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Research Commons is the University of Waikato's Open Access research repository, housing research publications and theses produced by the University's staff and students.
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Item Eutrophication effects on stream macrophytes(Thesis, The University of Waikato, 2024-07-10)Macrophytes are large, autotrophic organisms residing in aquatic environments. In streams they play important roles as substrate, shelter, and food for higher trophic levels, alter water movements and perform biochemical transformations. Unfortunately, macrophyte diversity worldwide is under threat from multiple anthropogenic factors. Eutrophication, the process of nutrient enrichment following land use intensification, is a major driver of negative stream ecosystem change, often in combination with other anthropogenic pressures such as deforestation and introduction of non-native species. The current paradigm of macrophyte response to eutrophication notes the importance of the hydrological setting and substrate type, but always encompasses modification to competitive interactions between macrophyte growth forms as nutrient concentrations become less limiting and competition for light increases. However, details of the responses of macrophytes to increased nutrient inputs under multiple stressor environments are complex and still warrant investigation if effective guidance on macrophyte management is to be developed. In this thesis, I have addressed questions related to nutrient concentrations at which macrophytes start to accrue excessive biomass, how this relates to community shifts, what these community shifts look like and how they may be modulated by other variables. Specifically, I have used a mix of field observations and mesocosm experiments to: i) investigate differences in community composition of macrophyte communities in streams along a eutrophication gradient. ii) experimentally explore how external nutrient concentrations affect internal nutrient status, and consequently the growth, morphology, and photosynthesis of stream macrophytes across a range of irradiances. iii) investigate if these responses lead to differences in competitive outcomes between species in mixed cultures. To investigate relationships between eutrophication and macrophytes in streams in Aotearoa New Zealand, I surveyed 30 lowland streams on the country’s North Island, focusing on the Waikato region. I targeted sites with as few confounding factors as possible by using existing stream classification data to select reaches in each stream that had low slope, were unshaded, and a discharge of around 1 m3 s-1. From those meeting these criteria I used a pre-existing, land-use based nutrient yield model to selected streams expected to provide a range of nutrient concentration. At each site I sampled nutrients (N and P) in water and sediment and analyzed the dominant macrophyte species for internal N and P content. I quantified community structure on five transects across each stream. To explore links between environment and macrophytes I combined stream descriptors from national datasets in combination with the macrophyte community data and a list of trait scores of the encountered species in a RLQ multivariate analysis. The results showed a gradient in macrophyte community structure, a striking feature of which was the change in percentage of non-native species in the streams: eutrophic streams have almost no native species present. Additionally, many nutrient enriched streams were heavily clogged by macrophyte biomass, with species showing traits related to high performance and effective dispersal. A subsidiary gradient in the RLQ analysis, driven by nitrate and sediment phosphorous, saw a high presence of emergent species in eutrophic streams. This can be because the emergent species have a high nitrogen use efficiency compared to submerged species and can deal with a high turbidity by growing out of the water. A second subsidiary gradient, driven by water column phosphorous, correlated with eutrophic streams having a high degree of submerged non-native species; Ceratophyllum demersum, Egeria densa, Lagarosiphon major, and Elodea canadensis, all species that disperse primarily through fragmentation and can utilize bicarbonate as a carbon source. Phosphorous and carbon availability probably is a major driver for the presence of these species in these streams. To test inferences made from observational field investigations, growth, morphological, and photosynthetic responses to different levels of nutrient concentration were investigated in a new experimental mesocosm setup. The system comprised four flumes fed by local groundwater stripped of ions by a reverse osmosis system, then dosed with major ions, macro- and micronutrient elements in controlled amounts to ensure finely controlled growth conditions. The first experiment addressed hypotheses around the impact of nitrate concentration on growth of two pondweed species