title: Investigating the anti-methanogenic properties of select species of seaweed in New Zealand.

authors: Mihaila, Alisa Andrea

abstract: Enteric methane emissions from ruminants constitute a large proportion of agricultural greenhouse gas emissions, particularly in New Zealand. The recent increase in enteric methane emissions has driven the development of innovative strategies for mitigating these emissions. Red seaweed from the genus Asparagopsis has demonstrated elimination of enteric methane due to the presence of the active anti-methanogenic component, bromoform.

Spatial variation in bromoform content for Asparagopsis armata throughout the North Island, New Zealand, was quantified to determine the region that produces the highest concentration of bromoform. Alongside Asparagopsis, the New Zealand red seaweed species Bonnemaisonia hamifera, Delisea compressa, Plocamium sp., Vidalia colensoi, and identified aquaculture-target seaweed species, Ecklonia radiata, and Ulva sp. B, were investigated as ruminant feed additives to reduce enteric methane emissions. Polyphenol quantification and compositional analyses were carried out for these seaweed species to provide a baseline for interpreting anti-methanogenic effects. Seaweed species were included at 0 %, 2 %, 6 %, and 10 % of feed organic matter (ryegrass hay) during in vitro fermentation assays using rumen inoculant from non-lactating cows. Total gas, methane, hydrogen, volatile fatty acid (VFA), and ammonia production were measured during the incubations.

Bromoform concentration was highest in A. armata sampled from Matheson’s Bay at 1 % of the biomass dry weight. Species of red seaweed had a high halogen content, while E. radiata and Ulva. sp. B had a high iodine and crude protein content, respectively. Inclusions of A. armata and B. hamifera demonstrated near elimination of enteric methane production at doses of 2 and 6 % organic matter, respectively, while the remaining species (except for Ulva sp. B) caused moderate reductions at doses of 6 and 10 % organic matter in comparison to these two species. The anti-methanogenic effects of A. armata and B. hamifera resulted in a 22 % reduction in total VFA production, accompanied by changes in the relative proportions of individual VFAs, and had little or no effect on organic matter degradation.

The effectiveness of A. armata and B. hamifera demonstrates the potential of these species for mitigating ruminant methane emissions at low inclusion rates, dependent on the concentration of their active components, while E. radiata and Ulva sp. B could be used as feed additives for nutritional benefit. The undertaking of larger scale sampling of A. armata throughout New Zealand, the identification of the active component(s) in B. hamifera, and the development of methods and infrastructure required for successful large-scale aquaculture and application of these seaweed species to livestock management systems are key areas of future research highlighted by this thesis.

text: Investigating the anti-methanogenic properties of select species of seaweed in New Zealand. Enteric methane emissions from ruminants constitute a large proportion of agricultural greenhouse gas emissions, particularly in New Zealand. The recent increase in enteric methane emissions has driven the development of innovative strategies for mitigating these emissions. Red seaweed from the genus Asparagopsis has demonstrated elimination of enteric methane due to the presence of the active anti-methanogenic component, bromoform.

Spatial variation in bromoform content for Asparagopsis armata throughout the North Island, New Zealand, was quantified to determine the region that produces the highest concentration of bromoform. Alongside Asparagopsis, the New Zealand red seaweed species Bonnemaisonia hamifera, Delisea compressa, Plocamium sp., Vidalia colensoi, and identified aquaculture-target seaweed species, Ecklonia radiata, and Ulva sp. B, were investigated as ruminant feed additives to reduce enteric methane emissions. Polyphenol quantification and compositional analyses were carried out for these seaweed species to provide a baseline for interpreting anti-methanogenic effects. Seaweed species were included at 0 %, 2 %, 6 %, and 10 % of feed organic matter (ryegrass hay) during in vitro fermentation assays using rumen inoculant from non-lactating cows. Total gas, methane, hydrogen, volatile fatty acid (VFA), and ammonia production were measured during the incubations.

Bromoform concentration was highest in A. armata sampled from Matheson’s Bay at 1 % of the biomass dry weight. Species of red seaweed had a high halogen content, while E. radiata and Ulva. sp. B had a high iodine and crude protein content, respectively. Inclusions of A. armata and B. hamifera demonstrated near elimination of enteric methane production at doses of 2 and 6 % organic matter, respectively, while the remaining species (except for Ulva sp. B) caused moderate reductions at doses of 6 and 10 % organic matter in comparison to these two species. The anti-methanogenic effects of A. armata and B. hamifera resulted in a 22 % reduction in total VFA production, accompanied by changes in the relative proportions of individual VFAs, and had little or no effect on organic matter degradation.

The effectiveness of A. armata and B. hamifera demonstrates the potential of these species for mitigating ruminant methane emissions at low inclusion rates, dependent on the concentration of their active components, while E. radiata and Ulva sp. B could be used as feed additives for nutritional benefit. The undertaking of larger scale sampling of A. armata throughout New Zealand, the identification of the active component(s) in B. hamifera, and the development of methods and infrastructure required for successful large-scale aquaculture and application of these seaweed species to livestock management systems are key areas of future research highlighted by this thesis.

