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The research carried out at AUT's Faculty of Health and Environmental Sciences can be broadly defined in three themes:
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Browsing Faculty of Health and Environmental Sciences by Subject "05 Environmental Sciences"
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- ItemDirectional Changes Over Time in the Species Composition of Tropical Vascular Epiphyte Assemblages(WILEY, 2021-11-28) Mendieta-Leiva, G; Buckley, HL; Zotz, GUnderstanding the degree to which deterministic and stochastic processes drive community assembly is an ongoing focus of research in community ecology. This effort is strongly biased towards ground-rooted plants, resulting in a limited understanding of communities of other life-forms, such as structurally dependent plants. Vascular epiphytes are sessile organisms growing non-parasitically on three-dimensional dynamic patches, their host plants. Since negative biotic interactions are thought to play a minor role in vascular epiphyte assembly, in some forests, epiphytes are fascinating model organisms to understand the prevalence of environmental filtering in shaping community assembly. We assessed the contribution of deterministic processes on the temporal dynamics of vascular epiphyte assemblages by tracking the direction of changes in composition, species richness and abundance in time at different ecological and spatial scales. We made use of a globally unique dataset from a lowland forest in Panama. We predict that if niche-based mechanisms dominate, (a) temporal changes will be directional and (b) differences in the species composition of epiphyte assemblages will be primarily related to host plant characteristics and, to a lesser degree, to the distance between host trees. We show that temporal changes in vascular epiphyte assemblages were directional at different ecological scales, such as the forest patch, host species or individual tree assemblages. Epiphyte assemblages on host trees became more similar in their composition over time than expected by chance, and these changes were not due to homogenisation. While host characteristics were related to these directional changes, host structure rather than host identity was more strongly related to variation in assemblage dissimilarity, while spatial distance among trees was of minor importance. The observed directionality was primarily due to environmental filtering. This study provides the first evidence that niche-based mechanisms dominate the dynamics of vascular epiphyte assemblages. Analysing temporal patterns of vascular epiphyte assemblages is a first important step towards understanding the relative importance of deterministic processes for diversity maintenance of one of the most diverse plant groups in the tropics. Synthesis. Directionality in the temporal changes of epiphyte assemblages suggests that niche-based mechanisms dominate these temporal changes. Host size over host identity is the most important environmental filter for epiphyte assemblages establishment.
- ItemDiversity of the Squid Genus Leachia (Oegopsida: Cranchiidae) in the Pacific Ocean(Springer Science and Business Media LLC, 2023-05-08) Evans, AB; Bolstad, KSRLeachia is a cosmopolitan tropical/temperate genus of ‘glass’ squids (Cranchiidae) whose taxonomy has been plagued with instability typical of the family. Eight species are currently believed to exist worldwide, including some not yet described. This review assesses the Pacific taxa, describes a novel species, L. separata, and provides updated diagnoses for the other Pacific species. Type material and original descriptions are compared, and brief remarks provided on the Atlantic taxa. The most useful characters for identifying Leachia species appear to be the number of ocular photophores and the configuration of the ventral cartilaginous strips and associated tubercles on the mantle, with arm and sucker-ring dentition also proving useful in some taxa. Further work on the genus is needed, ideally including molecular tools.
- ItemEcosystem Integrity of Active Sand Dunes: A Case Study to Implement and Test the SEEA-EA Global Standard, From Aotearoa New Zealand(Elsevier BV, 2023-05-01) Ryan, C; Case, BS; Bishop, CD; Buckley, HLBiodiversity and ecosystem functions are deteriorating worldwide, and there is an urgent need to reverse these declines and set ecosystems on a path to recovery. Effective monitoring, including a fit for purpose indicator framework, is essential to track progress towards targets but, as yet there is no universal framework that delivers timely data on biodiversity and ecosystem change. Ecosystem integrity is a unifying concept that refers to the capacity of an ecosystem to be resilient to natural or anthropogenic perturbations, and to maintain characteristic species composition, structure, functioning and self-organisation over time within a natural range of variability. Using a case study which can be generalised to international contexts, we implement and test a new global standard for the assessment, monitoring and ranking of ecosystem integrity of active sand dunes in Aotearoa New Zealand.
