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首页> 外文期刊>Journal of Experimental Marine Biology and Ecology >Degradation of diatom carbohydrates: A case study with N- and Si-stressed Thalassiosira weissflogii
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Degradation of diatom carbohydrates: A case study with N- and Si-stressed Thalassiosira weissflogii

机译：硅藻糖的降解：以N和Si胁迫下的Thalasiosira weissflogii为例

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Diatoms are a key phytoplanktonic group that affects the carbon cycle in the ocean. Although the effect of nutrient limitation on the primary productivity of diatoms is well-studied, the effect of such a limitation on the organic matter quality of diatoms and their vertical transport through the water column remains unclear. In this study, the diatom Thalassiosira weissflogii (TW) was grown under two different nutrient conditions, 'N-stress' and 'Si-stress', and was compared against healthy TW cells (Nutrient-replete). Biodegradation experiments of TW were performed for all of the above conditions, and the particulate fraction was monitored over time (similar to one month) in terms of the organic carbon (POC), nitrogen (PON), and sugars (PCHO), including prokaryotic counting. Using these results, we estimated the degradation rate constants for POC, PON, PCHO, and the individual carbohydrate monomers (monosaccharides) for the TW cells. Our results indicated that the N- and Si-limitations increase the organic carbon content of the TW cells with a concomitant decrease in the silicon content (bSiO(2)), suggesting a modification of the TIN cells. The PCHO content increased by a factor of 2.6 and 3.8 in the N-stress and Si-stress cells, respectively. At the beginning of the experiment (To), the N-stress and Si-stress cells were characterized by higher amounts of glucose (5-32 mol%) and xylose (13-19 mol%), compared with the Nutrient-replete cells, which were dominated by ribose (similar to 22 mol%), indicating differences in the physiological status of the TW cells and/or in the synthesis of storage/structural polysaccharides. The first order degradation rate constants (k(1)) for the POC were similar in all of the experiments (k(1) = 0.096-0.113 d(-1)), which was not the case for the PON in which the highest values (by a factor of similar to 2.5) were observed for the nutrient-replete experiment. This result indicates a different behavior in the utilization and/or accessibility to prokaryotes of carbon and nitrogen during the biodegradation experiment. Moreover, ribose, glucose, and galactose exhibited the highest degradation rate constants in all of the experiments, which further reflects the differences in their initial macromolecular origin (e.g., storage vs structural carbohydrates) and highlights the changes in the organic matter quality during growth under nutrient-limited conditions and degradation. These results suggest that the 'nutrient-stress' diatoms may affect the export of carbon (particularly carbohydrates) relative to nitrogen in the ocean interior compared with the diatoms grown under optimal conditions. (C) 2015 Elsevier B.V. All rights reserved.
机译：硅藻是影响海洋碳循环的重要浮游植物群。尽管研究了养分限制对硅藻初级生产力的影响，但这种限制对硅藻有机质的质量及其在水柱中的垂直迁移的影响仍不清楚。在这项研究中，硅藻Thalassiosira weissflogii（TW）在两种不同的营养条件下生长，即“ N胁迫”和“ Si胁迫”，并与健康的TW细胞（营养丰富）进行了比较。在上述所有条件下都进行了TW的生物降解实验，并随时间（类似于一个月）监测了颗粒部分的有机碳（POC），氮（PON）和糖（PCHO），包括原核生物。数数。使用这些结果，我们估算了TW细胞的POC，PON，PCHO和单个碳水化合物单体（单糖）的降解速率常数。我们的结果表明，N和Si限制增加了TW电池的有机碳含量，同时硅含量（bSiO（2））下降，表明了TIN电池的改性。在N应力和Si应力电池中，PCHO含量分别增加了2.6和3.8倍。在实验开始时（To），与营养充足的细胞相比，N应激和Si应激细胞的特征是葡萄糖（5-32 mol％）和木糖（13-19 mol％）含量更高其以核糖为主（约22mol％），表明TW细胞的生理状态和/或贮藏/结构多糖的合成上存在差异。在所有实验中，POC的一阶降解速率常数（k（1））都相似（k（1）= 0.096-0.113 d（-1）），而对于PON而言，最高在营养充足的实验中观察到数值（约2.5倍）。该结果表明在生物降解实验中碳和氮的原核生物的利用和/或可及性方面的行为不同。此外，核糖，葡萄糖和半乳糖在所有实验中均表现出最高的降解速率常数，这进一步反映了其初始大分子来源的差异（例如，储存与结构碳水化合物的差异），并突出了在生长过程中有机质的变化。营养有限的条件和降解。这些结果表明，与在最佳条件下生长的硅藻相比，“营养胁迫”硅藻可能会影响海洋内部碳（特别是碳水化合物）相对于氮的出口。 （C）2015 Elsevier B.V.保留所有权利。

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