title: Resolving Drivers of Microbial Community Structure in The Dry Valleys of Antarctica

authors: Bottos, Eric

subjects: Antarctica

abstract: Understanding the processes that underlie patterns of microbial distribution is fundamental to the field of microbial ecology, but extremely challenging given the complexity of natural systems. Antarctica’s ice-free regions possess unique ecosystems of simple trophic structure, shaped by the harsh environmental conditions that typify the continent. The Dry Valleys comprise the largest of these regions and have one of the simplest food webs on the planet, making them a tractable system to comprehensively define relationships that influence microbial distributions at the landscape scale. The New Zealand Terrestrial Antarctic Biocomplexity Survey (nzTABS) was aimed at identifying factors that control, and can predict, biological distributions in the Dry Valleys. As part of nzTABS, the goal of the research presented in this thesis was to elucidate the factors that influence bacterial community structure in Dry Valley soils.  

This study explored how topographic, physicochemical, and spatial variation influence bacterial diversity and community structure across a Dry Valley landscape. Bacterial communities were characterized in 471 soil samples using automated ribosomal intergenic spacer analysis (ARISA). Diversity and community composition were most strongly related to variation in physicochemical soil properties, though significant relationships with topographic and spatial variables were also observed. This identified, for the first time, the influence of environmental variables on bacterial diversity and community composition across the landscape, and presents a structural equation model identifying those relationships.

The phylogenetic diversity of bacterial communities in Dry Valley soils was also examined. High-throughput sequencing of 16S rRNA gene amplicons was used to analyze bacterial communities in 177 soil samples. This work identified significant relationships between the relative abundances of bacterial taxa and both abiotic and biotic variables, though these relationships explained only a small amount of community variation collectively. The relative abundances of several bacterial taxa were, however, significantly coupled to one another, suggesting that interactions between bacterial taxa may influence community compositions.

Lastly, the bacterial composition of aerosols above the Dry Valleys was examined. High-throughput sequencing of 16S rRNA gene amplicons was used to analyze two aerosol samples collected in the Miers Valley, and their compositions were compared to those of previously characterized aerosols and soils from across the continent. Bacteria present in the aerosols were found to be distinct from those of local soils; instead, aerosol compositions were more similar to those of air samples reported from elsewhere on the planet. Importantly, these findings suggest that local redistribution of Dry Valley soil bacteria through atmospheric processes may be largely restricted to periods when high winds mobilize soil particles and associated biota.

This study provides novel insights into the microbial ecology of the Dry Valleys. Despite the relative simplicity of the ecosystem, the factors that influence bacterial distributions within the Dry Valleys appear to be highly complex, and include a combination of abiotic and biotic drivers. Continued research will help to disentangle relationships that influence microbial community compositions in Antarctica’s ice-free ecosystems, and will improve understanding of processes that influence microbial community assembly globally.

text: Resolving Drivers of Microbial Community Structure in The Dry Valleys of Antarctica Understanding the processes that underlie patterns of microbial distribution is fundamental to the field of microbial ecology, but extremely challenging given the complexity of natural systems. Antarctica’s ice-free regions possess unique ecosystems of simple trophic structure, shaped by the harsh environmental conditions that typify the continent. The Dry Valleys comprise the largest of these regions and have one of the simplest food webs on the planet, making them a tractable system to comprehensively define relationships that influence microbial distributions at the landscape scale. The New Zealand Terrestrial Antarctic Biocomplexity Survey (nzTABS) was aimed at identifying factors that control, and can predict, biological distributions in the Dry Valleys. As part of nzTABS, the goal of the research presented in this thesis was to elucidate the factors that influence bacterial community structure in Dry Valley soils.  

This study explored how topographic, physicochemical, and spatial variation influence bacterial diversity and community structure across a Dry Valley landscape. Bacterial communities were characterized in 471 soil samples using automated ribosomal intergenic spacer analysis (ARISA). Diversity and community composition were most strongly related to variation in physicochemical soil properties, though significant relationships with topographic and spatial variables were also observed. This identified, for the first time, the influence of environmental variables on bacterial diversity and community composition across the landscape, and presents a structural equation model identifying those relationships.

The phylogenetic diversity of bacterial communities in Dry Valley soils was also examined. High-throughput sequencing of 16S rRNA gene amplicons was used to analyze bacterial communities in 177 soil samples. This work identified significant relationships between the relative abundances of bacterial taxa and both abiotic and biotic variables, though these relationships explained only a small amount of community variation collectively. The relative abundances of several bacterial taxa were, however, significantly coupled to one another, suggesting that interactions between bacterial taxa may influence community compositions.

Lastly, the bacterial composition of aerosols above the Dry Valleys was examined. High-throughput sequencing of 16S rRNA gene amplicons was used to analyze two aerosol samples collected in the Miers Valley, and their compositions were compared to those of previously characterized aerosols and soils from across the continent. Bacteria present in the aerosols were found to be distinct from those of local soils; instead, aerosol compositions were more similar to those of air samples reported from elsewhere on the planet. Importantly, these findings suggest that local redistribution of Dry Valley soil bacteria through atmospheric processes may be largely restricted to periods when high winds mobilize soil particles and associated biota.

