title: Enhancing the mathematics achievement of Pasifika students: Performance and progress on the numeracy development project.

authors: Young-Loveridge, Jennifer

subjects: mathematics

abstract: This paper reports on the analysis of data from approximately 30,000 Pasifika students whose teachers participated in the Numeracy Development Project (NDP) between 2002 and 2005. Most students' performance improved from the beginning of the year to the end, and performance and progress seemed to improve from 2002 to 2005. As a result, the gap between European and Pasifika students appeared to reduce fairly steadily over tune. These improvements coincided with changes in the composition of the cohort over time, most notably a reduction in the percentage of students from low-decile schools and an increase in the percentage of students from medium- and high-decile schools. Hence, it is difficult to conclude with any confidence that it is the NDP that is primarily responsible for the improvements. Although the gaps in achievement between European and Pasifika students were not completely eliminated, when these differences were put beside those found in other large-scale studies, it was evident that NDP differences were much smaller (a quarter of a standard deviation compared to a whole standard deviation). The use of an individual, orally presented assessment tool with an emphasis on explaining the strategies used to get answers, rather than a written test on which the number of correct answers is simply totalled, may help to explain the positive outcomes for NDP students.

text: Enhancing the mathematics achievement of Pasifika students: Performance and progress on the numeracy development project. This paper reports on the analysis of data from approximately 30,000 Pasifika students whose teachers participated in the Numeracy Development Project (NDP) between 2002 and 2005. Most students' performance improved from the beginning of the year to the end, and performance and progress seemed to improve from 2002 to 2005. As a result, the gap between European and Pasifika students appeared to reduce fairly steadily over tune. These improvements coincided with changes in the composition of the cohort over time, most notably a reduction in the percentage of students from low-decile schools and an increase in the percentage of students from medium- and high-decile schools. Hence, it is difficult to conclude with any confidence that it is the NDP that is primarily responsible for the improvements. Although the gaps in achievement between European and Pasifika students were not completely eliminated, when these differences were put beside those found in other large-scale studies, it was evident that NDP differences were much smaller (a quarter of a standard deviation compared to a whole standard deviation). The use of an individual, orally presented assessment tool with an emphasis on explaining the strategies used to get answers, rather than a written test on which the number of correct answers is simply totalled, may help to explain the positive outcomes for NDP students.

year: 2006

title: The ecological role of the suspension feeding bivalve, Austrovenus stutchburyi, in estuarine ecosystems

authors: Jones, Hannah Frances Emily

subjects: ecosystem function

abstract: Suspension feeding bivalves are described as key species in many aquatic ecosystems, where they can influence primary productivity and nutrient dynamics, are food for higher trophic levels, and may be harvested in commercial or recreational fisheries. In many areas where bivalve populations have declined, substantial changes to ecosystem structure and function have occurred. High-density beds of the infaunal suspension feeding bivalve, Austrovenus stutchburyi, are a dominant feature on intertidal flats in many New Zealand estuaries, but populations are declining in some areas, likely due to anthropogenic stressors such as overharvesting and sedimentation. This thesis examines the influence of Austrovenus on estuarine ecosystem function using laboratory, field and modelling studies.
The effects of bed density and flow speed on boundary layer dynamics and Austrovenus clearance rates (CR) were investigated in annular flumes. Bed shear stress increased with increasing bivalve density, and under certain conditions was also increased when Austrovenus were feeding, compared to when they were not. The bed roughness and siphonal currents generated by the bivalves may therefore influence food supply to the bed. Both individual and bed CR were significantly greater at the high flow speed. Bed CR did not scale proportionally with density, in part because individual CR decreased with increasing density, but also because the proportion of bivalves actively feeding decreased at high densities. Thus, scaling up individual CR obtained from animals at low densities will significantly overestimate population filtration capacity.
The effect of Austrovenus on ecosystem function was examined at two sites, one sandy, the other composed of muddy-sand, to determine whether sedimentary environment alters this key species’ role. Gross primary production (likely corresponding to microphytobenthos production) and ammonium uptake were significantly increased, and denitrification potential was also elevated, when Austrovenus was added, relative to removed, at the sandy site. In contrast, there was no effect of Austrovenus on any of these variables at the muddy-sand site. These results reveal the importance of considering sedimentary environment when examining the effect of key species on ecosystem function, and suggest that even moderate levels of sedimentation may reduce the positive effect of Austrovenus on primary productivity.
A food-web model was used to quantify the interactions between Austrovenus and other estuarine species, and to determine the effect of reducing Austrovenus biomass on ecosystem properties. The model revealed an estuarine system dominated by benthic species, characterised as a developing, rather than a mature ecosystem. Detritus production and export were high, while transfer efficiency and internal recycling were low. Decreasing Austrovenus biomass decreased system maturity, suggesting that reductions in Austrovenus populations may decrease ecosystem stability. The model also confirmed that within these estuarine systems Austrovenus and microphytobenthos are key species which impact greatly on all other trophic levels.
This thesis demonstrates that Austrovenus populations exert considerable influence on benthic communities and processes, and play a key role in the functioning of estuarine ecosystems. Reductions in Austrovenus populations will likely negatively impact on microphytobenthos and higher trophic levels, and may also reduce ecosystem maturity and stability.

