Whole-stream 13C tracer addition reveals distinct fates of newly fixed carbon
Whole-stream 13C tracer addition reveals distinct fates of newly fixed carbon
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DOI：
10.1890/14-0631.1
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发表时间：
2015-02-01
期刊：
影响因子：
4.8
通讯作者：
Hall, Robert O., Jr.
中科院分区：
文献类型：
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作者：
Hotchkiss, Erin R.;Hall, Robert O., Jr.
许多对淡水碳(C)通量的估计侧重于陆地碳的输入、加工和储存；然而内陆水域有很高的内部固定(原生)碳产生率。新固定碳的一部分可能在固定后不久以生物可利用的溶解有机碳(DOC)的形式释放出来，并刺激微生物驱动的生物地球化学循环，但原生C的去向很难直接测量。在淡水食物网和碳循环的背景下，追踪新固定的碳可以增加我们对原生碳的通量和去向的理解。我们使用溶解的无机碳稳定同位素加成(C-13(DIC))来追踪原地碳的固定和命运。我们在8月份的两天时间里向美国怀俄明州的北福克法兰西河添加了C-13(DIC)。我们在添加后44天内监测了C-13池、通量和存储的变化。用二室通量模型对新固定的C-13(DOC)和C-13(DIC)的净释放量进行了量化。我们将净C-13固定与示踪剂C-13(DIC)的去除和总初级生产量(GPP)进行比较，以说明固定、释放、损失到大气中并向下游输出的示踪剂的质量。许多固定的C代码迅速周转，没有进入较长期的存储池。净固定碳占氧分压的70%。藻类可能通过C-13(DOC)渗出和新固定C的呼吸释放剩余的30%。在C-13添加期间，初级生产者以每天高达16%的速率释放C-13(DOC)，但新的活性C的渗出在第6天下降到接近于零。新固定C的DIC产量在添加C-13后第二天占生态系统呼吸的21%。示踪剂加入1d后，所有测得的有机碳(OC)库均被C-13富集。固定C-13在底栖生物有机碳中的平均滞留时间为62d，固定C-13在底栖生物有机碳中的平均停留时间为44d。
Many estimates of freshwater carbon (C) fluxes focus on inputs, processing, and storage of terrestrial C; yet inland waters have high rates of internally fixed (autochthonous) C production. Some fraction of newly fixed C may be released as biologically available, dissolved organic C (DOC) and stimulate microbial-driven biogeochemical cycles soon after fixation, but the fate of autochthonous C is difficult to measure directly. Tracing newly fixed C can increase our understanding of fluxes and fate of autochthonous C in the context of freshwater food webs and C cycling. We traced autochthonous C fixation and fate using a dissolved inorganic C stable isotope addition (C-13(DIC)). We added C-13(DIC) to North Fork French Creek, Wyoming, USA during two days in August. We monitored changes in C-13 pools, fluxes, and storage for 44 d after the addition. Two-compartment flux models were used to quantify net release of newly fixed C-13(DOC) and C-13(DIC) into the water column. We compared net C-13 fixation with tracer C-13(DIC) removal and gross primary production (GPP) to account for the mass of tracer fixed, released, lost to the atmosphere, and exported downstream. Much of the fixed C turned over rapidly and did not enter longer-term storage pools. Net C fixed was 70% of GPP measured with O-2. Algae likely released the remaining 30% via C-13(DOC) exudation and respiration of newly fixed C. Primary producers released C-13(DOC) at rates of up to 16% per day during the C-13 addition, but exudation of new labile C declined to near zero by day 6. DIC production from newly fixed C accounted for 21% of ecosystem respiration the day after the C-13 addition. All measured organic C (OC) pools were enriched with C-13 1 d after the tracer addition. 20% of fixed C-13 remained in benthic OC by day 44, and average residence time of autochthonous C in benthic OC was 62 d. Newly fixed C had two distinct fates: short-term (