Pace Michael L, Cole Jonathan J, Carpenter Stephen R, Kitchell James F, Hodgson James R, Van De Bogert Matthew C, Bade Darren L, Kritzberg Emma S, Bastviken David
Institute of Ecosystem Studies, Millbrook, New York 12545, USA.
Nature. 2004 Jan 15;427(6971):240-3. doi: 10.1038/nature02227.
Ecosystems are supported by organic carbon from two distinct sources. Endogenous carbon is produced by photosynthesis within an ecosystem by autotrophic organisms. Exogenous carbon is produced elsewhere and transported into ecosystems. Consumers may use exogenous carbon with consequent influences on population dynamics, predator-prey relationships and ecosystem processes. For example, exogenous inputs provide resources that may enhance consumer abundance beyond levels supported by within-system primary production. Exogenous fluxes of organic carbon to ecosystems are often large, but this material is recalcitrant and difficult to assimilate, in contrast to endogenously produced organic matter, which is used more easily. Here we show, by the experimental manipulation of dissolved inorganic (13)C in two lakes, that internal primary production is insufficient to support the food webs of these ecosystems. Additions of NaH(13)CO(3) enriched the (13)C content of dissolved inorganic carbon, particulate organic carbon, zooplankton and fish. Dynamics of (13)C indicate that 40-55% of particulate organic carbon and 22-50% of zooplankton carbon are derived from terrestrial sources, showing that there is significant subsidy of these ecosystems by organic carbon produced outside their boundaries.
生态系统由两种不同来源的有机碳提供支持。内源碳是由自养生物在生态系统内通过光合作用产生的。外源碳在其他地方产生并输送到生态系统中。消费者可能会利用外源碳，从而对种群动态、捕食者 - 猎物关系和生态系统过程产生影响。例如，外源输入提供的资源可能会使消费者数量增加到超过系统内初级生产所支持的水平。有机碳向生态系统的外源通量通常很大，但与更容易被利用的内源产生的有机物质相比，这种物质难降解且难以同化。在这里，我们通过对两个湖泊中溶解无机（13）C 的实验操作表明，内部初级生产不足以支持这些生态系统的食物网。添加 NaH（13）CO3 提高了溶解无机碳、颗粒有机碳、浮游动物和鱼类的（13）C 含量。（13）C 的动态表明，40 - 55%的颗粒有机碳和 22 - 50%的浮游动物碳来自陆地来源，这表明这些生态系统受到其边界外产生的有机碳的显著补贴。
