title: Marine demosponge responses to a changing ocean; effects of sedimentation and temperature increases on Tethya burtoni metabolism

authors: Beets, Fenna Linde

subjects: Sponge

abstract: As atmospheric CO₂ levels currently increase at an unprecedented rate, the effects of climate change are increasingly recognized as a significant threat. Changes to climate are predicted to influence natural systems, including increased storm events, that for an erosion prone country like New Zealand means exacerbated sedimentation in coastal habitats. Additionally, climate change is increasing sea surface temperatures globally and will continue to do so in coming decades. More studies investigating the effects of climate related pressures on marine sponge physiology are needed. These unique invertebrates are a diverse, ubiquitous and functionally important group. Studies examining climate change effects on sponges tend to investigate tropical species and in this regard, limited work has been done in New Zealand.
This research investigates how the pressures of increasing sea surface temperature and sedimentation affects the metabolism of the temperate demosponge, Tethya burtoni. Aquaria based experiments were conducted while ancillary in situ data investigated current day temperature and sedimentation in various T. burtoni habitats. Experiments addressed the immediate respiration response of T. burtoni under four sediment concentration treatments (ambient loads; 20 and 100 mg l⁻¹, storm proxy loads; 500 and 1000 mg l⁻¹) and four sediment grain size classes (<500-250 µm, <250-125 µm, <125-63 µm, <63 µm) at 500 mg l⁻¹. An additional experiment investigated the effects of long-term exposure (20-days) to fine sediments (<63 µm) at a storm proxy load (500 mg l⁻¹). Finally, the effects of IPCC projected sea surface temperature increase of low change; 2°C and high change; 4°C were investigated. Temperature treatments were based on the Tauranga mean annual sea surface temperature; 18°C and summer maximum; 23°, while IPCC projections were added to the latter giving treatments of 25°C and 27°C. 
High sediment loads at storm proxy concentrations significantly reduced the respiration rate of T. burtoni, while ambient concentrations had no significant effect. The two finest sediment grain size classes also reduced respiration rates significantly. These results suggest a protective response to reduce further clogging of the aquiferous system. The long-term experiment did not indicate any differences in respiration in the treatment group. Supplementary observations indicate that this may have been due to an issue with aquaria conditions. Sedimentation results in situ found that T. burtoni habitats experience varying amounts of sedimentation, though grain size compositions show similarity across sites. The temperature experiment indicated that 25°C and 27°C had significant impacts on T. burtoni survival with significant disease prevalence and morphological changes. The 18°C and 23°C had no significant effect on survival despite some signs of physiological stress present in the latter. Temperature data collected in situ confirms experimental ranges used, though with greater variability. These results suggest that a temperature threshold between 23°C and 25°C may exist and that in the absence of adaptation or acclimation, T. burtoni may be compromised under future conditions. The loss of sponge populations and even increased reductions in metabolic processes, as they relate to important ecosystem services such as benthic carbon flux, could have a significant effect on coastal trophic dynamics.

text: Marine demosponge responses to a changing ocean; effects of sedimentation and temperature increases on Tethya burtoni metabolism As atmospheric CO₂ levels currently increase at an unprecedented rate, the effects of climate change are increasingly recognized as a significant threat. Changes to climate are predicted to influence natural systems, including increased storm events, that for an erosion prone country like New Zealand means exacerbated sedimentation in coastal habitats. Additionally, climate change is increasing sea surface temperatures globally and will continue to do so in coming decades. More studies investigating the effects of climate related pressures on marine sponge physiology are needed. These unique invertebrates are a diverse, ubiquitous and functionally important group. Studies examining climate change effects on sponges tend to investigate tropical species and in this regard, limited work has been done in New Zealand.
This research investigates how the pressures of increasing sea surface temperature and sedimentation affects the metabolism of the temperate demosponge, Tethya burtoni. Aquaria based experiments were conducted while ancillary in situ data investigated current day temperature and sedimentation in various T. burtoni habitats. Experiments addressed the immediate respiration response of T. burtoni under four sediment concentration treatments (ambient loads; 20 and 100 mg l⁻¹, storm proxy loads; 500 and 1000 mg l⁻¹) and four sediment grain size classes (<500-250 µm, <250-125 µm, <125-63 µm, <63 µm) at 500 mg l⁻¹. An additional experiment investigated the effects of long-term exposure (20-days) to fine sediments (<63 µm) at a storm proxy load (500 mg l⁻¹). Finally, the effects of IPCC projected sea surface temperature increase of low change; 2°C and high change; 4°C were investigated. Temperature treatments were based on the Tauranga mean annual sea surface temperature; 18°C and summer maximum; 23°, while IPCC projections were added to the latter giving treatments of 25°C and 27°C. 
High sediment loads at storm proxy concentrations significantly reduced the respiration rate of T. burtoni, while ambient concentrations had no significant effect. The two finest sediment grain size classes also reduced respiration rates significantly. These results suggest a protective response to reduce further clogging of the aquiferous system. The long-term experiment did not indicate any differences in respiration in the treatment group. Supplementary observations indicate that this may have been due to an issue with aquaria conditions. Sedimentation results in situ found that T. burtoni habitats experience varying amounts of sedimentation, though grain size compositions show similarity across sites. The temperature experiment indicated that 25°C and 27°C had significant impacts on T. burtoni survival with significant disease prevalence and morphological changes. The 18°C and 23°C had no significant effect on survival despite some signs of physiological stress present in the latter. Temperature data collected in situ confirms experimental ranges used, though with greater variability. These results suggest that a temperature threshold between 23°C and 25°C may exist and that in the absence of adaptation or acclimation, T. burtoni may be compromised under future conditions. The loss of sponge populations and even increased reductions in metabolic processes, as they relate to important ecosystem services such as benthic carbon flux, could have a significant effect on coastal trophic dynamics.

