This study represents an integrated and holistic assessment of the eziMbokodweni Estuary’s water and sediment quality. The estuary was once relatively un-impacted but now flows through a highly anthropogenically-modified catchment, comprising industrial and residential developments (formal and informal), and the eziMbokodweni Wastewater Treatment Works, furthermore the floodplain has been completely transformed to accommodate the Amanzimtoti golf course. Flow from the highly degraded Isipingo River and Estuary is occasionally diverted into the eziMbokodweni and the Southern Sewage Works Outfall, one of the largest deep sea sewage outfalls in the eThekwini Municipality, is located at sea, approximately 1.5 km south of the estuary mouth. Estuarine health can be studied on various fronts, in this study, the following variables were monitored in the water and sediment columns, seasonally for spring and neap tides: heavy metals, nutrients, bacteria and selected physico-chemical parameters. The results demonstrated that the eziMbokodweni catchment was a major contributor of heavy metals and nutrients to the estuarine system. The quantity of the majority of heavy metals and nutrients transported by the river at the upper estuary exceeded the amount exported to sea at the estuary mouth-nearshore interface, resulting in the estuary accruing large quantities of material seasonality. It was noted that the nearshore waters are enriched, as a variety of heavy metals and nutrients entered the estuary mouth during flood tide episodes. A range of heavy metals were detected within the sediment profiles obtained from the estuary, with fine to medium grained sediment exhibiting greater heavy metal content, in some cases, multi-fold higher than that detected in medium to coarse grained sediment. Geochemical indices were employed to ascertain the extent to which these metals constituted a pollution threat to the environment. The contamination factor calculated for all sediment layers and sampling sites implied low contamination. The enrichment factor calculated for the majority of heavy metals alluded to natural causes while some heavy metals exhibited significant to extremely high levels of enrichment thus implicating anthropogenic causes as likely sources of these heavy metals. The degree of contamination of the estuary was classified as low. Overall, the heavy metal and nutrient content detected in the sediments were low as compared to the large quantities detected from the budget. This indicates that natural mechanisms exist which facilitate the utilization or removal of these heavy metals and nutrients from the estuary. It is proposed that the most significant manner by which these heavy metals and nutrients are eliminated from the estuary is through episodic flood events that scour and strip fine grained sediment from the estuary bed. The pH assessment of the estuary revealed that this environment was slightly basic through most of the year with mildly acidic conditions noted during winter. The average Dissolved Oxygen levels were within acceptable levels, with the exception of winter when levels were very close to hypoxic conditions. The average Total Dissolved Solid content indicated that the estuary was compliant with the target water quality range for domestic use on selected seasonal-tidal cycles, and the average Electrical Conductivity levels were compliant with the ideal target water quality range for aquatic ecosystems and domestic use as per the South African water quality guidelines (DWAF, 1996a-e). A salinity gradient was evident in the estuary, as salinity levels decreased with distance from the estuary mouth. The saline nature of the lower estuary provided for the flocculation of material, which was alarming as large quantities of heavy metals and nutrients were detected in the estuary. The lower estuary is therefore susceptible to contamination due to the salinity regime and the dominance of fine grained sediment. The demand for oxygen in the estuary was high during summer, autumn and spring, and within acceptable levels for natural waters during winter. Extremely high levels of Chemical Oxygen Demand were recorded in the estuary which provides prime growth and survival opportunities for bacteria. This correlated with the results from microbiological investigations as high levels of bacteria were noted within the estuary, in both the sediment and water columns. The detected quantities of Total Coliforms, Faecal Coliforms and Escherichia Coliforms exceeded the target water quality thresholds for domestic and full contact recreational use. While at selected sites, the recorded Faecal Coliforms and Escherichia Coliforms levels were deemed compliant for intermediate contact recreational use. However, these sites were not compliant throughout the sampling period. Overall, the upper and mid-estuary exhibited greater counts of bacteria, in both the sediment and water column, than the estuary mouth and was attributed to factors such as flushing, sediment particle size, salinity and the ‘dilution effect’. Furthermore, the sediment of the eziMbokodweni Estuary is serving as a reservoir for bacteria. A number of options have been proposed to improve the degraded state of the eziMbokodweni Estuary and are ultimately aimed at curbing the anthropogenic input of these contaminants. The insight gained from this study provides the database from which more integrated and holistic estuarine management strategies can stem, that are applicable not just to the eziMbokodweni Estuary but estuaries in general. / M.Sc. University of KwaZulu-Natal, Durban 2013.

