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黄海南部浒苔绿潮暴发前、中、后期溶解有机物的化学组分变化特征

Chemical composition characteristics of dissolved organic matter before, during and after the outbreak of Ulva prolifera green tide in South Yellow Sea

  • 摘要: 为了探究浒苔(Ulva prolifera)绿潮暴发前、暴发中和暴发后对近海海水溶解有机物(DOM)的浓度和化学组分的影响,本研究通过对黄海南部海域的3次现场调查,分析了浒苔绿潮暴发前、中、后不同时期海水中的DOM浓度及其荧光组分特征。结果表明,浒苔绿潮暴发后海水中的溶解有机碳(DOC)浓度在3个时期中呈现最高值(182.99±35.85) µmol/L,比暴发前和暴发中的DOC浓度分别高出69.73%和51.66%;而溶解有机氮(DON)浓度则是在暴发前呈现最高值(13.26±3.00) µmol/L。相较于浒苔绿潮暴发前,暴发中和暴发后的DON浓度分别显著下降了44.72%和29.11%(P<0.05)。通过解析荧光溶解有机物(FDOM)的荧光组分特征,表明代表容易被生物利用的活性DOM组分(类蛋白组分)在暴发过程中出现明显增加的特征,而表征惰性DOM组分的类腐殖质组分则在暴发后出现小幅度积累,这表明浒苔暴发过程中释放的光合有机碳大部分是容易被微生物利用的活性组分,而暴发后释放的藻体DOM则由于主要来自于微生物对藻体颗粒碳的矿化且以惰性组分居多。因此,推测浒苔绿潮暴发在短时间内可以增加海洋中活性DOM的浓度,而在长期尺度上有增加近海惰性DOM储库的潜力。

     

    Abstract: To explore the impact of Ulva prolifera green tide on the concentration and chemical properties of dissolved organic matter (DOM) in different bloom stages, three field surveys were carried out in the Southern Yellow Sea. The investigations focused on analyzing the DOM concentration and fluorescence composition characteristics in seawater before, during, and after the Ulva prolifera blooms. Results showed that the dissolved organic carbon (DOC) concentration reached the peak of (182.99 ± 35.85) µmol/L after the green tide, which was 69.73% and 51.66% higher than those during the pre-outbreak and outbreak periods, respectively. The concentration of dissolved organic nitrogen (DON) was the highest before the outbreak (13.26 ± 3.00) µmol/L. The DON concentrations during and after the outbreak decreased significantly by 44.72% and 29.11% respectively (P<0.05) compared to that before the outbreak. According to main components of fluorescent dissolved organic matter (FDOM), the intensity of protein-like substances showed a significant increase during the outbreak process, which was usually used as an indicator of labile dissolved organic matter (LDOM). In contrast, the humus-like substance, which often represents recalcitrant dissolved organic matter (RDOM) component, showed a slight accumulation after the outbreak. This suggested that the majority of macroalgal biomass carbon is bioavailable and easily utilized by microorganisms. Moreover, due to the mineralization of LDOM by microorganisms, the macroalgal DOM after the outbreak consists mainly of recalcitrant components. Therefore, it is speculated that the macroalgal blooms can increase the concentration of LDOM in the coastal water in the short-term and have the potential to increase the accumulation of RDOM pool in the long-term. This study provides a novel insight into the characterization of changes in chemical components of DOM before, during and after the green tides in the Southern Yellow Sea.

     

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