Testing UV-B radiation as a proposed driver behind the end-Permian biotic crisis

测试 UV-B 辐射作为二叠纪末生物危机背后的驱动因素

• 批准号: 1457846
• 负责人: Cynthia Looy
• 金额: $ 19.35万
• 依托单位: University of California-Berkeley
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2015
• 资助国家: 美国
• 起止时间: 2015-04-15 至 2020-10-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1457846&HistoricalAwards=false
• 关键词: Testing; UV; radiation; proposed; driver

The ozone layer plays a vital role in intercepting harmful solar ultraviolet-B radiation (UV-B) from reaching Earth's surface. However, its effectiveness in doing so has fluctuated in the past and little is known of the impacts of a thinning ozone layer on vegetation. Anticipating potential consequences in the future depends on understanding time intervals with heightened UV stress in the past. The largest mass extinction in history at the end of the Permian Period (~252 million years ago) may have been one of these time intervals. Plant fossil records from this crisis show two odd features worldwide. Many pollen grains produced by vanishing woodland seed plants were malformed, and proliferating herbaceous plants (lycopsids) spread their spores frequently as unseparated clusters of four. Heightened UV exposure is hypothesized to have caused these abnormalities. Compounds produced by the largest volcanic province in history, the Siberian Traps, likely caused prolonged or frequent deterioration of the ozone shield. In this study researchers will test if high UV-B radiation levels could indeed explain the abnormalities and extinction patterns in plants observed during the end-Permian biotic crisis. This research is important to society because it will assess whether future activities weakening the ozone layer could destabilize forest ecosystems through reproductive failure of economically important groups of plants. Outreach from this work will raise public awareness of environmental changes in the past through developing a publicly accessible educational exhibit and web-module on ecosystems and extinctions of the Paleozoic Era.Using growth chamber and germination experiments, the researchers will determine whether elevated UV-B exposure triggers similar malformations in pollen and spores as observed in the fossil record, and whether this may lead to contrasting reproductive success between the tested living relatives of plant groups impacted by the crisis. They hypothesize high levels of UV-B will have a negative effect on conifer reproduction, but not severely affect fertility in lycopsids. In addition, they will also investigate whether UV-induced developmental responses appeared during times of active volcanism at its very source. For this, they will analyze end-Permian fossil pollen and spore assemblages from sediments within the Siberian Traps. Using observations in combination with a contemporary ecological experimental approach is a novel approach which will test an important hypothesis in paleoecology and may lend insight into species response under contemporary abiotic stressors.

臭氧层在拦截到达地球表面的有害太阳紫外线 B 辐射 (UV-B) 方面发挥着至关重要的作用。然而，其有效性在过去一直波动，而且人们对臭氧层变薄对植被的影响知之甚少。预测未来的潜在后果取决于了解过去紫外线胁迫加剧的时间间隔。二叠纪末期（约 2.52 亿年前）历史上最大规模的灭绝可能就是这些时间间隔之一。这场危机的植物化石记录显示出全球范围内的两个奇怪特征。消失的林地种子植物产生的许多花粉粒都是畸形的，而增殖的草本植物（石松类）经常以不分离的四个孢子簇的形式传播它们的孢子。据推测，增加的紫外线照射是导致这些异常的原因。历史上最大的火山省西伯利亚地盾产生的化合物可能导致臭氧层长期或频繁恶化。在这项研究中，研究人员将测试高 UV-B 辐射水平是否确实可以解释二叠纪末生物危机期间观察到的植物异常和灭绝模式。这项研究对社会很重要，因为它将评估未来削弱臭氧层的活动是否会通过重要经济植物群的繁殖失败而破坏森林生态系统的稳定。这项工作的推广将通过开发一个关于古生代生态系统和灭绝的公众教育展览和网络模块，提高公众对过去环境变化的认识。利用生长室和发芽实验，研究人员将确定增加的 UV-B 暴露是否会引发与化石记录中观察到的类似的花粉和孢子畸形，以及这是否可能导致测试的生物之间的繁殖成功率不同 受危机影响的植物群的亲属。他们假设高水平的 UV-B 会对针叶树的繁殖产生负面影响，但不会严重影响石松类的生育能力。此外，他们还将调查紫外线诱发的发育反应是否出现在火山活动的源头期间。为此，他们将分析西伯利亚陷阱内沉积物中的二叠纪末化石花粉和孢子组合。 将观察与当代生态实验方法相结合是一种新颖的方法，它将检验古生态学中的一个重要假设，并可能有助于深入了解当代非生物应激源下的物种反应。