Academic literature on the topic 'Estuaries – South Africa'
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Journal articles on the topic "Estuaries – South Africa"
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Slinger, J. H., and C. M. Breen. "Integrated research into estuarine management." Water Science and Technology 32, no. 5-6 (September 1, 1995): 79–86. http://dx.doi.org/10.2166/wst.1995.0566.
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Estuaries are under increasing pressure owing to agricultural, urban and industrial developments in their catchments and their status as favoured sites for coastal development and recreation. Effective research on South Africa estuaries requires the synthesis of available scientific knowledge to efficiently address management concerns and so ensure the sustainable utilisation of estuaries. The approach of the Consortium for Estuarine Research and Management to these problems and the results of a co-ordinated research programme on decision support for the management and conservation of estuarine systems are described in this paper. While the importance and current status of South African estuaries are considered, attention is devoted primarily to the development of an integrated modelling approach to the freshwater requirements of estuaries. In particular, the application of a linked system of five models to a case study, the Great Brak Estuary is described and the role of prediction in promoting wise decision making for estuaries is treated.
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Kisten, Yanasivan, Nadine A. Strydom, Renzo Perissinotto, and Sourav Paul. "Modelling the occurrence of postflexion stages of a marine estuarine-dependent fish in temperate South African estuaries." Scientia Marina 81, no. 1 (March 27, 2017): 27. http://dx.doi.org/10.3989/scimar.04521.05a.
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The movement of postflexion larvae of marine estuarine-dependent species into estuaries is critical for the survival of fishes reliant on estuaries as nurseries. However, detailed studies focused on environmental variability experienced by postflexion larvae entering a range of estuary types under varying conditions are rare. This study assessed the in situ conditions (temperature, salinity and water clarity) under which the southern African endemic fish Rhabdosargus holubi (Sparidae) recruits into estuaries. Postflexion larvae were sampled in three biogeographic regions (cool temperate, warm temperate and subtropical boundary), which included three estuary types (permanently open estuaries (POEs), temporarily open/closed estuaries and estuarine lake systems) on a seasonal basis, independent of each other. Rhabdosargus holubi larvae were more abundant in spring and summer, in POEs in the warm temperate region. Models predicted that higher larval occurrence in estuaries is a function of lower salinity (e.g. mesohaline zones of 5-17.9 salinity) and lower water clarity (e.g. 0-0.2 Kd, light extinction coefficient), particularly for warm, temperate POEs. This re-emphasizes the importance of freshwater for optimal nursery functioning, which may be compromised by impoundments, abstraction and climate change in water-short countries like South Africa.
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McGregor, Steven, and Nadine A. Strydom. "The abundance, diversity and distribution of small fishes in mangrove and non-mangrove estuaries in warm temperate South Africa." Scientia Marina 82, no. 2 (July 6, 2018): 81. http://dx.doi.org/10.3989/scimar.04744.31a.
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Mangroves in tropical and subtropical regions have been well documented in terms of the advantages they provide and their role in structuring ichthyofaunal assemblages, but little is known about their warm temperate counterparts. The study aimed to investigate the importance of warm temperate mangroves by comparing the abundance, diversity and distribution of small fishes in mangrove and non-mangrove estuaries in warm temperate South Africa. A 50x2 m (12-mm mesh) seine net was used over three summer seasons to sample small fishes in the Gonubie, Qora, Nahoon and Xhora estuaries (the latter two being mangrove estuaries). Fish abundance and diversity showed little variation among estuaries, despite the presence of mangroves. Estuaries in warm temperate areas are not only at the edge of mangrove distribution, but also offer alternative habitats which lend similar advantages to fish survival. It appears that warm temperate ichthyofauna have not yet evolved a dependence on mangrove systems in terms of the food, refuge and other ecological services they provide. Understanding the function of habitats and their value in enhancing fish survival in estuarine nursery areas is essential for fish conservation.
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Murray, Taryn S., Paul D. Cowley, Rhett H. Bennett, and Amber-Robyn Childs. "Fish on the move: connectivity of an estuary-dependent fishery species evaluated using a large-scale acoustic telemetry array." Canadian Journal of Fisheries and Aquatic Sciences 75, no. 11 (November 2018): 2038–52. http://dx.doi.org/10.1139/cjfas-2017-0361.
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Connectivity — movements of animals between and among numerous habitats — and the factors (rhythmic cycles and environmental variables) influencing connectivity of juvenile Lichia amia (Teleostei: Carangidae) were assessed in complementary acoustic telemetry studies in two geographically separated estuaries (620 km apart) in South Africa. The studies were conducted within a nationwide array of acoustic receivers moored in estuaries and coastal waters. Tagged fish in both the Kowie (n = 21) and Goukou (n = 17) estuaries displayed high levels of multiple habitat connectivity, with 81% and 76% visiting nearby marine and estuarine environments, respectively. The presence of tagged L. amia within the tagging estuaries was significantly influenced by river and sea temperature (Kowie) and river inflow and moon phase (Goukou). Tidal phase, time of day, and season were found to significantly influence marine excursions undertaken by Kowie- and Goukou-tagged fish. Our study provides an assessment of connectivity among multiple estuarine, port, and marine habitats, relating those movements to rhythmic cycles and environmental variables, and highlights the benefits of tracking animals using an extensive acoustic receiver array that spans multiple habitats.