year: 2020

title: In situ measurement of metal-ligand complex dissociation rates in cave dripwaters

authors: Guo, Xiaoli

abstract: The purpose of this study was to develop a new method for determining the trace metal binding properties of natural organic matter (NOM) in cave dripwaters. The methodology is based on the diffusive gradients in the thin-films (DGT) technique, but differs from DGT by using advective gradients along hydrogel to resolve temporal trends in dissociation. For this reason, it is referred to as advective gradients in thin-films (AGT). 
NOM is a ubiquitous component in natural waters. The complexation capacities of NOM ligands for metal ions in cave waters has a great impact on the transport of trace metals to, and their incorporation in, calcium carbonate cave deposits (speleothems). The relationship between the kinetics of metal-NOM complexes and the concentration of the metal-carbonate solid solution in actively forming cave precipitates, is the major focus in this study. The primary goal of this research is the determination of the mean kinetics of compositionally-unknown metal-NOM complexes in situ with the application of AGT.
The first part of this study was to calibrate the self-assembled AGT device containing a resin gel (for the binding of metal ions). A range of drip rates was tested to establish the relationship between drip rates and flow velocity within the gel with the aim of establishing a calibration function between drip discharge and flow rate within the gel. The second part of this study was to validate the method using metal-ligand complexes of known character. Synthetic solutions containing organic ligands at known concentrations were measured. The experimental data showed acceptable reproducibility, and the modelling results agreed well with the literature. 
After the laboratory-based study of the AGT method, the device was deployed in Aranui Cave, which is a natural cave located in the Waitomo District, New Zealand. Four transition metals were found in both resin gel samples and the water sample. The accumulation behaviour of the metals in the Chelex-100 resin gel demonstrated the capability of the AGT method to measure trace metals bound to unknown NOM ligands in cave dripwaters. The dynamics of the dissociation of metal-NOM complexes can be reflected by the distinct dissociation patterns of the metals.
This newly developed method can semi-qualitatively determine the dissociation rates of labile and partially labile metal-NOM complexes in natural waters. However, further optimisation of the method will be required to improve the precision and accuracy of measurements. In summary, this study provides the basic framework for further research of a new palaeoclimate proxy utilising trace meta-content in speleothems.

text: In situ measurement of metal-ligand complex dissociation rates in cave dripwaters The purpose of this study was to develop a new method for determining the trace metal binding properties of natural organic matter (NOM) in cave dripwaters. The methodology is based on the diffusive gradients in the thin-films (DGT) technique, but differs from DGT by using advective gradients along hydrogel to resolve temporal trends in dissociation. For this reason, it is referred to as advective gradients in thin-films (AGT). 
NOM is a ubiquitous component in natural waters. The complexation capacities of NOM ligands for metal ions in cave waters has a great impact on the transport of trace metals to, and their incorporation in, calcium carbonate cave deposits (speleothems). The relationship between the kinetics of metal-NOM complexes and the concentration of the metal-carbonate solid solution in actively forming cave precipitates, is the major focus in this study. The primary goal of this research is the determination of the mean kinetics of compositionally-unknown metal-NOM complexes in situ with the application of AGT.
The first part of this study was to calibrate the self-assembled AGT device containing a resin gel (for the binding of metal ions). A range of drip rates was tested to establish the relationship between drip rates and flow velocity within the gel with the aim of establishing a calibration function between drip discharge and flow rate within the gel. The second part of this study was to validate the method using metal-ligand complexes of known character. Synthetic solutions containing organic ligands at known concentrations were measured. The experimental data showed acceptable reproducibility, and the modelling results agreed well with the literature. 
After the laboratory-based study of the AGT method, the device was deployed in Aranui Cave, which is a natural cave located in the Waitomo District, New Zealand. Four transition metals were found in both resin gel samples and the water sample. The accumulation behaviour of the metals in the Chelex-100 resin gel demonstrated the capability of the AGT method to measure trace metals bound to unknown NOM ligands in cave dripwaters. The dynamics of the dissociation of metal-NOM complexes can be reflected by the distinct dissociation patterns of the metals.
This newly developed method can semi-qualitatively determine the dissociation rates of labile and partially labile metal-NOM complexes in natural waters. However, further optimisation of the method will be required to improve the precision and accuracy of measurements. In summary, this study provides the basic framework for further research of a new palaeoclimate proxy utilising trace meta-content in speleothems.

year: 2019

title: Māori loanwords: a corpus of New Zealand English tweets

authors: Trye, David

abstract: Māori loanwords are widely used in New Zealand English for various social functions by New Zealanders within and outside of the Māori community. Motivated by the lack of linguistic resources for studying how Māori loanwords are used in social media, we present a new corpus of New Zealand English tweets. We collected tweets containing selected Māori words that are likely to be known by New Zealanders who do not speak Māori. Since over 30% of these words turned out to be irrelevant (e.g., mana is a popular gaming term, Moana is a character from a Disney movie), we manually annotated a sample of our tweets into relevant and irrelevant categories. This data was used to train machine learning models to automatically filter out irrelevant tweets.

text: Māori loanwords: a corpus of New Zealand English tweets Māori loanwords are widely used in New Zealand English for various social functions by New Zealanders within and outside of the Māori community. Motivated by the lack of linguistic resources for studying how Māori loanwords are used in social media, we present a new corpus of New Zealand English tweets. We collected tweets containing selected Māori words that are likely to be known by New Zealanders who do not speak Māori. Since over 30% of these words turned out to be irrelevant (e.g., mana is a popular gaming term, Moana is a character from a Disney movie), we manually annotated a sample of our tweets into relevant and irrelevant categories. This data was used to train machine learning models to automatically filter out irrelevant tweets.

year: 2019