New Approaches to Measuring and Understanding the Effects of Ultraviolet Radiation on Photosynthesis by Antarctic Phytoplankton

与南极臭氧洞有关的紫外线-B辐射（UV-B，280-320）的增加已被证明会抑制浮游植物的光合作用，但对水柱生成的总体影响仍然是一个有争议和持续调查的问题。 调查还显示，即使在南极平流层臭氧“正常”水平，紫外线B和紫外线A（320-400纳米）似乎对水柱的产生有很大影响。 紫外线在浮游植物初级生产生态学中的作用在过去可能没有得到充分的重视，在垂直混合的情况下，紫外线对初级生产的估计可能特别重要。 本研究的重点是量化紫外线对南极浮游植物光合作用的影响，通过定义紫外线抑制的生物权重函数。 在过去，技术被开发来描述光合作用作为紫外线和可见光辐照度的函数，使用实验室培养。 对南极洲麦默多站自然组合的进一步实验表明，生物权重函数与光历史密切相关。 最近，在南大洋开阔沃茨进行的测量证实，浮游植物群落对紫外线的敏感性有很大的差异。 研究还发现，南极浮游植物光合作用的抑制在小时的时间尺度上逐渐恶化，没有恢复的证据。 即使在良好的条件下，光合能力的损失持续几个小时不变。 这与实验室培养物和一些自然组合形成对比，它们在暴露于紫外线期间迅速达到稳定的光合作用速率，反映了损害和恢复过程之间的平衡。 紫外线引起的损害的缓慢逆转对水柱光合作用，特别是在垂直混合有深远的影响。 迄今为止的结果已被用于模拟紫外线、臭氧消耗和垂直混合对南极沃茨光合作用的影响。 数据表明，正常水平的紫外线可对天然浮游植物产生重大影响，臭氧消耗和垂直混合可加剧这种影响。 然而，关键问题仍然没有得到很好的解决，这些问题是本提案的重点。 新的理论和实验方法将被用来调查在威德尔-斯科舍汇合处的开放沃茨和帕尔默站附近的沿海沃茨的紫外线响应。 特别是，将在从几分钟到几天的时间尺度上测量UV抑制和恢复的动力学。 将计算南大洋水层和沿海浮游植物之间生物加权函数的变异性。 结果将提供绝对估计光合作用下原位，以及根据改变，紫外线照射;扩大范围的组合生物加权函数已确定;并澄清如何抑制和恢复动力学应表示在混合层模型。

Neale 9615342 Increases in ultraviolet-B radiation (UV-B, 280-320) associated with the Antarctic ozone hole have been shown to inhibit the photosynthesis of phytoplankton, but the overall effect on water column production is still a matter of debate and continued investigation. Investigations have also revealed that even at "normal" levels of Antarctic stratospheric ozone, UV-B and UV-A (320-400 nm) appear to have strong effects on water column production. The role of UV in the ecology of phytoplankton primary production has probably been underappreciated in the past and could be particularly important to the estimation of primary production in the presence of vertical mixing. This research focuses on quantifying UV effects on photosynthesis of Antarctic phytoplankton by defining biological weighting functions for UV-inhibition. In the past, techniques were developed to describe photosynthesis as a function of UV and visible irradiance using laboratory cultures. Further experimentation with natural assemblages from McMurdo Station in Antarctica showed that biological weighting functions are strongly related to light history. Most recently, measurements in the open waters of the Southern Ocean confirmed that there is substantial variability in the susceptibility of phytoplankton assemblages to UV. It was also discovered that inhibition of photosynthesis in Antarctic phytoplankton got progressively worse on the time scale of hours, with no evidence of recovery. Even under benign conditions, losses of photosynthetic capability persisted unchanged for several hours. This was in contrast with laboratory cultures and some natural assemblages which quickly attained a steady- state rate of photosynthesis during exposure to UV, reflecting a balance between damage and recovery processes. Slow reversal of UV-induced damage has profound consequences for water-column photosynthesis, especially during vertical mixing. Results to date have been used to model th e influence of UV, ozone depletion and vertical mixing on photosynthesis in Antarctic waters. Data indicate that normal levels of UV can have a significant impact on natural phytoplankton and that the effects can be exacerbated by ozone depletion as well as vertical mixing. Critical questions remain poorly resolved, however, and these are the focus of the present proposal. New theoretical and experimental approaches will be used to investigate UV responses in both the open waters of the Weddell-Scotia confluence and coastal waters near Palmer Station. In particular, measurements will be made of the kinetics of UV inhibition and recovery on time scales ranging from minutes to days. Variability in biological weighting functions between will be calculated for pelagic and coastal phytoplankton in the Southern Ocean. The results will provide absolute estimates of photosynthesis under in situ, as well as under altered, UV irradiance; broaden the range of assemblages for which biological weighting functions have been determined; and clarify how kinetics of inhibition and recovery should be represented in mixed layer models.