Interactive effects of solar UV-B-radiation and nutrient supply on the formation and detoxification of oxidative stress and its consequences to growth of green marine macroalgae

海岸带生态系统的富营养化是全球范围内日益严重的问题。因此，促进了机会主义绿巨藻的快速生长，在适当的环境条件下可导致大型藻华。相反，由于人为的平流层臭氧耗竭，水圈中不成比例的高太阳紫外线B （UV-B）辐射在局部和季节性增加，严重损害了大藻的生长。本研究的目的是表征两种拮抗环境因子在空间和时间分辨率上的相互作用，并阐明其潜在的生理机制。一种形成花的绿色大藻属Ulva拟作为一种模式生物。氮同化对活性氧（ROS）形成和解毒的影响是本研究的中心主题。由此产生的对大型藻类生长的影响可以为其在野外不利条件下的生存提供解释。生理实验室研究了氮同化和梅勒反应之间的电子竞争，这源于光合作用中的电子传递。为了避免uv - b诱导的氧化应激，氮同化的潜力是这些研究的主要主题。为了了解自然条件下的这些过程，进行了与季节波动的氮有效性相关的uv - b实验。此外，在野外条件下，深入研究了不同无机氮历史对夏季高uv - b辐射引起的大藻氧化应激的影响。

The eutrophication of coastal ecosystems resulting from anthropogenic land-use is an increasingly growing problem worldwide. Thus, the rapid growth of opportunistic green macroalgae is promoted, which can lead under appropriate environmental conditions to large macroalgal blooms. In contrast, disproportionately high solar ultraviolet B (UV-B) radiation in the hydrosphere, which increases locally and seasonally as a consequence of anthropogenic stratospheric ozone depletion, impairs macroalgal growth significantly. The aim of this research is to characterize the interactive effects between the two antagonistic environmental factors in spatial and temporal resolution and to elucidate the underlying physiological mechanisms. A bloom-forming green macroalga of the genus Ulva is intended to serve as a model organism. The impact of nitrogen assimilation on the formation and detoxification of reactive oxygen species (ROS) is the central subject of the investigation. The resulting implications for the growth of the macroalga can provide explanations for its survival under adverse conditions in the field. The competition between nitrogen assimilation and the Mehler reaction for electrons, which originate from the photosynthetic electron transport, is investigated in physiological laboratory studies. The potential of nitrogen assimilation in order to avoid UV-B-induced oxidative stress is the main subject of these studies. To understand these processes under natural conditions, UV-B-experiments are conducted in relation to the seasonally fluctuating nitrogen availability. Furthermore, the impact of different inorganic nitrogen histories on macroalgal oxidative stress caused by high summer UV-B-radiation is thoroughly investigated under field conditions in Ulva sp.