Thesis (M.Sc.)-University of KwaZulu-Natal, Westville, 2010.

Estuaries in South Africa are important nursery areas for the juveniles of many fish species. The condition of many of these systems has, however, deteriorated as a result of degradation caused by urban, industrial and agricultural development. An assessment of the role of harbours, particularly in KwaZulu Natal, as nursery grounds has therefore become an important issue. Durban Bay has undergone considerable changes since the mid-1800s and further developments are proposed. If these developments continue, they will result in the loss of large areas of the sandbanks, but Portnet has recognised the need to integrate environmental considerations into future port developments and operations. It was the overall aim of this study to establish the nature of the association of the juveniles of four common fish species viz. Pomadasys commersonnii, Gerres filamentosus, Liza dumerilii and Leiognathus equula with these sandbanks and, thereby assess the impact of their removal. It was found that all species were abundant on the sandbanks and that the diets of P. commersonnii, G. fiiamentosus and L. equuia were very similar, consisting primarily of bivalve siphon tips, benthic crustaceans and polychaetes. The respective contributions of each food type to the diet varied with species. The diet of L. dumerilii differed from that of the other three species, consisting primarily of benthic floc, foraminiferans, ostracods and sponge spicules. Despite differences in selectivity, it was concluded, from studies of the benthos in the harbour, that all four species, irrespective of size, were feeding on these sandbanks, as opposed to in the channels, throughout the year. Removal of the sandbanks for the construction of a new pier would, thus, result in the elimination of important feeding grounds for the juveniles of these four species. / Thesis (M.Sc.)-University of Natal, 1994.

This thesis documents eight estuaries that are situated on the northern coastline of KwaZulu-Natal viz.: St Lucia, Mfolozi, Zinkwazi, Mvoti, Mngeni and those of the South i.e. Isipingo, Manzimtoti and Mkomazi. The documentation is aimed at undertaking a holistic approach on estuaries of KwaZulu-Natal approximately 10% and determines the influence of anthropogenic and natural impacts upon their health status. The study has also analysed selected sample estuaries of KZN in terms of their general natural characteristics, looked at the morphological features, riparian vegetation and land use directly from site visits and from aerial photographys, and determined the influence of anthropogenic and natural impacts in the estuaries. It also assessed the health status of the estuaries, proposed appropriate management strategies and reviewed the current status of estuaries in KZN / southern Africa. The researcher employed quantitative approach as a viable and the most relevant method where a holistic approach has been used. This was achieved through the execution of various techniques. For instance, reconnaissance survey was conducted including the usage of aerial photographys and topographical maps. Data was also collected using the YSI 6920 model. The study was also undertaken in order to determine whether the KwaZulu-Natal estuaries were still having a nursery function, which appeared to be losing when considering both primary and secondary activities that took place in the catchment areas. All of these estuaries were under a severe stress and pressure through natural and anthropogenic phenomenon. They were all suffering and gradually getting contaminated and depleted through anthropogenic activities that took place uncontrolled in their catchmenmt areas. Findings also show humans as the main culprits for estuarine contamination and degradation. It was discovered that about 84.2% of the catchment areas within the study area was human occupied. Their suffering differed as it depended on the extent in which catchment areas were utilized. Where anthropogenic activities took place alarmingly, estuaries also suffered a great deal. This posed a challenge to ecologists, hydrologist and environmentalists generally, and to physical geographers specifically since they regard estuaries as very important for their nursery functions and ecological balances. Mfolozi and St Lucia estuaries were found to be little affected from direct anthropogenic effects. Pollutants accumulating in the systems may have come from farmlands in the north of the Mfolozi and from the town of St Lucia in the case of the St Lucia estuary. However, more negative effects were clearly due to excessive sedimentation. The study has revealed that the Mfolozi mouth position had been artificially relocated on several occasions since 1952 by human intervention in the system. In these situations, the Mfolozi mouth may be located between one and two kilometres south of the St-Lucia mouth. Two estuaries, Mvoti in the north and Isipingo in the south were found to be the most affected water bodies by human activities occurring in the catchment areas and this has led to them having unhealthy water status. It was found that through anthropogenic interference, there were changes in the nature of runoff and water quality that was attributed to industrial pollution, runoff from agricultural activities, sewage effluent and the runoff from urban areas. There is evidence of extremely poor catchment management practices as proved by the poor state of many estuaries along the KwaZulu-Natal coast. The study recommended that for the important future well being of these estuaries, various tiers of catchment management authority must be put in place by the Department of Water Affairs and Forestry. The local authorities must proactively manage land uses and anthropogenic activities on and around the estuaries in order to minimise potential impacts on the systems. / Thesis (Ph.D.)-University of KwaZulu-Natal, 2008.

