After the industrial revolution, increasing anthropogenic CO₂ emission causes a number of changes in seawater. These changes are known as ocean acidification and affect the seaweeds in various ways. Therefore, this study is aimed to determine the ecological succession of Ulva flexuosa Wulfen 1803 in future predicted CO₂-induced low pH conditions alone and in combination with naturally relevant ultraviolet radiation (UVR). For this purpose, acidification experiments with and without UVR were conducted on U. flexuosa from the Mediterranean coast, and important physiological features of algae was investigated. In this study, the Fv/Fm ratios of U. flexuosa ranged from 0.718±0.01 to 0.754±0.009. While rETRmax values of samples exposed to elevated-CO₂ were measured between 112.13 – 151.93 µmol e^-m^-2s^-1, it was determined between 111.7 – 158.4 µmol e^-m^-2s^-1 in samples exposed to ambient sea water. According to our results, increased CO₂ concentration in seawater did not improve the photosynthetic efficiency of U. flexuosa. However, when the specimens were exposed to elevated-CO₂, nitrate reductase activity of U. flexuosa was declined drastically. According to the results, it is suggested that the elevated CO₂ may regulate the nitrogen preference of U. flexuosa. Besides, the data also show that U. flexuosa was not sensitive to UVR.

中文翻译：

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高CO2和UVR对石莼1803光合性能和硝酸还原酶活性的影响

工业革命后，人为CO ₂排放量的增加导致海水发生许多变化。这些变化被称为海洋酸化，并以各种方式影响海藻。因此，本研究旨在确定Ulva flexuosa Wulfen 1803 在未来预测的 CO ₂诱导的低 pH 条件下单独和结合自然相关的紫外线辐射 (UVR)的生态演替。为此，对来自地中海沿岸的弯弯曲藻进行了使用和不使用 UVR 的酸化实验，并研究了藻类的重要生理特征。在本研究中，U. flexuosa的 Fv/Fm 比值范围从 0.718±0.01 到 0.754±0.009。虽然暴露于高浓度 CO ₂的样品的 rETRmax 值在 112.13 – 151.93 µmol e ^- m ^-2 s ^-1之间测得，但在暴露于环境海水的样品中测得的rETRmax 值在 111.7 – 158.4 µmol e ^- m ^-2 s ^{-1 之间}. 根据我们的研究结果，海水中CO ₂浓度的增加并没有提高弯弯曲曲的光合效率。然而，当样品暴露于升高的CO _{2 时}，弯曲菌的硝酸还原酶活性急剧下降。根据结果​​，表明升高的 CO₂可以调节曲棍球对氮的偏好。此外，数据还表明，挠曲对UVR不敏感。