1,721,005 research outputs found
Ecophysiology of Grey-faced Petrels: Interannual Insights and Proxies of Body Condition
No full textAmidst a rapidly changing climate, bioindicator species, namely seabirds, emerge as sentinels for monitoring shifts in ecosystem dynamics. Investigations into seabird physiology contribute significantly to the burgeoning field of conservation physiology and aid in the management of
vulnerable populations. The present research delves into the stress response of grey-faced
petrels (Pterodroma gouldi), exploring the interplay of behaviour and metabolism under
varying ocean conditions, with a particular focus on the unusually warm ocean conditions of
2022.
This study builds upon prior observations of site-specific variations in the condition of both
adult and chick grey-faced petrels along the east and west coasts of the Auckland Region.
Metrics of body condition, including weight, haematological measurements and metabolomic
profiling, are examined within the context of changing interannual ocean conditions. These
metrics are assessed in eastern and western locations to discern differences in food availability
and metabolic expenditure.
Analysis of weight and haematological profiles reveals that low weight and elevated
haemoglobin concentrations act as proxies for heightened metabolic effort, as exemplified in
east coast birds in 2022. Metabolomic profiling identifies succinic acid and para-toluic acid as
key metabolites in determining between site-specific groups. It provides further evidence of
physiological stress in the regulation of metabolic functions.
This research underscores that, during marine heatwaves, a heightened energetic demand is
imperative to locate adequate food patches. Increased haemoglobin concentrations, low weight,
and succinic acid collectively signify imbalances in energy dynamics. Furthermore, succinic acid and para-toluic acid indicate metabolic stress, leading to the harmful production of reactive oxygen species (ROS). The importance of this research manifests in its contribution to the expanding body of knowledge concerning seabird health and endangerment and in its future value in assessing sea health
Comparative conservation physiology of Hoiho | Yellow-eyed penguins (Megadyptes antipodes)
No full textFull Text is available to authenticated members of The University of Auckland only.Studies of avian physiology provide insights into sub-lethal impacts of stress and diet, indicating potential underlying causes of decline and adaptive capacity. This knowledge can be used to improve conservation management of at-risk populations. Hoiho (Megadyptes antipodes) breeding on the south-eastern coast of the South Island, New Zealand, exhibit poor reproductive success and have small populations compared to subantarctic populations. This offers a unique opportunity to map broad physiological traits indicative of sub-lethal (chronic) stress and diet changes in a Sphenisciformes species. Diving is essential to seabird foraging and survival. This is the first study to estimate oxygen stores and dive capability (maximal dive depth), maximal dive duration and calculated aerobic dive limit in hoiho. Calculated maximum dive depth estimates exceeded reported depths, suggesting high adaptive capability in the event that hoiho prey shift to cooler, deeper waters, and that hoiho continue to employ a benthic foraging strategy. However, current maximum theoretical dive durations often exceed calculated aerobic dive limit (cADL), which suggests that performing deeper dives, should key prey shift to greater depths, will be more energetically expensive with longer wait times between them to recover oxygen debt. Nutritional stable isotopes and corticosteroid hormones can identify chronic stress or shifts in diet. As such, these were quantified to understand how hoiho populations vary spatially and among breeding seasons. Compared to subantarctic populations, mainland hoiho had higher carbon and nitrogen values that were indicative of inshore/benthic feeding on higher-trophic-level prey. This suggests that mainland birds have lower prey abundance and diversity, leading to lower diet quality. Comparisons across several seasons indicated a trophic increase, suggestive of a prey shift. Chick stress increased and adults fed further offshore during La Niña seasons, suggesting nutritional stress in hoiho chicks results from prey distribution shifts induced by warming sea temperatures. This work provides first insights into the diving and stress physiology of hoiho which may augment existing management plans for the species. Spatio-temporal differences in physiology and foraging ecology reflected contrasting environmental conditions experienced by each population which may finesse species distribution modelling methods to predict future locations. This validated the integrated use of feather corticosterone and stable isotopes of hoiho populations to monitor changes in marine ecosystem health. I recommend further studies should undertake compound-specific stable isotope analyses to determine if differences in stable isotopes are due to genuine differences in foraging niche or differing environmental baselines
