title: The biology of Asparagopsis armata for closed-life cycle cultivation in New Zealand

authors: Mihaila, Alisa Andrea

abstract: The red seaweed Asparagopsis armata is a target species for aquaculture due to its efficacy as an anti-methanogenic ruminant feed additive. However, limited knowledge regarding its reproductive biology and methods for closed-life cycle cultivation has delayed adoption of this method in aquaculture. This thesis therefore aimed to address these knowledge gaps by investigating (1) reproductive phenology, (2) techniques for inducing life-cycle transitions, (3) nursery requirements, and (4) internal mechanisms regulating reproductive processes in A. armata. 
A comparative analysis of A. armata reproductive phenology in New Zealand from 2021 to 2022, compared to 1978 to 1981, identified potential climate-driven shifts in phenology. Specifically, the occurrence period of gametophytes was shorter, and cystocarp production and viable carpospore release were delayed in comparison to 1978–1981. Discoloration, low reproductive output, and low survival rates in 2022 were likely caused by heat stress. These findings will help guide aquaculture practises and advance our understanding of climate change effects on seaweed reproductive phenology through future comparative studies.
Mass production and release of tetraspores in domesticated A. armata tetrasporophytes was demonstrated through a 14-day exposure to a reduced critical photoperiod of 8 h L:16 h D. Increasing the temperature from 15 to 18 °C resulted in a marked increase in tetraspore release, whereas exposure to 11 and 13 °C, along with lower light intensities and nutrient concentrations, did not initiate tetrasporogenesis. These results highlight the importance of temperature, among other environmental factors, in controlling reproductive output. A distinct bimodal pattern in tetraspore release was observed, and tetrasporogenesis could be re-induced in the same biomass by adjusting key environmental parameters. These findings collectively offer precise control over tetrasporogenesis, facilitating commercial hatchery production. 
Key parameters for enhancing the growth and development of juvenile gametophytes of A. armata were identified, notably moderate temperature and water flow, which resulted in substantial biomass productivity increases. Gametophytes developed more rapidly under a 12h L:12h D photoperiod, while growth was enhanced under lower irradiances. Additionally, lowering nutrient concentrations resulted in cleaner cultures without compromising growth. These results elucidate the influence of environmental factors during the early life stages of A. armata, providing essential insights to enable large-scale nursery operations. 
Finally, an analysis of metabolomic and transcriptomic dynamics during induction of tetrasporogenesis identified marked changes in gene expression. While metabolomic changes were less prominent, accumulation of several metabolites occurred. Multiple pathways and genes, such as those related to polyamine and steroid hormone production, environmental signalling, and carbon metabolism, were upregulated during induction. These results demonstrate a dynamic biochemical and molecular response, particularly in the early stages of initiating tetrasporogenesis, laying the groundwork for identifying candidate genes and metabolites that regulate this process.  
In summary, this thesis significantly advances the science and knowledge required for the successful cultivation of A. armata by creating foundations to (1) guide the selection of cultivation techniques, (2) develop climate-resilient management strategies, (3) enable the implementation of streamlined commercial hatcheries and nurseries, and (4) direct future research aimed at deciphering the fundamental internal mechanisms of reproductive transitions in seaweed.