text: The ecological role of the suspension feeding bivalve, Austrovenus stutchburyi, in estuarine ecosystems Suspension feeding bivalves are described as key species in many aquatic ecosystems, where they can influence primary productivity and nutrient dynamics, are food for higher trophic levels, and may be harvested in commercial or recreational fisheries. In many areas where bivalve populations have declined, substantial changes to ecosystem structure and function have occurred. High-density beds of the infaunal suspension feeding bivalve, Austrovenus stutchburyi, are a dominant feature on intertidal flats in many New Zealand estuaries, but populations are declining in some areas, likely due to anthropogenic stressors such as overharvesting and sedimentation. This thesis examines the influence of Austrovenus on estuarine ecosystem function using laboratory, field and modelling studies.
The effects of bed density and flow speed on boundary layer dynamics and Austrovenus clearance rates (CR) were investigated in annular flumes. Bed shear stress increased with increasing bivalve density, and under certain conditions was also increased when Austrovenus were feeding, compared to when they were not. The bed roughness and siphonal currents generated by the bivalves may therefore influence food supply to the bed. Both individual and bed CR were significantly greater at the high flow speed. Bed CR did not scale proportionally with density, in part because individual CR decreased with increasing density, but also because the proportion of bivalves actively feeding decreased at high densities. Thus, scaling up individual CR obtained from animals at low densities will significantly overestimate population filtration capacity.
The effect of Austrovenus on ecosystem function was examined at two sites, one sandy, the other composed of muddy-sand, to determine whether sedimentary environment alters this key species’ role. Gross primary production (likely corresponding to microphytobenthos production) and ammonium uptake were significantly increased, and denitrification potential was also elevated, when Austrovenus was added, relative to removed, at the sandy site. In contrast, there was no effect of Austrovenus on any of these variables at the muddy-sand site. These results reveal the importance of considering sedimentary environment when examining the effect of key species on ecosystem function, and suggest that even moderate levels of sedimentation may reduce the positive effect of Austrovenus on primary productivity.
A food-web model was used to quantify the interactions between Austrovenus and other estuarine species, and to determine the effect of reducing Austrovenus biomass on ecosystem properties. The model revealed an estuarine system dominated by benthic species, characterised as a developing, rather than a mature ecosystem. Detritus production and export were high, while transfer efficiency and internal recycling were low. Decreasing Austrovenus biomass decreased system maturity, suggesting that reductions in Austrovenus populations may decrease ecosystem stability. The model also confirmed that within these estuarine systems Austrovenus and microphytobenthos are key species which impact greatly on all other trophic levels.
This thesis demonstrates that Austrovenus populations exert considerable influence on benthic communities and processes, and play a key role in the functioning of estuarine ecosystems. Reductions in Austrovenus populations will likely negatively impact on microphytobenthos and higher trophic levels, and may also reduce ecosystem maturity and stability.

