The nitrogen cycle in Arctic and Antarctic macroalgae

在经济世界中，海洋和陆地生态系统中的氮循环正在长期改变（Ohkouchi等人，2015）：这些变化可以使用稳定的氮同位素比率（Delta 15N）来监测。然而，我们对高纬度极地环境中的氮循环知之甚少。在南极洲的原始环境中记录了现代世界单一生态系统中δ 15N的最大变化（Wada et al., 1981）。研究小组现在开始调查南极洲沙漠土壤中的硝酸盐浓度和三角洲15n （Diaz et al., 2020）。极地沉积岩心的氮同位素变化表明冰期和间冰期之间的重大转变（Ai等，2020），这可能代表南极洲周围沙漠土壤的湿润和干燥。雪冰中存在丰富的微生物群落（“绿冰”；Gray et al., 2020），它们对氮循环的影响目前尚不清楚。很明显，我们对南极氮循环的认识存在空白。未来的气候预测表明，北极和南极的冰将会消失，这可能会对该地区的氮循环产生灾难性的影响。与南极相比，我们对北极地区氮循环的理解更为彻底（例如，Pajares & Ramos, 2019）。南极洲对气候变化高度敏感，因此需要更深入地了解南极洲的氮循环，以预测冰川冰盖的消失对周围生态系统的环境影响。本博士将重点研究冰与深海沉积系统之间的微妙环境，沿海生态系统，特别是大型藻类。该博士学位将包括三个研究工作包（WP1-3）：工作包1 (WP1)：收集和存档来自南极半岛和斯瓦尔巴群岛（北极圈）的大型藻类在英国各地的各个博物馆（利物浦世界博物馆；威尔士国家博物馆；爱丁堡皇家植物园；伦敦自然历史博物馆）。他们现有的大型藻类标本室没有或只有很少的标本来自南极洲。从这些气候敏感的环境中收集样本将对未来的研究和教育有价值。收集到的标本将被存档并存入一个网络数据库，世界各地的科学家可以从中索取样本进行科学研究。工作包2 (WP2)：从WP1中使用的地点对沿海环境周围不同大型藻类物种进行氮同位素研究。在南极洲，Himantothallus肯定会被收集：它的叶片长达20米，可以提供Delta 15N的季节/历史记录。在北极，各种各样的海带将被收集。此外，将收集土壤、沉积物、冰/水和鸟粪样本，以确定当地氮循环的来源和汇的特征。工作包3 (WP3): SeDeltalect大型藻类样品将返回杜伦大学进行实验工作。将进行模拟未来气候状态的实验，如温度、光照和/或营养物质（如硝酸盐对氨）的增加。将在几个月的时间里对大型藻类进行监测和测量，以确定它们的反应。

The nitrogen cycle is chronically being altered in marine and terrestrial ecosystems in the economic world (Ohkouchi et al., 2015): these changes can be monitored using stable nitrogen isotope ratios (Delta 15N). However, our knowledge of the nitrogen cycle in high-latitude polar environments is poor. The greatest variation of Delta 15N in the modern world from a single ecosystem has been recorded in the pristine environment of Antarctica (Wada et al., 1981). Research groups are now starting to investigate nitrate concentration and Delta15N in the desert soils of Antarctica (Diaz et al., 2020). Nitrogen isotopic changes in polar sedimentary cores suggest major shifts between glacial and interglacial periods (Ai et al., 2020), which may represent wetting and drying of desert soils around Antarctica. Abundant microbiological communities exist in snow ice ("green ice"; Gray et al., 2020) and their impact on the nitrogen cycle is currently not known. There is clearly a gap in our knowledge of the nitrogen cycle in Antarctic. Future climate predictions indicate a loss of Arctic and Antarctic ice, which could have a catastrophic impact on the nitrogen cycle in the region. Our understanding of nitrogen cycle in the Arctic region is more thoroughly understood (e.g., Pajares & Ramos, 2019) in comparison to the Antarctic. The Antarctica is highly sensitive to climate change, and thus a more thorough understanding of the nitrogen cycle in Antarctica is required to predict the environmental impact that glacial ice sheet loss will have on the surrounding ecosystems. This PhD will focus on the delicate environment between the ice and deep marine sedimentary system, the coastal ecosystem, specifically macroalgae.This PhD will consist of three research work-packages (WP1-3):Work Package 1 (WP1): To collect and archive macroalgae from the Antarctic Peninsula and Svalbard (Arctic Circle) in various museums around the UK (World Museum, Liverpool; National Museum of Wales; Royal Botanic Garden of Edinburgh; Natural History Museum in London). Their existing macroalgae herbaria have none or very few specimens from Antarctica. Collecting samples from these climate-sensitive environments will be valuable for future research and education. The specimens collected will be archived and made into a web database from which scientists around the world can request samples for scientific research.Work Package 2 (WP2): To conduct a nitrogen isotope study of different macroalgae species around the coastal environment from the locations used in WP1. In Antarctica, Himantothallus will definitely be collected: it has blades up to 20m in length and could provide seasonal/historical records of Delta 15N. In the Arctic, various kelp species will be collected. In addition, soil, sediment, ice/water and guano samples will be collected to characterise sources and sinks in the local nitrogen cycle.Work Package 3 (WP3): SeDeltalect macroalgae samples will be returned to Durham University for experimental work. Experiments will be conducted to mimic future climate states, such as increasing temperature, light and/or nutrients (e.g., nitrate vs ammonia). The macroalgae will be monitored and measured over several months to determine their response.