title: Changes in flow and sediment trapping caused by bioturbating macrofauna (austrohelice crassa)

authors: Bredin-Grey, Holly Kate Josephine

subjects: austrohelice crassa

abstract: Intertidal ecosystems contribute a significant portion of the world’s ecosystem goods and services. Recently, an increasing amount of focus has been generated surrounding the central role of sediment mixing (bioturbation) in estuarine ecosystems. Bioturbating macrofauna such as the burrowing mud crab austrohelice crassa are found in many New Zealand ecosystems, and have been shown to be key ecosystem engineers in these environments. Burrow building extends the sediment-water interface, creating changes in solute and particle fluxes through modification of near-bed flows. Burrows and holes have been poorly studied compared with their above-ground counterparts and the exact manner in which burrows affect small-scale water movement at the sediment water interface is yet to be understood.

This project used measurements of fine scale flows surrounding austrohelice crassa burrows in situ as well as in a laboratory setting. Experiments used artificial burrows in a unidirectional flume to explore the impact that crab burrow orientation has on flow. Measurements of flow velocities were taken and it was found that flow extended further into the burrow when the burrow was aligned downstream with the flow rather than at right angles or aligned upstream to the flow.

Subsequently, the impact of burrow density on near-bed flows was quantified in the laboratory using different density arrays of artificial burrows. Measurements of velocity were used to calculate turbulent kinetic energy (TKE). It was found that with increasing burrow density there was a split in flow regimes between high and low flow speeds. At low flow speeds, the TKE increased to a peak followed by a decline, owing to the development of skimming flow.

Field experiments examined flows around arrays of artificial and natural burrows including a control, a sparse, and a dense artificial burrow array (0, 40, and 74 burrows/m2, respectively), as well as a control, a sparse, and a dense array of natural burrows (0, 30, and 62 burrows/m2, respectively). Measurements taken within these arrays found that for the artificial burrow array, TKE appeared to increase to a peak for the sparse array, and decreased again for the dense array. This relationship is similar to that found in the burrow array laboratory experiment. For the natural burrow array, TKE increased with burrow density. For all field experiments combined, a split in flow regimes between high and low flow speeds emerges, similar to the split found in the laboratory experiments.

Sediment trapping within the artificial burrows was measured for over one tidal cycle.  It was found that the dense array trapped a greater amount of sediment (1.95 g/L) compared with the sparse array (1.66 g/L). Overall, it appeared that the sediment caught within the burrows had a greater proportion of silt when compared with the local surficial sediment, indicating the possibility of ecosystem engineering. Volumes trapped of this magnitude have considerable potential to alter the morphology of tidal flats. Overall, these results offer intriguing insight into the role of burrowing fauna in affecting flows and sediment fluxes on intertidal sandflats.

text: Changes in flow and sediment trapping caused by bioturbating macrofauna (austrohelice crassa) Intertidal ecosystems contribute a significant portion of the world’s ecosystem goods and services. Recently, an increasing amount of focus has been generated surrounding the central role of sediment mixing (bioturbation) in estuarine ecosystems. Bioturbating macrofauna such as the burrowing mud crab austrohelice crassa are found in many New Zealand ecosystems, and have been shown to be key ecosystem engineers in these environments. Burrow building extends the sediment-water interface, creating changes in solute and particle fluxes through modification of near-bed flows. Burrows and holes have been poorly studied compared with their above-ground counterparts and the exact manner in which burrows affect small-scale water movement at the sediment water interface is yet to be understood.

This project used measurements of fine scale flows surrounding austrohelice crassa burrows in situ as well as in a laboratory setting. Experiments used artificial burrows in a unidirectional flume to explore the impact that crab burrow orientation has on flow. Measurements of flow velocities were taken and it was found that flow extended further into the burrow when the burrow was aligned downstream with the flow rather than at right angles or aligned upstream to the flow.

Subsequently, the impact of burrow density on near-bed flows was quantified in the laboratory using different density arrays of artificial burrows. Measurements of velocity were used to calculate turbulent kinetic energy (TKE). It was found that with increasing burrow density there was a split in flow regimes between high and low flow speeds. At low flow speeds, the TKE increased to a peak followed by a decline, owing to the development of skimming flow.