year: 2017

title: Visual Perception and Analysis of an Approaching Train at Railway Level Crossings in New Zealand

authors: Clark, Helen Elizabeth

subjects: vision science

abstract: The prevalence of railway level crossing accidents in New Zealand is a high profile issue that has warranted close scrutiny over the last 10 years. However, the incident rate has not decreased. This research examined the possibility that visual illusions and perceptual errors contribute to an underestimation of a train‟s arrival time by motorists. The first experiment was designed to analyze whether the Size-Arrival Effect, a theory that states that large-far objects are judged to arrive earlier than small-nearer objects, was applicable to trains. Participants were shown a computer simulation of a moving vehicle (train, motorcar or motorcycle) and asked to indicate when the point was reached where they would no longer cross in front of the approaching vehicle. Approach speeds were systematically varied (60 km/h, 70 km/h, 80 km/h, 100 km/h and 120km/h). Results found that participants adopted the greatest safety gap distance to cross for the train. However, there was no adjustment for velocity when adopting safety gaps for the train and the motorcycle with observers using the same gap distance, regardless of the approach speed. The second experiment sought to examine the Leibowitz hypothesis (Leibowitz, 1985), which proposes an illusory bias; a large object seems to be moving more slowly than a small object travelling at the same speed. Experiment 2 measured participants' ability to make a direct comparison between the speed of an approaching motorcar and a train. Participants were asked to judge which of the vehicles appeared faster, with the distance from the observer varied (far, middle or near). Participants significantly underestimated the speed of the train as compared to the car, in both the 'middle' and 'near' conditions, with the magnitude of underestimation greatest in the 'middle' condition. The overall findings offered support for both theories, which indicates that a combination of distance and speed perceptual errors may at least partly contribute to the high rates of level crossing collisions.

text: Visual Perception and Analysis of an Approaching Train at Railway Level Crossings in New Zealand The prevalence of railway level crossing accidents in New Zealand is a high profile issue that has warranted close scrutiny over the last 10 years. However, the incident rate has not decreased. This research examined the possibility that visual illusions and perceptual errors contribute to an underestimation of a train‟s arrival time by motorists. The first experiment was designed to analyze whether the Size-Arrival Effect, a theory that states that large-far objects are judged to arrive earlier than small-nearer objects, was applicable to trains. Participants were shown a computer simulation of a moving vehicle (train, motorcar or motorcycle) and asked to indicate when the point was reached where they would no longer cross in front of the approaching vehicle. Approach speeds were systematically varied (60 km/h, 70 km/h, 80 km/h, 100 km/h and 120km/h). Results found that participants adopted the greatest safety gap distance to cross for the train. However, there was no adjustment for velocity when adopting safety gaps for the train and the motorcycle with observers using the same gap distance, regardless of the approach speed. The second experiment sought to examine the Leibowitz hypothesis (Leibowitz, 1985), which proposes an illusory bias; a large object seems to be moving more slowly than a small object travelling at the same speed. Experiment 2 measured participants' ability to make a direct comparison between the speed of an approaching motorcar and a train. Participants were asked to judge which of the vehicles appeared faster, with the distance from the observer varied (far, middle or near). Participants significantly underestimated the speed of the train as compared to the car, in both the 'middle' and 'near' conditions, with the magnitude of underestimation greatest in the 'middle' condition. The overall findings offered support for both theories, which indicates that a combination of distance and speed perceptual errors may at least partly contribute to the high rates of level crossing collisions.

year: 2010

title: The experience of homemaking in unaffordable and precarious housing

authors: Barrett, Patrick

abstract: Housing is the platform on which people build their lives. The experience of homemaking in unaffordable and precarious housing (Barrett, P., Cram, F. & James, B, 2024) is a new monograph from the Affordable Housing for Generations programme. Across 110 pages, 10 housing researchers share experiences from different groups of people in Aotearoa, burdened by the insecurity of unaffordable housing. The findings show how institutional, social and market dynamics impacting on life circumstances can cause people to be in precarious housing situations. Yet people continue to love homemaking and being contributors to their communities. Reinforcing the pivotal nature of housing in supporting all peoples’ health and wellbeing, this research demonstrates how much more can be achieved through improving access to stable, affordable housing and by understanding what is at the heart of a home.

text: The experience of homemaking in unaffordable and precarious housing Housing is the platform on which people build their lives. The experience of homemaking in unaffordable and precarious housing (Barrett, P., Cram, F. & James, B, 2024) is a new monograph from the Affordable Housing for Generations programme. Across 110 pages, 10 housing researchers share experiences from different groups of people in Aotearoa, burdened by the insecurity of unaffordable housing. The findings show how institutional, social and market dynamics impacting on life circumstances can cause people to be in precarious housing situations. Yet people continue to love homemaking and being contributors to their communities. Reinforcing the pivotal nature of housing in supporting all peoples’ health and wellbeing, this research demonstrates how much more can be achieved through improving access to stable, affordable housing and by understanding what is at the heart of a home.

year: 2024