Ecological Impact of Enhance Solar Ultraviolet Radiation on Phytoplankton at High Latitudes in the Arctic

9907692Holm-Hansen最近的数据显示，春季期间(3月至5月)北半球平流层中的臭氧浓度每年都在下降，延续了过去十年中记录的下降趋势。大气臭氧消耗的幅度在北极高纬度地区最大，在低纬度地区逐渐减少。臭氧保护层的耗尽导致UV-B辐射(280-320 nm)的增加，入射到地球上的这些较短的UV波长的影响随着臭氧的逐渐丧失而呈指数级增加。由于UV-B光谱区的光子能量很高，而且它们的波长与许多重要细胞成分(如DNA)的吸收光谱重叠，因此臭氧消耗导致的UV-B辐射增强对暴露在太阳辐射下的任何生物都构成了重大威胁。在这项提案中，我们关注太阳UVR对北极海洋浮游植物的影响，这是海洋生态系统中整个食物网的基础。该项目将设在挪威特罗姆索大学的海洋生物站，该站位于北纬70度左右，因此代表着高纬度的北极环境，但也将包括在罗福滕群岛和靠近巴伦支海北部冰缘的船上研究。所有实验工作要么使用自然浮游植物组合，要么使用北极食物网中生态相关物种的单藻浮游植物培养。现场培养和配有适当滤光片的温控培养箱将用于确定增强的UV-B辐射(当柱臭氧层值较低时)、“正常”UV-B辐射和UV-A辐射(320-400 nm)对细胞内遗传物质(DNA)的结构破坏、初级生产的损失以及浮游植物组合物种组成可能发生的变化的影响。辅助数据将包括紫外线诱导的细胞损伤的大小与细胞所经历的紫外线影响和总剂量之间的关系。具体的实验还将确定紫外线诱导的细胞损伤是否及时可逆，以及细胞可以在多大程度上通过合成紫外线屏蔽化合物来缓解太阳紫外线辐射的不利影响。这些研究将得到相关环境因素的同时测量，包括入射光谱UVR和随水柱深度的可见光太阳辐射，以及上层水柱的稳定性。研究将与特罗姆索大学的人员合作进行，他们也从事挪威北部入射太阳UVR的长期监测。来自美国和挪威的学生将积极参与实地考察和数据分析。这一合作项目的结果将为我们更好地了解增强的太阳紫外线辐射对自然浮游植物组合的区系组成以及初级生产力的可能影响提供良好的数据基础。这些数据将是未来建模工作的重要投入，以估计北极上空大气臭氧逐渐枯竭对较高营养水平可获得的食物资源的影响。由于重要的渔业资源位于整个北极地区，这种知识在经济和社会关切方面也具有重要意义。

9907692Holm-HansenRecent data shows that ozone concentrations in the stratosphere over the Northern Hemisphere during the spring period (March-May) are decreasing each succeeding year, continuing the decline that has been documented during the past decade. The magnitude of the depletion in atmospheric ozone is maximal at the higher latitudes in the Arctic, with progressively less depletion at lower latitudes. Depletion of this protective layer of ozone results in enhancing UV-B radiation (280-320 nm), with the influence of these shorter UV wavelengths incident upon the earth increasing exponentially with progressive loss of ozone. As the photons in the UV-B spectral region are highly energetic and their wavelengths overlap the absorption spectrum of many important cellular components (e.g., DNA), this enhanced UV-B radiation resulting from ozone depletion represents a significant threat to any living organism which is exposed to solar radiation. In this proposal we are concerned with the impact of solar UVR on Arctic marine phytoplankton, which constitute the base of the entire food web in the marine ecosystem.The project will be based at the Marine Biological Station of the University of Tromso, Norway, which is located at approximately 70 N and hence represents a high-latitude Arctic environment, but will also include ship-board studies in the Lofoten Islands and close to the ice edge in the northern Barents Sea. All experimental work will use either natural phytoplankton assemblages or unialgal phytoplankton cultures of ecologically relevant species in the Arctic food web. Both in situ incubations and temperature-controlled incubators with appropriate optical filters will be used to determine the impact of enhanced UV-B radiation (when column ozone values are low), 'normal' UV-B radiation, and UV-A radiation (320-400 nm) on structural damage to the genetic material in cells (DNA), on the loss of primary production, and on possible changes in species composition of the phytoplankton assemblages. Ancillary data will include the relationship between the magnitude of UV-induced cellular damage and the influence and total dose of UVR experienced by cells. Specific experiments will also determine whether or not the UV-induced cellular damage is reversible in time, and also the extent to which cells can mitigate the adverse effects of solar UVR by synthesis of UV-screening compounds. These studies will be supported by simultaneous measurements of relevant environmental factors, including incident spectral UVR and visible solar radiation with depth in the water column, and stability of the upper water column.The studies will be done in cooperation with personnel from the University of Tromso, who are also engaged in long-term monitoring of incident solar UVR in northern Norway. Students from both the USA and Norway will be active participants in the field work and in analysis of the data. The results from this cooperative project should provide a good data base to better our understanding of the possible impact of enhanced solar UVR on the floristic composition of the natural phytoplankton assemblages as well as on the rate of primary production. Such data will be important inputs to future modeling efforts to estimate the impact of progressive depletion of atmospheric ozone over the Arctic on the food resources available to higher trophic levels. As important fishery resources are located throughout the Arctic regions, such knowledge is also of importance in regard to economic and societal concerns.