Factors influencing the retention of early juvenile green-lipped mussels, Perna canaliculus (Gmelin, 1791), in aquaculture production
No full textThe global mussel aquaculture industry relies heavily on the regular supply of wild seed
mussels, known as spat, to initiate aquaculture production. Supplies of wild mussel spat have a
lower cost than spat produced in a shellfish hatchery, but wild spat are often highly variable in
quantity, size and nutritional condition, which greatly affects their performance after being
seeded out onto coastal mussel farms. For example, high losses of more than 80% of spat
consistently occur within the first few weeks after seeding out in New Zealand’s green-lipped
mussel (Perna canaliculus) industry. These losses have often been associated with variability
of the size and nutritional condition of wild spat prior to seeding. This current study has
confirmed that variability of size of green-lipped mussel spat prior to seeding affects their
subsequent retention, where spat of larger than 1 mm in shell length have a higher propensity
to remain attached to aquaculture longlines when compared to spat of less than 1 mm. Wild
spat collected and transported for ~40 h from their collection site show reduced nutritional
condition, as indicated by their low glycogen reserves. When exposed to periods of
experimental starvation of up to two weeks, spat were found to utilise glycogen reserves as their
primary source of energy. Observations during this current study indicated that sufficient
supplies of high quality food appear to be important for spat retention both in the laboratory
and field situations. Spat that were experimentally starved for up to two weeks, to emulate
conditions experienced during spat transportation from the collection sites to the seeding sites,
showed a lower retention in the laboratory than spat that were well fed. However, once spat
were seeded out, the local environmental conditions at the seeding site at coastal mussel farms
appeared to play an important role in determining the subsequent retention of mussel spat. The
unfavourable environmental conditions at the mussel farm used for experimentation, may have
included low water velocities and insufficient food supply, the presence of which was thought
to reduce the retention of spat on the mussel farm, despite them being well fed prior to seeding.
The potential use of commercially available concentrated microalgal products were
experimentally evaluated as complete and partially substitutes for feeding live microalgae to
mussel spat. Concentrated microalgal products can be used to replace up to 50% of live
microalgae for feeding spat without compromising their survival and nutritional condition.
Overall, the research presented in this study improves our understanding of the effects of size
and nutritional condition of spat at the time of seeding out onto coastal mussel farms on their
subsequent retention, and the nutritional requirements of spat and how these may be met
through feeding live microalgae and substitute products
Conservation Physiology: Stress and the Development of New Monitoring Technologies
No full textFull Text is available to authenticated members of The University of Auckland only.Conservation of declining seabird species has become an increasing concern of local government and
conservation entities. Due to limited resources, the assessment for priority species must be accurately
executed so that conservationists appropriately aid at-risk species. Sooty shearwaters (Puffinus griseus)
migrate from the Northern Hemisphere to breed in New Zealand, where colonies are present in a latitudinal
gradient. This presented a unique opportunity to identify any spatial differences in physiological stress
between two sooty shearwater colonies. Additionally, sooty shearwaters were compared to the sympatric
flesh-footed shearwaters (Puffinus carneipes), present in the same northern colony, after observational
reports that sooty shearwaters were being displaced.
Initial plasma corticosterone and haematological parameters both provide insight into the physiological
stress experienced by avian species. Thus, these were quantified and compared across sooty shearwater
colonies, species (sooty and flesh-footed shearwaters) and breeding stages (pre-laying season and incubation
period). There were no significant differences in the initial plasma corticosterone between the two species,
breeding stages or sooty shearwater locations. However, the haematological profile was significantly
different across all comparisons in at least one haematological parameter, indicating differing life history
and stress responses.