River inflow is one of the most important factors influencing the density and biomass of estuarine biotic communities. The aim of this study was to obtain an understanding of the ecosystem functioning of selected estuaries on the east coast of South Africa and to represent their dynamics through ecosystem models. The responses of water column nutrients, plankton density and biomass to inlet phase changes for 16 temporarily open/closed estuaries (TOCEs) in South Africa were first determined. This analysis demonstrated that inlet phase and the duration of mouth closure were the most important factors determining plankton density and biomass of the analysed TOCEs. Estimates of planktonic standing stocks for four of these estuaries revealed that stocks can be from 26 to 10 000 times higher during the closed compared to the open phase. Also, slightly higher variability of planktonic density and biomass was recorded during the closed phase of TOCEs. The second major thrust of this study was to analyse the variability and temporal stability of planktonic and macrobenthic invertebrate density and biomass in two KwaZulu-Natal estuaries over a dry/wet cycle. The results suggest that “stable” variability and species synchronization could be the mechanisms whereby the estuarine biota of these systems compensate for environmental changes and attain a degree of environmental homeostasis. The third major thrust involved an assessment of the spatio-temporal variations in the elemental composition and stoichiometry of suspended and sediment detritus, zooplankton and macrobenthic taxa from two estuaries over a dry/wet cycle. Significant seasonal variations in the elemental composition of detritus, zooplankton and macrobenthic species were found, with the variations in the elemental content of sediment and suspended detritus being related to the seasonal changes in river inflow, while the among-taxa variability was mainly explained by feeding mode. Finally, static seasonal carbon and nitrogen ecosystem network models were developed for the East Kleinemonde, Mlalazi and Mpenjati estuaries to investigate their nutrient dynamics and ecosystem functioning. The results indicated that the East Kleinemonde and Mpenjati estuaries were mainly dependent on primary producers during the dry season, especially the high standing stocks of phytoplankton and microphytobenthos. Similarly, the dependency on detritus was higher during the wet season due to the high riverine imports during this season. Consequently, higher detritivory was recorded in all three study systems during the wet season. Cycling of nitrogen was higher than of carbon on a seasonal basis, with higher recycling of nitrogen during the dry season implying a lower availability of this element due to reduced freshwater inflow and nutrient input during the low rainfall period. System indices indicated that the organization of these systems was higher during the dry season, while the overheads on imports and exports peaked during the wet season. The ecosystem models analysed here provide an initial insight into the overall carbon and nitrogen dynamics of estuaries on the east coast of South Africa. / M.Sc. University of KwaZulu-Natal, Durban 2013.

