title: Local and regional influences over soil microbial metacommunities in the Transantarctic Mountains

authors: Sokol, Eric R.

subjects: Science & Technology

abstract: The metacommunity concept provides a useful framework to assess the influence of local and regional controls over diversity patterns. Culture‐independent studies of soil microbial communities in the McMurdo Dry Valleys of East Antarctica (77° S) have shown that bacterial diversity is related to soil geochemical gradients, while studies targeting edaphic cyanobacteria have linked local diversity patterns to dispersal‐based processes. In this study, we increased the spatial extent of observed soil microbial communities to cover the Beardmore Glacier region in the central Transantarctic Mountains (84° S). We used community profiling techniques to characterize diversity patterns for bacteria and the cyanobacterial subcomponent of the microbial community. Diversity partitioning was used to calculate beta diversity and estimate among‐site dissimilarity in the metacommunity. We then used variation partitioning to assess the relationship between beta diversity and environmental and spatial gradients. We found that dominant groups in the soil bacterial metacommunity were influenced by gradients in pH and soil moisture at the Transantarctic scale (800 km). Conversely, beta diversity for the cyanobacterial component of the edaphic microbial metacommunity was decoupled from these environmental gradients, and was more related to spatial filters, suggesting that wind‐driven dispersal dynamics created cyanobacterial biogeography at a local scale (<3 km).

text: Local and regional influences over soil microbial metacommunities in the Transantarctic Mountains The metacommunity concept provides a useful framework to assess the influence of local and regional controls over diversity patterns. Culture‐independent studies of soil microbial communities in the McMurdo Dry Valleys of East Antarctica (77° S) have shown that bacterial diversity is related to soil geochemical gradients, while studies targeting edaphic cyanobacteria have linked local diversity patterns to dispersal‐based processes. In this study, we increased the spatial extent of observed soil microbial communities to cover the Beardmore Glacier region in the central Transantarctic Mountains (84° S). We used community profiling techniques to characterize diversity patterns for bacteria and the cyanobacterial subcomponent of the microbial community. Diversity partitioning was used to calculate beta diversity and estimate among‐site dissimilarity in the metacommunity. We then used variation partitioning to assess the relationship between beta diversity and environmental and spatial gradients. We found that dominant groups in the soil bacterial metacommunity were influenced by gradients in pH and soil moisture at the Transantarctic scale (800 km). Conversely, beta diversity for the cyanobacterial component of the edaphic microbial metacommunity was decoupled from these environmental gradients, and was more related to spatial filters, suggesting that wind‐driven dispersal dynamics created cyanobacterial biogeography at a local scale (<3 km).

year: 2013

title: Nitrogen-15 isotope enrichment in benthic boundary layer gases of a stratified eutrophic iron and manganese rich lake

authors: Pearson, Lisa Kyle

subjects: nitrogen isotope

abstract: The applicability of the natural abundance of nitrogen gas isotope ratios was used to indicate the spatial distribution of nitrogen transformations in the water column and sediment pore waters of Lake Ngapouri, a small (area 0.19 km²), monomictic, eutrophic lake in the Taupo Volcanic Zone, North Island, New Zealand. Samples were collected from the epilimnion, hypolimnion, benthic boundary layer and at 5-cm intervals from the sediment pore waters at monthly intervals for 1 year. Values of δ¹⁵N [N2] ranged from -1 to 0.28%₀in the epilimnion, -1.5 to 1.25%₀ in the hypolimnion, -1.8 to 12.2%₀ in the benthic boundary layer and -0.7 to 3.5% in sediment pore waters. Values of δ¹⁵ [N₂] showed a strong seasonal pattern that was related to the loss of dissolved oxygen in the hypolimnion during seasonal stratification. Increases in 15N-enriched dinitrogen take place in the benthic boundary layer during the periods of anoxia (taken to be dissolved oxygen concentrations <6.3 µM) and may be related to abundant ammonium substrate (up to 275 µM) to support denitrification. Nitrate concentrations increased up to 36 µM with increasing duration of anoxia. We hypothesise that an alternative electron acceptor besides oxygen is required to support the nitrification needed for the production of nitrate. Iron and manganese hydroxides and oxides from material sedimenting out of the water column may have induced chemo-nitrification sufficient to oxidise ammonium in the anoxic benthic boundary layer. The nitrate formed would mostly be rapidly denitrified so that the δ¹⁵N[N₂] would continue to become enriched during the presence of anoxia, as observed in hypolimnion and benthic boundary layer of Lake Ngapouri. The changes in δ¹⁵N [N₂] values indicate the potential use of isotope ratios to identify and quantify potential chemonitrification/denitrification in the water column and sediment pore waters of lakes.

