Organic matter exudation by Emiliania huxleyi under simulated future ocean conditions
Organic matter exudation by Emiliania huxleyi under simulated future ocean conditions
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DOI：
10.5194/bg-9-3405-2012
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发表时间：
2012-01-01
期刊：
影响因子：
4.9
通讯作者：
Engel, A.
中科院分区：
文献类型：
--
作者：
Borchard, C.;Engel, A.
在磷控恒化器中，研究了不同营养、CO2和温度条件下，对Emiliania huxleyi（菌株B 92/11）有机碳分泌及颗粒有机碳（POC）和溶解有机碳（DOC）分配的影响。对初级生产（PP）和细胞外释放（ER）进行C-14孵育测量。化学分析包括高分子量（> 1 kDa）溶解的结合碳水化合物（HMW-dCCHO）、颗粒结合碳水化合物（pCCHO）和透明外聚合物颗粒（TEP-C）的碳含量的量和组成。施加的CO2和温度条件为300、550和900 μ atm pCO（2），14 A ℃，通过将稀释率（D）从D = 0.3 d（-1）降低到D = 0.1 d（-1）（D = mu）来增强营养胁迫在E. huxleyi。在mu = 0.3 d（-1）时，PP在升高的CO2和温度下显著更高，并且在所有处理中（DOC）-C-14产量与（POC）-C-14产量相关，导致细胞外释放的百分比（PER;（（DOC）-C-14产量/PP）x 100）相似，平均为3.74 +/-0.94%。在μ = 0.1 d（-1）时，（POC）-C-14的产生量显着下降，而（DOC）-C-14的渗出量增加。因此，表明从颗粒到溶解池的更强的分配。在高CO_2和温度条件下，当mu = 0.1 d（-1）时，PER最大值为16.3 +/- 2.3%，HMW-dCCHO、pCCHO和TEP的浓度在营养胁迫下普遍较高，而在各处理内和整个实验过程中，细胞密度保持不变。在mu = 0.3 d（-1）时，pCCHO浓度随CO2和温度升高而显著增加。在mu = 0.1 d（-1）时，CO2浓度升高和温度升高时，HMW-dCCHO对DOC的贡献（mol % C）较低，而pCCHO和TEP浓度较高。这在温室条件下最为明显。我们的研究结果表明，初级生产DOC转化为POC的营养限制下的渗出物凝结。我们的研究结果进一步表明，CO2浓度和温度的升高会增加E. huxleyi和可能会影响有机碳的分配在海洋中，由于高分子量-dCCHO的增强转移到TEP的聚集过程。
Emiliania huxleyi (strain B 92/11) was exposed to different nutrient supply, CO2 and temperature conditions in phosphorus controlled chemostats to investigate effects on organic carbon exudation and partitioning between the pools of particulate organic carbon (POC) and dissolved organic carbon (DOC). C-14 incubation measurements for primary production (PP) and extracellular release (ER) were performed. Chemical analysis included the amount and composition of high molecular weight (> 1 kDa) dissolved combined carbohydrates (HMW-dCCHO), particulate combined carbohydrates (pCCHO) and the carbon content of transparent exopolymer particles (TEP-C). Applied CO2 and temperature conditions were 300, 550 and 900 mu atm pCO(2) at 14 A degrees C, and additionally 900 mu atm pCO(2) at 18 A degrees C simulating a greenhouse ocean scenario.Enhanced nutrient stress by reducing the dilution rate (D) from D = 0.3 d(-1) to D = 0.1 d(-1) (D = mu) induced the strongest response in E. huxleyi. At mu = 0.3 d(-1), PP was significantly higher at elevated CO2 and temperature and (DOC)-C-14 production correlated to (POC)-C-14 production in all treatments, resulting in similar percentages of extracellular release (PER; ((DOC)-C-14 production/PP) x 100) averaging 3.74 +/- 0.94%. At mu = 0.1 d(-1), (POC)-C-14 production decreased significantly, while exudation of (DOC)-C-14 increased. Thus, indicating a stronger partitioning from the particulate to the dissolved pool. Maximum PER of 16.3 +/- 2.3% were observed at mu = 0.1 d(-1) at elevated CO2 and temperature.While cell densities remained constant within each treatment and throughout the experiment, concentrations of HMW-dCCHO, pCCHO and TEP were generally higher under enhanced nutrient stress. At mu = 0.3 d(-1), pCCHO concentration increased significantly with elevated CO2 and temperature. At mu = 0.1 d(-1), the contribution (mol % C) of HMW-dCCHO to DOC was lower at elevated CO2 and temperature while pCCHO and TEP concentrations were higher. This was most pronounced under greenhouse conditions. Our findings suggest a stronger transformation of primary produced DOC into POC by coagulation of exudates under nutrient limitation. Our results further imply that elevated CO2 and temperature will increase exudation by E. huxleyi and may affect organic carbon partitioning in the ocean due to an enhanced transfer of HMW-dCCHO to TEP by aggregation processes.