year: 2011

title: A core phyllosphere microbiome exists across distant populations of a tree species indigenous to New Zealand

authors: Noble, Anya S.

subjects: Science & Technology

abstract: The phyllosphere microbiome is increasingly recognised as an influential component of plant physiology, yet it remains unclear whether stable host-microbe associations generally exist in the phyllosphere. Leptospermum scoparium (mānuka) is a tea tree indigenous to New Zealand, and honey derived from mānuka is widely known to possess unique antimicrobial properties. However, the host physiological traits associated with these antimicrobial properties vary widely, and the specific cause of such variation has eluded scientists despite decades of research. Notably, the mānuka phyllosphere microbiome remains uncharacterised, and its potential role in mediating host physiology has not been considered. Working within the prevailing core microbiome conceptual framework, we hypothesise that the phyllosphere microbiome of mānuka exhibits specific host association patterns congruent with those of a microbial community under host selective pressure (null hypothesis: the mānuka phyllosphere microbiome is recruited stochastically from the surrounding environment). To examine our hypothesis, we characterised the phyllosphere and associated soil microbiomes of five distinct and geographically distant mānuka populations across the North Island of New Zealand. We identified a habitat-specific and relatively abundant core microbiome in the mānuka phyllosphere, which was persistent across all samples. In contrast, non-core phyllosphere microorganisms exhibited significant variation across individual host trees and populations that was strongly driven by environmental and spatial factors. Our results demonstrate the existence of a dominant and ubiquitous core microbiome in the phyllosphere of mānuka, supporting our hypothesis that phyllosphere microorganisms of mānuka exhibit specific host association and potentially mediate physiological traits of this nationally and culturally treasured indigenous plant. In addition, our results illustrate biogeographical patterns in mānuka phyllosphere microbiomes and offer insight into factors contributing to phyllosphere microbiome assembly.

text: A core phyllosphere microbiome exists across distant populations of a tree species indigenous to New Zealand The phyllosphere microbiome is increasingly recognised as an influential component of plant physiology, yet it remains unclear whether stable host-microbe associations generally exist in the phyllosphere. Leptospermum scoparium (mānuka) is a tea tree indigenous to New Zealand, and honey derived from mānuka is widely known to possess unique antimicrobial properties. However, the host physiological traits associated with these antimicrobial properties vary widely, and the specific cause of such variation has eluded scientists despite decades of research. Notably, the mānuka phyllosphere microbiome remains uncharacterised, and its potential role in mediating host physiology has not been considered. Working within the prevailing core microbiome conceptual framework, we hypothesise that the phyllosphere microbiome of mānuka exhibits specific host association patterns congruent with those of a microbial community under host selective pressure (null hypothesis: the mānuka phyllosphere microbiome is recruited stochastically from the surrounding environment). To examine our hypothesis, we characterised the phyllosphere and associated soil microbiomes of five distinct and geographically distant mānuka populations across the North Island of New Zealand. We identified a habitat-specific and relatively abundant core microbiome in the mānuka phyllosphere, which was persistent across all samples. In contrast, non-core phyllosphere microorganisms exhibited significant variation across individual host trees and populations that was strongly driven by environmental and spatial factors. Our results demonstrate the existence of a dominant and ubiquitous core microbiome in the phyllosphere of mānuka, supporting our hypothesis that phyllosphere microorganisms of mānuka exhibit specific host association and potentially mediate physiological traits of this nationally and culturally treasured indigenous plant. In addition, our results illustrate biogeographical patterns in mānuka phyllosphere microbiomes and offer insight into factors contributing to phyllosphere microbiome assembly.

year: 2020