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Whitfield, A. "Predation on small juvenile fishes in shallow estuarine nursery areas: Reply to Baker & Sheaves (2021)." Marine Ecology Progress Series 662 (March 18, 2021): 209–14. http://dx.doi.org/10.3354/meps13678.
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The key criticism by Baker & Sheaves (2021; Mar Ecol Prog Ser 662:205-208) of the Whitfield (2020; Mar Ecol Prog Ser 649:219-234) estuarine littoral predation paradigm review is that shallow water fish nursery habitats contain abundant predator assemblages which may create high predation pressure on the juvenile fish cohorts that occupy these areas. The primary arguments supporting Baker & Sheaves’ criticism arise from a series of papers published by them on piscivorous fish predation in certain tropical Australian estuaries. The counter-argument that shallow littoral areas in estuaries do indeed provide small juvenile fishes with refuge from small and large piscivorous fishes is provided by published papers from 4 different estuary types in South Africa, covering both subtropical and warm-temperate systems. Based on the overall published information, the argument for shallow (<1 m depth) estuarine waters providing major protection for newly settled juveniles appears to be weak in northern Australia but strong in South Africa. The global situation, as outlined in this response, is more supportive of low piscivorous predation in shallow nursery habitats, but further targeted research is needed before we can confirm that littoral estuarine waters are indeed a universal keystone attribute in this regard.
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Watt, D. A. "Estuaries of Contrasting Trophic Status in KwaZulu-Natal, South Africa." Estuarine, Coastal and Shelf Science 47, no. 2 (August 1998): 209–16. http://dx.doi.org/10.1006/ecss.1998.0345.
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Taljaard, Susan, Gavin Snow, Phumelele Gama, and Lara van Niekerk. "Verification of a conceptual model of water quality for small temporarily open/closed estuaries: East Kleinemonde Estuary, South Africa." Marine and Freshwater Research 60, no. 3 (2009): 234. http://dx.doi.org/10.1071/mf07226.
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The dynamics of the world’s larger permanently open estuaries have been well documented, but much less is known about the complex dynamics of smaller temporarily open/closed estuaries (TOCEs). Seventy per cent of South Africa’s 250 estuaries are classified as TOCEs, and many are less than 50 ha. A conceptual model of the water-quality dynamics of TOCEs has been proposed, primarily considering three hydrodynamic states (closed, semi-closed and open). This paper uses data from the East Kleinemonde Estuary, a small TOCE in the warm-temperate region of South Africa, to verify the model, focusing on physico-chemical parameters (salinity, temperature, pH, dissolved oxygen and turbidity) and inorganic macronutrients (dissolved inorganic nitrogen and dissolved inorganic phosphate) for the open and closed states. The results generally fitted the model in terms of the behaviour of the physico-chemical parameters and macronutrients in the water column. This knowledge provides a first approach to predict the water-quality dynamics in small TOCEs, thereby ensuring that the often limited resources are targeted at resolving uncertainties at appropriate temporal and spatial scales. TOCEs are not unique to South Africa and also occur along other coasts (Mediterranean and south-western Australia) where this type of model could also be applied.
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Bally, Roderick. "Conservation Problems and Management Options in Estuaries: The Bot River Estuary, South Africa, as a Case-history for Management of Closed Estuaries." Environmental Conservation 14, no. 1 (1987): 45–51. http://dx.doi.org/10.1017/s0376892900011097.
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Closed (or ‘blind’) estuaries are common features, practically throughout the world, of areas experiencing markedly seasonal rainfall. The Bot River vlei is a closed estuary which faces considerable problems of management and conservation. For the past 100 years or more, the estuary has been opened to the sea every 2 to 5 years by artificial means. This has resulted in a very great variability of physical conditions and a concomitantly low diversity of organisms that are able to occupy the estuary permanently. Nevertheless, those species that do exist in the Bot River vlei are mostly estuarine species.
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Naidoo, Trishan, David Glassom, and Albertus J. Smit. "Plastic pollution in five urban estuaries of KwaZulu-Natal, South Africa." Marine Pollution Bulletin 101, no. 1 (December 2015): 473–80. http://dx.doi.org/10.1016/j.marpolbul.2015.09.044.
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Montoya-Maya, P. H., and N. A. Strydom. "Zooplankton composition, abundance and distribution in selected south and west coast estuaries in South Africa." African Journal of Aquatic Science 34, no. 2 (August 2009): 147–57. http://dx.doi.org/10.2989/ajas.2009.34.2.5.892.
