An Assessment of Dissolved Organic Carbon Biodegradability and Priming in Blackwater Systems
An Assessment of Dissolved Organic Carbon Biodegradability and Priming in Blackwater Systems
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DOI：
10.1029/2018jg004470
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发表时间：
2018-09
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通讯作者：
Sadie R. Textor;F. Guillemette;P. Zito;R. Spencer
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作者：
Sadie R. Textor;F. Guillemette;P. Zito;R. Spencer
河流每年向海洋输送约260 Tg的溶解有机碳（DOC），但海洋中陆源DOC（tDOC）的证据很少。虽然tDOC在历史上被认为是稳定的，耐微生物降解，但最近的研究表明，淡水系统矿化的tDOC比原来想象的要多。启动效应是一种可能的机制，通过该机制，生物不稳定DOC的输入增强了水生系统中稳定DOC组分的生物利用度，从而导致更高的微生物生物矿化率。在这里，我们调查tDOC的生物降解性进行生物培养实验，并利用高分辨质谱表征黑水和渗滤液溶解有机物（DOM）样品的化学组成。在黑水生态系统中的启动的作用进行了评估，通过列入生物培养处理与各种简单的生物不稳定OC基板修正。1个月内，黑水水体DOC损失率为6.10 ± 3.85%，渗滤液DOC损失率为38.10 ± 16.74%。有没有显着差异，在控制和启动处理，表明启动是不是在黑水生态系统中的DOC的生物降解的重要因素。但可生物降解DOC的比例与DOM组成显著相关，这主要是由脂肪族化合物（H/C ≥ 1.5，O/C < 0.9）的贡献所决定的，而脂肪族化合物在渗滤液DOM中含量较高（9.3 ± 5.2%）。生物降解的渗滤液DOM的分子特征与稳定的黑水DOM相似，表明植物凋落物中生物有效DOM组分被迅速利用，稳定的DOM向下游输出。
Rivers deliver approximately 260 Tg of dissolved organic carbon (DOC) to the ocean annually, yet there is little evidence of terrigenous DOC (tDOC) in the ocean. While tDOC was historically believed to be stable and resistant to microbial degradation, it has recently been shown that freshwater systems mineralize more tDOC than originally thought. The priming effect is a possible mechanism by which inputs of biolabile DOC enhance the bioavailability of stable DOC components in aquatic systems, resulting in higher rates of microbial remineralization. Here we investigate tDOC biodegradability by conducting bioincubation experiments and utilizing ultrahigh resolution mass spectrometry to characterize the chemical composition of blackwater and leachate dissolved organic matter (DOM) samples. The role of priming in blackwater ecosystems was assessed through the inclusion of bioincubation treatments amended with a variety of simple biolabile OC substrates. Blackwaters lost 6.10 ± 3.85% DOC within 1 month, while leachates lost 38.10 ± 16.74% DOC. There were no significant differences between DOC remineralization in control and primed treatments, indicating that priming is not an important factor in the biodegradation of DOC in blackwater ecosystems. However, the proportion of biodegradable DOC and DOM composition were significantly correlated, mostly driven by the contribution of aliphatic compounds (H/C ≥ 1.5, O/C < 0.9) that were abundant (9.3 ± 5.2%) in leachate DOM. The molecular signature of biodegraded leachate DOM resembled that of stable blackwater DOM, indicating that bioavailable DOM components leached from plant litter are rapidly utilized and stable DOM is exported downstream.