Studies In other parts of the world have proved that turbidity affects aquatic life and work In Australia and North America has shown that the distribution of some fish species may be determined by the level of turbidity present. This, coupled with the fact that: (i) Natal estuaries are important as nursery areas for the juveniles of many marine fish species, (ii) the estuaries exhibit a wide range of turbidities and (iii) little was known of the effects of turbidity on the fish populations in estuaries, led to this study being undertaken. Turbidity and its effects on fish distribution In Natal estuaries was investigated from January 1980 to June 1983. Lake St. Lucia, which is predominantly turbid but also has clear water areas, was the main study area. Six other estuarine systems sampled were chosen to cover a wide range of estuarine types and turbidities. Field sampling was undertaken to determine which species were present under different turbidities, simultaneously physical factors which were potentially affecting fish distribution were also monitored. In addition to this, laboratory equipment which enabled a turbidity gradient to be established In a choice chamber tank was used to test the turbidity preferences of 10 common estuarine species for which field data were available. These tests allowed the elimination of all physical factors except turbidity. Of the physical parameters monitored In the field, turbidity, temperature and food availability In the benthos, were determined as being important In affecting fish distribution within estauries. However, comparison of fish distribution data for twenty species, with these factors showed that turbidity was exerting the major influence. It was also found that fish species occurred In one of five groups, inhabiting either clear, 'clear to partially turbid', intermediate or turbid waters or they were indifferrent to turbidity. Laboratory results for eight of ten species tested showed significant aoreement with the field data. The results of this study have shown that turbidity is the most important factor determining the distribution of juvenile marine fish In estuaries and that the greatest number of species are present in , waters which are not clear. The attraction to and presence in such systems appears to be related to the fact that turbid estuaries 'provide protection from fish and bird predators while also acting to reduce intraspecific predation. Of factors attracting juvenile fish into estuaries, turbidity is probably the single most important acting in this respect. / Thesis (Ph.D.)-University of Natal, Pietermaritzburg, 1984.

Typescript. / Bibliography: leaves [208]-221. / xix,, 221 leaves illus., maps, tables 28 cm

During 1973 data was collected to analyze the seasonal variations of the tidal dynamics, water quality and sediments of the Alsea Estuary. A summary of historical information with a list of all known alterations to the estuary was made. A complete physical description, including the geographical setting and mixing classification of the estuary, was done. Times of high and low water and tidal ranges at three locations were measured. Tide measurements made at Waldport indicated that the published tide predictions for that location were reliable. At a location upstream of the estuary embayment noticeable damping of the tidal wave amplitude was detected during periods of high river flow and high tidal range. High water lag times were found to decrease during periods of high river flow, but low water lag times were unaffected by river flow. The tide motion was found to be a damped, partially standing wave, which altered its behavior according to the volume of water in the estuary. The high and low tide water quality parameters of salinity, temperature, dissolved oxygen, turbidity and pH were measured at 10 to 18 locations during each season to determine any seasonal changes in them. The parameters at a given location were found to be a function of river flow and tidal range. Winter and summer sediment samples were analyzed for grain size distribution, volatile solids and porosity. The sediments from the main channel exhibited characteristics of a high velocity regime and those of the north channel, a low velocity regime. / Graduation date: 1975