text: The biology of Asparagopsis armata for closed-life cycle cultivation in New Zealand The red seaweed Asparagopsis armata is a target species for aquaculture due to its efficacy as an anti-methanogenic ruminant feed additive. However, limited knowledge regarding its reproductive biology and methods for closed-life cycle cultivation has delayed adoption of this method in aquaculture. This thesis therefore aimed to address these knowledge gaps by investigating (1) reproductive phenology, (2) techniques for inducing life-cycle transitions, (3) nursery requirements, and (4) internal mechanisms regulating reproductive processes in A. armata. 
A comparative analysis of A. armata reproductive phenology in New Zealand from 2021 to 2022, compared to 1978 to 1981, identified potential climate-driven shifts in phenology. Specifically, the occurrence period of gametophytes was shorter, and cystocarp production and viable carpospore release were delayed in comparison to 1978–1981. Discoloration, low reproductive output, and low survival rates in 2022 were likely caused by heat stress. These findings will help guide aquaculture practises and advance our understanding of climate change effects on seaweed reproductive phenology through future comparative studies.
Mass production and release of tetraspores in domesticated A. armata tetrasporophytes was demonstrated through a 14-day exposure to a reduced critical photoperiod of 8 h L:16 h D. Increasing the temperature from 15 to 18 °C resulted in a marked increase in tetraspore release, whereas exposure to 11 and 13 °C, along with lower light intensities and nutrient concentrations, did not initiate tetrasporogenesis. These results highlight the importance of temperature, among other environmental factors, in controlling reproductive output. A distinct bimodal pattern in tetraspore release was observed, and tetrasporogenesis could be re-induced in the same biomass by adjusting key environmental parameters. These findings collectively offer precise control over tetrasporogenesis, facilitating commercial hatchery production. 
Key parameters for enhancing the growth and development of juvenile gametophytes of A. armata were identified, notably moderate temperature and water flow, which resulted in substantial biomass productivity increases. Gametophytes developed more rapidly under a 12h L:12h D photoperiod, while growth was enhanced under lower irradiances. Additionally, lowering nutrient concentrations resulted in cleaner cultures without compromising growth. These results elucidate the influence of environmental factors during the early life stages of A. armata, providing essential insights to enable large-scale nursery operations. 
Finally, an analysis of metabolomic and transcriptomic dynamics during induction of tetrasporogenesis identified marked changes in gene expression. While metabolomic changes were less prominent, accumulation of several metabolites occurred. Multiple pathways and genes, such as those related to polyamine and steroid hormone production, environmental signalling, and carbon metabolism, were upregulated during induction. These results demonstrate a dynamic biochemical and molecular response, particularly in the early stages of initiating tetrasporogenesis, laying the groundwork for identifying candidate genes and metabolites that regulate this process.  
In summary, this thesis significantly advances the science and knowledge required for the successful cultivation of A. armata by creating foundations to (1) guide the selection of cultivation techniques, (2) develop climate-resilient management strategies, (3) enable the implementation of streamlined commercial hatcheries and nurseries, and (4) direct future research aimed at deciphering the fundamental internal mechanisms of reproductive transitions in seaweed.

year: 2024

title: Current singularities at Quasi-separatrix layers and three-dimensional magnetic nulls

authors: Craig, Ian J.D.

subjects: Science & Technology

abstract: The open problem of how singular current structures form in line-tied, three-dimensional magnetic fields is addressed. A Lagrangian magneto-frictional relaxation method is employed to model the field evolution toward the final near-singular state. Our starting point is an exact force-free solution of the governing magnetohydrodynamic equations that is sufficiently general to allow for topological features like magnetic nulls to be inside or outside the computational domain, depending on a simple set of parameters. Quasi-separatrix layers (QSLs) are present in these structures and, together with the magnetic nulls, they significantly influence the accumulation of current. It is shown that perturbations affecting the lateral boundaries of the configuration lead not only to collapse around the magnetic null but also to significant QSL currents. Our results show that once a magnetic null is present, the developing currents are always attracted to that specific location and show a much stronger scaling with resolution than the currents that form along the QSL. In particular, the null-point scalings can be consistent with models of "fast" reconnection. The QSL currents also appear to be unbounded but give rise to weaker singularities, independent of the perturbation amplitude.

text: Current singularities at Quasi-separatrix layers and three-dimensional magnetic nulls The open problem of how singular current structures form in line-tied, three-dimensional magnetic fields is addressed. A Lagrangian magneto-frictional relaxation method is employed to model the field evolution toward the final near-singular state. Our starting point is an exact force-free solution of the governing magnetohydrodynamic equations that is sufficiently general to allow for topological features like magnetic nulls to be inside or outside the computational domain, depending on a simple set of parameters. Quasi-separatrix layers (QSLs) are present in these structures and, together with the magnetic nulls, they significantly influence the accumulation of current. It is shown that perturbations affecting the lateral boundaries of the configuration lead not only to collapse around the magnetic null but also to significant QSL currents. Our results show that once a magnetic null is present, the developing currents are always attracted to that specific location and show a much stronger scaling with resolution than the currents that form along the QSL. In particular, the null-point scalings can be consistent with models of "fast" reconnection. The QSL currents also appear to be unbounded but give rise to weaker singularities, independent of the perturbation amplitude.