common to Aotearoa New Zealand, Potamogeton crispus and P. ochreatus, and possible interactions between nutrient and irradiance. Four nutrient concentrations (control ~0 µg NO3—N L-1, low ~20 µg NO3—N L-1, medium ~250 µg NO3—N L-1, and, high ~5000 µg NO3—N L-1) were combined with four light levels (67.7, 44.5, 30.9, and 7.8 mol photons m-2 d1) in a full factorial design. I measured internal nitrogen (N) and carbon (C) content, growth rates, and morphology and used pulse amplitude modulated fluorometry to make photosynthesis-irradiance curves. The four external nutrient concentrations gave rise to two distinct groupings of plants based on their final internal nutrient content: a high-N group (2-4 % N) from high and medium nitrate treatments and a low-N group (~1 % N) from the low and control nitrate treatments. High-N plants of both species had faster growth rates and grew wider and taller than the low-N plants, but P. crispus grew widest and branched more, especially at high light levels. Low light availability negated any significant difference between N groups and, notably, low-N individuals of P. ochreatus performed better in this treatment than those of P. crispus. In general, the native P. ochreatus performed better than the non-native P. crispus under low nutrient stress, and the latter was best at high light and high nutrients. The results suggest that P. crispus has a great proliferation potential in eutrophic areas, and that lowering resource levels can help manage not only macrophyte proliferation, but also invasive species. A potential competitive advantage can be inferred for P crispus in eutrophic, well-lit waters. The second mesocosm experiment investigated competitive interactions between the non-native and native pondweed. Four nutrient treatments were again used (0, 40, 120, and 400 µg NO3—N L-1), combined with two light treatments (18 and 3 mol photons m-2 d-1) in a full factorial design. In each treatment I compared growth of each species when plated in monoculture and mixed culture pots. For each replicate, growth rate and morphological traits (main stem length, lateral spread, branching degree, and root length) were measured. Neither species performed differently in mixed- or mono-specific cultures, indicating no inter-specific interactions under the experimental conditions. Rather, in mixed culture plots the outcome, in terms of growth differentials between taxa, reflected the responses of each species to the treatment. Increasing irradiance tended to result in P. crispus outperforming P. ochreatus, while increasing nutrient levels shifted allowed P. ochreatus to outperform P. ochreatus, particularly at low irradiance. Based on the results of this study, there is no direct short term competitive suppression of either species by the other, but differences in trait expression at different resource levels/combinations might still lead to competitive exclusion in a more natural setting. In this thesis I have shown that macrophytes respond to increases in external nutrient level by taking up more nutrients, increasing growth and expressing morphological plasticity. This is species dependent, however, and it is these differences in the ability to respond that appear to shape the macrophyte communities in streams. Streams with high light and nutrient supplies are susceptible to high accrual of biomass by a subset of responsive species that may ultimately end up being the only species present in these streams. I found that the eutrophication threshold for nitrogen is quite low, below 250 µg NO3-N L 1. Macrophyte growth was evident at nitrate concentrations only seen in quite pristine streams and several nutrient species seem to determine community compositions in streams. Thus, management actions for the protection of stream ecosystems would benefit from managing resource levels in general rather than focusing on a specific stressor.Item Automating test scripts for Android UI testing(Conference Contribution, Academy & Industry Research Collaboration Center, 2024)The Espresso capture/replay testing tool for Android applications creates tests that are prone to test fragility, in that when small changes occur to the user interface, tests break and are unable to be re-run. To reduce the fragility and its impact inherent in Espresso tests, we take a modeldriven development approach to test generation. Using interaction sequence models as the basis for generation, we are able to create test scripts that can be run in Android Studio identically to manually recorded tests. This process simplifies scripts when compared with those generated by recording and reduces the time required by developers to create and maintain the test suite, resulting in higher quality testing and validation of Android user interfaces.Item Teacher understanding and management of students with anxiety in New Zealand primary schools(Thesis, The University of Waikato, 2023)New Zealand has increasing rates of anxiety with 1 in 5 young people meeting the diagnostic criteria for an anxiety disorder