Antarctic Theses

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Now showing 1 - 5 of 50
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    Capturing the value of biosurveillance “big data” through natural capital accounting
    (Journal Article, Informa UK Limited, 2021) Castle, David; Hebert, Paul D. N.; Clare, ,Elizabeth L.; Hogg, Ian D.; Tremblay, Crystal
    Global biodiversity is in crises. Recognition of the scale and pace of biodiversity loss is leading to rapid technological development in biodiversity science to identify species, their interactions, and ecosystem dynamics. National and international policy developments to stimulate mitigation and remediation actions are escalating to meet the biodiversity crises. They can take advantage of biosurveillance “big data” as evidence for more sweeping and impactful policy measures. The critical factor is translating biosurveillance data into the value-based frameworks underpinning new policy measures. An approach to this integration process, using natural capital accounting frameworks is developed.
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    Resilience of microbial mats in Antarctic ponds to climate-relevant environmental disturbance
    (Thesis, The University of Waikato, 2021) Mills, Francesca
    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 fixation) over the salinity range. Acetylene reduction ranged between 22.4 ± 3.4 µMol/m²/h in Brack Pond (conductivity = 10.5 mS/cm) and 49.6 ± 17.1 µMol/m²/h in Casten Pond (conductivity = 2.3 mS/cm). The acetylene reduction difference was statistically significant between Brack Pond and Casten Pond (F = 0.006 (Bonferroni Correction significance of F ≤ 0.01)). Microbial mat composition changed across the conductivity gradient, but significant proportions of different N-fixing and mat-forming genera were evident along the salt gradient, suggesting functional resilience through species turnover. It was also identified that when receiving a 95-96% decrease in ambient light photosynthetic bacteria were able to maintain photosynthesis and respiration at similar rates within the microbial mats. However, in shaded plots the maximum net oxygen production occurred at an average irradiance between 350 – 450 µMol photons m-²s-¹ and was inhibited at higher levels. In control plots the maximum net oxygen production was ≥900 µMol photons m-²s-¹. In control samples net photosynthesis exceeds zero (photosynthesis exceeds respiration) at ~275 µMol photons m-²s-¹, in shaded samples this occurred at ~100 µMol photons m-²s-¹. Rapid shifts in the appearance of mats under, and after shading led to the conclusion that the acclimation may be based on vertical migration of cyanobacteria within the mats, which showed no significant changes in relative abundance of taxa. After physical removal of microbial mat, communities were shown to reform to similar relative abundances as control samples within two years of the disturbance, within this experiment a successional change in species abundance was observed. This research highlights the resilience of microbial mat populations on the MIS to the types of change that are anticipated to accompany climate change. It supports conclusions previously identified that cyanobacterial mats are functionally resilient to short-term and long-term disturbances. Ongoing research will improve the knowledge on the resilience of other functions required in these environments.
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    An investigation of microbial communities across two extreme geothermal gradients on Mt. Erebus, Victoria Land, Antarctica
    (Thesis, The University of Waikato, 2021) Smith, Emily
    The geothermal fumaroles present on Mt. Erebus, Antarctica, are home to numerous unique and possibly endemic bacteria. The isolated nature of Mt. Erebus provides an opportunity to closely examine how geothermal physico-chemistry drives microbial community composition and structure. This study aimed at determining the effect of physico-chemical drivers on microbial community composition and structure along extreme thermal and geochemical gradients at two sites on Mt. Erebus: Tramway Ridge and Western Crater. Microbial community structure and physico-chemical soil characteristics were assessed via metabarcoding (16S rRNA) and geochemistry (temperature, pH, total carbon (TC), total nitrogen (TN) and ICP-MS elemental analysis along a thermal gradient 10 °C–64 °C), which also defined a geochemical gradient. Diversity increased in alkaline soils suggesting pH to be the primary driver of microbial community structure across the gradients. Archaea dominated the microbial communities at Tramway Ridge compared to Western Crater, which was dominated by Bacteria. Western Crater has been sampled for the first time, widening the understanding of geothermal sites on Mt. Erebus. Organisms that were once considered cosmopolitan may not be as cosmopolitan as expected in Antarctica. These organisms may require specific niches that allow them to colonise new habitats. This study also showed that gathering more samples from Tramway Ridge has widened understanding of the changing environments that microbial communities on Mt. Erebus live in. The study provides a foundation on which to compare microbial and geochemical interactions across all geothermal sites within Victoria Land. This supports the effect of specific geothermal characteristics of the fumaroles in manipulating the microbial communities present.