Current methods of measuring stress in seabirds involve sampling blood which has raised concerns due to
the bleeding and handling process having potentially negative impacts on the health of adults and possibly
chick abandonment. Alternative, less invasive methods were tested in this study, including feather sampling
of sooty shearwaters for feather corticosterone as a physiological stress measure as well as developing a new
monitoring technology that could remotely trace feeding events from parents, chick mortality and chick
fledging. Both pilot studies were successful in their respective aims and provide a basis for future
investigations for optimal conservation techniques that have minimal impacts on wildlife population health.
The new monitoring technology especially has great potential in conservation work and could be
implemented across more seabird conservation work
Stress Physiology of Grey-Faced Petrels : interannual measures of feather corticosterone as a conservation tool
No full textSeabirds are ecologically relevant top predators and ecosystem engineers, but also the most threatened group of birds globally. Seabirds face many threats, but among the most critical is overall ocean health. Monitoring ocean health is difficult and expensive, but breeding seabirds have been touted as a potential low-cost bioassay of ocean health. However, the effectiveness of that relationship remains unclear and warrants further validation. Understanding how shifts in ocean conditions influence foraging opportunities for seabirds may assist the management of populations and inform on the dynamics of ocean conditions. Changes in food supply and potential nutritional challenges are often reflected in seabird physiology. Specifically, stress hormones often show a strong link to food supply, suggesting they are useful tool for linking ocean health, foraging conditions, and seabird population demographics. In birds, corticosterone (hereafter CORT) is the predominant stress hormone, and responses to stressors are reflected in changing CORT levels.
Because CORT levels are reflected in developing feathers, measures of feather CORT (fCORT) may provide useful estimates of environmental stressors. However, the pattern of variation in stress hormone levels varies among species and their environmental context, thus requires validation from intra-species studies to draw reliable conclusions. Grey-faced Petrels (Pterodroma gouldi) are long lived, have high site-fidelity and are widespread, which provides good scope for robust validation experiments. Here, I determine whether variation in fCORT can be used as a proxy of ocean conditions and as a monitoring tool for population breeding success. I used reproductive data and feather samples collected over four breeding seasons (2017, 2019, 2020, 2021). I measured fCORT levels from chicks at Ihumoana Island. To investigate whether fCORT reflects changes in relevant ocean conditions, I analysed the relationships between fCORT and remote sensing data (sea surface temperature - SST/chlorophyll-a - Chl-a), measurements of feather quality, stable isotopes, and breeding success (i.e., chick’s body condition, fledging success for laid eggs). I also examine measures of parent quality (fCORT and quality, mass, age) to determine which factors predict breeding success.
I found that chick stress levels fluctuated among seasons, but variation was not tightly coupled to ocean conditions. More stressful ocean conditions (High SST/low Chl-a) predicted lighter chicks, but also a decline in fCORT. Increased fCORT and lower feather quality (i.e., brightness) predicted reduced breeding success. Parental mass predicted chick body condition, but not chick fCORT. Further, foraging distance, as suggested by stable isotopes, varied annually, and increasing foraging trip distance from the colony was correlated with worse feather quality and showed year specific relationships with fCORT. This study reveals that taken together, fCORT and feather quality measures offer a promising tool for seabird conservation. Future studies should aim to confirm the underlying mechanisms of fCORT variation and relationship to study variables by exploring foraging behaviour and dietary patterns in search for the best proxy of ocean conditions affecting Grey-faced petrel populations
Advancing the nursery culture of juvenile green-lipped mussel, Perna canaliculus