Full textDissertations / Theses on the topic "Estuaries – South Africa"
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Lee, Deborah Ellen. "An application of the choice experiment method to estimate willingness-to-pay for and guide management on estuarine recreational services." Thesis, Nelson Mandela Metropolitan University, 2012. http://hdl.handle.net/10948/d1020239.
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Among the world‘s ecosystems, estuaries have the highest total economic value per hectare. They are dynamic coastal biomes that provide a host of different goods and services to the surrounding terrestrial and aquatic environments and the people who utilise them. These goods and services include, inter alia, nursery areas for marine organisms, harvested natural resources (such as fish, shell-fish, bait organisms, reeds and mangroves), flood attenuation, water purification, nutrient and sediment sinks, waste disposal, transport, aesthetic beauty and areas for swimming, boating and fishing. Assessing the condition of estuaries is difficult as their state can change depending on what is being measured. Assessments have been carried out on the health of estuaries in South Africa with the results of these studies being used as inputs to the process of assessing the minimum water supply requirements for each estuary (ecological reserve) in order to maintain or improve its functionality. These ecological reserve requirements are assigned using Resource Directed Measures (RDM). These measures, however, have been criticised for being highly complex and too costly to implement for all South African estuaries within a reasonable time period. Another concern is that the levels of demand for recreational goods and services provided by the estuary are not taken into account when assessing estuarine value. It is important to understand that the use of estuaries for recreational purposes is inextricably linked to their health and sound ecological functioning. Although South African estuaries have been quite well buffered from impacts until only very recently, their use and pressures have escalated faster than what conservation authorities and policy makers have been prepared for over the last couple of decades. There is thus mounting pressure on estuaries as recreational outlets, which, in turn, has led to their functional deterioration as well as deterioration in the quality of the recreational experience as a whole. One implication for management is that more and more trade-offs have to be made in an attempt to balance the conservation and recreational use of estuaries.
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Lemley, Daniel Alan. "Assessing symptoms of eutrophication in estuaries." Thesis, Nelson Mandela Metropolitan University, 2015. http://hdl.handle.net/10948/3427.
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Water quality and ecological integrity of estuaries reflect activities within the entire upstream catchment. Much emphasis has been placed on the response of estuaries to anthropogenic stressors through the use of monitoring programmes. Key to the success of these programmes is the use of indicators as they transform data into useful information. The ultimate aim of this study was to identify eutrophic symptoms in selected estuaries in the Gouritz Water Management Area (WMA) using a multi-metric classification method. The study sites included the permanently open Duiwenhoks, Goukou, Gouritz, and Kaaimans estuaries, as well as the temporarily open/closed Hartenbos, Klein Brak, Great Brak, Gwaing, and Goukamma estuaries. Initially, the “pressure” associated with all the estuaries in the Gouritz WMA was determined (e.g. total daily nutrient loads and changes in river inflow affecting flushing time) using long-term flow and water quality monitoring data provided by the Department of Water Affairs (DWA). Subsequently, the “state” of the selected estuaries was assessed using a variety of indicators, including: inorganic nutrients (~ N and P), phytoplankton, epiphytes and microphytobenthos. Estuaries with longer flushing time suggested greater vulnerability to eutrophication. For example, the Gwaing (281.11 kg DIN d-1; 78.85 kg DIP d-1) and Hartenbos (38.33 kg DIN d-1; 21.51 kg DIP d-1) estuaries generally received the highest daily inorganic nutrient loads. However, at the time of sampling, the Hartenbos Estuary had a longer flushing time (i.e. weeks) compared to the Gwaing Estuary (i.e. couple of days). Field data confirmed the greater vulnerability to eutrophication associated with longer flushing times, as the indicators measured in the Hartenbos Estuary exceeded all the proposed ‘thresholds’ of a eutrophic system (~ overall ‘Poor’ condition). The Great Brak Estuary (~ overall ‘Fair’ condition) provided an interesting example where eutrophic symptoms were only detected when assessing the microalgal primary producers (i.e. high biomass and low diversity). Furthermore, the need to distinguish between naturally and anthropogenically induced symptoms was highlighted. One such scenario was noted in the Kaaimans Estuary, where its natural hydro-morphological characteristics (i.e. steep banks, low river inflow, and deep/narrow channel) led to the possible exaggeration of its overall eutrophic condition, i.e. received a ‘Fair’ rather than ‘Good’ rating, arising from ‘Poor’ ratings for dissolved oxygen and benthic diatom diversity. Overall, this study demonstrated the importance of adopting a holistic approach when assessing the condition and trophic status of estuaries. Studies such as these allow for the detection of vulnerable and degraded systems, which can provide important information with regards to the identification of management priorities.
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Akoto, William. "Valuing preferences for freshwater inflows into selected Western and Southern Cape estuaries." Thesis, Nelson Mandela Metropolitan University, 2009. http://hdl.handle.net/10948/915.
