title: The use of gas–phase substrates to study enzyme catalysis at low hydration

authors: Dunn, Rachel V.

subjects: enzyme

abstract: Although there are varying estimates as to the degree of enzyme hydration required for activity, a threshold value of ca. 0.2 g of water per gram of protein has been widely accepted. The evidence upon which this is based is reviewed here. In particular, results from the use of gas–phase substrates are discussed. Results using solid–phase enzyme–substrate mixtures are not altogether in accord with those obtained using gas–phase substrates. The use of gaseous substrates and products provides an experimental system in which the hydration of the enzyme can be easily controlled, but which is not limited by diffusion. 
All the results show that increasing hydration enhances activity. The results using gas–phase substrates do not support the existence of a critical hydration value below which enzymatic activity is absent, and suggest that enzyme activity is possible at much lower hydrations than previously thought; they do not support the notion that significant hydration of the surface polar groups is required for activity. However, the marked improvement of activity as hydration is increased suggests that water does play a role, perhaps in optimizing the structure or facilitating the flexibility required for maximal activity.

text: The use of gas–phase substrates to study enzyme catalysis at low hydration Although there are varying estimates as to the degree of enzyme hydration required for activity, a threshold value of ca. 0.2 g of water per gram of protein has been widely accepted. The evidence upon which this is based is reviewed here. In particular, results from the use of gas–phase substrates are discussed. Results using solid–phase enzyme–substrate mixtures are not altogether in accord with those obtained using gas–phase substrates. The use of gaseous substrates and products provides an experimental system in which the hydration of the enzyme can be easily controlled, but which is not limited by diffusion. 
All the results show that increasing hydration enhances activity. The results using gas–phase substrates do not support the existence of a critical hydration value below which enzymatic activity is absent, and suggest that enzyme activity is possible at much lower hydrations than previously thought; they do not support the notion that significant hydration of the surface polar groups is required for activity. However, the marked improvement of activity as hydration is increased suggests that water does play a role, perhaps in optimizing the structure or facilitating the flexibility required for maximal activity.

year: 2004

title: Sedimentologic and hydrodynamic trends along a modern fluvial to marine transition zone: Mud deposition in the Lower Waihou River, Aotearoa-New Zealand

authors: Roche, Ben

subjects: Process-response

abstract: The fluvial to marine transition zone (FMTZ) is a dynamic environment, subject to a mixture of marine and riverine forcing mechanisms. These processes control deposition of sediments, which can hold valuable natural resources. However, due to the complex process regime, the sedimentary successions from these areas can be difficult to interpret. This study aims to improve depositional models by linking quantified measurements of the active processes to their deposits along the transition zone, using a modern example of these systems, the Waihou River in the North Island of Aotearoa-New Zealand. This study produced three main findings, which are relevant to people researching ancient shallow marine strata: 1) The locus of mud deposition occurs in the middle of the transition zone due the combined influence of depositional and preservational controls. Mixing of marine and freshwater reduces landward, which limits flocculation, and hence, deposition of mud upstream. In contrast, preservation of mud deposits is reduced towards the mouth of the river as a result of faster flow speeds. Midway between these two endpoints is a region where deposition and preservation of mud is the largest within the FMTZ. 2) Fluid mud deposits are poorly preserved in the deepest parts of channels, likely due to the high energy levels in this environment. Nevertheless, our results do not preclude the possibility that significant accumulations may occur in the shallow parts of the cross-channel profile. 3) Mud facies diversity is an indicator of depositional position along the FMTZ. Facies diversity was greatest at the middle observational site, which corresponds to the area that is subject to the most variable process regime. The landward and seaward ends of the transition zone exhibit a greater level of dominance in solely riverine or marine depositional processes, respectively. This study yields new insights into the process-response relationships for mud deposition at the interface of land to sea.

text: Sedimentologic and hydrodynamic trends along a modern fluvial to marine transition zone: Mud deposition in the Lower Waihou River, Aotearoa-New Zealand The fluvial to marine transition zone (FMTZ) is a dynamic environment, subject to a mixture of marine and riverine forcing mechanisms. These processes control deposition of sediments, which can hold valuable natural resources. However, due to the complex process regime, the sedimentary successions from these areas can be difficult to interpret. This study aims to improve depositional models by linking quantified measurements of the active processes to their deposits along the transition zone, using a modern example of these systems, the Waihou River in the North Island of Aotearoa-New Zealand. This study produced three main findings, which are relevant to people researching ancient shallow marine strata: 1) The locus of mud deposition occurs in the middle of the transition zone due the combined influence of depositional and preservational controls. Mixing of marine and freshwater reduces landward, which limits flocculation, and hence, deposition of mud upstream. In contrast, preservation of mud deposits is reduced towards the mouth of the river as a result of faster flow speeds. Midway between these two endpoints is a region where deposition and preservation of mud is the largest within the FMTZ. 2) Fluid mud deposits are poorly preserved in the deepest parts of channels, likely due to the high energy levels in this environment. Nevertheless, our results do not preclude the possibility that significant accumulations may occur in the shallow parts of the cross-channel profile. 3) Mud facies diversity is an indicator of depositional position along the FMTZ. Facies diversity was greatest at the middle observational site, which corresponds to the area that is subject to the most variable process regime. The landward and seaward ends of the transition zone exhibit a greater level of dominance in solely riverine or marine depositional processes, respectively. This study yields new insights into the process-response relationships for mud deposition at the interface of land to sea.

year: 2022

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