title: Characterising the temperature dependence of anaerobic CH₄ and CO₂ production from intact and drained New Zealand peatlands

authors: Wheatley-Wilson, Alice

subjects: Methane

abstract: Understanding the temperature response of anaerobic microbial processes in wetlands is important in determining consequences for carbon dynamics and the production of methane (CH₄) under climate warming scenarios. Natural wetlands, including peatlands, contribute roughly 30% of global CH₄ emissions, making them the largest natural source of CH₄. The transfer of carbon-based greenhouse gases (C-GHG) to the atmosphere produced from the significant amounts of organic matter stored in anaerobic environments could cause a positive feedback to climate warming. This is concerning for peatlands as these environments hold enormous global carbon stocks and given projected global temperature increases. The consensus of previous work suggests that climate warming will result in the acceleration of organic matter decomposition, stimulating CH₄ and carbon dioxide (CO₂) emissions from peatlands. However, the poorly constrained temperature response of CH₄ production continues to plague ecosystem models, due to a lack of understanding of the parameters controlling this process. Despite the importance of wetlands as global sources of CH₄, there is uncertainty among CH₄ production versus temperature models in these environments. Verifying models over a larger temperature range enables us to extract information from a dataset and capture important features such as the temperature optimum or point of rate decline. Therefore, to extract meaningful information on the temperature response of wetland methane production, we collected data on the response across a large temperature range to capture the full curvature of the response. We generated detailed temperature response curves of CH₄ production from two New Zealand peatlands. As far as we are aware, these data are unique in the international literature and provide new information for interpreting ecosystem-scale fluxes. To improve our understanding, we quantified the temperature response of anaerobic organic matter decomposition into CH₄ and anaerobic CO₂ for both an intact and a drained New Zealand peatland. We also compared anaerobic CH₄ and CO₂ production rates across different vegetation types by examining different locations within the intact site. Understanding the difference in C-GHG production potential from contrasting land uses has important implications for managing peat soils and when considering the effects of rewetting drained systems and for comparing the relative net climate forcing of each ecosystem. We developed a methodology for anaerobic peat sampling and performed laboratory incubations for both intact and drained peat. Peat samples were incubated for four days in a temperature gradient block ranging from 8.5–51°C, with 18 discrete temperatures that allowed three replicates at each temperature. Using Macromolecular Rate Theory (MMRT), we derived temperature response metrics for anaerobic CH₄ and CO₂ production, including the temperature optimum (Tₒₚₜ) and the inflection point (Tᵢₙբ). The Tₒₚₜ for CH₄ production ranged from 30.1–32.8°C and Tᵢₙբ values ranged from 23.3–25.6°C. The temperature response did not significantly differ between sites for CH₄, and each peak was relatively tightly constrained, with a sharp increase in production rates at around 15–20°C, followed by a rapid decline in rates above the Tₒₚₜ. On the other hand, the anaerobic CO₂ production curves were less constrained by temperature and differed across sites. Both Tₒₚₜ and Tᵢₙբ were higher for anaerobic CO₂ compared to CH₄, with Tₒₚₜ ranging from 35.4- 44°C and Tᵢₙբ ranging from 25–32.2°C. Overall, this study observed that anaerobic CH₄ and CO₂ production in intact and drained peatlands in New Zealand showed a response with temperature that was well described using MMRT. Despite differences in curvature, temperature metrics did not significantly differ between sites. Anaerobic CO₂ was produced at much higher rates than CH₄, however, the source of the CO₂ is unclear. Additionally, the molar ratio of CO₂:CH₄ increased dramatically above methanogenic Tₒₚₜ. This may provide a positive feedback to the carbon cycle and have important implications for the rewetting of drained peat.