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An estuary is the last stage of a river. It is where the river meets the sea. Estuaries are one of the most significant features of the South African coastline. In recent years, South Africa has witnessed an increase in the demand for freshwater for both industrial and domestic purposes. At the same time, there has been a gradual deterioration of river systems and their catchments. To add to this, there has been a gradual reduction in the amount of recorded rainfall, which is the primary source of freshwater for rivers. This has resulted in decreased freshwater inflow into estuaries, a situation which poses a serious threat to the biological functioning of these estuaries and the services rendered to its recreational users. A deterioration of estuary services reduces the yield for subsistence households and their appeal for recration. This study uses the contingent valuation method as its primary methodology to elicit users' willingness-to-pay to reduce the negative impacts of reduced freshwater inflow into selected western and southern Cape estuaries. Eight estuaries were selected for this study; the Breede, Duiwenhoks, Great Berg, Kleinemond West, Mhlathuze, Swartvlei and Olifants estuaries. The contingent valuation (CV) method is widely used for studies of this nature because of its ability to capture active, passive and non-use values. The CV method involves directly asking people how much they would be willing to pay for specific environmental services. In this case, users were asked what they would be willing to pay to sustain freshwater inflows into selected estuaries in order to prevent the negative impacts of reduced inflows. The travel cost method (TCM) was uesed to generate an alternative comparative set of values for the purposes of convergence testing. This is because convergence testing is highly desirable as a validity test for CV estimates.
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Kaselowski, Tanja. "Physico-chemical and microalgal characteristics of the Goukamma Estuary." Thesis, Nelson Mandela Metropolitan University, 2012. http://hdl.handle.net/10948/d1011130.
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Estuaries are intrinsically complex and dynamic ecosystems that display marked spatial and temporal variability. Because estuaries are situated at the receiving end of catchment activities, they are at particular risk of alterations to their natural complexity. The overarching objective of this study was to gain an overview of the abiotic conditions and biotic response of the Goukamma Estuary, a small temporarily open/closed estuary (TOCE) which is situated in a relatively undisturbed catchment in the Southern Cape. Physico-chemical properties drive estuarine ecology, and together with biological indicators, are commonly assessed to determine the present status of an estuary. During the study, physico-chemical parameters reflected great spatial and temporal variability in response to the mouth state over a 13 month period. Parameters ranged within expected limits, as proposed by the conceptual model for water quality of TOCE’s (Snow and Taljaard 2007). Of particular importance was the prominent occurrence of salinity stratification and hypoxic conditions (dissolved oxygen [DO] < 3 mg l-1) during both open and closed mouth states. Data indicated that in the wide and shallow lower reaches, weak stratification gradients were present and oxygenated conditions (DO > 6 mg l-1) were maintained throughout the water column mainly by wind and tidal action. However, stratification increased towards the deeper, channel-like middle and upper reaches of the estuary, followed by a significant reduction in bottom DO concentrations and development of hypoxia and anoxia. Bottom water hypoxia commonly occurs in microtidal estuaries due to the limited influence of mixing forces, mainly by wind and tidal action. The Goukamma Estuary is a channel-like microtidal estuary where stratification effectively limited oxygenation of the bottom water which resulted in frequent occurrence of bottom water hypoxia. During June 2010 when the highest local rainfall (75 mm) was recorded for the region, salinity and DO data showed that this amount of rainfall was insignificant as it did not replenish the water column of oxygen. Only the surface 0.5 m layer was fresh and oxygenated while below this, the water column was completely hypoxic. In an unimpacted state, the Goukamma Estuary is a blackwater system and is expected to be nutrient poor; however, farming activities in the catchment have resulted in elevated nutrient concentrations. This study showed that significantly higher nutrient concentrations were measured in the middle and upper reaches of the estuary, adjacent to cattle farms situated in the floodplain of these reaches. Nutrient concentrations represented mesotrophic (dissolved inorganic nitrogen [DIN] > 500 μg l-1) to eutrophic conditions (dissolved inorganic phosphorus [DIP] > 25 μg l-1). Nutrient input stimulated phytoplankton to attain a significantly high biomass, ranging between 0.3 – 112 μg l-1 (~ 7.7 ± 1.3 μg l-1; n = 128) and 0.8 – 289 μg l-1 (~ 21.1 ± 4.4 μg l-1; n = 80) during the open and closed states, respectively. High organic loads are associated with high oxygen demands which consequently result in hypoxia following decomposition. Exacerbated by natural salinity stratification which effectively limits oxygenation of the water column, unnaturally high nutrient concentrations and coinciding organic loads place the estuary at particular risk of degradation. This study captured key patterns and processes by quantifying salinity, oxygen and nutrient concentrations in addition to biological indicators (phytoplankton biomass and community composition). Considering possible budget constraints, it is recommended that monthly salinity and oxygen concentrations should be monitored as well as seasonal nutrient concentrations. It is also recommended that riparian buffer zones should be established in the middle and upper reaches of the estuary, as these vegetation buffers have been well documented to contribute to nutrient attenuation and improved water quality from agricultural run-off.
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Van, Niekerk Lara. "A framework for regional estuarine management : a South African case study." Thesis, Link to the online version, 2007. http://hdl.handle.net/10019/1659.
