- Title
- Thermal studies on three common mangrove-associated ectotherms in Mngazana Estuary, with emphasis on the survival of the salt marsh crab, Parasesarma catenatum (Ortman 1897
- Creator
- Nonyukela, Asandiswa Simamkele
- Subject
- Mangrove forests
- Date Issued
- 2020-02
- Date
- 2020-02
- Type
- Master's theses
- Type
- text
- Identifier
- http://hdl.handle.net/10353/20838
- Identifier
- vital:46627
- Description
- Ecological data on the development and distribution of mangroves over time suggest that mangroves were strictly tropical in nature but have extended to higher latitudes during warmer periods. Species distribution models show that the mangrove range may have since 1963 expand by 17 km in 2020 and by as much as 68 km southwards by 2050. More climate data obtained, and modelling of future climate have increased interest in the thermal tolerance or organisms. Critical thermal maxima (CTMax) and thermal tolerance were employed to determine the thermal limits of common estuarine species associated with the mangrove forests at Mngazana Estuary. Three species were selected, each representing a medium within the mangrove environment: for water, i) Palaemon peringueyi; ii) for air, Cerithidea decollata; and iii) Parasesarma catenatum on the substratum. Animals were acclimated for 48 hrs following the thermal history of the environment. Each individual was exposed to constant rate of water temperature increase of 1°C.h-1. Different size classes (adult, sub-adult, juveniles) of crabs were used to determine the CTMax performance. Parasesarma catenatum showed intraspecific variability in CTMax in both air and water. Palaemon Peringueyi had a CTMax value of 33.8°C±1.96 while C. decollata had a CTMax of 39.6°C±2.76 and P. catenatum had a CTMax of 36,38 ±1,57 in water and 34,1 ±1,67 in air. Different size classes (Adult, Sub-adult, Juveniles) of crabs were used to further determine their CTMax performance. Parasesarma catenatum showed of intraspecific variability in CTMax in both air and water. Juvenile crabs showed higher CTMax in water than in air, while adult and sub-adults showed a higher CTMax in air. The size classes of P. catenatum (Adult, Sub-adult, Juveniles) were exposed to a range of salinity treatments from 5-65 for both shock and acclimated exposures. For acclimated exposures, crabs were acclimated down/up at change of 5-10 untill the test salinity was reached, at which point the crabs were exposed. For the shock exposure, the crabs were directly exposed to the test salinity from the holding salinity of 35. This study shows P. catenatum is euryhaline, tolerating salinities been 10 and 50. Survival was highest across all cohorts for the short-term (shock) exposure, suggesting prolonged exposure to hypo/hypersaline conditions may be detrimental for this keystone Mngazana Estuary species. Juven.ile populations showed the highest survival rate for both shock and acclimated exposure. This study highlights the importance of microhabitat variability and its effect on the tolerance of different species to abiotic factors and so may be useful in modelling the effects of climate change in these systems.
- Description
- Thesis (MSc) (Zoology) -- University of Fort Hare, 2021
- Format
- computer
- Format
- online resource
- Format
- application/pdf
- Format
- 1 online resource (101 pages)
- Format
- Publisher
- University
- Publisher
- Faculty of Science and Agriculture
- Language
- English
- Rights
- University of Fort Hare
- Rights
- All Rights Reserved
- Rights
- Open Access
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UFH Department of Zoology & Entomology
| Thumbnail | File | Description | Size | Format | |||
|---|---|---|---|---|---|---|---|
| View Details Download | SOURCE1 | NONYUKELA_AS_FINAL MScDISSERTATION.pdf | 1 MB | Adobe Acrobat PDF | View Details Download |