Microbial abundance and diversity surrounding mummified seals in Miers Valley, Antarctica

• Main Author: Robson, Lisa Marie
• Other Authors: Farrell, Roberta L., Cary, S. Craig, Daniel, Roy M.
• Format: Thesis
• Language: English
• Published: The University of Waikato 2019
• Subjects: Dry Valleys; Antarctica; Miers Valley; Microbial diversity; Antarctic; Miers; New Zealand; The Antarctic; Antarc*
• Online Access: https://hdl.handle.net/10289/12860

The presence of a number of mummified seal carcasses have been reported in the Dry Valleys of Antarctica. The location of seal carcasses were observed up to 240km in-land, and approximately 1500m above sea level. The extremely cold and dry conditions in the Dry Valleys act to mummify the seal remams, preserving these anomalies for an undetermined length of time. Given the virtual absence of above ground plant biomass in the Dry Valleys, the primary source of soil organic matter sustaining microbial ecosystems was not obvious. It was hypothesised that these large sources of organic contamination, in the form of a seal carcass, may act to enrich the localised environment surrounding the carcasses with carbon and nitrogen. The increased levels of organic carbon and nitrogen would result in increased microbial abundance and diversity. A total of 100 environmental samples were taken by Professors S.C. Cary, and D.A. Cowan, surrounding, and directly beneath eleven mummified seals located in Miers Valley, the Antarctic Dry Valleys, on Event D023 Terrestrial Microbiology Antarctic New Zealand 2001/2002. Three of these seals (MVSl, MVS3 and MVS 13) and the areas surrounding, were sampled extensively, and were the basis of research in this Master of Science thesis. Microbial diversity was investigated using molecular cloning and sequence analysis, and Denaturing Gradient Gel Electrophoresis, of 16S and 18S rDNA amplicons. A large diversity in bacterial populations present in the environmental samples taken from directly beneath the Miers Valley seal carcasses was observed in comparison to control samples of Miers Valley soils. The levels of microbial abundance were determined by luciferase-dependent luminometric ATP analysis, and analysis of the total quantities of double stranded DNA extracted from the environmental samples. Microbial abundance was found to be increased in samples taken in closer proximity to a seal carcass. Carbon and nitrogen analysis were conducted on all samples, using a fully automated Europa Scientific 20/20 isotope analyser. The level of carbon present in an environmental sample appeared not to influence the abundance of microorganisms. The levels of nitrogen measured were higher in environmental samples collected in close proximity to the seal carcasses. These samples displayed the greatest microbial abundance, and indicated large differences in the bacterial diversity compared to Miers Valley control samples. On the basis of these results, and ATP data, the hypothesis of this MSc thesis was determined to be correct. Microbial abundance was found to increase with enrichment of nitrogen surrounding MVS 1 and MVS 13 seal carcasses, and large differences in bacterial diversity were found in environmental samples showing the highest levels of nitrogen enrichment, compared to samples taken further away from the seal, or in Miers Valley control samples. This thesis effectively described the utilisation of cloning and sequence analysis, and denaturing gradient gel electrophoresis to investigate microbial diversity in Antarctic environmental samples. This study gave a greater understanding in microbial ecology in Miers Valley, Antarctica.