title: Wrap up summary of the day

authors: Madsen, John

abstract: Summary of Day 1 2015 LakesWater Quality Society conference.

text: Wrap up summary of the day Summary of Day 1 2015 LakesWater Quality Society conference.

year: 2015

title: Efficacy of Borides in Grain Refining Al-Si Alloys

authors: Bolzoni, Leandro

abstract: The grain refining efficacy of titanium, aluminum, and niobium borides, as well as niobium aluminides, introduced via commercial and lab made master alloys on Al-Si alloys was investigated. Significant grain refinement is achieved via the introduction of these heterogeneous nuclei regardless of their chemistry, stoichiometry of the master alloy, and addition rate. However, the grain refinement is affected by variable such as contact time, as the inoculating particle may sediment or be poisoned, and cooling rate. Specifically, a faster cooling rate generally leads to finer grains due to the lower time for grain growth. In the case of borides, the chemical inoculation efficiency is greatly affected by their thermodynamic stability in molten Al-Si alloys. Conversely, the grain refining potency of properitectic Al3Nb remains unaffected. The underlying grain refining mechanism was finally investigated using current models based on the growth restriction factor Q to simultaneously consider the effect of nucleant potency and alloy chemistry. Among Ti-, Al-, and Nb-based borides with similar particle size and distribution, the latter are the most efficient to grain refine Al-Si alloys.

text: Efficacy of Borides in Grain Refining Al-Si Alloys The grain refining efficacy of titanium, aluminum, and niobium borides, as well as niobium aluminides, introduced via commercial and lab made master alloys on Al-Si alloys was investigated. Significant grain refinement is achieved via the introduction of these heterogeneous nuclei regardless of their chemistry, stoichiometry of the master alloy, and addition rate. However, the grain refinement is affected by variable such as contact time, as the inoculating particle may sediment or be poisoned, and cooling rate. Specifically, a faster cooling rate generally leads to finer grains due to the lower time for grain growth. In the case of borides, the chemical inoculation efficiency is greatly affected by their thermodynamic stability in molten Al-Si alloys. Conversely, the grain refining potency of properitectic Al3Nb remains unaffected. The underlying grain refining mechanism was finally investigated using current models based on the growth restriction factor Q to simultaneously consider the effect of nucleant potency and alloy chemistry. Among Ti-, Al-, and Nb-based borides with similar particle size and distribution, the latter are the most efficient to grain refine Al-Si alloys.

year: 2018

title: Pātangaroa: Co-developing management strategies for a starfish outbreak in Ōhiwa Harbour

authors: Ranapia, Megan

subjects: marine management

abstract: The management of marine environments often prioritises scientific information to address complex marine social-ecological issues. However, there is a wealth of learning to be gained from Indigenous people who have generated place-based intergenerational understandings and cultural ethics and practices. Consequently, Indigenous knowledge alongside science can offer better insights, holistic understanding, sustainable management strategies and greater sources of evidence. This research is located in Aotearoa New Zealand and engages in mātauranga Māori (Māori knowledge) alongside marine ecology as an appropriate method for contemporary marine research and management. The thesis study focused on Ōhiwa Harbour, aiming to co-develop a starfish management action plan (SMAP) with local iwi (tribe) Ngāti Awa and other affiliated iwi, district councils and regional council to address the overabundant starfish (species: Coscinasterias muricata and Patiriella regularis). By engaging in transdisciplinary research and collaborative decision-making, this study sought to bridge the gap between Indigenous knowledge and mainstream science, offering lessons for inclusive marine management practices.

To achieve this, I developed and prescribed a co-developed framework actively promoting a mixed-methods approach, inclusive of kaupapa Māori research methodologies, tikanga, participatory design, applied mātauranga ā iwi, quantitative marine scientific field methods and experimental study design. Through the collaborative process, I identified areas of appropriate research aims and methods. This included co-developing a novel starfish trapping methodology sensitive to local ecology and cultural values and an experimental starfish removal study to assist decision-makers in implementing an efficient and effective starfish removal regime as an approach to management.

