title: Microbial biogeography of 1,000 geothermal springs: spatial, temporal, and allopatric dynamics of extremophiles in the Taupō Volcanic Zone, Aotearoa-New Zealand

authors: Power, Jean Florence

subjects: Microbiology

abstract: Geothermal springs are model ecosystems to investigate microbial biogeography as they represent discrete, relatively homogeneous habitats, are distributed across multiple geographical scales, and span broad geochemical gradients. This thesis reports the largest consolidated study of geothermal ecosystems to determine causal factors that influence both spatial and temporal biogeographical patterns of extremophiles. Bacterial and archaeal community composition, 46 physicochemical parameters, and metadata from 925 geothermal spring water columns across the Taupō Volcanic Zone (TVZ), Aotearoa-New Zealand were measured. Standardised methodologies were employed to define microbial diversity via 16S rRNA gene amplicon sequencing, and associated physicochemistry, ensuring confidence in sample comparison. Over an 8,000 km² spatial scale, multivariate statistical analyses determined diversity was primarily influenced by pH at temperatures <70 °C; with temperature only having a significant effect at >70 °C. Further, community dissimilarity increased with increasing geographic distance across the region, highlighting niche selection driving assembly at a local scale.

This research also describes the first comprehensive temporal study of geothermal microbial communities in Aotearoa-New Zealand. One hundred and fifteen water column samples from 31 geothermal features were taken over a 34-month period to ascertain microbial community stability, community response to both natural and anthropogenic disturbances in the local environment, and temporal variation in spring diversity across the pH range found in the TVZ. Results indicated temperature and associated groundwater physicochemistry were the most likely parameters to vary stochastically in these geothermal features, with community abundances rather than composition more readily affected by a changing environment. However, variation in pH (pH ±1) had a more significant effect on community structure than temperature (±20 °C), with alpha diversity failing to be an adequate measure of temporal microbial disparity in geothermal features outside of circumneutral conditions. While a substantial physicochemical disturbance was required to shift community structures at the phylum level, geothermal ecosystems were resilient at this broad taxonomic rank and returned to a pre-disturbed state if environmental conditions re-established.

The discovery that genus 𝑉𝑒𝑛𝑒𝑛𝑖𝑣𝑖𝑏𝑟𝑖𝑜 (phylum Aquificota) exhibited the greatest average abundance (11.2 %) and distribution (74.2 %) of all taxa across 925 geothermal ecosystems in the TVZ, and an apparent absence of this taxon in global geothermal systems, led to the hypothesis that allopatric speciation enabled the evolution of an endemic bacterial genus to Aotearoa-New Zealand. Maximal read abundance of 𝑉𝑒𝑛𝑒𝑛𝑖𝑣𝑖𝑏𝑟𝑖𝑜 occurred in geothermal features with pH 4-6, 50-70 °C, and low oxidation-reduction potentials, highlighting a specific environmental niche that could enhance habitat isolation. Genomic analysis of the only characterised species for the genus, 𝑉𝑒𝑛𝑒𝑛𝑖𝑣𝑖𝑏𝑟𝑖𝑜 𝑠𝑡𝑎𝑔𝑛𝑖𝑠𝑝𝑢𝑚𝑎𝑛𝑡𝑖𝑠 CP.B2ᵀ, confirmed a chemolithoautotrophic metabolism dependent on hydrogen oxidation. While similarity between 𝑉𝑒𝑛𝑒𝑛𝑖𝑣𝑖𝑏𝑟𝑖𝑜 populations illustrated dispersal was not limited across the TVZ, extensive amplicon, metagenomic, and phylogenomic analyses of local and global microbial communities from DNA sequence databases indicated 𝑉𝑒𝑛𝑒𝑛𝑖𝑣𝑖𝑏𝑟𝑖𝑜 is geographically restricted to the Aotearoa-New Zealand archipelago. It was concluded that combined geographical and physicochemical constraints prevent this taxon from distributing on a broader scale, resulting in the establishment of an endemic bacterial genus.