Field experiments examined flows around arrays of artificial and natural burrows including a control, a sparse, and a dense artificial burrow array (0, 40, and 74 burrows/m2, respectively), as well as a control, a sparse, and a dense array of natural burrows (0, 30, and 62 burrows/m2, respectively). Measurements taken within these arrays found that for the artificial burrow array, TKE appeared to increase to a peak for the sparse array, and decreased again for the dense array. This relationship is similar to that found in the burrow array laboratory experiment. For the natural burrow array, TKE increased with burrow density. For all field experiments combined, a split in flow regimes between high and low flow speeds emerges, similar to the split found in the laboratory experiments.

Sediment trapping within the artificial burrows was measured for over one tidal cycle.  It was found that the dense array trapped a greater amount of sediment (1.95 g/L) compared with the sparse array (1.66 g/L). Overall, it appeared that the sediment caught within the burrows had a greater proportion of silt when compared with the local surficial sediment, indicating the possibility of ecosystem engineering. Volumes trapped of this magnitude have considerable potential to alter the morphology of tidal flats. Overall, these results offer intriguing insight into the role of burrowing fauna in affecting flows and sediment fluxes on intertidal sandflats.

year: 2016

title: Complex uncertainty: Long-term risk management decision making in New Zealand local government

authors: Robson, David

subjects: Local government

abstract: New Zealand’s natural hazardscape has long posed risks for government owned water infrastructure and its stakeholder communities. In the context of climate change, there are predictions that the frequency and intensity of natural hazard events are set to increase, but there are uncertainties about when such events might occur, and the severity and impact on water infrastructure. These threats are compounded by pressures such as population growth and constrained funding. There is a need, therefore, to consider the suitability of current governance arrangements and decision processes for the management of complex, long-term risk associated with state assets. This research, therefore, asks, are current local governance arrangements and associated decision-making processes for the management of water infrastructure appropriate for long-term risk management in an environment of uncertainty? The thesis addresses this question by critically evaluating the extent to which governance arrangements enable effective risk management decisions that protect government owned infrastructure from natural hazards. 
A novel conceptual framework which matches the type of problem within the scales of time and complexity is developed on the basis of a literature review on risk management, adaptability and resilience, and modes of governance across multiple levels. This framework is then used to inform an exploration of risk management decision processes. The examination of these processes involved a participatory design involving local and central government officials and associated risk management professionals. A mixed-methods approach was applied to explore experiences of risk management as it relates to water infrastructure within local government, within the context of wider relationships with central government. Following a pilot workshop with sector actors and risk professionals to establish the broad research focus, the research involved 36 semi-structured interviews and a further workshop with sector officials to discuss the findings and critique the resulting decision-making model.
The research found that current risk management decision making is characterised by, largely, a short-term horizon, this being connected with the tendency of elected representatives to operate within the three-year election cycle. The absence of a longer-term focus is explained in part by the autonomous environment within which councils operate, removed from central government oversight, and with little sharing of knowledge, expertise or costs of risk management. The key findings of the research indicate: a lack of consistent guidance and direction by central government to local government on adaptive risk management; a lack of coordination across the network of councils, specifically in terms of sharing knowledge, data and risk management activities; a lack of specificity in legislation regarding long term risk management which leaves risk decision making open to interpretation by councils; a culture of localised short term decision making in councils, with a low level of comprehension as to the management of long-term risks; short-term competing priorities for the financial resources required to manage risk; and a mistrust of internal guidance and advice due to the lack of in-house expertise, and a preference for external subject matter expertise. 
Overall, this research has identified that the complex nature of the environment of uncertainty posed by climate change has not been adequately acknowledged within local government and this is reflected in the prevailing risk management arrangements being largely reliant on annually renewed insurance arrangements based on in-house planning practices. The decision-making framework developed in this thesis acknowledges the nature of risk and the need for adaptive approaches within the constraints of time and complexity, and has potential to inform both governance arrangements and decision processes.

