title: The influence of sediment nutrient dynamics on the response of lake ecosystems to restoration and climate change

authors: Trolle, Dennis

subjects: Sediment

abstract: Human activities such as urban settlement, farming, forestry and recreation, have caused deterioration of water quality in many freshwater lakes worldwide. Apart from anthropogenic impacts, it is also recognized that climate has a direct influence on lake water temperature, nutrient loads, phytoplankton abundance and chemistry. However, little is known about the potential effects of future climate change on lake water quality. Understanding the dynamics, abundance and availability of nutrient pools in lake bottom sediments is fundamentally important for predicting how, and over what time-scales, lake ecosystems will respond to future scenarios such as climate change, in-lake restoration or altered external nutrient loading. Through a sediment field study on 14 different lakes, and applications of complex lake ecosystem models to three New Zealand lakes, this study examined the spatial and temporal dynamics of sediment nutrient concentrations, and made considerations of the effects of restoration measures and future climate change on lake water quality.

To gain insight into processes influencing the dynamics of horizontal and vertical gradients of sediment nutrient concentrations, intact sediment cores were collected from twelve lakes within the Bay of Plenty province, North Island of New Zealand. In addition, intact sediment cores were collected from shallow Lake Te Waihora (Ellesmere) in the Canterbury province, South Island of New Zealand and shallow Lake Taihu in the Jaingsu province, China. The observed vertical concentration profiles of total phosphorus (TP) in the sediments revealed that the shape of these profiles can be similar across gradients of widely differing trophic status. Empirical and mechanistic steady state profile models were derived to describe the vertical distribution of total carbon (TC), total nitrogen (TN) and TP concentrations in the sediments. These models revealed that density-driven burial and biodiffusive mixing, which in the models also includes effects of redox-driven gradients, are strongly correlated with vertical gradients of sediment TC, TN and TP content, whereas lake trophic status was not.

Despite enhancing knowledge of the processes influencing vertical gradients of sediment nutrient concentrations, little is known about the rates at which sediment nutrient concentrations may change as a response to changes in external loading or climate. Studies into the composition of bottom sediments have been undertaken intermittently over the past three decades for the 12 lakes in the Bay of Plenty. These studies, together with the data collected in this study, were used to quantify temporal changes in sediment chemistry across the lakes. Comparison of the data collected in this study with results from a survey in 1995 showed that surficial sediment (0-2 cm) TP concentrations have increased in three of the 12 lakes, at rates ranging from 27.5 to 114.4 mg P kg-1 dry wt yr-1. TN concentrations in surficial sediments have increased in nine of the 12 lakes at rates ranging from 51.8 to 869.2 mg N kg-1 dry wt yr-1. A correlation analysis revealed that temporal changes in sediment TP and TN concentrations were not significantly linearly related (pgt0.05) to catchment area or temporal changes of different water column indices considered to reflect lake trophic state, including annual mean water column concentrations of TP, TN or chlorophyll a (Chl a).

While vertical profiles of sediment nutrient concentrations can be used to provide information about historical changes of trophic status in lakes, little is known about horizontal variability of sediment nutrient concentrations, including possibly relationships with horizontal variations in water column variables. In the large, shallow and eutrophic Lake Taihu, China, there are distinct horizontal water column concentration gradients of nutrients and Chl a. Concentrations are generally high in the north, where some of the major polluted tributaries enter the lake, and relatively low in the south, where macrophytes generally are abundant. To test whether these water column concentration gradients are similarly reflected in spatial heterogeneity of nutrient concentrations within the bottom sediments of Lake Taihu, I examined correlations between concentrations of TP and TN in surficial sediments (0-2 cm) and TP, TN and Chl a concentrations in water column samples determined for 32 sites in 2005. Linear correlation analysis revealed that surficial sediment TP concentrations across the 32 stations were related significantly, though weakly, to annual mean water column concentrations of TP and TN as well as Chl a. Correlations of surficial sediment TN with water column variables were, however, not significant (p gt 0.05).
To better understand the effects of future climate change on lakes of different trophic status, I applied the one-dimensional lake ecosystem model, DYRESM-CAEDYM, to oligo-mesotrophic Lake Okareka, eutrophic Lake Rotoehu and highly eutrophic Lake Te Waihora. All three models were calibrated based on a three-year period (July 2002 - June 2005) and validated on a separate two-year period (July 2005 - June 2007). The model simulations generally showed good agreement with observed data for temperature, dissolved oxygen (DO), and total nutrient and Chl a concentrations. To represent a possible future climate of 2100, temperature predictions were derived from the regional climate model, DARLAM, based on the Intergovernmental Panel on Climate Change (IPCC) A2 scenario, which suggests that air temperatures by the year 2100 will increase by an average of 2.5 'C and 2.7 'C for the Bay of Plenty and the Canterbury province, respectively, relative to the base scenario (years 2002-2007). Model simulations of the future climate scenarios indicate that climatic changes generally will lead to a degradation of lake water quality in all three lakes, especially during summer months, and further suggest that the effects on annual mean surface concentrations of TP, TN and Chl a will be equivalent to an increase in external TN and TP loading by 25-50%. Simulations for Lake Rotoehu, where diatoms and cyanophytes were represented in the conceptual model, further suggest that cyanophytes will be more abundant in the future, increasing by gt15% in annual mean biomass. Although the effects of climate change may be delayed or slightly mediated by the chemical resilience of the sediment nutrient pools, the effects of climate change on lake water quality in the New Zealand lakes will be of a magnitude that should be considered as management strategies are planned and implemented, thus increasing the probability of successful preservation or improvement in water quality in future decades.

