Limited microbial degradation of elevated concentrations of dissolved organic carbon in the deep ocean

IF 3.8 1区 地球科学 Q1 LIMNOLOGY
Tao Liu, Yixian Li, Yuan Shen
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Abstract

Understanding the ocean's capacity potential to store dissolved organic carbon (DOC) is essential for predicting its role in long-term carbon sequestration and climate regulation. This capacity hinges on the behavior of DOC at elevated concentrations, a critical yet unresolved question that has produced mixed results due to narrow concentration ranges tested previously and limited molecular insights. This study addresses these gaps by investigating microbial degradation of DOC across a broad concentration range (2- to 55-fold) in year-long bioassay experiments using solid-phase extracted DOC (SPE-DOC) from 2000-m-deep waters. Specific SPE-DOC compounds (combined amino acids) were analyzed to provide a molecular-level understanding of DOC reactivity at varying concentrations. Our results show that microbial communities rapidly proliferated and became more uniform following SPE-DOC amendments, with Nitrosococcales, Flavobacteriales, and Alteromonadales dominating. Despite these shifts, microbial utilization of SPE-DOC was constrained, exhibiting a nonlinear relationship with concentration, from < 3% in the control to a maximum of 9% in DOC-enriched groups. Degradation was predominantly confined to the initial 28 d, with negligible additional removal (0–2%) thereafter. Compound-specific analysis showed only moderate utilization (7–11%) of amino acid compounds within the first 3 d, indicating restricted microbial access even when these individual compounds were concentrated. These results indicate that a fraction of deep-sea DOC molecules can persist for long at elevated concentrations. Our study demonstrates the ocean's substantial potential for DOC storage and suggests that modern ocean is capable of accommodating a larger DOC reservoir than is currently present.

Abstract Image

深海中高浓度溶解有机碳的微生物降解能力有限
了解海洋储存溶解有机碳(DOC)的能力潜力对于预测其在长期固碳和气候调节中的作用至关重要。这种能力取决于DOC在高浓度下的行为,这是一个关键但尚未解决的问题,由于先前测试的浓度范围狭窄和对分子的了解有限,因此产生了不同的结果。本研究通过使用固相萃取的DOC (SPE - DOC)从2000米深的水域进行为期一年的生物测定实验,研究了微生物在宽浓度范围内(2 - 55倍)对DOC的降解,从而解决了这些空白。分析了特定的SPE - DOC化合物(组合氨基酸),以提供不同浓度下DOC反应性的分子水平的理解。我们的研究结果表明,在SPE‐DOC修订后,微生物群落迅速增殖并变得更加均匀,亚硝基球菌、黄杆菌和互变单胞菌占主导地位。尽管发生了这些变化,但SPE - DOC的微生物利用受到限制,表现出与浓度的非线性关系。对照组为3%,富DOC组最高可达9%。降解主要局限于最初的28天,此后的额外去除率可以忽略不计(0-2%)。化合物特异性分析显示,在前3天内,氨基酸化合物的利用率只有适度(7-11%),这表明即使这些单独的化合物被浓缩,微生物的利用也受到限制。这些结果表明,一部分深海DOC分子可以在高浓度下持续存在很长时间。我们的研究证明了海洋储存DOC的巨大潜力,并表明现代海洋能够容纳比目前更大的DOC库。
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来源期刊
Limnology and Oceanography
Limnology and Oceanography 地学-海洋学
CiteScore
8.80
自引率
6.70%
发文量
254
审稿时长
3 months
期刊介绍: Limnology and Oceanography (L&O; print ISSN 0024-3590, online ISSN 1939-5590) publishes original articles, including scholarly reviews, about all aspects of limnology and oceanography. The journal''s unifying theme is the understanding of aquatic systems. Submissions are judged on the originality of their data, interpretations, and ideas, and on the degree to which they can be generalized beyond the particular aquatic system examined. Laboratory and modeling studies must demonstrate relevance to field environments; typically this means that they are bolstered by substantial "real-world" data. Few purely theoretical or purely empirical papers are accepted for review.
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