A preliminary assessment linking altered catchment land-cover to the health of four temporarily open/closed South African estuaries
- Authors: Masefield, Vincent Antony
- Date: 2014
- Subjects: Estuarine ecology -- South Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4877 , http://hdl.handle.net/10962/d1013096
- Description: Estuaries worldwide are being subjected to various degrees of catchment degradation, which is having severe consequences on the integrity of these aquatic ecosystems and their ability to function properly. This thesis investigated the relationship between catchment land-cover and estuarine health in four temporarily open/closed estuarine systems (TOCEs) in South Africa, namely the Groot Brak, East Kleinemonde, Mdloti and Tongati. GIS techniques were employed to delineate catchments, lower sections of catchments, 1 km and 100 m buffer zones, and to quantify the extent of land-cover classes present within these delineations. Anthropogenic activities outlined by the Department of Water Affairs and Forestry (DWAF) Resource Directed Measures (RDM) studies and their associated land-cover classes were described. The possible links between catchment and buffer zone land-cover class composition and health of the estuaries were explored. Results indicated that there was a relationship between catchment and estuarine health within the Coastal Protection Zone (CPZ) (1 km and 100 m) buffers, but not at a broader catchment level. Out of natural, urban built-up and cultivation land-cover classes, natural land was determined to be the best predictor of estuarine health within the CPZs. A method of rapidly assessing South African TOCE condition was applied and could be used to prioritise these estuaries for rehabilitation and/or conservation.
- Full Text:
Dynamics of larval fish and zooplankton in selected south and west coast estuaries of South Africa
- Authors: Montoya-Maya, Phanor Hernando
- Date: 2009
- Subjects: Marine zooplankton -- South Africa , Zooplankton -- South Africa , Fishes -- Larvae -- South Africa , Estuarine ecology -- South Africa , Estuaries -- South Africa -- Management , Environmental monitoring -- South Africa , Coastal zone management -- South Africa , Estuarine area conservation -- South Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5263 , http://hdl.handle.net/10962/d1005107 , Marine zooplankton -- South Africa , Zooplankton -- South Africa , Fishes -- Larvae -- South Africa , Estuarine ecology -- South Africa , Estuaries -- South Africa -- Management , Environmental monitoring -- South Africa , Coastal zone management -- South Africa , Estuarine area conservation -- South Africa
- Description: Larval fish and zooplankton assemblages were studied in nine south and west coast estuaries in the cool-temperate and the cool/warm-temperate boundary region between June 2003 and March 2004. This study served to provide new information on previously unstudied estuaries and expand on existing knowledge of larval fish and zooplankton assemblages associated with various estuary types. The south and west coast estuaries sampled in this study showed lower salinities (12.2 - 13.7), lower water temperatures (14.5 - 16.9 °C) and higher turbidities (k = 0.02 - 0.04) in winter and spring while higher salinities (21.7 - 21.8), higher water temperatures (21.7 - 23.1°C) and lower turbidities (k <0.02) were observed in summer and autumn. Mean winter and summer water temperatures in estuaries were lower than those observed in warm-temperate and subtropical systems by other researchers. A total of 49274 larval fishes were caught, comprising 9 orders, 20 families, 29 genera and 47 taxa. The clupeid Gilchristella aestuaria (78.8 %) dominated the larval fish assemblages and occurred in all estuaries. The majority (70 %) of identified species are endemic to southern Africa and 96.4 % of larval fishes caught were estuary-resident species. The zooplankton study yielded a total of 44 taxa, comprising 7 phyla, >20 orders and >35 families. The copepod Pseudodiaptomus hessei dominated (59 %) the zooplankton and occurred in similar densities to those observed in other South African estuaries. Larval fish and zooplankton varied across seasons, peaking simultaneously in summer although zooplankton showed additional density peaks during the closed phase of some estuaries. Both plankton components were more abundant in the oligohaline and mesohaline zones within the estuaries. Freshwater input, estuary type and the biogeography of the area influenced the composition and structure of larval fish and zooplankton assemblages in these estuaries. The findings suggest that the estuaries are functioning as successful breeding areas for the larvae of endemic estuary-resident fish species and that these estuaries have to be managed to ensure an adequate freshwater supply to maintain the biological integrity of the ecosystem, specially the maintenance of the highly productive River-Estuary Interface (REI) regions.