No full textThe green-lipped mussel, Perna canaliculus, has become one of the most valuable seafood exports from New Zealand with current annual export earnings of US$308 million based on the production of around 200,000 t each year. However, the green-lipped mussel aquaculture industry in New Zealand relies heavily on juvenile mussels, or spat, harvested from the wild. Consequently, with the rapid growth of the industry, shortages of spat have become an increasingly major constraint for the industry. One of the solutions is to optimise the quantity and quality of juvenile mussels produced from a hatchery. However, the production of juvenile mussels in a hatchery is costly compared to harvesting wild mussel spat, with the production of microalgal food for hatchery spat contributing around 30 – 50 % of total hatchery production costs. There is still limited information on the feed requirements of juvenile mussels and the optimum environmental conditions required to obtain the best performance from spat in the hatchery situation. Therefore, the aim of the research presented in this thesis was to investigate the feeding abilities of juvenile P. canaliculus of a range of sizes when exposed to microalgal food particles of various sizes, and to observe some of the potential key environmental conditions that may affect the performance of the mussels in a nursery situation (i.e., growth, retention and survival). Flow cytometry (FCM) was used to count microalgae to determine the filtering abilities of juvenile mussels of a range of sizes when exposed to a variety of microalgae species of different sizes. Potential key environmental conditions (i.e., light exposure, water motion and oxygen levels) were experimentally manipulated and the subsequent performance of juvenile mussels was measured to determine the optimal culture conditions. The results showed that during a short observation period (1 h) the smallest size class of juvenile mussels used in this study (0.5 – 0.9 mm) was more efficient at filtering larger sized microalgae species (i.e., > 6 μm cell diameter) compared to microalgae species of smaller size. This suggests that the current commercial practice of feeding juvenile mussels with small microalgae species (i.e., 3 – 5 μm cell diameter) is highly inefficient. Over a longer observation period (24 h), when a range of sizes of P. canaliculus spat were provided with a high concentration (40 cells μl⁻¹) of four microalgae species with different cell sizes (i.e., Diacronema lutheri, Tisochrysis lutea, Chaetoceros muelleri, and Tetraselmis suecica), the particle capture ability was found to increase in proportion to the size of the juvenile mussels. The largest microalgae species T. suecica tended to be captured at the lowest rate compared to a smaller microalgae species D. lutheri. Using the longer observation period (i.e., 24 h) with FCM measures found that juvenile mussels in the size class of 0.5 – 0.9 mm in shell length were highly efficient at capturing all four of the tested microalgae species at ~2.4 – 2.9 × 10⁵ cells mussel⁻¹ 24 h⁻¹. Results from the experiments testing the effects of environmental conditions on the performance of juvenile iv mussels under culture conditions indicated that a combination of light exposure (i.e., some period of light exposure within 24 h) produced better growth, while high water motion (i.e., > 33 ml s⁻¹ of aeration or > 5 cm³ s⁻¹ water flow) and high oxygen levels (i.e., > 80 %) increased the growth, retention and survival of juvenile P. canaliculus. Overall, the results of the research presented in this thesis provide valuable information that has the potential to greatly increase the efficiency of commercial nursery culture of juvenile P. canaliculus in New Zealand
Oceanic Storytellers Integrative methods for seabird conservation monitoring
No full textFaced with a rapidly changing climate, there is a need to improve methods for conservation monitoring and management of seabirds, the most threatened group of birds in the world. To better understand the impacts of environmental variables on seabird health, links must be drawn between their diet, distribution, health, and the fluctuations of the physical environment. Given a paucity of local data, my thesis aims to generate baseline information on these parameters for four Procellariiform species (fluttering shearwater, little shearwater, Buller’s shearwater, and fairy prion) breeding in northern Aotearoa New Zealand. I review the utility of ecophysiological tools for seabird conservation (Chapter 2) and test the fluctuations of haematological parameters in my four study species to determine if this tool has the sensitivity required to monitor seasonal changes in bird condition (Chapter 3). Haematological parameters are subject to within-season fluctuations but do appear to be useful for monitoring population health across seasons. I assess the isotopic niche partitioning of these four species during a period of high local resource competition during the breeding season (Chapter 4) and determine that there are within-season shifts for two species for targeting higher trophic level prey during chick-rearing, and a consistent trophic structure between the species that could be impacted by local scale environmental change. I use GPS tracking to profile the at-sea distributions of these four species during chick-rearing (Chapter 5) and illustrate the variable scales at which environmental conditions can impact each species, as well as providing evidence for different foraging strategies, spatial overlap and partitioning, and a lack of overlap with current Marine Protected Areas. A marine heatwave in December 2021 enabled a targeted assessment of physiological, dietary, and foraging stability in fluttering shearwaters, the most inshore-foraging species of the four, and showed evidence for the sublethal impacts of anomalous sea surface temperatures (Chapter 6). Taken together, these data are discussed in the context of improving the ability of conservation monitoring techniques to detect and respond to rapid change (Chapter 7), by assessing sublethal signs of stress as an ‘early-warning signal’ for seabird populations
