Impacts of Increased Solar UVB on Antarctic Marine Heterotrophs

* Malloy 9614892最近平流层臭氧的减少导致到达地球表面的中紫外线（UVB）通量急剧增加，特别是在南极洲上空，在温带地区也有较小程度的增加。 预计臭氧消耗将持续到下一个世纪，并随着时间的推移在低纬度地区恶化。 最近的证据表明，目前的UVB强度足以对南大洋的浮游植物群落产生重大影响，并对热带海洋群落和温带两栖动物种群产生不利影响。 南极海洋生态系统的营养结构缩短，使初级消费者和次级消费者，特别是许多种类的浮游动物更加重要，因为它们是初级生产与成鱼、海洋哺乳动物和鸟类等顶级捕食者之间的关键联系。 虽然这些浮游动物物种和其他异养生物，包括仔鱼和成鱼，磷虾和桡足类，是南极生态系统营养结构的重要组成部分，但没有关于UVB增加对这些生物自然种群的影响的信息。 然而，对非极地物种的实验室和实地研究表明，紫外线增加对南极异养生物的影响，从而对南极生态系统的影响可能是巨大的。 拟议的研究将使用已建立的方法：1）在野外和实验室中测量南极浮游动物对UVB损伤的脆弱性; 2）在环境温度（-2至+40 ℃）下测量南极异养生物的DNA修复率;以及3）确定UVB暴露与生物体适应性下降之间的关系（以RNA：DNA比率和转录率测量）。 这项研究的实地部分是一项独特的努力，旨在确定南极异养生物自然种群在正常和臭氧消耗条件下的原地脆弱性。 实验室实验将确定臭氧消耗期间数量最多的浮游动物类群的剂量：反应（UVB通量：DNA光产物）关系，以确定特定物种对UVB增加的脆弱性。 然而，在自然种群中测量的DNA损伤代表了UVB增加的净损伤和DNA修复去除的净损伤。 因此，DNA修复率的几个丰富的浮游异养生物将进行测量，以促进更全面地了解每个类群的潜在脆弱性。 将对已经克隆的南极鱼类光裂合酶基因进行测序，并将推导出的氨基酸序列与其他光裂合酶序列进行比较，以更好地了解低温下DNA修复的基本机制。 最后，UVB照射的亚致死影响，以及相关的DNA损伤，将通过测量长期（RNA：DNA比例）和短期（核运行分析）的生化条件的措施进行评估。 总之，这些研究是至关重要的发展预测模型的相对影响，增加紫外线对南极海洋异养生物和相关的臭氧消耗减少健身，生存和人口动态的这些物种。 ***

*** Malloy 9614892 Recent decreases in stratospheric ozone have resulted in dramatic increases in the flux of mid-ultraviolet light (UVB) reaching the earth's surface, especially over Antarctica and, to a lesser extent, in temperate zones. Ozone depletion is expected to continue well into the next century, and to worsen at lower latitudes over time. Recent evidence suggests that present intensities of UVB are sufficient to produce significant impacts on phytoplankton communities in the Southern Ocean, as well as to negatively impact tropical marine communities and populations of temperate amphibians. The abbreviated trophic structure of the Antarctic marine ecosystem places an increased importance on primary and secondary consumers, especially on many species of zooplankton which form a critical link between primary production and top predators such as adult fish, marine mammals and birds. Although these zooplankton species and other heterotrophs, which include larval and adult fish, krill, and copepods, are important components of the trophic structure in the Antarctic ecosystem, there is no information regarding the effects of increased UVB on natural populations of these organisms. However, laboratory and field studies on non-polar species suggest that the impact of increased UV on Antarctic heterotrophs, and therefore on the Antarctic ecosystem, could be substantial. The proposed research will use established methods: 1) to measure the vulnerability of Antarctic zooplankton to UVB damage in the field and in the laboratory; 2) to measure DNA repair rates of Antarctic heterotrophs at ambient temperatures (-2 to +40C); and 3) to determine the relationship between UVB exposure and decreases in organismal fitness (measured as RNA:DNA ratios and transcription rates). The field component of this research is a unique effort to determine the in situ vulnerability of natural populations of Antarctic heterotrophs during normal and depleted ozone conditions. Laboratory experiments will deter mine dose:response (UVB fluence:DNA photoproducts) relationships for the zooplankton taxa which are most abundant during ozone depletion in order to determine species-specific vulnerabilities to increased UVB. However, DNA damage measured in natural populations represents both the net damage added by UVB and that removed by DNA repair. Therefore, DNA repair rates of several abundant pelagic heterotrophs will be measured to facilitate a more complete understanding of the potential vulnerability of each taxa. Photolyase genes from Antarctic fishes that have already been cloned will be sequenced and the deduced amino acid sequences will be compared to other photolyase sequences to better understand the underlying mechanisms of DNA repair at low temperatures. Finally, the sub-lethal impacts of UVB exposure, and the associated DNA damage, on fitness will be evaluated by measuring long-term (RNA:DNA ratios) and short-term (nuclear run-on assays) measures of biochemical condition. Together, these studies are critical for developing predictive models of the relative impact of increased UVB on Antarctic marine heterotrophs and for relating ozone depletion on decreased fitness, survival, and population dynamics of these species. ***