Can pelagic net heterotrophy account for carbon fluxes from eastern Canadian lakes?
Can pelagic net heterotrophy account for carbon fluxes from eastern Canadian lakes?
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DOI：
10.1016/j.apgeochem.2009.03.001
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发表时间：
2009-05-01
影响因子：
3.4
通讯作者：
Veizer, Jan
中科院分区：
文献类型：
--
作者：
Dubois, Kristal;Carignan, Richard;Veizer, Jan
世界各地的湖泊通常是过饱和的二氧化碳，但这种二氧化碳过饱和的来源还没有很好的理解。为了研究大气中碳通量的大小，并确定呼吸（R）超过总初级生产力（GPP）是否足以解释这种碳通量，在23个魁北克湖泊中测量了溶解O-2和C的代谢参数和稳定同位素。在采样期间，所有采样的湖泊都被二氧化碳过饱和，平均为221 +/-25%。然而，几乎没有证据表明，这种CO2过饱和是由于过量的远洋R超过GPP。在克罗什湖和阿图尔湖，每周测量CO2通量、R和GPP，浮游GPP和R或净初级生产力之间的年度差异不足以说明进入大气的CO2通量的大小。在克罗什湖，年平均净初级生产力为14.4 mg Cm（-2）d（-1），而向大气中排放的CO2的年平均通量为34 mg Cm（-2）d（-1）。在Lac a l 'Ours，年平均NPP为-9.1 mg C m（-2）d（-1），而向大气的CO2年平均通量为55 mg C m（-2）d（-1）。在所有采样的湖泊中，在无冰季节，O-2饱和度平均为104.0 +/- 1.7%，溶解O-2的同位素组成（δ O-18（DO））为22.9 +/-0.3%，低于大气值，表明净自养。碳逃逸是不是一个功能的R，也没有溶解在湖泊中的二氧化碳的同位素签名的证据过量R超过GPP。因此，C的外部输入必须补贴湖泊，以解释持续的CO2过饱和。溶解无机碳（δ C-13（DIC））的同位素组成表明，CO2过饱和不能归因于原位好氧呼吸。δ C-13（DIC）揭示了C-13中富集的过量C的来源，这可以通过厌氧沉积物呼吸或地下水输入来解释，随后是开放系统条件下脱气期间的动力学同位素分馏。(C)2009爱思唯尔有限公司保留所有权利。
Lakes worldwide are commonly oversaturated with CO2, however the source of this CO2 oversaturation is not well understood. To examine the magnitude of the C flux to the atmosphere and determine if an excess of respiration (R) over gross primary production (GPP) is sufficient to account for this C flux, metabolic parameters and stable isotopes of dissolved O-2 and C were measured in 23 Quebec lakes. All of the lakes sampled were oversaturated with CO2 over the sampling period, on average 221 +/- 25%. However, little evidence was found to conclude that this CO2 oversaturation was the result of an excess of pelagic R over GPP. In lakes Croche and a l'Ours, where CO2 flux, R and GPP were measured weekly, the annual difference between pelagic GPP and R, or net primary production (NPP), was not sufficient to account for the size of the CO2 flux to the atmosphere. In Lac Croche average annual NPP was 14.4 mg C m(-2) d(-1) while the average annual flux Of CO2 to the atmosphere was 34 mg C m(-2) d(-1). In Lac a l'Ours average annual NPP was -9.1 mg C m(-2) d(-1) while the average annual flux Of CO2 to the atmosphere was 55 mg C m(-2) d(-1). In all of the lakes sampled, O-2 Saturation averaged 104.0 +/- 1.7% during the ice-free season and the isotopic composition of dissolved O-2 (delta O-18(DO)) was 22.9 +/- 0.3%, lower than atmospheric values and indicative of net autotrophy. Carbon evasion was not a function of R, nor did the isotopic signature of dissolved CO2 in the lakes present evidence of excess R over GPP. External inputs of C must therefore subsidize the lake to explain the continued CO2 oversaturation. The isotopic composition of dissolved inorganic C (delta C-13(DIC)) indicates that the CO2 oversaturation cannot be attributed to in situ aerobic respiration. delta C-13(DIC) reveals a source of excess C enriched in C-13, which may be accounted for by anaerobic sediment respiration or groundwater inputs followed by kinetic isotope fractionation during degassing under open system conditions. (C) 2009 Elsevier Ltd. All rights reserved.