title: Measuring and modelling estuarine macroalgae blooms and water column nutrients

authors: Port, Marvin Alexander (Alex)

subjects: macroalgae

abstract: This thesis examines the dynamics of estuarine macroalgae blooms of the genus Ulva and the environmental factors controlling them, using process-based mathematical models as well as observation data from Tauranga Harbour (North Island, New Zealand).  
Based on long-term monitoring datasets of water column nutrients, temperature and irradiance, the Ulva tissue nitrogen concentration is modelled using an algebraic short-term equilibrium solution to a classic set of ordinary differential equations describing tissue nutrient dynamics. A detailed sensitivity analysis of this equilibrium solution shows that although the variability in ambient concentration of inorganic nitrogen explains 60% of model output variance, the uncertainty in two of the most influential physiological parameters has a similar magnitude of influence (32% of variance). Repeated calibrations using an algorithm with random starting points and evolutionary adaptions lead to broad and in some cases multimodal distributions of physiological parameters. Although the model performs well in reproducing observations, calibrated parameter values from individual calibrations should therefore not be interpreted as reliable estimates of physiological properties.  
Using a zero-dimensional simulation model of Ulva tissue nitrogen and phosphorus concentrations and biomass, seasonal and long-term population dynamics of Ulva are examined. Calibrating against a combination of all three state variables, long-term tissue nitrogen and biomass dynamics are reproduced well, while the seasonal amplitude of tissue phosphorus variability is underestimated. From the long-term observation datasets, seasonal scenarios are derived based on annual cosine fits to monthly percentiles of the observed forcing data. These scenarios represent above and below average seasons in the environmental conditions of ammonia, nitrate and phosphate concentrations in the water as well as temperature and irradiance. Comparison of the different scenarios points to the inorganic nitrogen concentrations (both ammonia and nitrate) as most influential in determining Ulva seasonal peak biomass and timing.  
To improve upon the existing long-term observations of water column nutrients available for Tauranga Harbour, a sampling programme was designed taking into account the challenges of accurately measuring nutrients in a tidally dominated estuary with complex geometry. Samples were taken at consecutive ebb and flood tides at the same local tidal phase at sites representing distinct subregions within the estuary. Bimonthly samples at eight sites and fortnightly samples at two sites over one year show that the statistical distributions of nutrient fractions vary between sites and between tides. At the estuary mouth, phosphate is exported, while at site further upstream, ammonia and nitrate are exported. Modelling the passive transport of nutrients using a numerical hydrodynamical model shows differences in the connectivity between subregions, and in some cases mid-term upstream transport. The contribution of upstream subregions to individual sites changes rapidly during the tidal cycle, emphasising the importance of the local tidal phase. The data collected may help to improve the sampling design of the long-term monitoring programmes in Tauranga Harbour and provide a more accurate basis for future modelling studies of Ulva population dynamics.

text: Measuring and modelling estuarine macroalgae blooms and water column nutrients This thesis examines the dynamics of estuarine macroalgae blooms of the genus Ulva and the environmental factors controlling them, using process-based mathematical models as well as observation data from Tauranga Harbour (North Island, New Zealand).  
Based on long-term monitoring datasets of water column nutrients, temperature and irradiance, the Ulva tissue nitrogen concentration is modelled using an algebraic short-term equilibrium solution to a classic set of ordinary differential equations describing tissue nutrient dynamics. A detailed sensitivity analysis of this equilibrium solution shows that although the variability in ambient concentration of inorganic nitrogen explains 60% of model output variance, the uncertainty in two of the most influential physiological parameters has a similar magnitude of influence (32% of variance). Repeated calibrations using an algorithm with random starting points and evolutionary adaptions lead to broad and in some cases multimodal distributions of physiological parameters. Although the model performs well in reproducing observations, calibrated parameter values from individual calibrations should therefore not be interpreted as reliable estimates of physiological properties.  
Using a zero-dimensional simulation model of Ulva tissue nitrogen and phosphorus concentrations and biomass, seasonal and long-term population dynamics of Ulva are examined. Calibrating against a combination of all three state variables, long-term tissue nitrogen and biomass dynamics are reproduced well, while the seasonal amplitude of tissue phosphorus variability is underestimated. From the long-term observation datasets, seasonal scenarios are derived based on annual cosine fits to monthly percentiles of the observed forcing data. These scenarios represent above and below average seasons in the environmental conditions of ammonia, nitrate and phosphate concentrations in the water as well as temperature and irradiance. Comparison of the different scenarios points to the inorganic nitrogen concentrations (both ammonia and nitrate) as most influential in determining Ulva seasonal peak biomass and timing.  
To improve upon the existing long-term observations of water column nutrients available for Tauranga Harbour, a sampling programme was designed taking into account the challenges of accurately measuring nutrients in a tidally dominated estuary with complex geometry. Samples were taken at consecutive ebb and flood tides at the same local tidal phase at sites representing distinct subregions within the estuary. Bimonthly samples at eight sites and fortnightly samples at two sites over one year show that the statistical distributions of nutrient fractions vary between sites and between tides. At the estuary mouth, phosphate is exported, while at site further upstream, ammonia and nitrate are exported. Modelling the passive transport of nutrients using a numerical hydrodynamical model shows differences in the connectivity between subregions, and in some cases mid-term upstream transport. The contribution of upstream subregions to individual sites changes rapidly during the tidal cycle, emphasising the importance of the local tidal phase. The data collected may help to improve the sampling design of the long-term monitoring programmes in Tauranga Harbour and provide a more accurate basis for future modelling studies of Ulva population dynamics.

