Light is a primary driver of lake ecosystem metabolism, and the dependence of primary production on light is often quantified as a photosynthesis‐irradiance or “P‐I” curve. The parameters of the P‐I curve (e.g., the maximum primary production when light is in excess) can change through time due to a variety of biological factors (e.g., changes in biomass or community composition), which themselves are subject to external drivers (e.g., herbivory or nutrient availability). However, the relative contribution of variation in the P‐I curve to overall ecosystem metabolism is largely unknown. I developed a statistical model of ecosystem metabolism with time‐varying parameters governing the P‐I curve, while also accounting for the influence of temperature. I parameterized the model with dissolved oxygen time series spanning six summers from Lake Mývatn, a shallow eutrophic lake in northern Iceland with large temporal variability in ecosystem metabolism. All of the estimated parameters of the P‐I curve varied substantially through time. The sensitivity of primary production to light under light‐limiting conditions was particularly variable (>15‐fold) and had a compensatory relationship with ambient light levels. However, the 3.5‐fold variation in the maximum potential primary production made the largest contribution to variation in ecosystem metabolism, accounting for around 90% of the variance in net ecosystem production. Much of the variation in maximum primary production was attributable to cyanobacterial blooms, which occur in some but not all years in Mývatn. Overall, these results illustrate how changes in the P‐I curve contribute substantially to temporal variation in lake ecosystem metabolism.

中文翻译：

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湖泊新陈代谢对光和温度的时变响应

光是湖泊生态系统新陈代谢的主要驱动力，初级生产对光的依赖性通常被量化为光合作用辐照度或“ P-1”曲线。P‐I曲线的参数（例如，光线过多时的最大初级产量）可能会由于各种生物因素（例如，生物量或群落组成的变化）而随时间变化，这些因素本身受外部驱动力的影响（例如，食草或营养供应）。但是，P-I曲线变化对整个生态系统新陈代谢的相对贡献尚不清楚。我开发了一个生态系统代谢的统计模型，该模型具有控制P-I曲线的时变参数，同时也考虑了温度的影响。我用溶解氧时间序列对模型进行了参数化，该时间序列来自米湖的六个夏天，冰岛北部的浅水富营养化湖泊，其生态系统新陈代谢具有较大的时间变化。P-I曲线的所有估计参数随时间变化很大。在光限制条件下，初级产品对光的敏感性特别可变（> 15倍），并且与环境光水平具有补偿性关系。但是，最大潜在初级生产量的3.5倍变化对生态系统新陈代谢的变化贡献最大，约占生态系统净生产量变化的90％。最大初级产量的大部分变化都归因于蓝藻绽放，这种开花发生在梅凡州，但不是全部年份。总体，