text: The influence of sediment nutrient dynamics on the response of lake ecosystems to restoration and climate change Human activities such as urban settlement, farming, forestry and recreation, have caused deterioration of water quality in many freshwater lakes worldwide. Apart from anthropogenic impacts, it is also recognized that climate has a direct influence on lake water temperature, nutrient loads, phytoplankton abundance and chemistry. However, little is known about the potential effects of future climate change on lake water quality. Understanding the dynamics, abundance and availability of nutrient pools in lake bottom sediments is fundamentally important for predicting how, and over what time-scales, lake ecosystems will respond to future scenarios such as climate change, in-lake restoration or altered external nutrient loading. Through a sediment field study on 14 different lakes, and applications of complex lake ecosystem models to three New Zealand lakes, this study examined the spatial and temporal dynamics of sediment nutrient concentrations, and made considerations of the effects of restoration measures and future climate change on lake water quality.

To gain insight into processes influencing the dynamics of horizontal and vertical gradients of sediment nutrient concentrations, intact sediment cores were collected from twelve lakes within the Bay of Plenty province, North Island of New Zealand. In addition, intact sediment cores were collected from shallow Lake Te Waihora (Ellesmere) in the Canterbury province, South Island of New Zealand and shallow Lake Taihu in the Jaingsu province, China. The observed vertical concentration profiles of total phosphorus (TP) in the sediments revealed that the shape of these profiles can be similar across gradients of widely differing trophic status. Empirical and mechanistic steady state profile models were derived to describe the vertical distribution of total carbon (TC), total nitrogen (TN) and TP concentrations in the sediments. These models revealed that density-driven burial and biodiffusive mixing, which in the models also includes effects of redox-driven gradients, are strongly correlated with vertical gradients of sediment TC, TN and TP content, whereas lake trophic status was not.

Despite enhancing knowledge of the processes influencing vertical gradients of sediment nutrient concentrations, little is known about the rates at which sediment nutrient concentrations may change as a response to changes in external loading or climate. Studies into the composition of bottom sediments have been undertaken intermittently over the past three decades for the 12 lakes in the Bay of Plenty. These studies, together with the data collected in this study, were used to quantify temporal changes in sediment chemistry across the lakes. Comparison of the data collected in this study with results from a survey in 1995 showed that surficial sediment (0-2 cm) TP concentrations have increased in three of the 12 lakes, at rates ranging from 27.5 to 114.4 mg P kg-1 dry wt yr-1. TN concentrations in surficial sediments have increased in nine of the 12 lakes at rates ranging from 51.8 to 869.2 mg N kg-1 dry wt yr-1. A correlation analysis revealed that temporal changes in sediment TP and TN concentrations were not significantly linearly related (pgt0.05) to catchment area or temporal changes of different water column indices considered to reflect lake trophic state, including annual mean water column concentrations of TP, TN or chlorophyll a (Chl a).