This study provides novel insights into the microbial ecology of the Dry Valleys. Despite the relative simplicity of the ecosystem, the factors that influence bacterial distributions within the Dry Valleys appear to be highly complex, and include a combination of abiotic and biotic drivers. Continued research will help to disentangle relationships that influence microbial community compositions in Antarctica’s ice-free ecosystems, and will improve understanding of processes that influence microbial community assembly globally.

year: 2014

title: Sink or swim? Sleep in highly trained adolescent swimmers during the in-season phase of training

authors: Ashby, Claudia Renee Georgia

abstract: Sleep is vital to the physiological and cognitive functioning in humans, however, disruption to sleep is a growing issue. Requirements of training in high performing adolescent athletes is increasing but it is largely unknown what effect this has upon their sleep. Extra-curricular activities such as sport, music, and part-time work are all contributing factors to the sleep disturbances adolescents’ experience. Until now, limited research has been available on high performing adolescent athletes sleep as most research has focused on sleep in elite adult athletes. Research to date has illustrated that elite adult athletes experience disruptions to their sleep due to training and competitions which subsequently impacts their recovery, performance and fatigue. The few studies to investigate adolescent athletes have found that sleep has significant effects on injury occurrence, academic performance, mental health, and obesity, as discussed in the literature review in the first chapter of this thesis. Furthermore, through the limited previous research, it has been found that adolescent athletes sleep is disrupted on nights preceding early morning training sessions. The second chapter of this thesis includes an original study investigating the sleep of highly trained adolescent swimmers. Fifteen adolescent swimmers volunteered to participate in this study, where their sleep was measured via subjective and objective measures over a two-week ‘normal’ in-season training phase. Participants subjectively recorded their total sleep time (TST), sleep latency (SL), and wake episodes (WE) through a daily sleep diary. In conjunction, objective sleep indices (TST, SL, WE, total time in bed (TTB), wake after sleep onset (WASO), sleep efficiency (SE), sleep onset time (SOT), and wake time (WT) were measured through a wrist actigraph device. Analysis revealed that participants significantly overestimated their sleep duration by approximately one hour per night compared to their objective TST. Furthermore, on evenings preceding early morning training (EARLY), participants TST and TTB was significantly less compared to nights preceding day trainings (DAY) and rest days (REST). Finally, the third chapter of this thesis summarises the overall findings of the thesis, as well as highlighting practical applications, and potential future research directions.

text: Sink or swim? Sleep in highly trained adolescent swimmers during the in-season phase of training Sleep is vital to the physiological and cognitive functioning in humans, however, disruption to sleep is a growing issue. Requirements of training in high performing adolescent athletes is increasing but it is largely unknown what effect this has upon their sleep. Extra-curricular activities such as sport, music, and part-time work are all contributing factors to the sleep disturbances adolescents’ experience. Until now, limited research has been available on high performing adolescent athletes sleep as most research has focused on sleep in elite adult athletes. Research to date has illustrated that elite adult athletes experience disruptions to their sleep due to training and competitions which subsequently impacts their recovery, performance and fatigue. The few studies to investigate adolescent athletes have found that sleep has significant effects on injury occurrence, academic performance, mental health, and obesity, as discussed in the literature review in the first chapter of this thesis. Furthermore, through the limited previous research, it has been found that adolescent athletes sleep is disrupted on nights preceding early morning training sessions. The second chapter of this thesis includes an original study investigating the sleep of highly trained adolescent swimmers. Fifteen adolescent swimmers volunteered to participate in this study, where their sleep was measured via subjective and objective measures over a two-week ‘normal’ in-season training phase. Participants subjectively recorded their total sleep time (TST), sleep latency (SL), and wake episodes (WE) through a daily sleep diary. In conjunction, objective sleep indices (TST, SL, WE, total time in bed (TTB), wake after sleep onset (WASO), sleep efficiency (SE), sleep onset time (SOT), and wake time (WT) were measured through a wrist actigraph device. Analysis revealed that participants significantly overestimated their sleep duration by approximately one hour per night compared to their objective TST. Furthermore, on evenings preceding early morning training (EARLY), participants TST and TTB was significantly less compared to nights preceding day trainings (DAY) and rest days (REST). Finally, the third chapter of this thesis summarises the overall findings of the thesis, as well as highlighting practical applications, and potential future research directions.

year: 2021

title: A critical race analysis of Māori representation in university strategic documents in Aotearoa New Zealand

authors: Waitoki, Waikaremoana

subjects: critical race theory

abstract: Following the recent claims lodged at two universities in Aotearoa New Zealand alleging the existence of racism, there has been scepticism towards the professed commitments by universities to create an inclusive and safe environment for Indigenous Māori. As a Kaupapa Māori-informed study, we (a group of Māori and Tauiwi scholars) employed tenets of Critical Race Theory to examine how the representation of Māori is racialised and subordinated in university strategic documents. We located five predominant discourses portraying different mechanisms that reify whiteness in university practices such as the selective interpretation of Te Tiriti articles, targeted recruitment of Māori, framing of Māori as dependent on the Crown to succeed, commodification of mātauranga Māori, and avoidance of conversations about structural racism, colonisation, and racial equity. Our findings suggest that university strategic goal statements need to incorporate a critical race analysis, or else risk perpetuating practices that fall short of challenging the status quo.

text: A critical race analysis of Māori representation in university strategic documents in Aotearoa New Zealand Following the recent claims lodged at two universities in Aotearoa New Zealand alleging the existence of racism, there has been scepticism towards the professed commitments by universities to create an inclusive and safe environment for Indigenous Māori. As a Kaupapa Māori-informed study, we (a group of Māori and Tauiwi scholars) employed tenets of Critical Race Theory to examine how the representation of Māori is racialised and subordinated in university strategic documents. We located five predominant discourses portraying different mechanisms that reify whiteness in university practices such as the selective interpretation of Te Tiriti articles, targeted recruitment of Māori, framing of Māori as dependent on the Crown to succeed, commodification of mātauranga Māori, and avoidance of conversations about structural racism, colonisation, and racial equity. Our findings suggest that university strategic goal statements need to incorporate a critical race analysis, or else risk perpetuating practices that fall short of challenging the status quo.

year: 2024