Resilience of microbial mats in Antarctic ponds to climate-relevant environmental disturbance

• Main Author: Mills, Francesca
• Other Authors: Hawes, Ian
• Format: Thesis
• Language: English
• Published: The University of Waikato 2021
• Subjects: Antarctica; Microbial mats; Cyanobacteria; McMurdo Ice Shelf; Bratina Island; Meltwater ponds; Nitrogen fixation; Disturbance; Photosynthesis; Resilience; Microbial ecology; Microbial mats > Climatic factors > Antarctica > McMurdo Ice Shelf; Hydrology > Environmental aspects > Antarctica > McMurdo Ice Shelf; Microbial mats > Antarctica > McMurdo Ice Shelf > Composition; Microbial ecology > Environmental aspects > Antarctica > McMurdo Ice Shelf; Melt ponds > Environmental aspects > Antarctica > McMurdo Ice Shelf; Cyanobacteria > Environmental aspects > Antarctica > McMurdo Ice Shelf; Photosynthetic bacteria > Climatic factors > Antarctica > McMurdo Ice Shelf; Nitrogen > Fixation > Environmental aspects > Antarctica > McMurdo Ice Shelf; McMurdo Ice Shelf (Antarctica) > Environmental aspects; Antarctic; Antarc*; Ice Shelf
• Online Access: https://hdl.handle.net/10289/14427

Continental Antarctica is a cold desert, where the hydrologic system is dependent on melting of snow and ice. In a warming climate it is projected that there will be a significant change in precipitation, evaporation, cloud formation, all affecting the ice-water dynamic. Hydrology is considered vulnerable to climatic change. Hydrological change cascades through the environment affecting Antarctic ponds which are important centres for inland microbial biodiversity. An understanding of community vulnerability to anticipated change can be developed through assessing organism and functional resilience to climate-related and other forms of disturbance. The aim of this study is to identify the effects of disturbance on microbial communities, specifically cyanobacterial mats, with a particular focus on changes that may occur resultant to anthropogenic climate change. This study undertook three experiments, which identified impacts of disturbance on three key cyanobacterial mat functions – nitrogen fixation, photosynthesis/respiration, and recovery after a physical disturbance. Sampling was undertaken in the McMurdo Ice Shelf (MIS) meltwater ponds in late January 2019. The design for the nitrogen fixation experiment used a natural gradient of conductivity across five ponds (Fresh, Casten, P70, Brack and Salt) in a space-for-time approach that compared microbial composition and nitrogen fixation rates. The light disturbance study completed in New and P70 ponds tested mat ability to retain photosynthesis and respiration under a pulsed disturbance – covering microbial mats with shade cloth for 12 months. In this study the light-photosynthesis response and mat composition were analysed when shaded and not shaded (control plots). The third experiment examined short-term response to physical disturbance by observing the recovery of mat structure and community composition for 2 years was also completed in New and P70 ponds. It was identified that there was no significant change in acetylene reduction (as a proxy for nitrogen ...