A review of the ecology and management of temporarily open/closed estuaries in South Africa, with particular emphasis on river flow and mouth state as primary drivers of these systems
- Authors: Whitfield, Alan K , Bate, G C , Adams, Janine B , Cowley, Paul D , Froneman, P William , Gama, P T , Strydom, Nadine A , Taljaard, S , Theron, A K , Turpie, J K , Van Niekerk, L , Wooldridge, T H
- Date: 2012
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/480849 , vital:78487 , https://doi.org/10.2989/1814232X.2012.675041
- Description: Research in South African temporarily open/closed estuaries that includes studies on the hydrodynamics, sediment dynamics, macronutrients, microalgae, macrophytes, zoobenthos, hyperbenthos, zooplankton, ichthyoplankton, fishes and birds is used as a basis to review the ecology and management of this estuary type on the subcontinent. Particular attention is given to the responses of the different ecosystem components to the opening and closing of the estuary mouth and how this is driven by riverine and marine events, as well as anthropogenic influences. In addition, the wider implications of these research findings for the management of temporarily open/closed estuaries in terms of freshwater supply are explored, together with the role of government legislation in maintaining the ecological integrity of these important wetland systems.
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A multidisciplinary study of a small, temporarily open/closed South African estuary, with particular emphasis on the influence of mouth state on the ecology of the system
- Authors: Whitfield, Alan K , Adams, Janine B , Bate, G C , Bezuidenhout, K , Bornman, Thomas G , Cowley, Paul D , Froneman, P William , Gama, P T , James, Nicola C , Mackenzie, B , Riddin, T , Snow, G C , Strydom, Nadine A , Taljaard, S , Terörde, A I , Theron, A K , Turpie, J K , Van Niekerk, L , Vorwerk, Paul D , Wooldridge, T H
- Date: 2008
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/480839 , vital:78481 , https://doi.org/10.2989/AJMS.2008.30.3.2.636
- Description: In 2005/2006 a multidisciplinary research programme that included studies on the hydrodynamics, sediment dynamics, macronutrients, microalgae, macrophytes, zoobenthos, hyperbenthos, zooplankton, ichthyoplankton, fish and birds of the temporarily open/closed East Kleinemonde Estuary was conducted. Particular attention was given to the responses of the different ecosystem components to the opening and closing of the estuary mouth and how this is driven by both riverine and marine events. Using a complementary dataset of daily estuary mouth conditions spanning a 14-year period, five distinct phases of the estuary were identified, including closed (average = 90% of the days), outflow (below1%), tidal (9%) and semi-closed (below1%). The open-mouth phase is critical for the movements of a number of estuary-associated fish (e.g. Rhabdosargus holubi) and invertebrates (e.g. Scylla serrata) between the estuary and sea.
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The role of estuarine type in characterizing early stage fish assemblages in warm temperate estuaries, South Africa
- Authors: Strydom, Nadine A , Whitfield, Alan K , Wooldridge, T H
- Date: 2003
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/447658 , vital:74664 , https://doi.org/10.1080/15627020.2003.11657192
- Description: Assemblages of early stage fishes (larval and early juvenile stages) were investigated and compared in seven permanently open and five intermittently open estuarine systems on the warm temperate Eastern Cape coast of South Africa. Estuarine type, by virtue of mouth state and prevailing physico chemical conditions, played a defining role in the structure of these fish assemblages. Clupeidae and Gobiidae were the dominant fish families in both estuarine types. Permanently open estuaries were characterized by the predominance of larvae and early juveniles of estuary dependent marine fish species while estuary resident fishes dominated intermittently open estuaries. Seasonal changes were observed in species density and diversity in both estuarine types. Species richness and diversity were highest in the permanently open Swartkops Estuary that is characterized by large nursery habitat availability. Species diversity was high in estuaries with a good supply of freshwater, that results in good recruitment of estuary dependent marine species. Similarly, freshwater deprived estuaries also displayed high species diversity and this was due to the higher incidence of marine straggler species in these systems. Salinity zones appeared to play a significant role in both species density and the presence or absence of species in both estuarine types. Mesohaline zones were found to be the most productive in terms of accumulator regions for larval stages.
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