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    Origin of palaeo proglacial lake sediments in Taylor Valley, Antarctica
    (Thesis, The University of Waikato, 2005) Milicich, Sarah
    The origin of carbonates found at three locations in the Taylor Valley and their association with different glacial advances is presented. Samples were collected from three locations through the Taylor Valley, specifically Nussbaum Riegel west of Lake Fryxell, Sollas Bench on the slopes above Lake Bonney, and from Pearse Valley. Carbonates were collected primarily from the surficial glacial sediment, though at one site at Nussbaum Riegel a pit indicated the stratigraphy contained multiple carbonate horizons. The carbonate from Nussbaum Riegel was in situ, while at the other two sites the carbonate was incorporated into moraines. The oxygen isotope values indicate that carbonates were deposited in lakes with two different origins. δ¹⁸ values of approximately -28% to -32% for the Nussbaum Riegel carbonate samples indicate "Glacial Lake Nussbaum" likely formed during glacial conditions when grounded ice expanded in McMurdo Sound pushing a lobe of ice up the mouth of the Taylor Valley. δ¹⁸ values of approximately -33 %to 38% for carbonate samples from Pearse Valley and Sollas bench indicate that "Glacial Lake Pearse" and the proglacial lake in which the Sollas Bench carbonates were deposited would have formed during interglacial conditions. It is proposed that an expanded Taylor Glacier was advancing though its own proglaical lakes, reworking carbonate sediment deposited in the lakes. The carbon isotopes reflect the nature of the carbon dioxide cycling within the lakes. Strongly positive δ¹³C values are interpreted as reflecting low temperature equilibrium with atmospheric carbon dioxide or freezing processes causing precipitation. The trace element chemistry of the carbonates is inferred to indicate that the origin of their composition is primarily controlled by the composition of the precipitating fluid and the mineralogy of the carbonate. Samples containing higher proportions of aragonite have higher concentrations of the larger ions such as barium and strontium, while those with more calcite in the mineral structure contain more of the smaller ions such as magnesium. XRD analyses indicate that the Nussbaum Riegel carbonate samples are a mix of dominantly aragonite with some calcite. SEM images of the carbonate crystals show that they are cementing detrital material. Petrographic analysis of the Nussbaum Riegel carbonates indicate that much of the detrital material is volcanic in nature and was likely sourced from the McMurdo Volcanics. The Sollas Bench and Pearse Valley carbonate samples are predominantly aragonite as shown by XRD analyses. SEM images show the crystals in these samples are a mix of radiating needles and randomly oriented needles, pointing to two different processes during precipitation. SEM images also showed the presence of halite within the carbonate samples. The Nussbaum Riegel carbonates are inferred to have been deposited during periods of lake level fluctuation, where draining of ground water towards a lower lake level resulted in evaporation at the lake margins and cementation of the surficial sediment. The Sollas Bench and Pearse Valley carbonates were likely deposited under a regime of water removal, either via evaporation or freezing, making these carbonates a mix of evaporites and "cryorites". Cryorite is a new term, being defined as deposits precipitated as a result of concentration by removal of water due to freezing. In this case they appear to be primarily "cryorites". Halite was identified within many of the carbonate samples and gypsum was found associated with them. This suggests that there was a strongly concentrated brine present at the time of precipitation. The source of the salt in the western end in the Taylor Valley is likely to be an evaporate sequence in a subglacial depression indicated on subglacial profiles, currently being overridden by Taylor Glacier. The evaporites could have deposited during a warmer period when the Ferrar Valley was a fjord. Seawater would then have overflowed into Taylor Valley at its convergence with the Ferrar Valley. The resulting lakes then evaporating in the deep depression. Salts are currently being reworked into the valley, a similar situation is proposed for the Sollas Bench carbonates
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    Microbial diversity in relation to human activity in historic areas of Ross Dependency, Antarctica
    (Thesis, The University of Waikato, 2003) Minasaki, Ryuji
    The goal of this study was to undertake a relatively broad microbiological investigation at historic areas of Cape Evans and Ross Island. The two phylogenetically diverse targets were Bacillus anthracis, the causative agent for anthrax disease, and filamentous micro-fungi associated food products. The human activities were presumed to have played a significant contribution to the introduction of non-indigenous Bacillus anthracis and many filamentous micro-fungi at the historic areas on Ross Island. Bacillus anthracis was suspected to be present at Cape Evans based on a circumstantial clinical analysis of the death of the member in Captain Robert F Scott's Terra Nova Expedition in 1912. Detection methods based on polymerase chain reaction (PCR) targeting B. anthracis specific genes on chromosome and two plasmids were employed. DNA extraction was performed by a bead-beating technique from 74 environmental samples. PCR efficiency was compromised probably due to inhibitors in DNA extracts, but improved with higher concentrations of Taq polymerase. Initially a total of 74 environmental samples were screened with one set of primers before positively tested 19 samples were rigorously investigated with seven sets of primers. Nested PCR also increased the target specificity and detection levels. Sequence analyses of the several positive samples from PCR reactions were characteristic to B. anthracis. A diverse range of filamentous micro-fungi were isolated on three different media at two different temperatures, 15 °C and 25 °C, and identified by classical morphological taxonomy from the foodstuffs and internal environmental samples of Captain Robert F Scott's historic hut at Hut Point built in 1901. In total, there were 22 taxa and 14 genera recorded including many cosmopolitan species isolated from the samples, in particular Penicillium species. An extensive literature review of the :filamentous micro-fungi found in Antarctica identified that 7 taxa isolated in the study were not reported previously. Many isolates were obtained at 15 °C while some isolates grew in the presence of antibiotics.

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