一项将可降解有机碳添加进北极水域的实验获得了反直觉的发现：在某些条件下，碳的添加实际上会减少生态系统中的总有机碳。实验结果取决于食物链内物种相互作用以及它们怎样受营养供应的影响。当矿物营养有限时，有机碳会在系统中积累，而在一个有机碳有限的系统中，海洋细菌能够竞争过浮游植物，其净结果为总有机碳数量减少。
这一结果凸现了这样一个关系，即对海洋碳循环当前和未来状态的描述，怎样依赖于对海洋食物链内的碳与限制生长的矿物营养之间的化学计量耦合的认识。（生物谷Bioon.com）
生物谷推荐原始出处：
Nature 455, 387-390 (18 September 2008) | doi:10.1038/nature07235
Counterintuitive carbon-to-nutrient coupling in an Arctic pelagic ecosystem
T. F. Thingstad, R. G. J. Bellerby, G. Bratbak, K. Y. B?rsheim, J. K. Egge, M. Heldal, A. Larsen, C. Neill, J. Nejstgaard, S. Norland1, R.-A. Sandaa1, E. F. Skjolda, T. Tanaka, R. Thyrhaug1 & B. T?pper
Predicting the ocean's role in the global carbon cycle requires an understanding of the stoichiometric coupling between carbon and growth-limiting elements in biogeochemical processes. A recent addition to such knowledge is that the carbon/nitrogen ratio of inorganic consumption and release of dissolved organic matter may increase in a high-CO2 world1. This will, however, yield a negative feedback on atmospheric CO2 only if the extra organic material escapes mineralization within the photic zone. Here we show, in the context of an Arctic pelagic ecosystem, how the fate and effects of added degradable organic carbon depend critically on the state of the microbial food web. When bacterial growth rate was limited by mineral nutrients, extra organic carbon accumulated in the system. When bacteria were limited by organic carbon, however, addition of labile dissolved organic carbon reduced phytoplankton biomass and activity and also the rate at which total organic carbon accumulated, explained as the result of stimulated bacterial competition for mineral nutrients. This counterintuitive 'more organic carbon gives less organic carbon' effect was particularly pronounced in diatom-dominated systems where the carbon/mineral nutrient ratio in phytoplankton production was high. Our results highlight how descriptions of present and future states of the oceanic carbon cycle require detailed understanding of the stoichiometric coupling between carbon and growth-limiting mineral nutrients in both autotrophic and heterotrophic processes.
