ABSTRACT Carbon incorporated into diatom frustule walls is protected from degradation enabling analysis for carbon isotope composition (δ13Cdiatom). This presents potential for tracing carbon cycles via a single photosynthetic host with well‐constrained ecophysiology. Improved understanding of environmental processes controlling carbon delivery and assimilation is essential to interpret changes in freshwater δ13Cdiatom. Here relationships between water chemistry and δ13Cdiatom from contemporary regional data sets are investigated. Modern diatom and water samples were collected from river catchments within England and lake sediments from across Europe. The data suggest dissolved, biogenically produced carbon supplied proportionately to catchment productivity was critical in the rivers and soft water lakes. However, dissolved carbon from calcareous geology overwhelmed the carbon signature in hard water catchments. Both results demonstrate carbon source characteristics were the most important control on δ13Cdiatom, with a greater impact than productivity. Application of these principles was made to a sediment record from Lake Tanganyika. δ13Cdiatom co‐varied with δ13Cbulk through the last glacial and Holocene. This suggests carbon supply was again dominant and exceeded authigenic demand. This first systematic evaluation of contemporary δ13Cdiatom controls demonstrates that diatoms have the potential to supply a record of carbon cycling through lake catchments from sediment records over millennial timescales.

中文翻译：

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淡水硅藻中碳同位素比值的解读及应用

摘要 硅藻壳壁中的碳可以防止降解，从而可以分析碳同位素组成（δ13C硅藻）。这为通过具有良好生态生理学约束的单一光合宿主追踪碳循环提供了潜力。更好地理解控制碳输送和同化的环境过程对于解释淡水 δ13C 硅藻的变化至关重要。这里研究了当代区域数据集中的水化学与 δ13C硅藻之间的关系。现代硅藻和水样是从英格兰境内的河流流域和欧洲各地的湖泊沉积物中收集的。数据表明，与集水区生产力成比例地供应的溶解的、生物产生的碳在河流和软水湖泊中至关重要。然而，来自钙质地质的溶解碳压倒了硬水流域的碳特征。这两个结果都表明碳源特性是对 δ13C硅藻最重要的控制，其影响大于生产力。将这些原则应用于坦噶尼喀湖的沉积物记录。δ13​​C硅藻在末次冰期和全新世期间与δ13Cbulk共同变化。这表明碳供应再次占主导地位，并超过了自生需求。对当代 δ13C 硅藻控制的首次系统评估表明，硅藻有可能通过千年时间尺度的沉积物记录提供通过湖泊集水区的碳循环记录。这两个结果都表明碳源特性是对 δ13C硅藻最重要的控制，其影响大于生产力。将这些原则应用于坦噶尼喀湖的沉积物记录。δ13​​C硅藻在末次冰期和全新世期间与δ13Cbulk共同变化。这表明碳供应再次占主导地位，并超过了自生需求。对当代 δ13C 硅藻控制的首次系统评估表明，硅藻有可能通过千年时间尺度的沉积物记录提供通过湖泊集水区的碳循环记录。这两个结果都表明碳源特性是对 δ13C硅藻最重要的控制，其影响大于生产力。将这些原则应用于坦噶尼喀湖的沉积物记录。δ13​​C硅藻在末次冰期和全新世期间与δ13Cbulk共同变化。这表明碳供应再次占主导地位，并超过了自生需求。对当代 δ13C 硅藻控制的首次系统评估表明，硅藻有可能通过千年时间尺度的沉积物记录提供通过湖泊集水区的碳循环记录。这表明碳供应再次占主导地位，并超过了自生需求。对当代 δ13C 硅藻控制的首次系统评估表明，硅藻有可能通过千年时间尺度的沉积物记录提供通过湖泊集水区的碳循环记录。这表明碳供应再次占主导地位，并超过了自生需求。对当代 δ13C 硅藻控制的首次系统评估表明，硅藻有可能通过千年时间尺度的沉积物记录提供通过湖泊集水区的碳循环记录。