SGER: Estimating Effects of Ultraviolet Irradiance on Periphyton Primary Production in Streams

在许多浅水系统中，底栖藻类及其伴生异养生物是最重要的固定碳来源。藻类组合的上层暴露在高水平的辐照下，因此可能容易受到紫外线辐射增加的抑制。关于入射紫外线辐射预期增加对周围植物光合速率影响的数据极为有限；如果这种影响很严重，可能会损害生态系统的功能。研究人员将构建设备，利用O2微电极估算完整周围植物群落的原位光合速率，探索高紫外线照射和光抑制之间的关系，并开发光微探针来评估紫外线照射和光衰减。紫外线将辅以被动式太阳能紫外线集中器。聚光器将使用抛物面镜来聚光，用滤光片除去光谱中除紫外线外的所有区域，并通过光纤将光引导到周围植物组合。该提案将允许建造和测试太阳能紫外线聚光器。该系统将在康扎草原研究自然区的溪流中进行为期数周的浮游生物实验。拟议的研究是独特的，因为长期（数周）的紫外线补充实验的自然组合没有发生。所开发的技术将能够评估全球紫外线辐照度增加的长期影响。

9411380 Dodds Periphyton (benthic algae and associated heterotrophs) is the most important source of fixed carbon in many shallow aquatic systems. The upper layer of the algal assemblage is exposed to high levels of irradiance, and thus may be susceptible to inhibition from increased UV radiation. Data on the effect of expected increases in incident UV radiation on photosynthetic rates of periphyton are extremely limited; if such effects are severe, they could impair ecosystem function. Equipment will be constructed to explore the relationships between high UV irradiance and photoinhibition in intact periphyton assemblages using O2 microelectrodes to estimate in situ photosynthetic rates, and light microprobes will be developed to assess UV exposure and light attenuation. UV will be supplemented with a passive solar UV concentrator. The concentrator will use parabolic mirrors to concentrate sunlight, and remove all but the ultra-violet regions of the spectrum with filters, and guide the light to periphyton assemblages with fiber optics. This proposal will allow construction and testing of the solar UV concentrator. The system will be tested with experiments of several weeks duration on periphyton inhabiting the streams of Konza Prairie Research Natural Area. The proposed research is unique because long term (weeks) UV supplementation experiments of natural assemblages have not occurred. The techniques developed will allow assessment of long term effects of global increases of UV irradiance.