text: Characterising the temperature dependence of anaerobic CH₄ and CO₂ production from intact and drained New Zealand peatlands Understanding the temperature response of anaerobic microbial processes in wetlands is important in determining consequences for carbon dynamics and the production of methane (CH₄) under climate warming scenarios. Natural wetlands, including peatlands, contribute roughly 30% of global CH₄ emissions, making them the largest natural source of CH₄. The transfer of carbon-based greenhouse gases (C-GHG) to the atmosphere produced from the significant amounts of organic matter stored in anaerobic environments could cause a positive feedback to climate warming. This is concerning for peatlands as these environments hold enormous global carbon stocks and given projected global temperature increases. The consensus of previous work suggests that climate warming will result in the acceleration of organic matter decomposition, stimulating CH₄ and carbon dioxide (CO₂) emissions from peatlands. However, the poorly constrained temperature response of CH₄ production continues to plague ecosystem models, due to a lack of understanding of the parameters controlling this process. Despite the importance of wetlands as global sources of CH₄, there is uncertainty among CH₄ production versus temperature models in these environments. Verifying models over a larger temperature range enables us to extract information from a dataset and capture important features such as the temperature optimum or point of rate decline. Therefore, to extract meaningful information on the temperature response of wetland methane production, we collected data on the response across a large temperature range to capture the full curvature of the response. We generated detailed temperature response curves of CH₄ production from two New Zealand peatlands. As far as we are aware, these data are unique in the international literature and provide new information for interpreting ecosystem-scale fluxes. To improve our understanding, we quantified the temperature response of anaerobic organic matter decomposition into CH₄ and anaerobic CO₂ for both an intact and a drained New Zealand peatland. We also compared anaerobic CH₄ and CO₂ production rates across different vegetation types by examining different locations within the intact site. Understanding the difference in C-GHG production potential from contrasting land uses has important implications for managing peat soils and when considering the effects of rewetting drained systems and for comparing the relative net climate forcing of each ecosystem. We developed a methodology for anaerobic peat sampling and performed laboratory incubations for both intact and drained peat. Peat samples were incubated for four days in a temperature gradient block ranging from 8.5–51°C, with 18 discrete temperatures that allowed three replicates at each temperature. Using Macromolecular Rate Theory (MMRT), we derived temperature response metrics for anaerobic CH₄ and CO₂ production, including the temperature optimum (Tₒₚₜ) and the inflection point (Tᵢₙբ). The Tₒₚₜ for CH₄ production ranged from 30.1–32.8°C and Tᵢₙբ values ranged from 23.3–25.6°C. The temperature response did not significantly differ between sites for CH₄, and each peak was relatively tightly constrained, with a sharp increase in production rates at around 15–20°C, followed by a rapid decline in rates above the Tₒₚₜ. On the other hand, the anaerobic CO₂ production curves were less constrained by temperature and differed across sites. Both Tₒₚₜ and Tᵢₙբ were higher for anaerobic CO₂ compared to CH₄, with Tₒₚₜ ranging from 35.4- 44°C and Tᵢₙբ ranging from 25–32.2°C. Overall, this study observed that anaerobic CH₄ and CO₂ production in intact and drained peatlands in New Zealand showed a response with temperature that was well described using MMRT. Despite differences in curvature, temperature metrics did not significantly differ between sites. Anaerobic CO₂ was produced at much higher rates than CH₄, however, the source of the CO₂ is unclear. Additionally, the molar ratio of CO₂:CH₄ increased dramatically above methanogenic Tₒₚₜ. This may provide a positive feedback to the carbon cycle and have important implications for the rewetting of drained peat.

year: 2021

title: The quantification of external colour changes during sexual transition in the protogynous spotty wrasse Notolabrus celidotus

authors: de Farias e Moraes, Carlos Eduardo

subjects: sex change

abstract: Hermaphroditism in fish has been well documented. Protogynous hermaphrodites (female to male sex change) are normally found in a polygamous social hierarchy. The male is the dominant within the group, followed by the largest female and it is common to observe aggressive behaviour as an exercise of dominance. Most of the studies relating to sex change used tropical species as models, however, little is known about temperate species. In this research, Notolabrus celidotus, a temperate protogynous wrasse, was used to investigate sex change. The overall goal was to develop an accurate methodology to assist with colour analysis of an external landmark. Ten males and ten females had pictures taken from the whole body. Digital photography and computational image analysis programs were used to help quantify the colour. Results were found through circular statistics, as hue is read as an angle. It was found that the anal fin presented the most significant mean variation of hue, within the body (female = 95.353 ± 3.16°; male = 141.138 ± 17.23°). The technique was then used to quantify the colour changes of the anal fin as individuals transitioned from female to male. Histological examination was also analysed and classified according to the transitional phase of every fish. The developed technique was able to track the colour changes and allocate them into distinct sexual transition stages. Statistical analysis showed that major colour changes began at the mid-transitional stage and progressed until the terminal phase male was achieved. The histological analysis of the gonads contributed to the study demonstrating internal changes through each sexual stage, additionally showing connection between the changes internally and externally. Through the development of a method to quantify external colour in relation to sexual state, this work creates opportunities for future studies. Investigations of sex change in this species can now be conducted without the need for invasive or destructive sampling to identify sex changing individuals. Further to this, individuals that are at different stages of sexual transition may be identified and selected for sampling by their external colour. Overall, this study was able to quantify and allocate external colour changes into distinct stages that map the restructure of the gonads during sex change.

