A Framework for Understanding Variation in Pelagic Gross Primary Production of Lake Ecosystems
A Framework for Understanding Variation in Pelagic Gross Primary Production of Lake Ecosystems
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DOI：
10.1007/s10021-018-0226-4
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发表时间：
2018-11-01
期刊：
影响因子：
3.7
通讯作者：
Jones, Stuart E.
中科院分区：
文献类型：
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作者：
Kelly, Patrick T.;Solomon, Christopher T.;Jones, Stuart E.
光和养分可用性是初级生产的关键生理限制。广泛的环境变化导致陆地溶解有机碳（DOC）和从流域到湖泊的养分含量发生变化，从而导致光和养分供应同时发生变化。实验证据强调了这些流域负荷有可能对湖内初级生产产生复杂且依赖于环境的响应；然而，该领域缺乏研究这些反应的预测模型。我们将一个完善的浮游植物生长生理模型嵌入养分和 DOC 供应的生态系统模型中，以评估 DOC 和养分负荷的同时变化如何影响湖泊中的中上层初级生产。当 DOC 和营养物质的负荷在空间或时间上紧密相关时，该模型生成 GPP 和 DOC 浓度之间的单峰关系。在这种单峰关系中，峰值 GPP 的大小主要由负荷的 DOC 与养分之比决定，峰值沿 DOC 轴的位置主要由湖泊面积决定。相对于 DOC 负荷而言，更大的养分供应有助于提高生产力，而由于湖泊面积和表层深度之间的正相关关系，较大的湖泊面积在给定的 DOC 浓度下增加了初级生产者的光照限制。当 DOC 和营养物质的负荷在空间或时间上不紧密相关时，该模型会在 GPP 和 DOC 之间生成楔形模式，这与全球湖泊的空间调查一致。因此，我们的模型能够统一文献中所观察到的湖泊生产力对 DOC 和矿物质养分供应的空间和时间响应的多样性，并为湖泊中上层初级生产力如何响应广泛的环境变化提供定性预测。
Light and nutrient availability are key physiological constraints for primary production. Widespread environmental changes are causing variability in loads of terrestrial dissolved organic carbon (DOC) and nutrients from watersheds to lakes, contributing to simultaneous changes in both light and nutrient supply. Experimental evidence highlights the potential for these watershed loads to create complex and context-dependent responses of within-lake primary production; however, the field lacks a predictive model to investigate these responses. We embedded a well-established physiological model of phytoplankton growth within an ecosystem model of nutrient and DOC supply to assess how simultaneous changes in DOC and nutrient loads could impact pelagic primary production in lakes. The model generated a unimodal relationship between GPP and DOC concentration when loads of DOC and nutrients were tightly correlated across space or time. In this unimodal relationship, the magnitude of the peak GPP was primarily determined by the DOC-to-nutrient ratio of the load, and the location of the peak along the DOC axis was primarily determined by lake area. Greater nutrient supply relative to DOC load contributed to greater productivity, and larger lake area increased light limitation for primary producers at a given DOC concentration, owing to the positive relationship between lake area and epilimnion depth. When loads of DOC and nutrients were not tightly correlated in space or time, the model generated a wedge-shaped pattern between GPP and DOC, consistent with spatial surveys from a global set of lakes. Our model is thus capable of unifying the diversity of empirically observed spatial and temporal responses of lake productivity to DOC and mineral nutrient supply presented in the literature, and provides qualitative predictions for how lake pelagic primary productivity may respond to widespread environmental changes.