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Community composition, migration and trophic positions of micronekton in two biogeochemical provinces of the South West Indian Ocean
Inlcudes bibliographical references
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| Format: | Thesis |
| Language: | English |
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Department of Biological Sciences
2016
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| _version_ | 1867613265607000064 |
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| access_status_str | Open Access |
| author | Annasawmy, Pavanee |
| author2 | Moloney, Coleen L |
| author_browse | Annasawmy, Pavanee Moloney, Coleen L |
| author_facet | Moloney, Coleen L Annasawmy, Pavanee |
| author_sort | Annasawmy, Pavanee |
| collection | Thesis |
| description | Inlcudes bibliographical references |
| format | Thesis |
| id | oai:open.uct.ac.za:11427/19970 |
| institution | University of Cape Town (South Africa) |
| language | eng |
| last_indexed | 2026-06-10T12:33:23.204Z |
| license_str | Not specified — see source repository |
| provenance_str_mv | Harvested via OAI-PMH from UCTD — University of Cape Town Open Access Repository |
| publishDate | 2016 |
| publishDateRange | 2016 |
| publishDateSort | 2016 |
| publisher | Department of Biological Sciences |
| publisherStr | Department of Biological Sciences |
| record_format | dspace |
| source_str | UCTD — University of Cape Town Open Access Repository |
| spelling | oai:open.uct.ac.za:11427/19970 Community composition, migration and trophic positions of micronekton in two biogeochemical provinces of the South West Indian Ocean Annasawmy, Pavanee Moloney, Coleen L Menard, Frederic Ternon Jean-Francois Potier, Michel Applied Marine Science Inlcudes bibliographical references Micronekton fauna was investigated as part of a multi-disciplinary research project carried out in two different bioregions of the South West Indian Ocean: the East African Coastal Province (EAFR) and the Indian South Subtropical Gyre (ISSG). Food web structure was addressed using stable isotopes. Since particulate organic matter had high δ 15 N values in the ISSG province, copepods were chosen as baseline in trophic level estimations. Feeding regime and size were shown to influence the trophic position of micronekon. In the ISSG, carnivores (fishes and squids) and omnivores (crustaceans) had higher δ 15 N values and trophic positions than filter feeder s (gelatinous organisms such as salps and pyrosomes) and detritivores (leptocephali larvae). Fishes and squids encompassed a wide range of overlapping isotopic niches suggesting that organisms across different trophic levels feed on the same resources. Estimated trophic levels ranged from 1.67 to 4.73, showing that micronekton in the ISSG can be tertiary consumers. An average enrichment value of 6.7 ‰ was recorded between the sampled micronekton specimens and swordfish Xiphias gladius in the ISSG. Trawls, being selective in nature, were shown to sa mple smaller - sized micronekton with a lower trophic position than the micronekton being eaten by swordfish. In the EAFR, mean δ 15 N values of micronekton were higher than in the ISSG, exhibiting slightly higher trophic levels. Mesoscale dynamics in the EAFR provide mechanisms that enrich surface layers in nutrients and chlorophyll - a, therefore contributing to a higher abundance and micronekton species richness. In the ISSG, the large - scale wind - driven anticyclonic gyre pushes the nitracline, thermocline and deep chlorophyll maximum deeper in the water column , influencing the diel migration patterns of micronekton , with a significant proportion of micronekton staying in deep layers or slightly above the thermocline at dusk . Regardless of the differences in the ISSG and EAFR in δ 15 N values and trophic positions of micronekton, larger - sized swordfish sampled from these two provinces had similar mean δ 15 N values since swordfish are highly migratory and forage in different p arts of the Indian Ocean. However, smaller - sized swordfish specimens had lower mean δ 15 N values. With a combination of trawl surveys, stable isotope estimates, stomach content and acoustic analyses, this study shed new light on trophic interactions in the oligotrophic ISSG province. 2016-06-09T11:19:19Z 2016-06-09T11:19:19Z 2015 Master Thesis Masters MSc http://hdl.handle.net/11427/19970 eng application/pdf Department of Biological Sciences Faculty of Science University of Cape Town |
| spellingShingle | Applied Marine Science Annasawmy, Pavanee Community composition, migration and trophic positions of micronekton in two biogeochemical provinces of the South West Indian Ocean |
| thesis_degree_str | Master's |
| title | Community composition, migration and trophic positions of micronekton in two biogeochemical provinces of the South West Indian Ocean |
| title_full | Community composition, migration and trophic positions of micronekton in two biogeochemical provinces of the South West Indian Ocean |
| title_fullStr | Community composition, migration and trophic positions of micronekton in two biogeochemical provinces of the South West Indian Ocean |
| title_full_unstemmed | Community composition, migration and trophic positions of micronekton in two biogeochemical provinces of the South West Indian Ocean |
| title_short | Community composition, migration and trophic positions of micronekton in two biogeochemical provinces of the South West Indian Ocean |
| title_sort | community composition migration and trophic positions of micronekton in two biogeochemical provinces of the south west indian ocean |
| topic | Applied Marine Science |
| url | http://hdl.handle.net/11427/19970 |
| work_keys_str_mv | AT annasawmypavanee communitycompositionmigrationandtrophicpositionsofmicronektonintwobiogeochemicalprovincesofthesouthwestindianocean |