- Full Text:
The population structure of two estuarine fish species, atherina breviceps (Pisces: Atherinidae) and gilchristella aestuaria (Pisces: Clupeidae), along the Southern African coastline
- Authors: Norton, Olivia Bridget
- Date: 2006
- Subjects: Estuarine fishes -- South Africa , Estuarine ecology -- South Africa , Clupeidae -- South Africa , Silversides -- South Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5745 , http://hdl.handle.net/10962/d1005431 , Estuarine fishes -- South Africa , Estuarine ecology -- South Africa , Clupeidae -- South Africa , Silversides -- South Africa
- Description: Phylogeographic patterns of coastal organisms with different life histories and breeding strategies may reveal patterns not consistent with the current delineation of the biogeographic provinces around South Africa. The subdivision of the South African coastline into these three main climatological or biogeographic regions: namely the cool temperate west coast, the warm temperate south coast and the subtropical east coast, is based on average seawater temperatures and hydrological conditions. Genealogies of two estuarine fish species Atherina breviceps, a marine breeder, and Gilchristella aestuaria, an estuarine spawner, were reconstructed using mitochondrial DNA (mtDNA) control region sequences. The study comprised two components, an assessment of a small dataset of both fish species to compare their population structure along the South African coastline and a more comprehensive investigation of the phylogeography of G. aestuaria collected from 21 estuaries around the coast. The comparative study of A. breviceps and G. aestuaria indicate different population distribution patterns along the South African coastline. Results of the A. breviceps analysis demonstrate substantial gene flow due to the random mixing of alleles, while the comparative G. aestuaria dataset indicates a more structured population and considerably less gene flow. The G. aestuaria population demonstrates geographic separation into four groups, namely the west coast (Great Berg), Bot (south coast), Seekoei (south coast) and east coast (Bushmans, Kasouga and Cefane). Results from the larger G. aestuaria dataset indicate that the phylogeographic patterns observed during this study do not conform to existing biogeographic boundaries along the southern African coastline. The delineation identified during this study between the warm temperate and subtropical regions is further south than originally perceived and this southward extension can be ascribed to the prevailing hydrology. The life history patterns and ecology of these two estuarine fish species appears key to understanding their population structure. These factors interact with environmental characteristics such as physical oceanography and the distribution of estuaries (along the coastline) to explain the observed distribution patterns and population structure of A. breviceps and G. aestuaria.
- Full Text:
Primary production of Swartvlei in mid-summer 1980, with emphasis on the production ecology of the littoral zone
- Authors: Taylor, David Ian
- Date: 1981
- Subjects: Estuarine ecology -- South Africa , Estuarine ecology -- South Africa -- Swartvlei , Ecology -- Research -- South Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5820 , http://hdl.handle.net/10962/d1007320 , Estuarine ecology -- South Africa , Estuarine ecology -- South Africa -- Swartvlei , Ecology -- Research -- South Africa
- Description: From Introduction: Energy passes through an ecosystem via a multiplicity of interconnected routes, which can be broadly categorised into trophic and detrital pathways. The "metabolic activity" of most lakes will be governed predcminantly at the base of these two routes; namely, the primary producer and decanposer levels, respectively (Wetzel and Allen, 1972). The importance of the littoral primary producers (especially the aquatic macrophytes) in the functioning of the Swartvlei ecosystem has been emphasised in a comprehensive report by Howard-Williams and Allanson (1978) dealing with the lake system fran 1975 to 1978. They noted that although the littoral shelf (<2m below low water level) occupies only 43% of the lake's surface area it contributed 64% of the total annual primary production during the period investigated. This was largely due to the dense Potamogeton pectinatus stands which alone accounted for 52% of the total carbon input into the lake by plants. The fact that the production/biomass ratio for P. pectinatus was only 1,2:1 suggested that its importance as a primary producer in Swartvlei was largely due to its high bianass. (Biomass, or standing stock, is used in this report as defined by Waters (1977); namely, "the amount present at a point in time, expressed best as quantity per spatial unit".)
- Full Text:
A preliminary investigation of the ecology of the Larger Kleinmond River Estuary, Bathurst District
- Authors: Brown, Alexander Claude, 1931-2005
- Date: 1953
- Subjects: Kleinemonde River Estuary (South Africa) , Estuaries -- South Africa , Estuarine ecology -- South Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5904 , http://hdl.handle.net/10962/d1014611
- Description: Introduction. On the coast of the Bathurst Division, Eastern Cape Province, some 42 miles south- east of Grahamstown, lie two estuaries opening within a few yards of one another. These are known as the Kleinemonde. This paper embodies the results of an ecological survey of the fauna of the Larger Kleinmond Estuary. The chief concern has been the aquatic fauna but animals living along the banks have also been dealt with as far as possible, as have the birds. This is the second of South Africa's blind estuaries to be studied, the Klein River, Hermanus, having been investigated in 1947-49 by workers from the University of Cape Town. Though common in South Africa, blind estuaries are rare in parts of the world such as Europe, and present an almost entirely new field of research for the ecologist. It is hoped, therefore, that the investigation of the Kleinmond Estuary and a comparison with the results obtained from the Klein River, Hermanus, will add to our knowledge of this subject and be of service to future investigators. The history of the Kleimnond River is worthy of mention, for the lagoon was not always blind and shallow. The early maps of the 1820 settlers show the river as a navigable stream; sailing vessels anchored out at sea and sent lighters up what was then known as the Lydendoch River to collect fresh meat. The area at the mouth of the river was called Port Jessie. In these early days the region abounded with game. Hippo and elephant were common. the former inhabiting deep pools in the upper reaches of the river; pools which have since completely silted up. Constant ploughing of the slopes adjoining the river has caused vast amounts of soil to be washed by rains into the stream, and today what was within living memory a deep, clear stream is a shallow, blind and muddy river, a reflection of man's destructive methods of farming. These changes must have had a far-reaching effect on the fauna of the estuary; an effect about which we can, alas, only speculate. It is perhaps significant that though rich in numbers, the fauna is poor in species, tunicates and echinoderms being apparently entirely absent. The work involved in this survey was undertaken between September 1952 and November 1953, under the direction of Professor J . Omer-Cooper of Rhodes University, frequent and regular visits being made to the estuary. The entire month of February, 1953, was spent on the shore of the lagoon, so that animals could be observed over a continuous period. The starting date of the survey was particularly fortunate, as on September 28th, 1952, the river came down in flood and broke through the sand-bar separating the lagoon from the sea. The work thus began at a definite point in the estuarine cycle, the importance of which it is hoped to show.
- Full Text: