Dissolved oxygen concentration is a critical point for microalgae in large scale cultivation systems. Highly productive cultures inevitably generate a build-up of oxygen gradients along the reactor which can affect photosynthetic performance. In this study, a fast-growing strain of Chlorella vulgaris R117 was cultured outdoors in a thin-layer cascade during a one-week trial reaching a biomass productivity of 4 g DW L⁻¹ d⁻¹ (27 g DW m⁻² d⁻¹). High photosynthetic activity led to oxygen oversaturation of up to 400% in some parts along the culture units at midday. The aim was to examine the effect of high dissolved oxygen concentration on diurnal changes in the photosynthetic performance and growth of the Chlorella culture using multi-technique approach. Photosynthetic activity of Chlorella R117 culture was estimated in situ and ex situ using oxygen production and in vivo Chl a fluorescence measurements, which showed good correlation. The rates of electron transport and of oxygen production were related, but the values of the μmol_electrons/μmolO₂ ratio was higher than predicted, suggesting the probable involvement of electron and oxygen consuming processes such as photorespiration and Mehler reaction. These processes probably function as photoprotective mechanisms, since no photodamage was observed in the Chlorella R-117 cultures. Depression (down-regulation) of photosynthetic activity due to the exposition to high dissolved oxygen concentration along the cascade area over time was observed. The usefulness of on-line measurements was demonstrated to obtain immediate and in-situ information on the physiological status of the culture. This data can be used in models of operation control for large-scale microalgae production units.

溶解氧浓度是大规模培养系统中微藻的关键点。高产培养物不可避免地会在反应器上产生氧气梯度的积累，这会影响光合作用。在这项研究中，快速培养的小球藻R117菌株在一个星期的试验中以薄层级联在室外培养，达到了4 g DW L ^-1 d ^-1（27 g DW m ^-2 d ^-1）。高的光合作用活性导致中午沿培养单元某些部位的氧过饱和度高达400％。目的是研究高溶解氧浓度对光合作用和生长的昼夜变化的影响。使用多种技术培养小球藻。的光合活性小球藻R117培养估计原位和易地使用的氧气生产和体内叶绿素一个荧光测量，其表现出良好的相关性。电子传递和氧生产速率有关的，但微摩尔的值_的电子/μmolO ₂比为高于预测，表明电子和耗氧工艺如光呼吸和梅勒反应的可能参与。这些过程可能起到光保护作用，因为在小球藻中未观察到光损伤。R-117文化。观察到随着时间的流逝，由于沿级联区域暴露于高溶解氧浓度，导致光合活性降低（下调）。证明了在线测量的有用性，以获得关于培养物的生理状态的即时和原位信息。该数据可用于大型微藻生产装置的运行控制模型。