by the age of 19 (Ministry of Health, 2018). As of June 2023, over 666,000 children aged between 5 and 14 years old were diagnosed with anxiety, equating to 12.8% of the total population of New Zealand (Stats NZ, 2022). As these children are likely to be engaged in formal education, this study investigated teachers understanding and management of students with anxiety in New Zealand primary schools. Twenty-three teachers from three primary schools completed a questionnaire exploring their definitions of anxiety, the training and support they received, and their identification of the manifestations of anxiety in primary school students. Teachers were also asked about their perceptions of the impacts of COVID-19 on student anxiety. Results revealed that while teachers had a general understanding of anxiety and could identify mild and severe anxiety symptoms, they reported a lack of training and confidence in the area and could not consistently distinguish normal anxiety from excessive anxiety, often defining all anxiety to be a generally negative experience. This study provides a first look into teachers understanding of anxiety in New Zealand primary school students.Item Pregnancy in a new home: Refugee mothers in New Zealand(Thesis, The University of Waikato, 2023)Purpose: Pregnancy signifies a delicate phase for women and is associated with potential adverse negative outcomes. Refugee woman are more at risk of experiencing heightened stress and negative pregnancy outcomes. As the population of refugee women in New Zealand continues to grow, it becomes imperative to comprehend their unique challenges, needs, and available supports during their pregnancy in New Zealand. Despite this, no research on this topic has been conducted in New Zealand. Therefore, the current research aims to explore what are the needs and challenges of former refugee woman in New Zealand during their pregnancy and how are they being supported? Methods: A thematic analysis was conducted on eight semi-structured interviews to understand the experiences of former refugee mothers. Participants consisted of four former refugee mothers who had recent given birth in the last three years at New Zealand and four service providers who had supported refugee mothers during their pregnancy. Results: The study identified six key themes critical to supporting pregnant refugee women in New Zealand. These encompassed the need for language assistance, guidance in navigating available systems, fostering relationships, cultural awareness within services, and recognizing the interconnected nature of their challenges, which often resulted in inadequate support for some pregnant refugee women. Additionally, the research highlighted a sense of appreciation among refugee mothers for the services provided by New Zealand. Conclusion: This study highlights the need for a holistic approach when supporting pregnant refugee woman and the significance of developing tailored community programs to educate and provide opportunity for socialisation.Item Understanding contemporary Māori demographic fertility patterns and trends in Aotearoa New Zealand(Thesis, The University of Waikato, 2024)This thesis re-examines demographic studies of contemporary Māori fertility patterns and trends. Analysing fertility is a core undertaking in demography, and in studies that include Māori fertility, most have been undertaken by non-Māori demographers who instinctively draw on Western-based frameworks to analyse and interpret these trends. Consequently, Māori perspectives are virtually invisible. Incorporating Māori perspectives are needed because despite a convergence of fertility similar to Pākehā, important fertility patterns persist. Notably, Māori women bear their babies earlier and over a longer period. Fertility studies of other Indigenous peoples in settler-colonial states share striking similarities. While demographic and economic factors are important in fertility outcomes, this thesis primarily explores the potential influence of culture, which has received little attention. Hence, this doctoral study asks: To what extent does culture influence contemporary Māori fertility patterns? This thesis draws on Kaupapa Māori and Mana Wahine frameworks, along with the tools of demography, to deploy a mixed methods design of statistical techniques – using secondary data from the 2013 Aotearoa NZ Census and the 1995 New Zealand Women: Family, Employment, and Education Survey – and thematic analysis of interviews with nine Māori women. While acknowledging the limitations of the analyses, the empirical results suggest that ‘cultural identity’ is an important factor in Māori fertility, and that ‘whakapapa’ and ‘whānau’ are at the heart of fertility decisions. These findings broadly imply that taken-for-granted demographic theories and analytical practices need to incorporate Indigenous-centred frameworks and perspectives for a better understanding of Indigenous fertility and population change.
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