Microbial control of oceanic carbon flux: The plot thickens
Microbial control of oceanic carbon flux: The plot thickens
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DOI：
10.1126/science.280.5364.694
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发表时间：
1998-05-01
期刊：
影响因子：
56.9
通讯作者：
Azam, F
中科院分区：
文献类型：
--
作者：
Azam, F
光合作用将碳固定成海洋中的有机物。然后，生物力量在海洋空间和时间中描绘出复杂的碳通量模式，因为它流经食物网，储存在沉积物中并与大气交换。预测这些碳通量模式如何对全球变化（或人类操纵）做出反应是了解更多海洋碳循环运作的主要原因。通量模式是不同生物群与物理和化学复杂的有机物池之间复杂相互作用的结果。现在看来，事情在变得简单之前会变得更加复杂。在我们希望构建生态系统模型来预测碳通量模式之前，必须正确吸收关于微生物在有机物命运中的作用以及最近关于有机物本身性质的新的基本发现（1-4）。这种推动力可能会导致一种强大的新合成。什么生物力量作用于海洋中光合作用产生的有机物？从历史上看，基本上所有的初级生产都停留在颗粒阶段（5），它被食草动物吃掉，碳的命运由“放牧食物链”决定（见下图中的图表）。几乎没有溶解的有机物溢出供细菌使用。因此，在研究有机物的命运时，忽略细菌、原生动物和病毒被认为是安全的--它们太稀疏，不够活跃。这一点现在改变了（5-8）：有机物的主要通量，往往在数量上超过放牧食物链，通过溶解的有机物进入细菌和“微生物循环”（7，8）（下图）。以前的方法错过了> 99%的微生物，并且严重低估了它们的代谢。现在，我们从广泛的实地研究中了解到，在大多数海洋中，有机物质流入细菌是一个主要途径;平均一半的海洋初级生产通过细菌进入微生物循环（7，8）-海洋中的主要生物力量。
Photosynthesis fixes carbon into organic matter in the ocean. Biological forces then paint intricate flux patterns for carbon in ocean space and in time, as it flows through the food web, becomes stored in the sediments and exchanged with the atmosphere. Predicting how these carbon flux patterns might respond to global change (or to human manipulation) is a primary reason for learning more about the workings of the ocean's carbon cycle. The flux patterns are a result of intricate interactions of a diverse biota with a physically and chemically complex pool of organic matter. It now seems that things will get even more complicated before they get simpler. New fundamental findings on the roles of microbes in the fate of organic matter and, recently, on the nature of the organic matter itself (1-4) must be properly assimilated before we can hope to construct ecosystem models to predict the patterns of carbon flux. This impetus could lead to a powerful new synthesis.What biological forces act on photosynthetically produced organic matter in the ocean? Historically, the paradigm has been that essentially all primary production stays within the particle phase (5), it is eaten by herbivores, and the fate of carbon is determined by the “grazing food chain”(see the diagram in the figure below). Little dissolved organic matter is spilled for bacteria to use. It had, therefore, been implicitly assumed to be safe to ignore bacteria, protozoa, and viruses in studying the fate of organic matter—they were too sparse and not active enough (5). This is now changed (5-8): Major fluxes of organic matter, often eclipsing the grazing food chain in quantity, move via dissolved organic matter into bacteria and the “microbial loop”(7, 8)(figure below). Previous methods had missed> 99% of microorganisms and had grossly underestimated their metabolism. Now we know from extensive field studies that in most of the ocean, organic matter flux into bacteria is a major pathway; one-half of oceanic primary production on average is channeled via bacteria into the microbial loop (7, 8)—a major biological force in the ocean.