year: 2014-11-10

title: He Māori, He Turi, He Turi, He Māori. Advancing the aspirations of Māori Deaf with their indigenous Connections: A case study

authors: Dunn, Katie Merepaea

subjects: Māori Deaf

abstract: Indigenous peoples consider their connection to whenua (land), whakapapa (genealogy), te reo (language) and tikanga (cultural values) to be an integral part of their worldview (Mead, 2003 & Barlow, 1991).

The identity struggle for indigenous minorities living within a colonised environment has been well documented (Bishop, 1995; Smith G, 1997; Smith L, 1999, & Walker, 2004). The controversies over land, customs, culture and language are major issues to understanding and maintaining one’s own cultural identity and, when considering the Deaf indigenous minorities, the task seems colossal.

When a Māori individual belongs to the hearing majority, the ability to find a place to stand, a connection to one’s turangawaewae (standing place), whakapapa, and marae (village) can be a personal struggle; however, this can often be overcome through a shared experience, through communication at a whānau (family), hapū (sub tribe) and iwi (tribe) level.  However, when the individual is part of a double minority such as the Māori Deaf community, the ability to engage and establish a relationship to enhance their connection to their turangawaewae, can become difficult due to the need to communicate in three different languages: English, Māori and Sign Language.  These language issues can create barriers for the Deaf, Māori and hearing communities at a whānau, hapū and iwi level.

This thesis examines a series of workshops created to advance the indigenous connections and understanding within the Māori Deaf community and Te Ao Māori (Māori worldview). It explores how the integration of the Deaf and hearing, indigenous Māori language and New Zealand Sign Language along with practical workshops can assist the aspirations of Māori Deaf within the advancement of Te Ao Māori and Te Reo Māori.  Within this thesis I will undertake a series of interviews with participants who are at the forefront of the Māori Deaf community. A suggestion of moving forward to address the needs of the Māori Deaf community within the desire to connect to their Māori language and customs is also offered within this thesis.

text: He Māori, He Turi, He Turi, He Māori. Advancing the aspirations of Māori Deaf with their indigenous Connections: A case study Indigenous peoples consider their connection to whenua (land), whakapapa (genealogy), te reo (language) and tikanga (cultural values) to be an integral part of their worldview (Mead, 2003 & Barlow, 1991).

The identity struggle for indigenous minorities living within a colonised environment has been well documented (Bishop, 1995; Smith G, 1997; Smith L, 1999, & Walker, 2004). The controversies over land, customs, culture and language are major issues to understanding and maintaining one’s own cultural identity and, when considering the Deaf indigenous minorities, the task seems colossal.

When a Māori individual belongs to the hearing majority, the ability to find a place to stand, a connection to one’s turangawaewae (standing place), whakapapa, and marae (village) can be a personal struggle; however, this can often be overcome through a shared experience, through communication at a whānau (family), hapū (sub tribe) and iwi (tribe) level.  However, when the individual is part of a double minority such as the Māori Deaf community, the ability to engage and establish a relationship to enhance their connection to their turangawaewae, can become difficult due to the need to communicate in three different languages: English, Māori and Sign Language.  These language issues can create barriers for the Deaf, Māori and hearing communities at a whānau, hapū and iwi level.

This thesis examines a series of workshops created to advance the indigenous connections and understanding within the Māori Deaf community and Te Ao Māori (Māori worldview). It explores how the integration of the Deaf and hearing, indigenous Māori language and New Zealand Sign Language along with practical workshops can assist the aspirations of Māori Deaf within the advancement of Te Ao Māori and Te Reo Māori.  Within this thesis I will undertake a series of interviews with participants who are at the forefront of the Māori Deaf community. A suggestion of moving forward to address the needs of the Māori Deaf community within the desire to connect to their Māori language and customs is also offered within this thesis.

year: 2012