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

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 across two Antarctic climate extremes: Signy Island (maritime) and McMurdo Dry Valleys (continental). 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. Frozen microbial mat biomass from lakes and streams across Signy Island and Dry Valleys are
readily available for investigation, as well as frozen core material from 3 sites in Signy Island and one site in the Dry Valleys. 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.