At present, there is a general lack of information regarding the spatial genetic architecture and genetic diversity of estuarine and coastal freshwater fish in Australia or about the interacting intrinsic, extrinsic and historical influences responsible for sculpting these patterns. This thesis represented the first investigation of the phylogeographic structure and recent evolutionary histories of teleost fishes from the coastal and estuarine environments of south-western Australia, using the resolution afforded by mtDNA sequence data. Available evidence indicated that, to different degrees, these species have limited potential for dispersal amongst local assemblages from different water bodies. As this theoretically reduces the confounding effects of recent gene flow on extant genetic structure, these fishes were well suited to studying the influences of historical factors. Historical influences were expected to be particularly profound, given that these coastal environments underwent massive modifications during Late Quaternary eustatic fluctuations. The thesis consists of four major components, which explored different aspects of interspecific and intraspecific phylogeny and p hylogeograp hy of three teleost species, based on mtDNA control region and cytochrome b fragments. First, the relationship between the endemic, 'strictly estuarine' Leptatherina wallacei (Atherinidae) and the more widespread, 'estuarine & marine' 6. presbyteroides was examined, with a view to establishing whether 6. wallacei represents a monophyletic or polyphyletic lineage and whether this species was derived recently (i.e. in Holocene estuaries). Second, the phylogeographic structure and genetic diversity of L. wallacei were investigated and compared with data from L. presbyteroides, with a view to using this information to interpret the recent evolutionary histories of each congener. Third, the divergence between assemblages of L. wallacei inhabiting two isolated coastal lakes was used to estimate a maximal substitution rate for the control region, which was then used to infer general time frames for the divergence between the two Leptatherina species and between the major phylogeographic partitions within each species. Fourth, investigations were initiated into phylogeographic patterns and levels of genetic diversity within and among assemblages of Pseudogobius olorum (Gobiidae) from several coastal lakes and an estuary. Phylogenetic analyses indicated that the two Leptatherina species were characterised by exclusive and reciprocally-monophyletic lineages of haplotypes from both mtDNA regions, supporting the monophyletic origins of L. wallacei. Both 6. wallacei and 6. presbyteroides exhibited high levels of genetic diversity and extensive overall subdivision (e.g. Qsr = 0.691 & 0.644 respectively for control region data). There was a profound phylogeographic break in both species between all conspecific assemblages from the lower west coast (LWC phylogroup) and all those from the south coast (SC phylogroup), which suggested the influences of shared extrinsic and/or historical factors. There was limited genetic structuring within the two major phylogroups of either Leptatherina species, apparently reflecting recent connectivity amongst local assemblages, with subsequent fragmentation and insufficient time for lineage sorting. However, two major phylogeographic breaks distinguished monophyletic control region phylogroups of L. wallacei from the isolated coastal Lake Clifton and Lake Walyungup, consistent with their independent evolution following lacustrine entrapment during the Holocene. The divergence between these two isolated lacustrine assemblages of Leptatherina wallaceiformed the basis for an estimate of the maximal substitution rate of the control region. While these data were unable to provide a precise estimate of the actual rate of molecular evolution, all the evidence suggested that it was proceeding very rapidly. The maximal rate estimate of 172.3% lineage-' MY-' was among the fastest ever reported. Based on this rate, the two Leptatherina species diverged at least 1 SKya, thus rejecting a Holocene origin for L. wallacei. The divergence between the LWC and SC phylogroups of L. wallacei has been ongoing for at least GKya, while the equivalent divergence in L. presbyteroides has been ongoing for at least 11 Kya. As the time frames of these divergences were consistent with periods of massive environmental modifications associated with the end-Pleistocene fall in sea level and the HMT, it was likely that these factors have played important roles in sculpting the species' divergence and intra-specific genetic structure. Although useful in temporally scaling genetic divergences within and between the two Leptatherina species, wider application of this rate estimate to questions regarding other taxa was limited. For example, evident rate heterogeneity between the genera precluded its use with even the relatively closely-related atherinid Atherinosoma elongafa. Phylogeographic analyses identified high levels of genetic diversity and extensive genetic subdivision (e.g. st = 0.652 for control region) amongst an estuarine and several lacustrine assemblages of Pseudogobius olorum, although phylogeographic structure was shallower than in either Leptatherina species. There was increased divergence between three assemblages from the lower west coast and two from the south coast, consistent with the profound break evident in the Leptatherina. One lacustrine assemblage appeared to represent a distinct lineage and a preliminary maximal rate estimate (~61.4% lineage-1 MY-1) was calculated based on the minimum divergence of this assemblage from its nearest conspecifics. Although slower than the rate calculated for L. wallacei, this was still high for teleost fishes. Overall, this study indicated that historical environmental factors, especially those related to Quaternary eustatic changes, have played important roles in sculpting the phylogeography and evolution of three teleost species from south-western Australia. Moreover, as these species have differential dependencies on estuarine environments (is. 'strictly estuarine' vs 'estuarine & marine') and represented two different taxonomic groups (i.e. Atherinoidei & Gobioidei), historical environmental factors may have exerted similar influences on other coastal species in the region.

Thesis (M.Sc. (Ichthyology & Fisheries Science)) - Rhodes University, 2008.

Thesis (M.Sc. (Zoology & Entomology)) - Rhodes University, 2008.

Thesis (M.S.)--Mississippi State University. Department of Geosciences. / Title from title screen. Includes bibliographical references.

Thesis (M.S.)--Mississippi State University. Department of Civil and Environmental Engineering. / Title from title screen. Includes bibliographical references.