text: Nitrogen-15 isotope enrichment in benthic boundary layer gases of a stratified eutrophic iron and manganese rich lake The applicability of the natural abundance of nitrogen gas isotope ratios was used to indicate the spatial distribution of nitrogen transformations in the water column and sediment pore waters of Lake Ngapouri, a small (area 0.19 km²), monomictic, eutrophic lake in the Taupo Volcanic Zone, North Island, New Zealand. Samples were collected from the epilimnion, hypolimnion, benthic boundary layer and at 5-cm intervals from the sediment pore waters at monthly intervals for 1 year. Values of δ¹⁵N [N2] ranged from -1 to 0.28%₀in the epilimnion, -1.5 to 1.25%₀ in the hypolimnion, -1.8 to 12.2%₀ in the benthic boundary layer and -0.7 to 3.5% in sediment pore waters. Values of δ¹⁵ [N₂] showed a strong seasonal pattern that was related to the loss of dissolved oxygen in the hypolimnion during seasonal stratification. Increases in 15N-enriched dinitrogen take place in the benthic boundary layer during the periods of anoxia (taken to be dissolved oxygen concentrations <6.3 µM) and may be related to abundant ammonium substrate (up to 275 µM) to support denitrification. Nitrate concentrations increased up to 36 µM with increasing duration of anoxia. We hypothesise that an alternative electron acceptor besides oxygen is required to support the nitrification needed for the production of nitrate. Iron and manganese hydroxides and oxides from material sedimenting out of the water column may have induced chemo-nitrification sufficient to oxidise ammonium in the anoxic benthic boundary layer. The nitrate formed would mostly be rapidly denitrified so that the δ¹⁵N[N₂] would continue to become enriched during the presence of anoxia, as observed in hypolimnion and benthic boundary layer of Lake Ngapouri. The changes in δ¹⁵N [N₂] values indicate the potential use of isotope ratios to identify and quantify potential chemonitrification/denitrification in the water column and sediment pore waters of lakes.

year: 2012

title: Kia whakatōmuri te haere whakamua – A Māori framework for coastal climate change adaptation

authors: Bailey-Winiata, Akuhata

subjects: Climate Change Adaptation

abstract: Current climate change adaptation frameworks do not sufficiently represent or acknowledge the intricacies and complex nature of climate adaptation for all communities. This thesis contributes a Māori (Indigenous peoples of Aotearoa New Zealand (A-NZ)) climate adaptation framework that is informed by Te Ao Māori world views, mātauranga Māori (Māori knowledge), Te Tiriti o Waitangi (Treaty of Waitangi) and research at the interface of Western knowledge and mātauranga Māori. This is needed to promote a more equitable and culturally sensitive approach to the current climate change adaptation process for hapū (sub-tribes) and iwi (tribes). To achieve this, this thesis is rooted in the whakataukī (proverb) “Kia whakatōmuri te haere whakamua – I walk backwards into the future with my eyes fixed on my past”, which exemplifies the power of acknowledging Māori history and intergenerational knowledge, while moving forward to a prosperous future. This thesis had four key aims. First, I looked to the past to understand ways Māori ancestors adapted and relocated in response to natural hazards to inform a future climate adaptation or relocation process. Second, I took stock of the contemporary risk to coastal marae (Māori meeting grounds) from sea level rise. Third, I looked internationally at other Indigenous communities' adaptation challenges and how they have overcome them as a mutual learning opportunity. And finally, I developed a conceptual Māori climate adaptation framework based on existing models and informed by a wānanga (workshop) with over 100 Māori participants. This two-part framework emphasises the importance of fostering Te Tiriti-centric relationships and partnerships that are essential for climate adaptation with hapū and iwi. In addition, it serves as a guide to support adaptation decision-making for hapū and iwi Māori. This thesis took a multidisciplinary approach to achieve these aims, incorporating historical and archival analyses, semi-structured interviews, a systematic review, coastal flooding and exposure analyses using spatial information, and wānanga. The findings highlighted that relocation due to natural hazards is not uncommon for Māori, as this thesis identified 51 examples of where relocation was completed or discussed in response to natural hazards. Furthermore, in a case study with Tūhourangi and Ngāti Rangitihi, this thesis identified vital aspects that enabled their relocation following the 1886 Tarawera eruption, the most influential being tuku whenua – the gifting of land to relocate to. This thesis also identified that by 2150, under shared socio-economic pathway (SSP) 5-8.5, 27% and 28% of coastal marae (total of 186 nationally) are exposed to a 100–year and 1000–year annual recurrence interval (ARI) extreme sea level events, respectively. Overall, this thesis contributes to our understanding of the requirements to support hapū and iwi Māori in climate adaptation, with parallels to other Indigenous communities. Requirements include resourcing, partnerships, autonomy, intergenerational planning, recognition, respect and redress. In Chapter 8 – the discussion of this thesis, we focus on four overall contributions this thesis has made, which are: 1) Hapū and iwi Māori are at risk of climate change, 2) We’ve done it before we can do it again, 3) Adaptation approach cannot be one-size-fits-all, and 4) Adaptation in Aotearoa needs a Te Tiriti-centric approach. Ultimately, this thesis underscores the urgent need for inclusive climate adaptation strategies that honour Indigenous knowledge systems, ensuring that hapū and iwi Māori are not only heard but are actively supported in navigating the impacts of climate change.

