title: Dynamics of silicon in lakes of the Taupo Volcanic Zone, New Zealand, and implications for diatom growth

authors: Pearson, Lisa Kyle

subjects: cyanobacteria

abstract: Intact sediment cores were taken from the deepest basins of 9 lakes in the Taupo Volcanic Zone, New Zealand, to investigate the factors controlling silicon (Si) concentrations in sediment pore waters and the flux of Si to the overlying lake water. The lakes ranged in trophic state from oligotrophic to highly eutrophic. A Si vertical flux model simulated Si gradients in the pore water with high precision (r2 > 0.95, p < 0.01) in lakes with no volcanic tephra layers or significant geothermal inflows. The ubiquitous presence of diatom frustules in the sediment was likely responsible for release of Si to the pore waters and subsequent diffusion to overlying lake waters. Fluxes of Si were related to the trophic status of the lake and were greatest in eutrophic lakes where diatom populations reduced epilimnetic Si concentrations to <1 mg L-1. Temporal variations in the concentrations of Si, nitrogen (N), and phosphorus (P) suggest that over most of the year diatom growth in the oligotrophic lakes is limited by N, or co-limited by N and P. In some eutrophic lakes, Si may limit diatom growth during homothermal conditions, and P and/or N may limit growth when the lake is stratified. The reduction of surface Si concentrations to <0.1 mg L-1 following homothermy in some eutrophic lakes is likely to restrict the growth of diatoms, potentially resulting in increased dominance of nonsiliceous flagellated species and cyanobacteria.

text: Dynamics of silicon in lakes of the Taupo Volcanic Zone, New Zealand, and implications for diatom growth Intact sediment cores were taken from the deepest basins of 9 lakes in the Taupo Volcanic Zone, New Zealand, to investigate the factors controlling silicon (Si) concentrations in sediment pore waters and the flux of Si to the overlying lake water. The lakes ranged in trophic state from oligotrophic to highly eutrophic. A Si vertical flux model simulated Si gradients in the pore water with high precision (r2 > 0.95, p < 0.01) in lakes with no volcanic tephra layers or significant geothermal inflows. The ubiquitous presence of diatom frustules in the sediment was likely responsible for release of Si to the pore waters and subsequent diffusion to overlying lake waters. Fluxes of Si were related to the trophic status of the lake and were greatest in eutrophic lakes where diatom populations reduced epilimnetic Si concentrations to <1 mg L-1. Temporal variations in the concentrations of Si, nitrogen (N), and phosphorus (P) suggest that over most of the year diatom growth in the oligotrophic lakes is limited by N, or co-limited by N and P. In some eutrophic lakes, Si may limit diatom growth during homothermal conditions, and P and/or N may limit growth when the lake is stratified. The reduction of surface Si concentrations to <0.1 mg L-1 following homothermy in some eutrophic lakes is likely to restrict the growth of diatoms, potentially resulting in increased dominance of nonsiliceous flagellated species and cyanobacteria.

year: 2016

title: Cost Optimal Area Allocation in Heat Exchanger Networks

authors: Walmsley, Timothy Gordon

abstract: This paper discusses the cost optimal area allocation in heat exchanger networks.

text: Cost Optimal Area Allocation in Heat Exchanger Networks This paper discusses the cost optimal area allocation in heat exchanger networks.

year: 2013-10-01

title: “It is about enabling Tino Rangatiratanga and Mana Motuhake”: An analysis of submissions on the Pae Ora (Healthy Futures) Bill 2021 endorsing a Māori health authority

authors: Edmonds, Moengaroa

subjects: Health Equity

abstract: Indigenous leadership in healthcare is one way for Indigenous peoples to exercise sovereignty over their health. In Aotearoa New Zealand, the establishment of the Māori Health Authority (MHA) was grounded in a decades-long imperative to address Māori health inequities and operationalise te Tiriti o Waitangi within the health system. However, the populist National-led coalition government formed in November 2023 included the abolishment of the MHA in their first 100-day plan and eventually disestablished it in February 2024. This study analysed 155 public group submissions on the Pae Ora (Healthy Futures) Bill made in 2021 and representing health professionals, iwi, hapū, and community groups. Core themes endorsing the MHA as a statutory entity included honouring te Tiriti, advocating for Māori-led solutions to health inequities, decolonising health systems, and affirming Indigenous rights. The political decision to remove the MHA is antithetical to the explicit endorsement statements made by an overwhelming majority of group submitters with expertise in health organisational structures and healthcare provision. Our study has implications for future local and international research in documenting counter-narratives for Indigenous struggles in health systems.

text: “It is about enabling Tino Rangatiratanga and Mana Motuhake”: An analysis of submissions on the Pae Ora (Healthy Futures) Bill 2021 endorsing a Māori health authority Indigenous leadership in healthcare is one way for Indigenous peoples to exercise sovereignty over their health. In Aotearoa New Zealand, the establishment of the Māori Health Authority (MHA) was grounded in a decades-long imperative to address Māori health inequities and operationalise te Tiriti o Waitangi within the health system. However, the populist National-led coalition government formed in November 2023 included the abolishment of the MHA in their first 100-day plan and eventually disestablished it in February 2024. This study analysed 155 public group submissions on the Pae Ora (Healthy Futures) Bill made in 2021 and representing health professionals, iwi, hapū, and community groups. Core themes endorsing the MHA as a statutory entity included honouring te Tiriti, advocating for Māori-led solutions to health inequities, decolonising health systems, and affirming Indigenous rights. The political decision to remove the MHA is antithetical to the explicit endorsement statements made by an overwhelming majority of group submitters with expertise in health organisational structures and healthcare provision. Our study has implications for future local and international research in documenting counter-narratives for Indigenous struggles in health systems.

year: 2025