Changing environmental conditions in Signy Island and McMurdo Dry Valleys and its impact on diatoms in lake microbial mats

南极洲已进入一个气候和环境迅速变化的时期，这在很大程度上影响了沼泽生态系统的功能和生产力。大多数沼泽生态系统最突出的特征之一是广泛的微生物席，它们主导着整个南极洲的初级生产。微生物席是水平和垂直分层的微生物群落，由环境内的物理化学梯度构成。在极地地区，与气候相关的变量，如浊度、盐度、营养物质浓度和温度，是构成底栖微生物群落的最关键变量。南极湖泊的光合垫主要由丝状蓝藻组成，它们形成基质，容纳对恶劣条件耐受性较低的生物，如硅藻。这些微生物垫中的硅藻对环境变量的变化特别敏感，因此可以作为南极洲各地正在发生的快速环境变化的有用指标。在本项目中，我们将利用遗传数据、硅藻分类和形态学来更好地了解气候和营养物富集对Signy岛淡水系统的影响。项目将分为两部分，分别使用(1)2016年和1990年的现代微生物垫样品(2)沉积湖岩心样品，了解环境变量变化对硅藻群落的短期影响和长期影响。结合古沉积DNA （aDNA）和形态-物种鉴定，确定Signy岛和干谷湖泊中硅藻组成的时间和空间，然后可以将其与温度变化和降水等环境变量相关。该项目还将通过研究现代和核心样品中硅藻物种的形态变化，探索驱动硅藻表型可塑性的环境因素。研究硅藻的形态可以揭示南极洲正在发生的快速环境变化的其他复杂细节。利用现在和古代DNA的形态和遗传数据将使我们能够评估随着未来气候变化而增加的温度和融水将如何影响南极淡水生态系统中的硅藻多样性和功能，并有助于环境监测。

Antarctica has entered a period of rapid climate and environmental change which is largely impacting the functioning and productivity of the limnetic ecosystem. One of the most prominent features of most limnetic ecosystems are the extensive microbial mats that dominate primary production across Antarctica. Microbial mats are horizontally and vertically stratified microbial communities that are structured by a physiochemical gradient within the environments. In polar regions climate-related variables such as turbidity, salinity, and nutrient concentration and temperature are the most critical variables structuring the benthic microbial community. The photosynthetic mats in Antarctic lakes are dominated by filamentous cyanobacteria which form a matrix which harbours organisms with a lower tolerance for harsh conditions such diatoms. The diatoms within these microbial mats are particularly responsive to a change in environmental variables and therefore, can be useful indicators of the rapid environmental change that is occurring across Antarctica. In this project, we will use genetic data, diatom taxonomy and morphology to better understand impacts of climate and nutrient enrichment in freshwater systems of Signy Island The project would be in two parts to understand both short-term impacts and long-term impacts of the changing environmental variables on diatom communities using (1) modern microbial mat samples from 2016 and 1990 (2) sedimentary lake core samples.. A combination of ancient sedimentary DNA (aDNA) and morpho- species identification to identify diatom composition in lakes of Signy Island and Dry Valleys across both time and space, which can then be related to environmental variables such as temperature change and precipitation. The project will also explore environmental factors driving phenotypic plasticity in diatoms by studying morphological changes in diatom species in both modern and core samples. Studying the morphology of diatoms can reveal other intricate details of the rapid environmental change that is occurring across Antarctica. Using a both morphology and genetic data on present and ancient DNA would allow us to assess how increasing temperatures and meltwater with future climate change will affect diatom diversity and functioning in Antarctic freshwater ecosystems and contribute to environmental monitoring.