Results from the field studies showed the efficacy of starfish traps is dependent on environmental conditions, physical characteristics and soaking time (the length of time the trap is left in the water). A soaking time of 48 h maintained the highest starfish catch per unit effort (CPUE) while minimising time to re-bait and reset traps. Observations also indicated an open trap design had less bycatch than a semi-enclosed box trap and could withstand the tidal currents for a longer period. The findings found that bait type did not impact on CPUE. In the starfish removal study, the combined effort of diver removals and trapping produced higher daily catch rates than the single treatments (i.e., diver removals only or trapping only), therefore was themost efficient removal method. The empirical information gathered from the field studies was then used to inform the SMAP and was accepted unanimously at the highest local/regional co-management level. Furthermore, through the findings I identified future research opportunities that would further close gaps in our knowledge around the best management approaches for a starfish outbreak. These included investigation into the predation impacts of P. regularis on mussel recruitment, identification of alternative restoration sites less susceptible to starfish predation pressures and investigation of potential drivers of the starfish outbreak.

Overall, the acceptance of the SMAP by local iwi/hapū and government authorities underscores the success of the collaborative approach. The collaborative process not only addresses the immediate concerns of starfish infestation but contributed to the broader goal of supporting kaitiakitanga (active guardianship) responsibilities and promoting Indigenous perspectives in marine management. This thesis demonstrates and recommends a new approach to starfish management in coastal marine areas using both marine science and mātauranga Māori understandings, practices and ethics, furthermore, it demonstrates the commitment to the inclusion of multiple knowledge systems and involvement of communities.

text: Pātangaroa: Co-developing management strategies for a starfish outbreak in Ōhiwa Harbour The management of marine environments often prioritises scientific information to address complex marine social-ecological issues. However, there is a wealth of learning to be gained from Indigenous people who have generated place-based intergenerational understandings and cultural ethics and practices. Consequently, Indigenous knowledge alongside science can offer better insights, holistic understanding, sustainable management strategies and greater sources of evidence. This research is located in Aotearoa New Zealand and engages in mātauranga Māori (Māori knowledge) alongside marine ecology as an appropriate method for contemporary marine research and management. The thesis study focused on Ōhiwa Harbour, aiming to co-develop a starfish management action plan (SMAP) with local iwi (tribe) Ngāti Awa and other affiliated iwi, district councils and regional council to address the overabundant starfish (species: Coscinasterias muricata and Patiriella regularis). By engaging in transdisciplinary research and collaborative decision-making, this study sought to bridge the gap between Indigenous knowledge and mainstream science, offering lessons for inclusive marine management practices.

To achieve this, I developed and prescribed a co-developed framework actively promoting a mixed-methods approach, inclusive of kaupapa Māori research methodologies, tikanga, participatory design, applied mātauranga ā iwi, quantitative marine scientific field methods and experimental study design. Through the collaborative process, I identified areas of appropriate research aims and methods. This included co-developing a novel starfish trapping methodology sensitive to local ecology and cultural values and an experimental starfish removal study to assist decision-makers in implementing an efficient and effective starfish removal regime as an approach to management.

Results from the field studies showed the efficacy of starfish traps is dependent on environmental conditions, physical characteristics and soaking time (the length of time the trap is left in the water). A soaking time of 48 h maintained the highest starfish catch per unit effort (CPUE) while minimising time to re-bait and reset traps. Observations also indicated an open trap design had less bycatch than a semi-enclosed box trap and could withstand the tidal currents for a longer period. The findings found that bait type did not impact on CPUE. In the starfish removal study, the combined effort of diver removals and trapping produced higher daily catch rates than the single treatments (i.e., diver removals only or trapping only), therefore was themost efficient removal method. The empirical information gathered from the field studies was then used to inform the SMAP and was accepted unanimously at the highest local/regional co-management level. Furthermore, through the findings I identified future research opportunities that would further close gaps in our knowledge around the best management approaches for a starfish outbreak. These included investigation into the predation impacts of P. regularis on mussel recruitment, identification of alternative restoration sites less susceptible to starfish predation pressures and investigation of potential drivers of the starfish outbreak.

Overall, the acceptance of the SMAP by local iwi/hapū and government authorities underscores the success of the collaborative approach. The collaborative process not only addresses the immediate concerns of starfish infestation but contributed to the broader goal of supporting kaitiakitanga (active guardianship) responsibilities and promoting Indigenous perspectives in marine management. This thesis demonstrates and recommends a new approach to starfish management in coastal marine areas using both marine science and mātauranga Māori understandings, practices and ethics, furthermore, it demonstrates the commitment to the inclusion of multiple knowledge systems and involvement of communities.

year: 2025-05