While vertical profiles of sediment nutrient concentrations can be used to provide information about historical changes of trophic status in lakes, little is known about horizontal variability of sediment nutrient concentrations, including possibly relationships with horizontal variations in water column variables. In the large, shallow and eutrophic Lake Taihu, China, there are distinct horizontal water column concentration gradients of nutrients and Chl a. Concentrations are generally high in the north, where some of the major polluted tributaries enter the lake, and relatively low in the south, where macrophytes generally are abundant. To test whether these water column concentration gradients are similarly reflected in spatial heterogeneity of nutrient concentrations within the bottom sediments of Lake Taihu, I examined correlations between concentrations of TP and TN in surficial sediments (0-2 cm) and TP, TN and Chl a concentrations in water column samples determined for 32 sites in 2005. Linear correlation analysis revealed that surficial sediment TP concentrations across the 32 stations were related significantly, though weakly, to annual mean water column concentrations of TP and TN as well as Chl a. Correlations of surficial sediment TN with water column variables were, however, not significant (p gt 0.05).
To better understand the effects of future climate change on lakes of different trophic status, I applied the one-dimensional lake ecosystem model, DYRESM-CAEDYM, to oligo-mesotrophic Lake Okareka, eutrophic Lake Rotoehu and highly eutrophic Lake Te Waihora. All three models were calibrated based on a three-year period (July 2002 - June 2005) and validated on a separate two-year period (July 2005 - June 2007). The model simulations generally showed good agreement with observed data for temperature, dissolved oxygen (DO), and total nutrient and Chl a concentrations. To represent a possible future climate of 2100, temperature predictions were derived from the regional climate model, DARLAM, based on the Intergovernmental Panel on Climate Change (IPCC) A2 scenario, which suggests that air temperatures by the year 2100 will increase by an average of 2.5 'C and 2.7 'C for the Bay of Plenty and the Canterbury province, respectively, relative to the base scenario (years 2002-2007). Model simulations of the future climate scenarios indicate that climatic changes generally will lead to a degradation of lake water quality in all three lakes, especially during summer months, and further suggest that the effects on annual mean surface concentrations of TP, TN and Chl a will be equivalent to an increase in external TN and TP loading by 25-50%. Simulations for Lake Rotoehu, where diatoms and cyanophytes were represented in the conceptual model, further suggest that cyanophytes will be more abundant in the future, increasing by gt15% in annual mean biomass. Although the effects of climate change may be delayed or slightly mediated by the chemical resilience of the sediment nutrient pools, the effects of climate change on lake water quality in the New Zealand lakes will be of a magnitude that should be considered as management strategies are planned and implemented, thus increasing the probability of successful preservation or improvement in water quality in future decades.

year: 2009

title: Tertiary education experiences of students with visual impairment

authors: Otu-Danquah, Kwame

abstract: An increasing number of students with disabilities are attending tertiary education institutions in New Zealand. Understanding the experiences of students with disabilities will enable education providers to develop policies and practices that promote the inclusion of these students. This study examined the tertiary experiences of students with visual impairment, an understudied group of students with disabilities in New Zealand. It examined their transition, social, and academic experiences.

Qualitative research, critical theory, and participatory research were adopted as the research approach, paradigm, and design, respectively. Semistructured interviews were used to collect data from six students with visual impairment, two accessibility advisors, and an official of Blind Low Vision New Zealand. Students with visual impairment also participated in a focus group discussion. Due to the participatory nature of the study, students with visual impairment were involved in the formulation of focus group questions. The coconstruction of focus group questions ensured that the questions were relevant to participants’ lived experiences. The process of coconstruction was also empowering for participants as their feedback shaped the “direction” of the research. For example, the incorporation of transition experience into the study was at the request of participants. The focus group was also empowering as the conversation produced new insights among participants. Three themes emerged from thematic analysis, and these were transition experiences, negotiating the social environment, and learning experiences.

The findings indicate that tertiary institutional support offered to students with visual impairment relates mostly to academic participation (note-taking and examinations) and, thereby, seems to neglect other aspects of students’ inclusion. This study found that aspects of tertiary education other than academic issues are equally important to students’ inclusion and must be given the needed attention by tertiary institutions. For instance, the social environment, according to some participants, was the most important barrier to inclusion. Further, it emerged that the transition, specifically pre-enrolment factors, could influence students’ tertiary experiences.