text: Complex uncertainty: Long-term risk management decision making in New Zealand local government New Zealand’s natural hazardscape has long posed risks for government owned water infrastructure and its stakeholder communities. In the context of climate change, there are predictions that the frequency and intensity of natural hazard events are set to increase, but there are uncertainties about when such events might occur, and the severity and impact on water infrastructure. These threats are compounded by pressures such as population growth and constrained funding. There is a need, therefore, to consider the suitability of current governance arrangements and decision processes for the management of complex, long-term risk associated with state assets. This research, therefore, asks, are current local governance arrangements and associated decision-making processes for the management of water infrastructure appropriate for long-term risk management in an environment of uncertainty? The thesis addresses this question by critically evaluating the extent to which governance arrangements enable effective risk management decisions that protect government owned infrastructure from natural hazards. 
A novel conceptual framework which matches the type of problem within the scales of time and complexity is developed on the basis of a literature review on risk management, adaptability and resilience, and modes of governance across multiple levels. This framework is then used to inform an exploration of risk management decision processes. The examination of these processes involved a participatory design involving local and central government officials and associated risk management professionals. A mixed-methods approach was applied to explore experiences of risk management as it relates to water infrastructure within local government, within the context of wider relationships with central government. Following a pilot workshop with sector actors and risk professionals to establish the broad research focus, the research involved 36 semi-structured interviews and a further workshop with sector officials to discuss the findings and critique the resulting decision-making model.
The research found that current risk management decision making is characterised by, largely, a short-term horizon, this being connected with the tendency of elected representatives to operate within the three-year election cycle. The absence of a longer-term focus is explained in part by the autonomous environment within which councils operate, removed from central government oversight, and with little sharing of knowledge, expertise or costs of risk management. The key findings of the research indicate: a lack of consistent guidance and direction by central government to local government on adaptive risk management; a lack of coordination across the network of councils, specifically in terms of sharing knowledge, data and risk management activities; a lack of specificity in legislation regarding long term risk management which leaves risk decision making open to interpretation by councils; a culture of localised short term decision making in councils, with a low level of comprehension as to the management of long-term risks; short-term competing priorities for the financial resources required to manage risk; and a mistrust of internal guidance and advice due to the lack of in-house expertise, and a preference for external subject matter expertise. 
Overall, this research has identified that the complex nature of the environment of uncertainty posed by climate change has not been adequately acknowledged within local government and this is reflected in the prevailing risk management arrangements being largely reliant on annually renewed insurance arrangements based on in-house planning practices. The decision-making framework developed in this thesis acknowledges the nature of risk and the need for adaptive approaches within the constraints of time and complexity, and has potential to inform both governance arrangements and decision processes.

year: 2021

title: Consequences of cultural satisfaction at work: A study of New Zealand Māori

authors: Haar, Jarrod M.

subjects: cultural satisfaction at work

abstract: To expand our understanding of indigenous workers and the importance of indigenous culture in the workplace, we tested the outcomes of cultural satisfaction at work using structural equation modelling with a sample of 174 Māori employees. We show that, consistent with social exchange theory, Māori who are more satisfied with the level of understanding of their cultural values in the workplace report better job outcomes. Cultural satisfaction at work directly predicted loyalty and organisational citizenship behaviours (OCBs). Furthermore, direct-effects and mediation models were tested, showing that loyalty fully mediated the influence of cultural satisfaction at work on OCBs. The implications for HRM are that indigenous workers who are more satisfied with the way their cultural beliefs are valued in the workplace are likely to be more loyal and may be superior performance. The findings highlight the importance for employers of having regard to the culture of their indigenous workers.

text: Consequences of cultural satisfaction at work: A study of New Zealand Māori To expand our understanding of indigenous workers and the importance of indigenous culture in the workplace, we tested the outcomes of cultural satisfaction at work using structural equation modelling with a sample of 174 Māori employees. We show that, consistent with social exchange theory, Māori who are more satisfied with the level of understanding of their cultural values in the workplace report better job outcomes. Cultural satisfaction at work directly predicted loyalty and organisational citizenship behaviours (OCBs). Furthermore, direct-effects and mediation models were tested, showing that loyalty fully mediated the influence of cultural satisfaction at work on OCBs. The implications for HRM are that indigenous workers who are more satisfied with the way their cultural beliefs are valued in the workplace are likely to be more loyal and may be superior performance. The findings highlight the importance for employers of having regard to the culture of their indigenous workers.

year: 2011