Carbon fixation, flux and burial efficiency in two contrasting eutrophic lakes in the UK (Rostherne Mere & Tatton Mere)
Carbon fixation, flux and burial efficiency in two contrasting eutrophic lakes in the UK (Rostherne Mere & Tatton Mere)
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英国两个对比鲜明的富营养化湖泊的碳固定、通量和埋藏效率（Rostherne Mere
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发表时间：
2014
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通讯作者：
Daniel R. Scott
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作者：
Daniel R. Scott
目前对小型湖泊中碳（C）处理和储存的研究大多集中在北极和北方湖泊系统，因为它们在全球范围内丰富。然而，这导致了对湖泊功能的解释不平衡。寡营养型湖泊在北极和寒带地区普遍存在，但由于集水区溶解有机碳（DOC）的负载改变了它们的代谢平衡，因此通常是净异养的。相比之下，温带湖泊系统往往更富营养，通常是由于人类活动，因此，预计将表现出净自养的迹象，作为较高的总初级生产力（GPP）和较低的率集水区衍生DOC潜在补贴呼吸（R）的结果。
为了检验这一假设，温带，富营养化湖泊净自养（GPP > R）每年的C-动态的罗斯海（最大深度，ZM，31米）和塔顿海（ZM = 11米），两个monomictic柴郡-什罗普郡海，从2010年至2012年的18个月期间进行了量化。这项监测研究使用高分辨率（每小时）氧（O2）探头测量，结合高分辨率的数据，从一个自动化的湖上监测浮标在Rostherne Mere（作为国家UKLEON湖网络的一部分），以计算率的表层C-固定。对于这两个湖泊，沉积物捕集器也被用来确定水柱C-通量和沉积物岩心数据，以建立这些强烈分层湖泊的C-埋藏效率。溶解O2和CO2的水柱剖面也测量在2 - 4周的时间间隔横跨两个湖泊。特别注意的是：一）富营养化，单胞湖泊的长期C-存储;二）规模扩大C-积累估计从这两个海的Cheshire-什罗普郡海地区和所有英国富营养化沃茨;和iii）方法的敏感性，估计C-固定，通量和埋葬效率和规模扩大C-积累估计。结果表明，这两个湖泊均为净自养型，年平均固定碳121 ± 2 g C m-2 yr-1，固碳68 ± 4 g C m-2 yr-1，碳埋藏效率约为60%。
如果按比例放大到Cheshire-Shropshire meres地区，自1900年以来，每年的碳积累量估计为506 ± 32吨C yr-1或0.05 ± 0.001吨C。由此，据估计，英国富营养化沃茨自1900年以来每年可螯合0.12 ± 0.01 Mt C或13.3 ± 0.2 Mt C。英国每年的CO2排放量约为128.85 Mt C yr-1，因此英国富营养化沃茨目前抵消了英国每年CO2排放量的0.09%。
尽管发现富营养化的分层湖泊具有高的固碳和封存值，但地球仪其他区域（如北极和寒带）的湖泊通常是更重要的长期碳汇，因为它们在景观中更丰富，并且当地土壤通常在低碳保持率下非常贫乏。需要进一步调查湖泊在区域和国家范围内的功能，湖泊类型和数量的重要性时，扩大碳积累的估计和未来的碳积累的潜在影响，作为一个不断变化的环境和超区域的政策，如欧洲等地区。
Much of the current research into the processing and storage of carbon (C) in small lakes has focused on arctic and boreal lake systems, due to their global abundance. However this has led to an imbalance in the interpretation of lake functioning. Oligotrophic lakes are prevalent in the arctic and boreal zone, but are typically net heterotrophic due to loading of catchment-derived dissolved organic carbon (DOC) which alters their metabolic balance. In comparison, temperate lake systems tend to be more nutrient rich, typically due to anthropogenic activity, and would therefore be expected to exhibit the signs of net autotrophy, as a result of higher rates of gross primary production (GPP) and lower rates of catchment-derived DOC potentially subsidising respiration (R).
In order to test the hypothesis that temperate, eutrophic lakes are net autotrophic (GPP > R) on an annual basis the C-dynamics of Rostherne Mere (maximum depth, zm, 31 m) and Tatton Mere (zm = 11 m), two monomictic Cheshire-Shropshire meres, were quantified over an 18 months period from 2010 2012. This monitoring study used high-resolution (hourly) oxygen (O2) sonde measurements, combined with high-resolution data from an automated on-lake monitoring buoy at Rostherne Mere (as part of the national UKLEON lake network) to calculate rates of epilimnion C-fixation. For both lakes, sediment traps were also used to determine water column C-flux and sediment core data to establish C-burial efficiency of these strongly stratifying lakes. Water column profiles of dissolved O2 and CO2 was also measured at 2 4 weekly intervals across both lakes. Particular attention was focused on: i) the long term C-storage of eutrophic, monomictic lakes; ii) up-scaling C-accumulation estimates from these two meres to the Cheshire-Shropshire meres region and all UK eutrophic waters; and iii) methodological sensitivity for estimating C-fixation, flux and burial efficiency and upscaling C-accumulation estimates. The results show that both lakes are net autotrophic on an annual basis, on average fixing 121 ± 2 g C m-2 yr-1 and sequestering 68 ± 4 g C m-2 yr-1, a C-burial efficiency of ~60%.
If up-scaled to the Cheshire-Shropshire meres region, annual C-accumulation was estimated to be 506 ± 32 t C yr-1 or 0.05 ± 0.001 Mt C since 1900. From this, it was estimated that UK eutrophic waters could be sequestering 0.12 ± 0.01 Mt C yr-1 or 13.3 ± 0.2 Mt C since 1900. Annual UK CO2 emissions are ~128.85 Mt C yr-1, therefore UK eutrophic waters currently offset 0.09% of yearly UK CO2 emissions.
Despite the finding that eutrophic, stratifying lakes have high C-fixation and sequestration values, lakes in other areas of the globe such as the arctic and boreal zones are typically a more important long term C-sink as they are far more abundant within the landscape and local soils are typically very poor within low C retention rates. Further investigation is needed into how lakes function on a regional and national scale, the importance of lake type and number when up-scaling C accumulation estimates and the potential impact on future C accumulation as a result of a changing environment and supra-regional policies in areas such as Europe.