It was observed in the study that participants experienced both barriers and enablers to inclusion in tertiary education. However, participants experienced more barriers than enablers. The barriers included delays in the provision of support, problems of the physical environment, perceived misconception of disability by peers, disregard for participants’ request for support, and inexperienced reader–writers. Some of the enablers were psychosocial and practical support from peers, the contacting of participants prior to enrolment, and support with laboratory experiments. The barriers faced by participants imply disconnect between inclusive education policy and practice in tertiary education. Inclusion is about creating a tertiary environment and system that is barrier-free, flexible, equitable, and supportive for all students.

Based on the findings of the study, it is recommended that tertiary institutions include nonacademic programmes, such as social participation initiatives and transition programmes, in the support they offer to students with visual impairment. Moreover, accessibility advisors and academic staff should be provided with training on disability issues.

text: Tertiary education experiences of students with visual impairment An increasing number of students with disabilities are attending tertiary education institutions in New Zealand. Understanding the experiences of students with disabilities will enable education providers to develop policies and practices that promote the inclusion of these students. This study examined the tertiary experiences of students with visual impairment, an understudied group of students with disabilities in New Zealand. It examined their transition, social, and academic experiences.

Qualitative research, critical theory, and participatory research were adopted as the research approach, paradigm, and design, respectively. Semistructured interviews were used to collect data from six students with visual impairment, two accessibility advisors, and an official of Blind Low Vision New Zealand. Students with visual impairment also participated in a focus group discussion. Due to the participatory nature of the study, students with visual impairment were involved in the formulation of focus group questions. The coconstruction of focus group questions ensured that the questions were relevant to participants’ lived experiences. The process of coconstruction was also empowering for participants as their feedback shaped the “direction” of the research. For example, the incorporation of transition experience into the study was at the request of participants. The focus group was also empowering as the conversation produced new insights among participants. Three themes emerged from thematic analysis, and these were transition experiences, negotiating the social environment, and learning experiences.

The findings indicate that tertiary institutional support offered to students with visual impairment relates mostly to academic participation (note-taking and examinations) and, thereby, seems to neglect other aspects of students’ inclusion. This study found that aspects of tertiary education other than academic issues are equally important to students’ inclusion and must be given the needed attention by tertiary institutions. For instance, the social environment, according to some participants, was the most important barrier to inclusion. Further, it emerged that the transition, specifically pre-enrolment factors, could influence students’ tertiary experiences.

It was observed in the study that participants experienced both barriers and enablers to inclusion in tertiary education. However, participants experienced more barriers than enablers. The barriers included delays in the provision of support, problems of the physical environment, perceived misconception of disability by peers, disregard for participants’ request for support, and inexperienced reader–writers. Some of the enablers were psychosocial and practical support from peers, the contacting of participants prior to enrolment, and support with laboratory experiments. The barriers faced by participants imply disconnect between inclusive education policy and practice in tertiary education. Inclusion is about creating a tertiary environment and system that is barrier-free, flexible, equitable, and supportive for all students.

Based on the findings of the study, it is recommended that tertiary institutions include nonacademic programmes, such as social participation initiatives and transition programmes, in the support they offer to students with visual impairment. Moreover, accessibility advisors and academic staff should be provided with training on disability issues.

year: 2022

title: Kia mau ki tō Māoritanga - The role of Māori teachers in English medium primary schools

authors: Coffin, Rachel Marie

subjects: Māori  teachers

abstract: The achievement levels between Māori and non-Māori students remains increasingly wide within a westernised education system. This system has continued to perpetuate the ongoing failure of Māori students. We need to look at ways in which Māori students can best be supported in English medium education settings as these are where the majority of Māori students receive their schooling, and how we can close the gap between Māori and non-Māori achievement. 

Māori teachers are a minority group within English medium education and their potential to raise Māori student achievement is often overlooked (Lee, 2009). This thesis used a case study approach framed by kaupapa Māori methodology to examine how one primary school, whose Māori students are achieving at similar levels to their non-Māori peers, utilises Māori staff to enhance the cultural pedagogy of the school and how this contributes to the success of Māori students.

The literature review takes an historic look at Māori within a westernised education system and looks at how Māori underachievement is not a recent occurrence but an ongoing issue, dating back over one hundred years.  It draws on international literature around the experiences of other indigenous peoples who have experienced colonisation, and highlights the similar struggles that they have had, and continue to have as minority students. 

