UV induzierte toxische Effekte von gelösten Huminstoffen auf Süßwasserorganismen

在淡水中，溶解有机碳（DOC）的发色UV/VIS吸收化合物主要以腐殖物质（HS）为代表。通过吸收太阳辐射，HS起到防晒霜的作用，保护水生生物免受有害的紫外线辐射。这种光吸收的一个结果是HS的光解降解，导致低分子物质的释放，这些物质可能作为异养细菌的潜在营养物。同时，产生瞬时活性氧（ROS），其可被水或HS分子本身淬灭。一些研究指出，紫外线照射对腐殖水中的水生生物产生不利影响，这表明ROS引起的光毒性效应。我们想调查的光毒性潜力的HS在曝光实验与异养细菌，藻类和水蚤。潜在的光毒性将与光诱导的净ROS相关，其将通过使用自旋陷阱和激光光谱方法的电子顺磁共振（EPR）进行定量。此外，与水蚤的HS和光激发之间的直接相互作用应使用自旋标记的EPR断层扫描研究。该项目的目的是确定在何种条件下以及在何种营养水平上，HS的光毒性可能对生态系统的结构产生影响。EPR层析成像方法将首次适用于淡水生物。

In freshwater, the chromophoric UV/VIS-absorbing compounds of dissolved organic carbon (DOC) are mostly represented by humic substances (HS). By absorption of solar radiation, HS act like sun screens and protect aquatic organisms against harmful UV radiation. One consequence of this light absorption is the photolytical degradation of HS leading to the release of low molecular substances which may serve as potential nutrients for heterotrophic bacteria. At the same time, transient reactive oxygen species (ROS) are generated, which can be quenched by water or HS molecules itself. Some studies point to UV irradiation induced adverse effects on aquatic organisms in humic water, suggesting phototoxic effects caused by ROS. We want to investigate the phototoxic potential of HS in exposure experiments with heterotrophic bacteria, algae, and daphnids. The potential phototoxicity will be correlated with the photoinduced net-ROS, which will be quantified by electron paramagnetic resonance (EPR) using spin traps and laser spectroscopic methods. Furthermore, with daphnids the direct interaction between HS and light excitation shall be studied by EPR-tomography using spinlabels. The aim of this project is to figure out under which conditions and at which trophic level phototoxicity of HS may contribute to the structure of the ecosystem. EPR tomographic methods will be adapted to freshwater organisms for the first time.