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Cowie, Meredith. "Environmental flows, health and importance of macrophytes in the estuaries of water management area 11." Thesis, Nelson Mandela Metropolitan University, 2015. http://hdl.handle.net/10948/7930.
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Estuaries require sufficient quantity, quality and appropriate timing of freshwater inflow, referred to as environmental flow requirements, to ensure adequate health and functioning. In South Africa the environmental flow requirements of estuaries is determined using Resource Directed Measures (RDM). The present health and importance of an estuary must be considered when determining the ecological flow required to maintain an estuary in its desired state. An Estuarine Health Index that quantifies changes in abiotic and biotic components from natural conditions to present day is used. Health of biotic components is assessed according to changes in species richness, abundance and community composition. There has, however, been debate regarding the calculation of these attributes. In particular, for macrophytes, the inclusion of all habitat within the Estuarine Functional Zone (i.e. 5 m topographical contour) would affect the health and changes over time determined in past assessments. This is due to different areas being included as different areas would be included The aim of this study was to test the validity and suggest improvements to South Africa’s RDM macrophyte health score determination. The health of macrophytes were assessed at varying levels of intensity from desktop studies to thorough field studies. Rapid field studies provided a visual estimate of macrophyte health; while the intermediate and comprehensive assessments quantified change by mapping the distribution of macrophyte habitats from aerial photographs. These approaches were applied to the 64 estuaries within the Mvoti-Mzimkulu Water Management Area (WMA 11), situated in KwaZulu-Natal (KZN) on the subtropical east coast. Historically, these estuaries have supported restricted macrophyte habitats. Consequently, estuaries that presently or historically supported range limited habitats such as mangroves and swamp forest are considered important. Submerged macrophytes are scarce in KZN estuaries due to siltation and low turbidity and thus estuaries supporting this macrophyte habitat are also important. Based on available literature important estuaries were highlighted and selected for field studies. Transects spanning from the estuary water channel to the boundary of the EFZ provided a generalised distribution of KZN vegetation along an elevation gradient. The transition from estuarine to terrestrial vegetation can be used to improve the current EFZ boundaries, as estuarine area has been found to occur outside of the 5 m contour in some estuaries. Results from the desktop assessment indicated that most of the estuaries are moderately modified. There was a 50 % similarity in the macrophyte health scores determined by the desktop assessment to the 2011 National Biodiversity Assessment (NBA). Field studies mostly confirmed the desktop assessment aside from seven estuaries that had different scores. There has been a significant loss of macrophyte habitat with 100% loss of certain habitats from 9 of the 22 estuaries for which there were field assessments. Submerged macrophytes were not found at any of the estuaries that were assessed in the field. Black mangroves, Bruguiera gymnorrhiza (L.) Lam., were rediscovered at Ngane Estuary, however the few individuals could not be considered a ‘mappable’ community (i.e. <0.5 ha). Mtamvuna and Mkomazi estuaries both supported small stands of mangroves that, compared to data from 2006, appeared healthy. Macrophyte habitats and surrounding coastal forest matched the species composition described in the Vegetation Map of South Africa. The freshwater mangrove or Powder puff tree, Barringtonia racemosa (L.) Roxb, was not abundant in the estuaries. It was only found at four (Damba, Fafa, Little Amanzimtoti and Mvoti) of the estuaries that were assessed in the field. Important estuaries, from a botanical perspective, included some of the larger estuaries such as Mgeni, Durban Bay and Sipingo. Smaller, healthier estuaries that presently support mangrove and swamp forest habitat were also identified as important from a botanical perspective. Macrophyte habitats have mainly been lost due to non-flow related pressures. Sugarcane cultivation occurred within the floodplain of 25% of the estuaries. Nutrient enrichment was evident for 12.5% of the estuaries and reed encroachment was evident for 27% of estuaries for which there were field assessments. Development, aside from the N2 road bridges, was evident for 40% of the estuaries assessed in the field. Invasive plant species, including aquatic invasive plants, were present in all estuaries assessed in the field. The extent of invasive plant species was related to the degree of disturbance and surrounding land use pressures. The Mkomazi and Mvoti estuaries that were assessed at a comprehensive level, as they have earmarked for further water abstraction, had the poorest macrophyte health scores. The macrophyte health of these estuaries was much lower than previously determined by the NBA. The decline in health was attributed to the removal of macrophyte habitat for sugarcane cultivation and development as well as displacement by invasive plant species. The areas covered by the macrophyte habitats also differed from the NBA highlighting the importance of updated mapping and ground truthing. Largely differing macrophyte health scores were produced when attributes were calculated using different combinations of macrophyte habitats. Results indicate that only macrophyte habitats and no other floodplain vegetation should be included when calculating abundance. All macrophyte habitats, physical habitats and floodplain should be incorporated when calculating community composition. The minimum of these attributes is used as the overall macrophyte health score as a precautionary approach is followed. Scoring of health is subjective and the only benchmark for determining the most appropriate method is comparion with previous RDM studies. This study illustrates the need for a standardised RDM scoring method that is presented in a manner that ensures the same results irregardless of the speciliast conducting the study. The updated estuary health and importance scores for WMA 11 are necessary to inform management, particularly as few of the estuaries receive formal protection. In conclusion, this study contributed to the limited knowledge of the estuaries of WMA 11 and assisted in determining appropriate methods for assessing the health and importance of estuary macrophytes.