The literature review also looks at the ways in which indigenous peoples are working to lift indigenous achievement and the role of indigenous teachers in supporting this process. It looks at the role that culture plays in the belief of indigenous peoples in their own ability to succeed, which is referred to in this thesis as self-efficacy (Bandura, 1997, Schunk, 1986).

In contrast to this  students with low self-efficacy will typically avoid difficult tasks in order to minimize risk to self-worth and protect self-esteem (McRae et al., 2010). 

The findings indicate that Māori teachers at Te Kauri School have some level of proficiency in tikanga and te reo Māori and that this plays a vital role in the schools ability to create a culturally responsive learning environment. The Māori staff have the support of the school leadership team, which promotes and values the inclusion of tikanga and te reo Māori. 

This culturally responsive environment instils in Māori students at Te Kauri School a sense of pride in who they are as culturally located beings. This pride means that they do not feel pressure to conform to the ways of the dominant culture, rather that they are able to be Māori. This also corresponds with achievement data for the school, which shows that Māori achievement levels are at similar levels to that of non-Māori students, and in some year and gender levels above. 

The findings indicate that the relationship between Māori whānau (families) and the school is vital in creating a supportive environment and that Māori teachers are especially valuable in this process. Having cultural practices such as kapa haka, waiata and karakia give Māori whānau a connection to the school and provide them with an opportunity to support not only their children but also the school community. 

The findings also indicate that Māori staff and whānau participants view Māori teachers as role models and that having Māori role models within the school adds to Māori student’s sense of pride in being Māori, thus enhancing their self-efficacy and success.

text: Kia mau ki tō Māoritanga - The role of Māori teachers in English medium primary schools The achievement levels between Māori and non-Māori students remains increasingly wide within a westernised education system. This system has continued to perpetuate the ongoing failure of Māori students. We need to look at ways in which Māori students can best be supported in English medium education settings as these are where the majority of Māori students receive their schooling, and how we can close the gap between Māori and non-Māori achievement. 

Māori teachers are a minority group within English medium education and their potential to raise Māori student achievement is often overlooked (Lee, 2009). This thesis used a case study approach framed by kaupapa Māori methodology to examine how one primary school, whose Māori students are achieving at similar levels to their non-Māori peers, utilises Māori staff to enhance the cultural pedagogy of the school and how this contributes to the success of Māori students.

The literature review takes an historic look at Māori within a westernised education system and looks at how Māori underachievement is not a recent occurrence but an ongoing issue, dating back over one hundred years.  It draws on international literature around the experiences of other indigenous peoples who have experienced colonisation, and highlights the similar struggles that they have had, and continue to have as minority students. 

The literature review also looks at the ways in which indigenous peoples are working to lift indigenous achievement and the role of indigenous teachers in supporting this process. It looks at the role that culture plays in the belief of indigenous peoples in their own ability to succeed, which is referred to in this thesis as self-efficacy (Bandura, 1997, Schunk, 1986).

In contrast to this  students with low self-efficacy will typically avoid difficult tasks in order to minimize risk to self-worth and protect self-esteem (McRae et al., 2010). 

The findings indicate that Māori teachers at Te Kauri School have some level of proficiency in tikanga and te reo Māori and that this plays a vital role in the schools ability to create a culturally responsive learning environment. The Māori staff have the support of the school leadership team, which promotes and values the inclusion of tikanga and te reo Māori. 

This culturally responsive environment instils in Māori students at Te Kauri School a sense of pride in who they are as culturally located beings. This pride means that they do not feel pressure to conform to the ways of the dominant culture, rather that they are able to be Māori. This also corresponds with achievement data for the school, which shows that Māori achievement levels are at similar levels to that of non-Māori students, and in some year and gender levels above. 

The findings indicate that the relationship between Māori whānau (families) and the school is vital in creating a supportive environment and that Māori teachers are especially valuable in this process. Having cultural practices such as kapa haka, waiata and karakia give Māori whānau a connection to the school and provide them with an opportunity to support not only their children but also the school community. 

The findings also indicate that Māori staff and whānau participants view Māori teachers as role models and that having Māori role models within the school adds to Māori student’s sense of pride in being Māori, thus enhancing their self-efficacy and success.

year: 2013