- ItemFirst Reports of Trace Element Bioaccumulation in the Antarctic Deep-Sea Squid Psychroteuthis glacialis(Springer Science and Business Media LLC, 2023-10-16) Lischka, A; Braid, HE; Gaw, S; Bolstad, KSRTrophic interactions in the Antarctic Ocean are likely to be affected by changing environmental conditions. Some of these impacts can be observed, and predicted, by monitoring trace element concentrations in the tissues of animals at certain trophic levels. The ‘glacial’ squid (Psychroteuthis glacialis) is an ideal indicator species for measuring trace element bioaccumulation in the Ross Sea because it plays a central role in local marine food webs. Trace elements (Al, As, Cd, Co, Cu, Fe, Hg, Ni, Mn, Pb, U, V, and Zn) were measured in mantle and digestive gland tissues of 57 P. glacialis specimens, including juvenile and mature individuals. Significant differences in Al, As, Cd, Cu, Fe, Mn, V, and Zn concentrations were observed across life stages, with juveniles generally having the highest concentrations. As the bioaccumulation of most trace elements is influenced by diet, our results suggest different feeding patterns between juvenile and mature P. glacialis. In turn, it is likely that the life stage of P. glacialis individuals consumed by predators will determine trace element exposure higher up the trophic web. Overall, this Antarctic squid appears to be influenced by the trace element cycling in the Ross Sea and contains lower concentrations of trace elements than have been observed in squids in warmer waters.
- ItemInteractive Effects of Elevated Temperature and Photobacterium swingsii Infection on the Survival and Immune Response of Marine Mussels (Perna canaliculus): A Summer Mortality Scenario(Elsevier BV, 2024-02-03) Azizan, Awanis; Venter, Leonie; Zhang, Jingjing; Young, Tim; Ericson, Jessica A; Delorme, Natalí J; Ragg, Norman LC; Alfaro, Andrea CThe New Zealand Greenshell™ mussel (Perna canaliculus) is an economically important aquaculture species. Prolonged increases in seawater temperature above mussel thermotolerance ranges pose a significant threat to mussel survival and health, potentially increasing susceptibility to bacterial infections. Using challenge experiments, this study examined the combined effects of increased seawater temperature and bacterial (Photobacterium swingsii) infection on animal survival, haemocyte and biochemical responses of adult mussels. Mussels maintained at three temperatures (16, 20 and 24 °C) for seven days were either not injected (control), injected with sterile marine broth (injection control) or P. swingsii (challenged with medium and high doses) and monitored daily for five days. Haemolymph and tissue samples were collected at 24, 48, 72, 96, 120 h post-challenge and analysed to quantify bacterial colonies, haemocyte responses and biochemical responses. Mussels infected with P. swingsii exhibited mortalities at 20 and 24 °C, likely due to a compromised immune system, but no mortalities were observed when temperature was the only stressor. Bacterial colony counts in haemolymph decreased over time, suggesting bacterial clearance followed by the activation of immune signalling pathways. Total haemocyte counts and viability data supports haemocyte defence functions being stimulated in the presence of high pathogen loads at 24 °C. In the gill tissue, oxidative stress responses, measured as total antioxidant capacity and malondialdehyde (MDA) levels, were higher in infected mussels (compared to the controls) after 24h and 120h post-challenge at the lowest (16 °C) and highest temperatures (24 °C), indicating the presence of oxidative stress due to temperature and pathogen stressors. Overall, this work confirms that Photobacterium swingsii is pathogenic to P. canaliculus and indicates that mussels may be more vulnerable to bacterial pathogens under conditions of elevated temperature, such as those predicted under future climate change scenarios.
- ItemPropagating Uncertainty in Predicting Individuals and Means Illustrated with Foliar Chemistry and Forest Biomass(Springer Science and Business Media LLC, 2024-01-22) Yanai, RD; Drake, JE; Buckley, HL; Case, BS; Lilly, PJ; Woollons, RC; Gamarra, JGPQuantifying uncertainty is important to establishing the significance of comparisons, to making predictions with known confidence, and to identifying priorities for investment. However, uncertainty can be difficult to quantify correctly. While sampling error is commonly reported based on replicate measurements, the uncertainty in regression models used to estimate forest biomass from tree dimensions is commonly ignored and has sometimes been reported incorrectly, due either to lack of clarity in recommended procedures or to incentives to underestimate uncertainties. Even more rarely are the uncertainty in predicting individuals and the uncertainty in the mean both recognized for their contributions to overall uncertainty. In this paper, we demonstrate the effect of propagating these two sources of uncertainty using a simple example of calcium concentration of sugar maple foliage, which does not require regression, then the mass of foliage and calcium content of foliage, and finally an entire forest with multiple species and tissue types. The uncertainty due to predicting individuals is greater than the uncertainty in the mean for studies with few trees—up to 30 trees for foliar calcium concentration and 50 trees for foliar mass and calcium content in the data set we analyzed from the Hubbard Brook Experimental Forest. The most correct analysis will take both sources of uncertainty into account, but for practical purposes, country-level reports of uncertainty in carbon stocks can safely ignore the uncertainty in individuals, which becomes negligible with large enough numbers of trees. Ignoring the uncertainty in the mean will result in exaggerated confidence in estimates of forest biomass and carbon and nutrient contents.