year: 2016

title: Water vapor transfer over the Southwest Pacific: Mean patterns and variations during wet and dry periods

authors: Khatep, M.M.

abstract: The mean water vapor transfer of the Southwest Pacific, as determined from radiosonde records near the 170°E meridional transect, is computed for the 1960–73 period. Emphasis is placed on defining average patterns, then examining variations that arise during the wettest and driest years and seasons in New Zealand over that period. Over the midlatitudes, the mean transfer is predominantly from the west, and most developed in summer. Over the subtropics, the mean summer transfer is predominantly from the north or northeast, but in winter a northwest flow prevails. Patterns of water vapor transfer during wet and dry periods over New Zealand differ more in direction than in magnitude, with the subtropical easterlies extending farther poleward during wet periods, especially in summer.

text: Water vapor transfer over the Southwest Pacific: Mean patterns and variations during wet and dry periods The mean water vapor transfer of the Southwest Pacific, as determined from radiosonde records near the 170°E meridional transect, is computed for the 1960–73 period. Emphasis is placed on defining average patterns, then examining variations that arise during the wettest and driest years and seasons in New Zealand over that period. Over the midlatitudes, the mean transfer is predominantly from the west, and most developed in summer. Over the subtropics, the mean summer transfer is predominantly from the north or northeast, but in winter a northwest flow prevails. Patterns of water vapor transfer during wet and dry periods over New Zealand differ more in direction than in magnitude, with the subtropical easterlies extending farther poleward during wet periods, especially in summer.

year: 1984

title: Tangihanga: The ultimate form of Māori cultural expression - overview of a research programme

authors: Nikora, Linda Waimarie

subjects: Māori

abstract: Death, observed through the process of tangihanga (time set aside to grieve and mourn, rites for the dead) or tangi (to grieve and mourn), is the ultimate form of Māori cultural expression. It is also the topic least studied by Māori or understood by outsiders, even after televised funeral rites of Māori leaders and intrusive media engagements with more humble family crises. It has prevailed as a cultural priority since earliest European contact, despite missionary and colonial impact and interference, and macabre Victorian fascination. Change is speculative rather than confirmed. Tangi and death rituals have yet to be rigorously examined in the Māori oral canon, or in the archival and historic record that may be discarded or reinforced by current practice. As researchers we are committed to studying tangi, conscious of the belief that such work carries the inherent risk of karanga aituā (inviting misfortune or even death itself) by drawing attention to it. Contemporary Aotearoa New Zealand is constantly touched by aspects of tangi practice through popular media and personal exposure.

This volatile subject nevertheless demands careful and comprehensive scrutiny in order to extend and enrich the knowledge base, reveal the logic that guides ritual, inform the wider New Zealand community and, more importantly, support the cultural, social, ritual, economic and decision making processes of bereaved whānau (family, including extended family), people affiliated with marae (communal meeting complex) and iwi (tribe, tribal). This paper provides an overview of a research programme that began in July 2009, based at The University of Waikato. The programme is funded by Ngā Pae o te Māramatanga, the Marsden Fund of New Zealand and the Health Research Council of New Zealand.

text: Tangihanga: The ultimate form of Māori cultural expression - overview of a research programme Death, observed through the process of tangihanga (time set aside to grieve and mourn, rites for the dead) or tangi (to grieve and mourn), is the ultimate form of Māori cultural expression. It is also the topic least studied by Māori or understood by outsiders, even after televised funeral rites of Māori leaders and intrusive media engagements with more humble family crises. It has prevailed as a cultural priority since earliest European contact, despite missionary and colonial impact and interference, and macabre Victorian fascination. Change is speculative rather than confirmed. Tangi and death rituals have yet to be rigorously examined in the Māori oral canon, or in the archival and historic record that may be discarded or reinforced by current practice. As researchers we are committed to studying tangi, conscious of the belief that such work carries the inherent risk of karanga aituā (inviting misfortune or even death itself) by drawing attention to it. Contemporary Aotearoa New Zealand is constantly touched by aspects of tangi practice through popular media and personal exposure.

This volatile subject nevertheless demands careful and comprehensive scrutiny in order to extend and enrich the knowledge base, reveal the logic that guides ritual, inform the wider New Zealand community and, more importantly, support the cultural, social, ritual, economic and decision making processes of bereaved whānau (family, including extended family), people affiliated with marae (communal meeting complex) and iwi (tribe, tribal). This paper provides an overview of a research programme that began in July 2009, based at The University of Waikato. The programme is funded by Ngā Pae o te Māramatanga, the Marsden Fund of New Zealand and the Health Research Council of New Zealand.

year: 2010