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Chege, Jedidah. "Valuing preferences for freshwater inflows into five Eastern Cape and Kwazulu-Natal estuaries." Thesis, Nelson Mandela Metropolitan University, 2009. http://hdl.handle.net/10948/932.
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An estuary, according to the National Water Act of 1998, is a partially or fully enclosed body of water which is open periodically or permanently to the sea within which the sea water can be diluted, to an extent that is measurable with freshwater from inland. Estuaries and the lands surrounding them are places of transition from land to sea, and from freshwater to saltwater. Although influenced by the tides, estuaries are protected from the full force of ocean waves, winds, and storms by the reefs, barrier islands, or fingers of land, mud, or sand that surround them. South Africa’s estuaries are important and irreplaceable habitats, especially for prawns, fish, wading birds and mangroves. They are home to numerous plants and animals that live in water that is partly fresh and partly salty. Estuaries are also homes to growing coastal communities as increasing number of people occupy watersheds. However, estuaries are also threatened. One of the threats is reduced river water inflow. This study applies the contingent valuation method (CVM) to elicit user’s willingness to pay to mitigate the negative impacts of reduced freshwater inflow into selected five Eastern Cape and Kwazulu-Natal estuaries: the Sundays, Gamtoos, Mdloti, Mgeni and Mvoti estuaries. In addition to the contingent valuation method, the travel cost method was used to generate comparative values. The contingent valuation method is a technique to establish the value of a good (or service) that is not bought or sold in an actual market. The CVM establishes the economic value of the good by asking the users of an environmental good to state their willingness to pay (WTP) for a hypothetical project to prevent, or bring about, a change in the current condition of the environmental good. The users’ WTP is aggregated to establish a total willingness to pay (TWTP) for the population of the users of the environmental good.
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Harrison, Trevor D. "Biogeography and community structure of fishes in South African estuaries." Thesis, Rhodes University, 2003. http://hdl.handle.net/10962/d1005078.
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The biogeography and community structure of the fishes of South African estuaries was investigated. In all, 109 systems were examined representing two broad types: temporarily closed and permanently open estuaries. Multivariate analyses of the fish communities identified three biogeographic regions. A cool-temperate region extended along the west and southwest coasts; a warmtemperate zone stretched along the south, southeast and east coasts and a subtropical region occurred along the east coast. The boundaries of these biogeographic regions were also delineated. The general physico-chemical characteristics of the estuaries within the three biogeographic regions also reflected regional differences in climate, rainfall and ocean conditions. Estuarine temperatures followed the trend for marine coastal waters, decreasing from subtropical estuaries toward cool-temperate systems. The low rainfall and runoff in the warm-temperate region together with high evaporation rates and strong seawater input resulted in higher salinities in these estuaries. These factors also accounted for the predominantly clearer waters in warm-temperate estuaries. The estuaries in the three biogeographic regions were also shown to contain somewhat distinctive fish assemblages. Temperature and salinity appeared to be the two main factors affecting the distribution and abundance of fishes in South African estuaries. Subtropical systems were characterised by fishes mostly of tropical origin as well as certain south coast endemic species. Warm-temperate estuaries were dominated by endemic taxa with some tropical species also present. The fish fauna of cooltemperate estuaries mostly comprised south coast endemic species with cosmopolitan and temperate taxa also present. Certain functional components of the ichthyofauna also exhibited slight differences between regions. Freshwater fishes were a major component of closed subtropical estuaries while estuarine resident species were more abundant in warm-temperate estuaries. Overall, estuarine-dependent marine species dominated the fish fauna of the estuaries in all biogeographic regions, signifying that South African estuaries perform a vital nursery function for this group of fishes. Slight differences were also apparent in the trophic structure of the fishes; these were related to environmental differences between regions. Zooplanktivores and fishes that feed on aquatic macrophytes/invertebrates assumed a relatively higher importance in warm-temperate systems. Overall, detritivores dominated the estuarine fish fauna in all regions, indicating that detritus forms the main energy source in South African estuaries.
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Gama, Phumelele Thuthuka. "Phytoplankton chlorophyll a concentration and community structure in two temporarily open/closed estuaries in the Eastern Cape, South Africa." Thesis, Nelson Mandela Metropolitan University, 2008. http://hdl.handle.net/10948/707.