text: The quantification of external colour changes during sexual transition in the protogynous spotty wrasse Notolabrus celidotus Hermaphroditism in fish has been well documented. Protogynous hermaphrodites (female to male sex change) are normally found in a polygamous social hierarchy. The male is the dominant within the group, followed by the largest female and it is common to observe aggressive behaviour as an exercise of dominance. Most of the studies relating to sex change used tropical species as models, however, little is known about temperate species. In this research, Notolabrus celidotus, a temperate protogynous wrasse, was used to investigate sex change. The overall goal was to develop an accurate methodology to assist with colour analysis of an external landmark. Ten males and ten females had pictures taken from the whole body. Digital photography and computational image analysis programs were used to help quantify the colour. Results were found through circular statistics, as hue is read as an angle. It was found that the anal fin presented the most significant mean variation of hue, within the body (female = 95.353 ± 3.16°; male = 141.138 ± 17.23°). The technique was then used to quantify the colour changes of the anal fin as individuals transitioned from female to male. Histological examination was also analysed and classified according to the transitional phase of every fish. The developed technique was able to track the colour changes and allocate them into distinct sexual transition stages. Statistical analysis showed that major colour changes began at the mid-transitional stage and progressed until the terminal phase male was achieved. The histological analysis of the gonads contributed to the study demonstrating internal changes through each sexual stage, additionally showing connection between the changes internally and externally. Through the development of a method to quantify external colour in relation to sexual state, this work creates opportunities for future studies. Investigations of sex change in this species can now be conducted without the need for invasive or destructive sampling to identify sex changing individuals. Further to this, individuals that are at different stages of sexual transition may be identified and selected for sampling by their external colour. Overall, this study was able to quantify and allocate external colour changes into distinct stages that map the restructure of the gonads during sex change.

year: 2019

title: Indigenous service programs plus indigenous evaluator equals Whitestream evaluation - What's wrong with this picture? (Reflections from my PhD)

authors: Masters-Awatere, Bridgette

abstract: For the past 100 or so years, formal evaluation has taken its lead from frameworks that originate from a culturally blind standpoint. Worldwide the major influence on evaluation practice comes from the United States of America. The absence of non-dominant (or indigenous) culturally constructed frameworks has been replicated around the world.
Before the formation of the Aotearoa New Zealand Evaluation Association (ANZEA), as a NZ specific evaluation group, practitioners generally belonged to the Australasian Evaluation Society (AES) and joined in the sharing, adoption and adaptation of USAs Program Evaluation Standards. However, the context of evaluation in New Zealand has been somewhat different from the rest of the world, becoming more culturally centred than other countries. The role and place of the Treaty of Waitangi has been acknowledged as an attributing factor by ANZEA.
Four indigenous, externally evaluated “By Maori for Maori”, health & wellbeing programmes were used as case studies within my research. I draw upon examples from the cases studies to highlight the vulnerable and contentious position indigenous service providers and indigenous evaluators were in. Adapting Sandra Grande’s (2003) analysis, I critiqued the context of the case study evaluations that commissioners considered as Kaupapa Maori. In this presentation I argue that while stakeholders perceived the work to be an indigenous evaluation, the case studies demonstrate that whitestream evaluation was prevalent.

text: Indigenous service programs plus indigenous evaluator equals Whitestream evaluation - What's wrong with this picture? (Reflections from my PhD) For the past 100 or so years, formal evaluation has taken its lead from frameworks that originate from a culturally blind standpoint. Worldwide the major influence on evaluation practice comes from the United States of America. The absence of non-dominant (or indigenous) culturally constructed frameworks has been replicated around the world.
Before the formation of the Aotearoa New Zealand Evaluation Association (ANZEA), as a NZ specific evaluation group, practitioners generally belonged to the Australasian Evaluation Society (AES) and joined in the sharing, adoption and adaptation of USAs Program Evaluation Standards. However, the context of evaluation in New Zealand has been somewhat different from the rest of the world, becoming more culturally centred than other countries. The role and place of the Treaty of Waitangi has been acknowledged as an attributing factor by ANZEA.
Four indigenous, externally evaluated “By Maori for Maori”, health & wellbeing programmes were used as case studies within my research. I draw upon examples from the cases studies to highlight the vulnerable and contentious position indigenous service providers and indigenous evaluators were in. Adapting Sandra Grande’s (2003) analysis, I critiqued the context of the case study evaluations that commissioners considered as Kaupapa Maori. In this presentation I argue that while stakeholders perceived the work to be an indigenous evaluation, the case studies demonstrate that whitestream evaluation was prevalent.

year: 2015