- Title
- The cultivation of Gracilaria gracilis in the Swartkops estuary, South Africa
- Creator
- Blewett, Alec
- Subject
- Gracilaria -- South Africa -- Port Elizabeth
- Subject
- Marine algae Algae -- South Africa
- Date Issued
- 2019
- Date
- 2019
- Type
- Thesis
- Type
- Masters
- Type
- MSc
- Identifier
- http://hdl.handle.net/10948/31446
- Identifier
- vital:31391
- Description
- Gracilaria gracilis (Stackhouse) M. Steentoft, L. M. Irvine & W. F. Farnham is a species of red macroalgae which occurs naturally within the Swartkops Estuary in South Africa. Bunches of the species were inserted into the lay of ropes, which were then either suspended in the water column at the Tiger Bay Marina, or staked at the surface of the sediment in the mudflats where the initial material was harvested from. The first site was used for the suspended growth trial, while the second site was for the bottom grown trial. Both of the growth trials ran for the same time period, which was approximately three weeks per season. This study examined three facets of the G. gracilis material that was grown. The growth rate and biomass were recorded in order to examine the potential for the growth of the species on longlines within the estuary. Secondly, the crude nutritional content of the species was determined in order to assess its potential for use as an abalone feed, specifically the dry and ashed weights, and the protein, carbohydrate and lipid contents. Lastly, the cultivated biomass was examined in terms of its agar gel yield and properties, which included the gel strength and the gel –melting and –forming temperatures. The growth rates for the cultivated G. gracilis were poor, and the largest positive growth rate of 1.17 ± 3.2% was found in spring, for the bottom grown trial. This season also saw the only increase in biomass above that which was seeded onto the line, and the final average weight after 22 days was 354.28 ± 68.04 g. All other growth rates were negative, and biomass declined in both growth trials across all the seasons. The suspended growth trials showed more extreme declines, and were heavily contaminated with epiphytic material, while the bottom grown trial had more gradual decrease, and it is likely that conditions associated with the culture systems were not ideal. The largest percentage of protein was found in autumn, where the bottom grown trial had a value of 88 ± 2.32%. For all the seasons, the lipid content had an average percentage of 1.80 ± 0.75% for the bottom grown trial, while the suspended trial was very similar, and had a value of 1.74 ± 0.58%. The nutritional composition of the cultivated biomass was not found to be a good abalone feed in comparison to other studies in land-based aquaculture facilities. Agar characteristics extracted in the present study showed the greatest potential for use as a valuable economic resource. The native agar extracted from the cultivated material was very close to the standards set by United States Pharmacopeia for all the characteristics, and has the potential to possibly be improved further by using an alkali treatment.
- Format
- v, 148 leaves
- Format
- Publisher
- Nelson Mandela University
- Publisher
- Faculty of Science
- Language
- English
- Rights
- Nelson Mandela University
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| Thumbnail | File | Description | Size | Format | |||
|---|---|---|---|---|---|---|---|
| View Details Download | SOURCE1 | Alec Blewett.pdf | 3 MB | Adobe Acrobat PDF | View Details Download |