Seabirds as Tohu of Ocean State : Tohu Informed and Guided Kaitiakitanga
No full textBioaccumulation and toxicity of heavy metal pollutants has the potential to contaminate
marine systems when present in high concentrations. For centuries, seabirds have been
used by Indigenous communities to determine the health of marine systems. More recently,
Western science has also recognized seabirds as useful indicators to monitor elevated risk
of marine pollutants. This project aims to explore the role of seabirds as indicators of ocean
state using a ‘tohu’ framework that reflects a kaitiakitanga-based natural resource
management. This advocates for a natural resource co-governance model by drawing upon
the knowledges, values and ethics of western and Māori world views. Following a kaupapa
Māori based methodology, three customary harvest mutton-bird species (Ōi (Pterodroma
gouldi/grey faced petrel); Tītī (Puffinus griseus/sooty shearwater; and Toanui (Ardenna
carneipes/flesh-footed shearwater) were investigated using both qualitative and quantitative
methods. Semi-structured interviews identified three key themes in resource management of
these birds by Māori: harvesting practices, kaitiakitanga, and whanaungatanga. Harvest
practices had a bottom-up governance approach creating diverse harvesting techniques that
adapt to local environments. Kaitiakitanga identified mana whenua rights in and power-
sharing in natural resource management as a requirement for success. Whanaungatanga
also identified relationships and collaboration as a vital component. Inductively coupled
plasma mass spectrometry (ICP-MS) and laser ablation ICP-MS (LA-ICP-MS) were used to
analyse a 22-elemental suite of feather ōi, tītī, and toanui feathers. These were compared
against species, sex, age, blood heterophil-lymphocyte (H:L) ratios, feather deposition
patterns, and life stage. Compared with tītī and toanui, ōi had the highest levels of Hg whilst
toanui recorded the lowest concentrations of Mn and Cu of the three species. As these
species forage and migrate to different marine areas, this may reflect marine elemental
compositions. In adult ōi, Hg and Se were positively correlated with age. Whereas ōi chicks
had the highest Hg feather concentrations compared to fledged chicks and adults. This may
have implications for the consumption safety of ōi chicks. Variations in feather metal
deposition in mid-to-upper sections of the feather rachis. Thus, clipping samples from these
sections is sufficient for sampling which is far less invasive than removing an entire feather.
No differences were found between ōi feather elemental composition and H:L ratios and sex.
These novel findings inform both conservation efforts and customary harvest practices.
Genuine cross-cultural collaboration is imperative to successfully address the health of these
birds, marine health, and the communities consuming these birds
Optimising the larval rearing environment for the New Zealand Greenshell™ mussel (Perna canaliculus)
No full textFull Text is available to authenticated members of The University of Auckland only.The Greenshell™ mussel (Perna canaliculus, Gmeiln, 1791) is New Zealand’s largest aquaculture export earner. Larvae supplied to industry are increasingly coming from shellfish hatcheries. Like many marine invertebrates, Greenshell™ mussels respond to metals in their aquatic environments, which may influence larval growth and competency. However, culture waters with the appropriate conditions to optimize development of Greenshell™ mussels have not been properly studied and existing GreenshellTM hatcheries are potentially operating at rather inefficient levels due to high mortality rates of larvae. My research aimed to test if early larval development of Greenshell™ mussels can be improved by altering concentrations and presence of beneficial metals. To test the effects of different metals treatments (i.e., strontium, magnesium and two commercial aquaria blends ‘trace’ and ‘amino acid’ solutions), mussel larvae were set up in tanks with different types and concentrations of metals. Growth, survival, competency and metal uptake were recorded. Furthermore, due to rising ocean acidification levels, there is also interest to test treatments which may buffer the acidity levels. To do this, calcium carbonate and a pH buffer blend treatment were also trialled on mussel larvae and shell strength tested using a nanoindentor.
