Modeling the release of dissolved organic matter by phytoplankton
Modeling the release of dissolved organic matter by phytoplankton
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DOI：
10.1111/j.1529-8817.2008.00562.x
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发表时间：
2008-10-01
影响因子：
2.9
通讯作者：
Xue, Yao
中科院分区：
文献类型：
--
作者：
Flynn, Kevin J.;Clark, Darren R.;Xue, Yao
建立了三个描述溶解有机物(DOM)通量和浮游植物死亡的模型，每个模型的复杂程度不同，并针对一个蓝藻、一个绿藻、两个硅藻、两个甲藻和两个裸藻的实验数据进行了检验。最简单的模型只描述了DOM的整体碳(C)和氮(N)形式(DOMC和DOMN)，并采用了浮游植物营养状态与DOM释放和死亡率之间的固定关系。最复杂的模型将DOM的部分描述为低分子量溶解有机碳(DOC；糖，低分子量碳水化合物[DOC])、低分子含氮物质(包括C和N作为DOC与含有氨基酸和/或核酸的低分子化合物[DOCA]有关，N与DOCA[DONA]有关，其中包括溶解的游离氨基酸[DFAA])，以及更复杂的物质(DOC与通常需要在微生物吸收或利用之前进行细胞外降解的化合物[DOCx]和N与DOCx[DONx]相关)。它还采用了与营养状况和生长速度有关的DOM通量和细胞死亡的描述。在所有情况下，从死亡细胞裂解的物质都有助于DOM池。这三个模型都反映了原始数据(溶解无机C[DIC]、溶解无机N[DIN]、颗粒有机碳[POC]、颗粒有机N[PON]、DOC、溶解有机N[DON])的总体动态，但随着模型复杂性的增加，拟合度几乎没有改善。然而，最简单的模型往往采用过高的增长率来补偿较高的固定死亡率。虽然新固定的碳以DOMC(DOCS+DOCA)的形式释放的比例随着营养状况的下降而增加，但实际的释放速率通常不会这样做，而且往往会下降。最复杂的模型预测了释放的糖类和DFAA的变化，与预期一致。未来进展的主要障碍是缺乏合适的、大量平衡的数据集来进行进一步的模型测试。
Three models describing dissolved organic matter (DOM) flux and phytoplankton death, each of different levels of complexity, were constructed and tested against experimental data for a cyanobacterium, a chlorophyte, two diatoms, two dinoflagellates, and two prymnesiophytes. The simplest model described only bulk carbon (C) and nitrogen (N) forms of DOM (DOMC and DOMN) and employed a fixed relationship between phytoplankton nutrient status and DOM release and death rate. The most complex model described fractions of DOM as low molecular weight dissolved organic carbon (DOC; saccharides, low molecular weight carbohydrates [DOCs]), low molecular weight nitrogenous material (comprising C and N as DOC associated with low molecular weight compounds containing amino acids and/or nucleic acids [DOCa] and N associated with DOCa [DONa], which included dissolved free amino acids [DFAA]), and more complex materials (DOC associated with high molecular weight compounds typically requiring extracellular degradation prior to uptake or use by microbes [DOCx] and N associated with DOCx [DONx]). It also employed descriptions of DOM flux and cell death related to nutrient status and growth rates. In all instances, material lysed from dead cells contributed to the DOM pool. All three models captured the gross dynamics of the primary data (dissolved inorganic C [DIC], dissolved inorganic N [DIN], particulate organic carbon [POC], particulate organic N [PON], DOC, dissolved organic N [DON]), but there was little or no improvement of the fit with increasing model complexity. However, the simplest models tended to employ excessively high growth rates to compensate for high fixed death rates. While the proportion of newly fixed C being liberated as DOMC (DOCs plus DOCa) increased as nutrient status declined, the actual rate of release typically did not do so and often declined. The most complex model gave predictions for changes in released saccharides and DFAA in keeping with expectations. The major obstacle to future progress is the lack of suitable, mass balanced data sets for further model testing.