text: Kia whakatōmuri te haere whakamua – A Māori framework for coastal climate change adaptation Current climate change adaptation frameworks do not sufficiently represent or acknowledge the intricacies and complex nature of climate adaptation for all communities. This thesis contributes a Māori (Indigenous peoples of Aotearoa New Zealand (A-NZ)) climate adaptation framework that is informed by Te Ao Māori world views, mātauranga Māori (Māori knowledge), Te Tiriti o Waitangi (Treaty of Waitangi) and research at the interface of Western knowledge and mātauranga Māori. This is needed to promote a more equitable and culturally sensitive approach to the current climate change adaptation process for hapū (sub-tribes) and iwi (tribes). To achieve this, this thesis is rooted in the whakataukī (proverb) “Kia whakatōmuri te haere whakamua – I walk backwards into the future with my eyes fixed on my past”, which exemplifies the power of acknowledging Māori history and intergenerational knowledge, while moving forward to a prosperous future. This thesis had four key aims. First, I looked to the past to understand ways Māori ancestors adapted and relocated in response to natural hazards to inform a future climate adaptation or relocation process. Second, I took stock of the contemporary risk to coastal marae (Māori meeting grounds) from sea level rise. Third, I looked internationally at other Indigenous communities' adaptation challenges and how they have overcome them as a mutual learning opportunity. And finally, I developed a conceptual Māori climate adaptation framework based on existing models and informed by a wānanga (workshop) with over 100 Māori participants. This two-part framework emphasises the importance of fostering Te Tiriti-centric relationships and partnerships that are essential for climate adaptation with hapū and iwi. In addition, it serves as a guide to support adaptation decision-making for hapū and iwi Māori. This thesis took a multidisciplinary approach to achieve these aims, incorporating historical and archival analyses, semi-structured interviews, a systematic review, coastal flooding and exposure analyses using spatial information, and wānanga. The findings highlighted that relocation due to natural hazards is not uncommon for Māori, as this thesis identified 51 examples of where relocation was completed or discussed in response to natural hazards. Furthermore, in a case study with Tūhourangi and Ngāti Rangitihi, this thesis identified vital aspects that enabled their relocation following the 1886 Tarawera eruption, the most influential being tuku whenua – the gifting of land to relocate to. This thesis also identified that by 2150, under shared socio-economic pathway (SSP) 5-8.5, 27% and 28% of coastal marae (total of 186 nationally) are exposed to a 100–year and 1000–year annual recurrence interval (ARI) extreme sea level events, respectively. Overall, this thesis contributes to our understanding of the requirements to support hapū and iwi Māori in climate adaptation, with parallels to other Indigenous communities. Requirements include resourcing, partnerships, autonomy, intergenerational planning, recognition, respect and redress. In Chapter 8 – the discussion of this thesis, we focus on four overall contributions this thesis has made, which are: 1) Hapū and iwi Māori are at risk of climate change, 2) We’ve done it before we can do it again, 3) Adaptation approach cannot be one-size-fits-all, and 4) Adaptation in Aotearoa needs a Te Tiriti-centric approach. Ultimately, this thesis underscores the urgent need for inclusive climate adaptation strategies that honour Indigenous knowledge systems, ensuring that hapū and iwi Māori are not only heard but are actively supported in navigating the impacts of climate change.

year: 2024-05-28