The strontium, magnesium and amino acid treatments had negative effects on D-yield (the percentage of newly born larvae that reach the D-larval stage) and shell length. D-Yield of strontium and magnesium groups were 0%, with and without EDTA, while the Amino group had a D-yield of 74.64% with EDTA and 0.63% without EDTA in tissue culture dishes (TCDs). In 5 litre aquaria, D-Yields of Amino treatments were 78.91% with EDTA and 0% without EDTA. Shell lengths of Amino treatments were 87.36mm and 80.42mm in the presence and absence of EDTA, respectively. For the strontium, this was due to low pH levels caused during treatment while the other two treatments may have been above ideal doses. The trace metal blend displayed very minor D-yield benefits. Calcium carbonate and buffer had positive effects on shell length and D-yield. The buffer blend was the superior of the two treatments and displayed the highest shell strength values.
Lastly induced physiological resilience was tested via immersing larval mussels in prickly pear (Opuntia sp.) solutions (either a commercially available extract i.e., Pro-tex™ or powders). Both, Pro-tex and the pricky pear powder both improved stress tolerance. Pro-tex was more beneficial at LT99 while the powder was superior at LT50. Cumulatively, these results provide suggestions for improving hatchery culturing practices while initiating research into unexplored sub-fields of aquaculture science for future studies
The global diversity and biogeography of Isopoda
No full textThe order Isopoda is a species-rich and morphologically diverse taxon of peracarid crustaceans.
They not only occur in marine environments but have also successfully conquered freshwaters
and the terrestrial realm. This thesis examines the global diversity and biogeographic patterns
of isopods within all three environments. After summarising what is known about their natural
history, distribution, and ecological and economic importance, attention is drawn to the
taxonomic diversity of isopods and their rate of description. A global list of accepted species
names, including their authorities and the year of first description, was gathered from the World
Register of Marine Species (WoRMS). Since the first formal description of an isopod species
by Linnaeus in 1758, 10,687 isopod species in 1,557 genera and 141 families have been
described by a cohort of 755 first authors. Although the number of authors has increased manyfold
over time, the average number of species described per first author has declined, and the
description rate has slowed down. Shifting the attention to global biodiversity patterns within
isopods, the latitudinal diversity gradient (LDG) in species richness is first examined, followed
by bioregionalisations within aquatic and terrestrial environments. To do so, a dataset of
worldwide occurrence records was compiled from the Ocean Biogeographic Information
System (OBIS) and the Global Biodiversity Information Facility (GBIF). Isopods exhibit a
bimodal LDG with higher species richness in the southern hemisphere for marine isopods and
in the northern hemisphere for non-marine isopods. Sampling bias in the data does not
significantly affect the overall shape of the LDG. However, when accounted for, the location
of diversity peaks tends to move towards tropical latitudes compared to the observed species
richness, which is highest in mid-latitudes. A clustering algorithm was employed to identify
distinct biogeographic regions based on their species composition. It delineated 33 marine, 28
terrestrial, and 23 freshwater bioregions – all with high endemicity – many of which agree with
other biogeographical frameworks in the respective environments. The analysis also revealed
substantial geographical gaps in the data, especially in Africa, Asia, Indonesia, South America,
and offshore marine areas, which future research should aim to close
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