- ItemTemperature Dependency of Litter Decomposition Is Not Demonstrated Under Reciprocal Transplantation of Tussock Leaves Along an Altitudinal Gradient(Wiley, 2023-01-17) Krna, Matthew A; Tate, Kevin R; Saggar, Surinder; Buckley, Hannah L; Rapson, Gillian LDecomposition rates are an important component of carbon sequestration rates in soils, potentially mitigating future climate change. Here we aim to better understand decomposition's relationship with temperature in natural conditions. In snow-tussock grassland dominated by Chionochloa rubra on Mount Tongariro, Tongariro National Park, New Zealand, we measured decomposition of Chionochloa leaf litter along an ≈ 700 m altitudinal gradient, as a space-for-temperature experiment, representing 4.2°C of warming. We examined decomposition rates in a full reciprocal translocation of litter bags between eight plots as both the origin of eight litter types and the eight destinations of plating out of litter bags, over 4 years using six replicates, and modelled their relationships to environmental variates. Litter decomposed progressively over time, but at the same rate along the altitudinal gradient. There was no home-field advantage. In terms of litter quality, decomposition rates were related only to litter lignin, or fibre or litter N. Only decomposition at Year 4, and that only when organised by litter destination, showed a relationship to mean annual temperature jointly with soil C, and this was only weak and implausible. When studied across the full reciprocal transplant, there were no significant interactions between Origin and Destination data with or without Years. Therefore litter from each plot decomposed at the same rate as other plots' litter at all altitudes, allowing for small, often irregular differences in litter quality and micro-environment. Despite the few modelled differences, decomposition rates show no plausible trends in our altitude-for-temperature substitution. We suggest this may be a universal finding, except perhaps under different moisture regimes. Thus, under projected climate warming scenarios, changes in temperature will not directly affect decomposition rates, and cannot influence C sequestration in nature. Read the free Plain Language Summary for this article on the Journal blog.
- ItemWhen Things Get MESI: The Manipulation Experiments Synthesis Initiative – A Coordinated Effort to Synthesize Terrestrial Global Change Experiments(Wiley, 2023-01-06) Van Sundert, Kevin; Leuzinger, Sebastian; Bader, Martin K-F; Chang, Scott X; De Kauwe, Martin G; Dukes, Jeffrey S; Langley, J Adam; Ma, Zilong; Mariën, Bertold; Reynaert, Simon; Ru, Jingyi; Song, Jian; Stocker, Benjamin; Terrer, César; Thoresen, Joshua; Vanuytrecht, Eline; Wan, Shiqiang; Yue, Kai; Vicca, SaraResponses of the terrestrial biosphere to rapidly changing environmental conditions are a major source of uncertainty in climate projections. In an effort to reduce this uncertainty, a wide range of global change experiments have been conducted that mimic future conditions in terrestrial ecosystems, manipulating CO2 , temperature, nutrient and water availability. Syntheses of results across experiments provide a more general sense of ecosystem responses to global change, and help to discern the influence of background conditions such as climate and vegetation type in determining global change responses. Several independent syntheses of published data have yielded distinct databases for specific objectives. Such parallel, uncoordinated initiatives carry the risk of producing redundant data collection efforts and have led to contrasting outcomes without clarifying the underlying reason for divergence. These problems could be avoided by creating a publicly available, updatable, curated database. Here, we report on a global effort to collect and curate 57,089 treatment responses across 3,644 manipulation experiments at 1,145 sites, simulating elevated CO2 , warming, nutrient addition and precipitation changes. In the resulting Manipulation Experiments Synthesis Initiative (MESI) database, effects of experimental global change drivers on carbon and nutrient cycles are included, as well as ancillary data such as background climate, vegetation type, treatment magnitude, duration, and, unique to our database, measured soil properties. Our analysis of the database indicates that most experiments are short-term (one or few growing seasons), conducted in the USA, Europe or China, and that the most abundantly reported variable is aboveground biomass. We provide the most comprehensive multifactor global change database to date, enabling the research community to tackle open research questions, vital to global policymaking. The MESI database, freely accessible at doi.org/10.5281/zenodo.7153253, opens new avenues for model evaluation and synthesis-based understanding of how global change affects terrestrial biomes. We welcome contributions to the database on GitHub.