceros gracilis

为研究碳源对赤潮藻生长的影响,以赤潮藻纤细角毛藻(Chaetoceros gracilis)为研究对象,在密闭条件下进行培养,模拟赤潮发生时碳源缺乏的生长环境;分析碳源不足对纤细角毛藻不同生长阶段的差异影响,采用密闭培养的方法,分别在正常组和缺氮组的营养条件下培养纤细角毛藻,测定生物量、营养盐浓度和碳氮稳定同位素组成等重要监测指标.结果表明:不同营养条件对纤细角毛藻的生物量存在显著影响.在正常组,c(NO3--N)(NO3--N为硝酸盐)随着培养时间呈下降趋势,ρ(NO2--N)(NO2--N为亚硝酸盐)和ρ(NH4+-N)(NH4+-N为铵盐)与藻类生物量呈显著正相关,ρ(PO43--P)(PO43--P为磷酸盐)和c(Si O42--Si)(Si O42--Si为硅酸盐)与藻类生物量呈显著负相关;在缺氮组,c(NO3--N)、ρ(NO2--N)、ρ(NH4+-N)、ρ(PO43--P)和c(Si O42--Si)均与藻类生物量呈显著负相关.整个试验周期中,正常组和缺氮组δ13C和δ15N值越来越正.其中,正常组的δ13C值比缺氮组的更正,平均高2.286‰;缺氮组的δ15N值比正常组的更正,平均高3.307‰.正常组和缺氮组的δ13C、δ15N值与生物量均呈显著正相关.研究显示,碳源和氮源的不足分别会导致更正的δ13C和δ15N值,推测赤潮发生会导致δ13C和δ15N值偏正,赤潮藻的碳氮稳定同位素组成可以作为赤潮监测的指标和方法.

Chaetoceros gracilis was cultured in a closed environment to simulate carbon source limitation during the occurrence of red tides.The microalgae were maintained under both normal nutrient conditions and nitrogen deficient conditions. Biomass,stable carbon,nitrogen isotopes and nutrient concentration were measured to determine how the two different nutrient condition affects C. gracilis growth at different growth phases. The results showed that the two different conditions produced significant differences in biomass during different growth phases. Under the normal nutrient condition,the concentration of nitrate,phosphate,and silicate decreased over time,while nitrite and ammonium increased. Under the nitrogen deficient condition,all five nutrient conditions were negatively correlated with the biomass of the algae. δ13 C and δ15 N values increased throughout the experiment. The δ13 C value of the normal nutrient group was 2. 286‰ higher than that of the nitrogen deficient group. The δ15 C value of the nitrogen deficient group was 3. 307‰ higher than that of the normal nutrient group. Both δ13 C and δ15 N values had a significant positive correlation with biomass in both groups. The occurrence of red tides resulted in higher levels of δ13 C and δ15 N,which could be used as an indicator of red tide events.