Collectively, the findings from this thesis provide an insight into ecological behaviour in geothermal springs, highlighting the diverse controls between different taxa within the same habitat-type, and expand understanding of microbial biogeography in extreme ecosystems.

text: Microbial biogeography of 1,000 geothermal springs: spatial, temporal, and allopatric dynamics of extremophiles in the Taupō Volcanic Zone, Aotearoa-New Zealand Geothermal springs are model ecosystems to investigate microbial biogeography as they represent discrete, relatively homogeneous habitats, are distributed across multiple geographical scales, and span broad geochemical gradients. This thesis reports the largest consolidated study of geothermal ecosystems to determine causal factors that influence both spatial and temporal biogeographical patterns of extremophiles. Bacterial and archaeal community composition, 46 physicochemical parameters, and metadata from 925 geothermal spring water columns across the Taupō Volcanic Zone (TVZ), Aotearoa-New Zealand were measured. Standardised methodologies were employed to define microbial diversity via 16S rRNA gene amplicon sequencing, and associated physicochemistry, ensuring confidence in sample comparison. Over an 8,000 km² spatial scale, multivariate statistical analyses determined diversity was primarily influenced by pH at temperatures <70 °C; with temperature only having a significant effect at >70 °C. Further, community dissimilarity increased with increasing geographic distance across the region, highlighting niche selection driving assembly at a local scale.

This research also describes the first comprehensive temporal study of geothermal microbial communities in Aotearoa-New Zealand. One hundred and fifteen water column samples from 31 geothermal features were taken over a 34-month period to ascertain microbial community stability, community response to both natural and anthropogenic disturbances in the local environment, and temporal variation in spring diversity across the pH range found in the TVZ. Results indicated temperature and associated groundwater physicochemistry were the most likely parameters to vary stochastically in these geothermal features, with community abundances rather than composition more readily affected by a changing environment. However, variation in pH (pH ±1) had a more significant effect on community structure than temperature (±20 °C), with alpha diversity failing to be an adequate measure of temporal microbial disparity in geothermal features outside of circumneutral conditions. While a substantial physicochemical disturbance was required to shift community structures at the phylum level, geothermal ecosystems were resilient at this broad taxonomic rank and returned to a pre-disturbed state if environmental conditions re-established.

The discovery that genus 𝑉𝑒𝑛𝑒𝑛𝑖𝑣𝑖𝑏𝑟𝑖𝑜 (phylum Aquificota) exhibited the greatest average abundance (11.2 %) and distribution (74.2 %) of all taxa across 925 geothermal ecosystems in the TVZ, and an apparent absence of this taxon in global geothermal systems, led to the hypothesis that allopatric speciation enabled the evolution of an endemic bacterial genus to Aotearoa-New Zealand. Maximal read abundance of 𝑉𝑒𝑛𝑒𝑛𝑖𝑣𝑖𝑏𝑟𝑖𝑜 occurred in geothermal features with pH 4-6, 50-70 °C, and low oxidation-reduction potentials, highlighting a specific environmental niche that could enhance habitat isolation. Genomic analysis of the only characterised species for the genus, 𝑉𝑒𝑛𝑒𝑛𝑖𝑣𝑖𝑏𝑟𝑖𝑜 𝑠𝑡𝑎𝑔𝑛𝑖𝑠𝑝𝑢𝑚𝑎𝑛𝑡𝑖𝑠 CP.B2ᵀ, confirmed a chemolithoautotrophic metabolism dependent on hydrogen oxidation. While similarity between 𝑉𝑒𝑛𝑒𝑛𝑖𝑣𝑖𝑏𝑟𝑖𝑜 populations illustrated dispersal was not limited across the TVZ, extensive amplicon, metagenomic, and phylogenomic analyses of local and global microbial communities from DNA sequence databases indicated 𝑉𝑒𝑛𝑒𝑛𝑖𝑣𝑖𝑏𝑟𝑖𝑜 is geographically restricted to the Aotearoa-New Zealand archipelago. It was concluded that combined geographical and physicochemical constraints prevent this taxon from distributing on a broader scale, resulting in the establishment of an endemic bacterial genus.

