Data from: Thermodynamic constraints on the utility of ecological stoichiometry for explaining global biogeochemical patterns

Carbon and nitrogen cycles are coupled through both stoichiometric requirements for microbial biomass and dissimilatory metabolic processes in which microbes catalyse reduction-oxidation reactions. Here, we integrate stoichiometric theory and thermodynamic principles to explain the commonly observed trade-off between high nitrate and high organic carbon concentrations, and the even stronger trade-off between high nitrate and high ammonium concentrations, across a wide range of aquatic ecosystems. Our results suggest these relationships are the emergent properties of both microbial biomass stoichiometry and the availability of terminal electron acceptors. Because elements with multiple oxidation states (i.e. nitrogen, manganese, iron and sulphur) serve as both nutrients and sources of chemical energy in reduced environments, both assimilative demand and dissimilatory uses determine their concentrations across broad spatial gradients. Conceptual and quantitative models that integrate rather than independently examine thermodynamic, stoichiometric and evolutionary controls on biogeochemical cycling are essential for understanding local to global biogeochemical patterns.碳循环与氮循环通过两类途径实现耦合：其一为微生物生物量的化学计量需求（stoichiometric requirements），其二为微生物催化氧化还原反应（reduction-oxidation reactions）的异化代谢过程（dissimilatory metabolic processes）。本研究整合化学计量理论（stoichiometric theory）与热力学原理（thermodynamic principles），对广泛水生生态系统（aquatic ecosystems）中普遍观测到的两类权衡（trade-off）关系进行解释：一是高硝酸盐（nitrate）浓度与高有机碳（organic carbon）浓度间的权衡，二是高硝酸盐浓度与高铵态氮（ammonium）浓度间的更强权衡。研究结果显示，上述关系是微生物生物量化学计量特征与末端电子受体（terminal electron acceptors）可获得性共同作用产生的涌现属性（emergent properties）。由于具有多种氧化态（oxidation states）的元素（即氮、锰、铁与硫）在还原环境（reduced environments）中同时兼具营养物质与化学能量源的双重身份，因此同化需求（assimilative demand）与异化利用共同决定了它们在大范围空间梯度（spatial gradients）上的浓度分布。若要理解从局地到全球尺度的生物地球化学模式（biogeochemical patterns），亟需构建整合而非独立考察热力学、化学计量学与进化调控（evolutionary controls）对生物地球化学循环（biogeochemical cycling）影响的概念模型与定量模型（conceptual and quantitative models）。