Organic carbon decay mediated by a mesopelagic microbial community: The relevance of carbon pools and broad biochemical composition

IF 3.8 1区 地球科学 Q1 LIMNOLOGY
Noah J. Craft, Alexander B. Bochdansky
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Abstract

The mesopelagic zone is a site of strong microbially driven particle attenuation with depth and thus plays a crucial role in controlling the transfer efficiency of the ocean's biological pump. However, little quantitative information exists on the dependency of decay processes on the source material. Here we followed the decay of 14C-labeled dead particulate organic carbon (POC) and dissolved organic carbon (DOC) from three different phytoplankton species, and two incubations of live diatoms, in mesopelagic water over 3 months. Commonly used first-order kinetics failed to adequately describe the decay of organic material as rate constants varied from day to day. Over extended periods, decay rates for organic material exhibited two distinct phases, with rates in the second phase being inversely related to rates in the first phase. Microbial biomass (measured via adenosine triphosphate and cell counts) increased substantially during phase 1 and ebbed during phase 2. Decay rates were significantly different among the three algal sources; however, differences were even more pronounced among carbon pools and followed a distinct pattern (combined average per-day decay rates at 12°C): fresh DOC (0.6) > fresh POC (0.1) > live cells (0.06) > aged DOC/POC (0.01). Separation of POC into four broad biochemical fractions showed that components in the operationally defined lipid fraction contained the most degradable compounds for fresh material. Our research highlights the need to include the dynamics of the most easily digestible fractions of freshly released organic material, and live plankton resilient to digestion, in calculations of vertical carbon flux budgets.

Abstract Image

中上层微生物群落介导的有机碳衰变:碳库与广泛生化组成的相关性
中远洋区是微生物驱动的颗粒随深度衰减较强的区域,因此对海洋生物泵的转运效率起着至关重要的控制作用。然而,关于衰变过程对源物质依赖性的定量信息很少。在这里,我们跟踪了三种不同浮游植物和两种活硅藻在中上层水中3个多月的14C标记的死颗粒有机碳(POC)和溶解有机碳(DOC)的衰变。由于速率常数每天都在变化,常用的一级动力学不能充分描述有机物质的衰变。在较长时间内,有机物质的衰变率表现出两个不同的阶段,第二阶段的速率与第一阶段的速率成反比。微生物生物量(通过三磷酸腺苷和细胞计数测量)在第一阶段大幅增加,在第二阶段下降。三种藻源的腐烂率差异显著;然而,碳库之间的差异更加明显,并遵循一种独特的模式(12°C下每天的综合平均衰变率):新鲜DOC (0.6) >;新鲜POC (0.1) >;活细胞(0.06)>;老化DOC/POC(0.01)。将POC分离成四个广泛的生化组分表明,在操作上定义的脂质组分中含有最易降解的化合物。我们的研究强调,在计算垂直碳通量预算时,需要包括新鲜释放的有机物质中最容易消化的部分的动态,以及对消化有弹性的活浮游生物。
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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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