- Title
- Thermal physiology of juvenile red roman seabream, Chrysoblephus laticeps after long-term exposure to low pH conditions
- Creator
- Allison, Caitlin
- Subject
- Climatic changes
- Subject
- Ocean acidification
- Subject
- Basal metabolism
- Subject
- Chrysoblephus laticeps
- Subject
- Thermal tolerance (Physiology)
- Subject
- Phenotypic plasticity
- Subject
- Fishes Climatic factors
- Date Issued
- 2023-10-13
- Date
- 2023-10-13
- Type
- Academic theses
- Type
- Master's theses
- Type
- text
- Identifier
- http://hdl.handle.net/10962/424323
- Identifier
- vital:72143
- Description
- Climate change has caused a combination of effects on the physiology of fishes. Of particular concern are the effects of thermal variability and ocean acidification. Organismal energy budgets change throughout ontogeny and research into the metabolic scope during early life stages is particularly useful in identifying potential bottlenecks. The first part of this thesis aimed to assess the absolute aerobic scope (AAS, described as the difference between the maximum and standard metabolic rates) of individual juveniles from a protected population of the endemic, commercially important seabream, Chrysoblephus laticeps, across a range of ecologically relevant temperatures (T = 11, 14, 18, 22˚C) under present-day conditions (pH = 8.03, pCO2 ≈ 420 μatm) using intermittent flow respirometry. The second component sought to investigate how long-term exposure (from fertilisation to juvenile, ~100 days exposure) to high-pCO2/hypercapnic conditions (pH = 7.63, pCO2 ≈ 1400 μatm), would affect the AAS of juvenile C. laticeps over a range of temperatures. Lower pH conditions were predicted to cause a decrease in the AAS of treatment animals due to additional energetic costs of acid-base regulation. The findings of the first data chapter demonstrated that juvenile C. laticeps reared under current CO2 conditions are tolerant to a wide range of thermal conditions, and individuals with a broad aerobic scope will be the best suited to coping with enhanced thermal variability. In contrast to the expected outcomes of the second data chapter, juvenile C. laticeps reared under high pCO2 conditions displayed greater AAS at high and low temperatures when compared with specimens from high pH conditions. Whilst a high degree of individual phenotypic variation was observed in the metabolic response of both groups, this was reduced at the lower and upper extreme temperatures for high pH and low pH animals respectively. Notably, the variation in treatment animal’s SMR was significantly diminished across all temperatures tested, compared to only a localised reduction in the SMR of high pH animals at cold temperatures. This may be indicative of compensatory pathways affecting energy restructuring and thermally-governed physiological trade-offs under hypercapnia. Given these results, juvenile C. laticeps appear to be more resilient to ocean acidification than anticipated, potentially owing to intrapopulation metabolic phenotypic diversity. This is likely attributed to the parental lineage originating in the Tsitsikamma MPA, which is thought to boast greater phenotypic diversity as a consequence of the refuge that these conservation areas offer from exploitation. Owing to the restriction imposed by the availability of surviving, captive-reared juveniles, the sample size used in this study was relatively low. However, owing to the repeated-measures nature of this research the sample size was sufficient to offer suitable statistical power for the polynomial mixed model used in the analysis. Future research should incorporate both physiological and behavioural responses to multiple environmental stressors to better understand covariation between these two traits, and to detect any behavioural trade-offs that might arise through compensation. In addition, these trials should be repeated using offspring from outside of the MPA to compare whether the same level of resilience and metabolic phenotypic diversity would be present in an exploited population.
- Description
- Thesis (MSc) -- Faculty of Science, Ichthyology and Fisheries Science, 2023
- Format
- computer
- Format
- online resource
- Format
- application/pdf
- Format
- 1 online resource (141 pages)
- Format
- Publisher
- Rhodes University
- Publisher
- Faculty of Science, Ichthyology and Fisheries Science
- Language
- English
- Rights
- Allison, Caitlin
- Rights
- Use of this resource is governed by the terms and conditions of the Creative Commons "Attribution-NonCommercial-ShareAlike" License (http://creativecommons.org/licenses/by-nc-sa/2.0/)
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| Thumbnail | File | Description | Size | Format | |||
|---|---|---|---|---|---|---|---|
| View Details Download | SOURCE1 | ALLISON-MSC-TR23-127.pdf | 3 MB | Adobe Acrobat PDF | View Details Download |