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River flow is important in controlling phytoplankton distribution in estuaries. Data on the effect of river inflow on phytoplankton distribution patterns in temporarily open/closed estuaries is lacking. This study investigated the influence of river inflow on size-fractionated phytoplankton biomass (Chl a), community composition and environmental parameters measured monthly over three years in two temporarily open/closed estuaries in the Eastern Cape, South Africa. A once-off primary production study over an annual cycle was completed in the Van Stadens and Maitland estuaries. The study monitored physical, chemical and biological characteristics in both estuaries to examine the effects of changes in environmental factors and river inflow. Daily sampling of physico-chemical and biological variables from river to sea was carried out in the Van Stadens to investigate short-time scale effects of changes in environmental factors and river inflow on the phytoplankton biomass. Five and three stations in the main channel of the Van Stadens and Maitland estuaries respectively were sampled at 0.5 m below the water surface and 0.5 m above the sediment surface for biological and chemical variables and at the surface, 0.25 m and every 0.5 m thereafter for physical parameters. Five stations adjacent to the main channel along the estuary were monitored for groundwater macronutrient concentrations and five additional sites located within the upper catchment of the Van Stadens River were sampled on a quarterly basis over two years. Both estuaries were characterised by distinct hydrological conditions, an overwash, an open, a closed and a semi-closed mouth phase. Flooding in the Maitland and Van Stadens estuaries in 2001 and 2002 caused sediment scour, altered channel morphology and brought about breaching of the mouth. Flood driven mouth-breaching events occurred three and four times in each of the estuaries during the study. The mouth stayed open 20 – 25 percent and was closed 60 – 65 percent of the time. In the Van Stadens the closed overwash mouth condition occurred approximately 10 – 20 percent of the time while in the Maitland it occurred less with the semi-closed mouth condition occurring 10 – 20 percent of the time. Incidents related to mouth opening not associated with strong river floods occurred approximately 10 – 15 percent of the time, although in the Maitland a semi-closed mouth state persisted more frequently than in the Van Stadens Estuary. During flooding events salinity dropped to low levels (< 5 psu) but soon recovered to brackish conditions when river flow was reduced and marine water penetrated deep upstream. Reduction in river flow combined with marine sediment deposition resulted in the closure of the mouth. During closed mouth conditions strong onshore storm surges and spring high tides introduced marine water through overwash that kept salinity high. In both estuaries salinity showed a negative correlation with rainfall (R2 = 0.12), indicative of the strong influence of marine overwash that kept salinity high thus masking the influence of freshwater. High rainfall in the Van Stadens Estuary caused high levels of turbidity that reduced light penetration at depth. Light attenuation was positively correlated with the high rainfall (R 2 = 0.26) suggesting that increased turbidity was linked to rainfall induced discharge. In contrast, in the Maitland Estuary light attenuation did not show any correlation with increased rainfall possibly because of the reduced water depth and increased euphotic zone following the floods in 2002. High river inflow introduced macronutrients in both estuaries such that dissolved inorganic phosphates (DIP) and dissolved inorganic nitrogen (DIN) concentrations in the Van Stadens Estuary were strongly correlated with rainfall (R2 = 0.78 and 0.57 respectively). In the Maitland Estuary DIP and DIN concentrations remained significantly higher (p < 0.05) compared to that in the Van Stadens suggesting that the Maitland catchment contributed greater nutrient input into the estuary and may be associated with farming activities. Phytoplankton chlorophyll a (Chl a) ranged from 0.8 – 13.9 μg L-1 in the Van Stadens and in the Maitland Estuary from 5.3 – 138 μg L-1 during the 3-year study. During the open mouth condition Chl a biomass and primary production ranged from 5.4 – 52.9 μg Chl a L-1 and 1.2 – 11.7 mg C m-2 d-1 in the Maitland and in the Van Stadens from 1.6 – 9.8 μg Chl a L-1 and 1.2 - 14 mg C m-2 d-1 respectively. Maximum annual primary production in the Maitland and Van Stadens estuaries was 8.8 and 5.1 g C m-2 y-1 respectively. When the mouth was open in the Van Stadens Estuary the microphytoplankton (> 20 μm) accounted for > 65 percent of the Chl a, whereas during closed mouth conditions they accounted for about 55 percent of the Chl a biomass. Chlorophytes became the dominant taxon in the dry summer months but were replaced by cryptophytes and dinoflagellates during the wet season. When nutrient concentrations were low during low flow conditions in the Van Stadens Estuary mixotrophic microphytoplankton became an important fraction of the water column together with phototrophic dinoflagellates and cryptophytes. In the Maitland large sized chlorophytes were the dominant taxa in late spring and summer seasons and made up more than 80 percent of the cell numbers. In the Maitland before the floods in 2002 cyanophytes were the dominant group in late spring contributing more than 75 percent in cell abundance. Data from the short-term study in the Van Stadens Estuary showed similarities and differences in the Chl a response to increased river inflow. High river inflow initially reduced Chl a biomass followed by a recovery period of a couple of days compared to a 8 – 10 week recovery period in studies monitored over seasonal and annual temporal scales. The responses may be dissimilar but help to illustrate that there are similar response patterns to environmental forcing necessary to support phytoplankton biomass at different temporal scales. This study has demonstrated that flooding events caused by strong river flow cause breaching of the mouth, a reduction in salinity and marked nutrient input. Although the causes of flooding can be similar in both estuaries the resultant effects are varied and can alter the ability of the estuary to retain water. This study was able to demonstrate that the supply of macronutrients from the catchment was strongly correlated with rainfall (R2 = 0.67) and that phytoplankton growth mainly depended on an allochthonous source of macronutrients although internal supplies could be critical at times in controlling microalgal biomass.
