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Decadal shifts in macrobenthic community structure in a permanently open freshwater-deprived Eastern Cape Estuary
The decadal shifts in the macrobenthic community structure in the permanently open, freshwater-deprived Kariega Estuary along the southeastern coastline of South Africa were investigated between 2010 and 2022. The macrobenthic community structure was investigated at six stations in four distinct eco...
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| Format: | Thesis |
| Language: | English English |
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Department of Biological Sciences
2026
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| _version_ | 1869483678583750656 |
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| access_status_str | Open Access |
| author | Limbada, Zahrah |
| author2 | Froneman, Pierre |
| author_browse | Froneman, Pierre Limbada, Zahrah |
| author_facet | Froneman, Pierre Limbada, Zahrah |
| author_sort | Limbada, Zahrah |
| collection | Thesis |
| description | The decadal shifts in the macrobenthic community structure in the permanently open, freshwater-deprived Kariega Estuary along the southeastern coastline of South Africa were investigated between 2010 and 2022. The macrobenthic community structure was investigated at six stations in four distinct ecological zones: Zone I was made up of Zostera capensis, Zone II was made up of mud, Zone III was made up of Spartina maritima, and Zone IV was made up of Sarcocornia perrenis along the length of the estuary. The average abundance and biomass of macrobenthic organisms during the 2010 survey ranged from 16 to 504 ind/m2 and from 0.03 to 245 g wwt/m2, respectively. In 2022, the average abundance of macrobenthic organisms ranged from 6 to 216 ind/m2. The average macrobenthos biomass was 2.60 to 93.40 g wwt/m2. There were no significant differences in the estimates of the total macrobenthic abundance and biomass between the two surveys or the different ecological zones (P > 0.05 in all cases). Site-specific differences were, however, evident. During both surveys, the highest abundance and biomass values were recorded in the middle reach, corresponding to the region with the highest biomass of submerged macrophytes. Multidimensional scaling revealed a high degree of overlap in the macrobenthic community compositi on between the two surveys. The absence of any significant spatial or temporal patterns in the microbenthic community structure along the length of the estuary can likely be related to the reduced freshwater inflow into the estuary, creating a homogenous marine-dominated system. Closer inspection of the macrobenthic community structure, however, revealed that there have been species-specific declines in the abundance of several species routinely collected for bait by subsistence fishers, including the mud prawn (Upogebia africana), pencil bait (Solen cylindraceus) and redworm (Marphysa sanguina). The decline of these species suggests increased exploitation of estuarine resources over the past decade, most likely in response to high levels of unemployment and poverty. |
| format | Thesis |
| id | oai:open.uct.ac.za:11427/43411 |
| institution | University of Cape Town (South Africa) |
| language | English eng |
| last_indexed | 2026-07-01T04:02:49.206Z |
| license_str | Not specified — see source repository |
| provenance_str_mv | Harvested via OAI-PMH from UCTD — University of Cape Town Open Access Repository |
| publishDate | 2026 |
| publishDateRange | 2026 |
| publishDateSort | 2026 |
| 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:11427/43411 Decadal shifts in macrobenthic community structure in a permanently open freshwater-deprived Eastern Cape Estuary Limbada, Zahrah Froneman, Pierre Eastern Cape Estuary water The decadal shifts in the macrobenthic community structure in the permanently open, freshwater-deprived Kariega Estuary along the southeastern coastline of South Africa were investigated between 2010 and 2022. The macrobenthic community structure was investigated at six stations in four distinct ecological zones: Zone I was made up of Zostera capensis, Zone II was made up of mud, Zone III was made up of Spartina maritima, and Zone IV was made up of Sarcocornia perrenis along the length of the estuary. The average abundance and biomass of macrobenthic organisms during the 2010 survey ranged from 16 to 504 ind/m2 and from 0.03 to 245 g wwt/m2, respectively. In 2022, the average abundance of macrobenthic organisms ranged from 6 to 216 ind/m2. The average macrobenthos biomass was 2.60 to 93.40 g wwt/m2. There were no significant differences in the estimates of the total macrobenthic abundance and biomass between the two surveys or the different ecological zones (P > 0.05 in all cases). Site-specific differences were, however, evident. During both surveys, the highest abundance and biomass values were recorded in the middle reach, corresponding to the region with the highest biomass of submerged macrophytes. Multidimensional scaling revealed a high degree of overlap in the macrobenthic community compositi on between the two surveys. The absence of any significant spatial or temporal patterns in the microbenthic community structure along the length of the estuary can likely be related to the reduced freshwater inflow into the estuary, creating a homogenous marine-dominated system. Closer inspection of the macrobenthic community structure, however, revealed that there have been species-specific declines in the abundance of several species routinely collected for bait by subsistence fishers, including the mud prawn (Upogebia africana), pencil bait (Solen cylindraceus) and redworm (Marphysa sanguina). The decline of these species suggests increased exploitation of estuarine resources over the past decade, most likely in response to high levels of unemployment and poverty. 2026-06-29T10:44:31Z 2026-06-29T10:44:31Z 2026 2026-06-29T10:35:26Z Thesis / Dissertation Masters MPhil http://hdl.handle.net/11427/43411 en eng application/pdf Department of Biological Sciences Faculty of Science University of Cape Town |
| spellingShingle | Eastern Cape Estuary water Limbada, Zahrah Decadal shifts in macrobenthic community structure in a permanently open freshwater-deprived Eastern Cape Estuary |
| thesis_degree_str | Master's |
| title | Decadal shifts in macrobenthic community structure in a permanently open freshwater-deprived Eastern Cape Estuary |
| title_full | Decadal shifts in macrobenthic community structure in a permanently open freshwater-deprived Eastern Cape Estuary |
| title_fullStr | Decadal shifts in macrobenthic community structure in a permanently open freshwater-deprived Eastern Cape Estuary |
| title_full_unstemmed | Decadal shifts in macrobenthic community structure in a permanently open freshwater-deprived Eastern Cape Estuary |
| title_short | Decadal shifts in macrobenthic community structure in a permanently open freshwater-deprived Eastern Cape Estuary |
| title_sort | decadal shifts in macrobenthic community structure in a permanently open freshwater deprived eastern cape estuary |
| topic | Eastern Cape Estuary water |
| url | http://hdl.handle.net/11427/43411 |
| work_keys_str_mv | AT limbadazahrah decadalshiftsinmacrobenthiccommunitystructureinapermanentlyopenfreshwaterdeprivedeasterncapeestuary |