Vertical motion is an important driver of sunlight exposure in aquatic environments, shaping the growth and fate of materials and organisms. We derive a simple model accounting for turbulent depth fluctuations of particles to predict the depth that contributes the most sunlight exposure (effective depth) as well as the single depth that, if measured at one place over time, produces the same total sunlight exposure as a moving particle (functional depth). Field measurements of light and depth in rivers using neutrally buoyant drifters and buoys validate our model. Effective depth varied from 0.1 to 1.5 m below the water surface and was ~ 30% of the overall water depth on average. Functional depth varied from 0.67 to 2.3 m and was ~ 50% of the overall water depth on average. Functional and effective depth are physically based concepts incorporating turbulent motion, spatial variability, and water clarity offering new approaches to characterize light exposure in aquatic environments.

中文翻译：

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河流、湖泊和海洋阳光照射的新指标

垂直运动是水生环境中阳光照射的重要驱动因素，影响着物质和生物体的生长和命运。我们推导出一个简单的模型，考虑了粒子的湍流深度波动，以预测贡献最大阳光照射的深度（有效深度），以及如果在一个地方随时间测量，产生与一个地方相同的总阳光照射的单一深度。移动粒子（功能深度）。使用中性浮力漂流器和浮标对河流中的光和深度进行的现场测量验证了我们的模型。有效深度从水面以下 0.1 到 1.5 m 不等，平均约为总水深的 30%。功能深度从 0.67 到 2.3 m 不等，平均约为总水深的 50%。功能深度和有效深度是基于物理的概念，结合了湍流运动、空间变化和水体透明度，提供了表征水生环境中光照特征的新方法。