Collectively, the findings from this thesis provide an insight into ecological behaviour in geothermal springs, highlighting the diverse controls between different taxa within the same habitat-type, and expand understanding of microbial biogeography in extreme ecosystems.

year: 2023

title: Recent progress in remanufacturing technologies using metal additive manufacturing processes and surface treatment

authors: Kahhal, Parviz

subjects: additive manufacturing

abstract: Remanufacturing has emerged as an effective strategy to promote sustainability, reduce waste, and enhance resource efficiency in modern manufacturing processes. However, traditional remanufacturing methods have limitations in producing complex geometries and restoring parts to their original condition, leading to reduced performance and durability. Metal additive manufacturing (AM) methods have shown significant potential in overcoming these limitations and enhancing the quality and reliability of remanufactured parts. Metal AM enables the production of replacement parts with high geometrical complexity and tight tolerances. On the other hand, surface treatment techniques, such as polishing and coating, can improve the surface properties of additively manufactured parts. Recent advancements in metal AM have led to significant progress in manufacturing technologies, including the development of hybrid methods combining metal AM with a surface treatment to achieve superior surface finish and accuracy while reducing production time and cost. Despite progress, challenges such as the need for cost-effective and scalable processing methods, the development of new materials, and the optimization of process parameters for specific applications still need to be addressed. Moreover, although surface modification techniques suitable for metal components fabricated through additive manufacturing can be employed for remanufactured parts, their adoption needs to be improved and necessitates additional advancement. This paper provides an overview of recent progress in manufacturing and remanufacturing technologies using metal additive manufacturing processes and surface treatments, highlighting their potential to significantly improve the quality and reliability of remanufactured parts. The paper concludes with a discussion of the future prospects of this field and the need for continued research and development to fully realize the potential of remanufacturing technologies.

text: Recent progress in remanufacturing technologies using metal additive manufacturing processes and surface treatment Remanufacturing has emerged as an effective strategy to promote sustainability, reduce waste, and enhance resource efficiency in modern manufacturing processes. However, traditional remanufacturing methods have limitations in producing complex geometries and restoring parts to their original condition, leading to reduced performance and durability. Metal additive manufacturing (AM) methods have shown significant potential in overcoming these limitations and enhancing the quality and reliability of remanufactured parts. Metal AM enables the production of replacement parts with high geometrical complexity and tight tolerances. On the other hand, surface treatment techniques, such as polishing and coating, can improve the surface properties of additively manufactured parts. Recent advancements in metal AM have led to significant progress in manufacturing technologies, including the development of hybrid methods combining metal AM with a surface treatment to achieve superior surface finish and accuracy while reducing production time and cost. Despite progress, challenges such as the need for cost-effective and scalable processing methods, the development of new materials, and the optimization of process parameters for specific applications still need to be addressed. Moreover, although surface modification techniques suitable for metal components fabricated through additive manufacturing can be employed for remanufactured parts, their adoption needs to be improved and necessitates additional advancement. This paper provides an overview of recent progress in manufacturing and remanufacturing technologies using metal additive manufacturing processes and surface treatments, highlighting their potential to significantly improve the quality and reliability of remanufactured parts. The paper concludes with a discussion of the future prospects of this field and the need for continued research and development to fully realize the potential of remanufacturing technologies.

year: 2024

title: The digital divide in New Zealand: The position of Maori and Pacific peoples

authors: Gibson, John

subjects: communication

abstract: Information and communication technology plays an ever-growing role in economic, political and social life and those who are unable to access such technologies are increasingly disadvantaged. Hence, what has come to be known as the 'digital divide' is of considerable significance. Here, indicators of that divide as it affects Maori and

text: The digital divide in New Zealand: The position of Maori and Pacific peoples Information and communication technology plays an ever-growing role in economic, political and social life and those who are unable to access such technologies are increasingly disadvantaged. Hence, what has come to be known as the 'digital divide' is of considerable significance. Here, indicators of that divide as it affects Maori and

year: 2002