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Montoya-Maya, Phanor Hernando. "Dynamics of larval fish and zooplankton in selected south and west coast estuaries of South Africa." Thesis, Rhodes University, 2009. http://eprints.ru.ac.za/1641/.
Full textBooks on the topic "Estuaries – South Africa"
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Allanson, Brian, and Dan Baird. Estuaries of South Africa. Cambridge: Cambridge University Press, 1999.
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Temporarily open/closed estuaries in South Africa. New York: Nova Science Publishers, 2010.
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Harrison, Trevor D. Ichthyofauna of South Africa estuaries in relation to the zoogeography of the region. Grahamstown, South Africa: South African Institute for Aquatic Biodiversity, 2005.
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Saltwater fly-fishing in South Africa: A guide to fly-fishing South Africa's estuaries, surf zone and offshore waters. Cape Town: Struik, 2008.
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Harrison, T. D. State of South African estuaries: Geomorphology, ichthyofauna, water quality and aesthetics. Pretoria: Department of Environmental Affairs and Tourism, 2000.
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Allanson, Brian, and Dan Baird, eds. Estuaries of South Africa. Cambridge University Press, 1999. http://dx.doi.org/10.1017/cbo9780511525490.
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R, Allanson Brian, and Baird Dan 1944-, eds. Estuaries of South Africa. Cambridge: Cambridge University Press, 1999.
Find full textBook chapters on the topic "Estuaries – South Africa"
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de Villiers, Pierre. "Estuary Management in South Africa – An Overview of the Challenges and Progress Made to Date." In Estuaries of the World, 301–11. Cham: Springer International Publishing, 2016. http://dx.doi.org/10.1007/978-3-319-25370-1_19.
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De Lecea, Ander M., and Rachel Cooper. "The Importance of the Thukela River Estuary, East Coast of South Africa, for the Biology of the Near-Shore Environment and Associated Human Aspects: A Review." In Estuaries of the World, 53–65. Cham: Springer International Publishing, 2016. http://dx.doi.org/10.1007/978-3-319-25370-1_4.
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Chikodzi, David, Kaitano Dube, and Nonkululeko Ngcobo. "Rethinking Harbours, Beaches and Urban Estuaries Waste Management Under Climate-Induced Floods in South Africa." In Sustainable Development Goals Series, 127–40. Cham: Springer International Publishing, 2021. http://dx.doi.org/10.1007/978-3-030-74192-1_7.
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Crafford, Jackie, and Rashid Hassan. "Valuing Regulating and Supporting Ecosystem Services of the Subtropical Estuaries of KwaZulu-Natal in South Africa." In Eco-Efficiency in Industry and Science, 207–18. Dordrecht: Springer Netherlands, 2012. http://dx.doi.org/10.1007/978-94-007-5323-5_8.
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Vosloo, Mathys C., and Martin G. J. Hendricks. "Marine and Estuarine Nematodes in South Africa." In Nematology in South Africa: A View from the 21st Century, 495–519. Cham: Springer International Publishing, 2017. http://dx.doi.org/10.1007/978-3-319-44210-5_24.
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Whitfield, Alan K. "Life-history styles of fishes in South African estuaries." In Alternative life-history styles of fishes, 295–308. Dordrecht: Springer Netherlands, 1990. http://dx.doi.org/10.1007/978-94-009-2065-1_19.
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Ajonina, Patience U., Francis A. Adesina, and Oluwagbenga O. I. Orimoogunje. "Plantation Agriculture as a Driver of Deforestation and Degradation of Central African Coastal Estuarine Forest Landscape of South-Western Cameroon." In Estuaries of the World, 167–75. Cham: Springer International Publishing, 2014. http://dx.doi.org/10.1007/978-3-319-06388-1_14.
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Steinke, Trevor. "Mangroves in South African estuaries." In Estuaries of South Africa, 119–40. Cambridge University Press, 1999. http://dx.doi.org/10.1017/cbo9780511525490.006.
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Schumann, Eckart, John Largier, and Jill Slinger. "Estuarine hydrodynamics." In Estuaries of South Africa, 27–52. Cambridge University Press, 1999. http://dx.doi.org/10.1017/cbo9780511525490.003.
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Hockey, Philip, and Jane Turpie. "Estuarine birds in South Africa." In Estuaries of South Africa, 235–68. Cambridge University Press, 1999. http://dx.doi.org/10.1017/cbo9780511525490.010.
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