Phytoplankton response to fluctuating light intensity and spectrum II - How fluctuations in the multiple dimensions of LIGHt shape phytoplankTON (LIGHT-ON)

波动的环境限制了人口或社区的适应能力。因此，高度可预测的波动将引发生物和群落的不同反应，而不是更随机的反应。这些响应是非线性的，因此不随时间平均，这阻碍了预测未来的生态系统功能的基础上平均环境。越来越多的研究表明，平均温度附近的热变率的重要性，但很少有研究存在的其他环境变量，除了温度。在这里，我们问的基本问题是浮游植物生物如何科普光的变化之间的压力和有利的条件，特别是如果人为强迫的变化超出了波动的水平，自然会发生在这些栖息地。光的波动范围从可预测的季节性和日变化到几秒钟内通过云层覆盖和散射的随机变化，包括光的强度和光谱组成，因为吸收和散射是特定波长的。因此，光需要作为一种多维和高变的资源来处理，因为可变性（振幅，频率和随机性）的时刻适用于多个波长。在水生系统中，高度可变的光照条件直接影响浮游植物的光合作用、呼吸作用、生长速率和生化组成。然而，大多数关于光的实证研究使用规律性波动作为群落动态的驱动因素，大多数集中在资源的单一维度（主要是总辐照度）。本文的创新点在于研究光强和光谱的交互作用，通过不同手段调控波动的频率、幅度和随机性，了解多种波动源对浮游植物的综合影响。我们首先分析自然界中光强度和光谱的波动，并使用单克隆培养物进行实验，以了解物种特异性反应。在下一步中，我们测试是否种间相互作用改变的反应，使用控制实验室设置和操作多物种组合。实验将与模拟相关联，以进一步阐明潜在的机制，并预测无法通过实验充分测试的场景。最后，我们将测试我们的假设在现场浮游植物群落在受控的室内围隔和现场实验。该项目有助于了解和预测物种和群落对光强变化和光谱组成波动的反应（例如，变化的幅度，频率和随机性）。

A fluctuating environment constrains the ability of a population or community to adapt. Thereby highly predictable fluctuations will trigger different responses of organisms and communities than more stochastic ones. These responses are non-linear and therefore do not average across time, which hampers predicting future ecosystem functionality based on mean environments. A steadily increasing number of studies demonstrate the importance of thermal variability around the average, but less studies exist for other environmental variables besides temperature. Here, we ask the fundamental question how phytoplankton organisms cope with light variation often between stressful and advantageous conditions, especially if anthropogenic forcing shifts the variance beyond the level of fluctuations that would naturally occur in these habitats. Light fluctuations range from predictable seasonal and diurnal components to stochastic changes within seconds through cloud cover and scattering, comprising the intensity and spectral composition of light, as absorption and scattering are wavelength-specific. Thus, light needs to be addressed as a multi-dimensional and hypervariable resource, as moments of variability (amplitude, frequency and stochasticity) apply to multiple wavelengths. Highly variable light conditions in aquatic systems directly impact phytoplankton photosynthesis, respiration, growth rates, and biochemical composition. However, most of the empirical studies on light used regular fluctuations as drivers of community dynamics and the majority focused on a single dimension of the resource (mostly total irradiance). The innovative approach here is to study the interactive effect of light intensity and light spectrum, to understand the combined effects of multiple fluctuating resources on phytoplankton by manipulating the frequency, amplitude and stochasticity of fluctuations around different means. We start with analyzing how fluctuations in light intensity and spectrum occur in nature and conduct experiments with monoclonal cultures to understand species-specific responses. In the next step we test whether interspecific interactions alter the responses using controlled lab settings and manipulations for multispecies assemblages. Experiments will be associated with simulations to shed further light into underlying mechanisms and predict scenarios that cannot be sufficiently tested experimentally. Finally, we will test our hypotheses on in-situ phytoplankton communities in controlled indoor mesocosms and in field experiments. This project helps understanding and predicting species and community responses to changes in light intensity and spectral composition fluctuations (e.g. changed amplitude, frequency and stochasticity, resp.).