Global shifts in environmental decision-making from technocratic, top-down models to democratic, open-ended forums to address environmental issues have highlighted the complexity of environmental issues. As a result, the definition of these environmental problems in the political arena is highly contested and thus the process of formalising environmental discourses through environmental policy-making has become very important. Hajer’s (1995; 2003) argumentative discourse analysis approach is used as a methodology to examine environmental policy-making regarding the St Lucia estuary mouth, in KwaZulu-Natal. This is also used to structure the presentation of the analysis particularly according to the terms of the policy discourses, such as the broad societal discourses, the local discourses and and the storylines. The environmental discourses are characterised using Dryzek’s (1997: 8) taxonomy of environmental discourses, based on his broad definition of discourse as “a shared way of apprehending the world”. This research aims to identify the environmental discourses that emerged in the 1940 to 2005 period regarding the management of the St Lucia estuary mouth and the shifts in discourses that have taken place during this time. An analysis of the shifts in environmental discourses in the Greater St Lucia Wetland Park over a 65 year period revealed two significant events that punctuated the management discourses of the protected area and effectively divided the analysis into three succinct periods. These two events were the Kriel Commission of Enquiry in 1966 and Cyclone Demoina in 1984. The promethean, ecological modernisation and survivalist discourses were dominant throughout the three periods analysed. The evidence also shows that there has been a shift from modernist engineering discourse to a more ecosystem discourse which advocates that ‘let nature take its own way’. Science remains a dominant force in shaping environmental policy-making in St Lucia; however environmental problems have become discursive in the post-apartheid period in a democratic South Africa and thus require a discourse that has wider stakeholder representation. / Thesis (M.Sc.)-University of KwaZulu-Natal, Durban, 2009.

Estuaries are complex ecosystems, typified by remarkable fluctuations in environmental conditions. In addition to this natural variability, stochastic events and anthropogenic influences effect change at different spatial and temporal scales. Macrozoobenthic invertebrates are preferable biological indicators because of their sensitivity to variations in habitat quality. This thesis describes inherent changes in the macrozoobenthos of temporarily open/closed estuaries (TOCEs) in KwaZulu-Natal, ‘change’ as measured in spatial and temporal community differences using various community metrics, namely species composition, abundance and diversity. Standard and widely published quantitative sampling techniques were employed, with simultaneous measurements of ambient physico-chemical conditions, including sediment characteristics. The thesis is in three parts. Regional distributions and long-term decadal-type changes in macrozoobenthic community structure were determined for 31 TOCEs using historical data (1998/9) compared with more recently collected data (2009/10). Results showed that, although of the same estuary type, the macrozoobenthic communities of these estuaries differed significantly. Furthermore, community composition did not reflect a north to south progression of predominantly tropical species to predominantly warm-temperate species. In the last decade, the macrozoobenthos of these systems had indeed changed (in composition, abundance and/or diversity), the scale of change within each estuary being estuary-dependent. The recolonisation of two urban and non-urban estuaries by macrozoobenthos following a stochastic flood disturbance was investigated, describing the short-term community changes during the recovery process. Differential recolonisation patterns were attributed to inherent differences in community composition and not to the influence of urbanisation. Recolonisation was marked by distinct changes in community structure, with the recovery trajectory being interrupted by localised disturbances (e.g. change of mouth state). Species indicative of the observed spatial and temporal community changes were examined for similarities in habitat association and trophic characteristics. The species that were representative of these KwaZulu-Natal TOCEs were identified and included common and highly abundant generalists of varying trophic groups. In conclusion, the present findings illustrated the effectiveness of using macrozoobenthic communities to depict ‘change’ over multiple temporal and spatial scales. This also supports their usefulness as a study group in environmental monitoring and detecting the loss of ecological functioning and biodiversity in estuaries in the long- and short-term. / Thesis (M.Sc.)-University of KwaZulu-Natal, Westville, 2011.

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.

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.

Estuaries are unique coastal bodies of water where water derived from land meets the sea. In order to preserve estuaries and minimise the effects of human interference in these sensitive areas, an understanding of the hydrodynamics is essential. South Africa has 259 estuaries, of which approximately 70% are temporary open. The aim of the project was to provide data to analyse the effect of different flow scenarios on the frequency, timing and duration of mouth closure for temporary open estuaries. To achieve the project aim, two case studies were undertaken, namely Mhlanga and Mdloti Estuaries. Achieving the terms of reference required monitoring of the mouth state, water level, flow rates and developing an understanding of breaching mechanisms. Observations of the mouth were used to monitor its state and initially photographs were used to monitor the water level within each estuary. During 2003 a continuous water level monitor was developed and placed in each estuary. Velocity readings were taken upstream of the estuaries at discrete time intervals and converted to flow rates using the velocity area method. A photographic survey of the berm at Mhlanga Estuary was used to observe the effect of beach processes on the mouth area. The survey observed the estuary as it shifted from closed through to open, then partially open and finally closed again, providing information on mouth mechanisms. The continuous water level monitoring provides useful information for Mhlanga Estuary in terms of breaching patterns, tidal exchange when in the open state and an indication of the time scales involved in mechanisms which change the mouth state. Similar information for Mdloti Estuary was not available as the estuary did not breach since the installation of the water level monitors, however salinity profiles from 2002 provided qualitative information on the existence of a saline intrusion into the estuary. The relationship between flow and mouth state is complex and relies on other influences such as water level and systems losses. In general estuaries will breach under high flows and remain closed under low flows, however in between these two regimes the estuary mouth state is less predictable based on flow alone. Mhlanga Estuary repeatedly breached at low tide. During the open phase tidal influence was both observed and captured by water level monitors despite the perched nature of the estuary. Closure generally occurred at high tide trapping saline water within the estuary. The two case studies provided a good basis for exploring the affects of different flow conditions on estuaries, with Mdloti Estuary experiencing the effects of the Hazelmere Dam and abstractions, while Mhlanga Estuary has increased flow due to the discharge of treated effluent to the system. / Thesis (M.Sc.Eng.)-University of Natal, Durban, 2004.

Coastal systems like lagoons and estuaries are faced with severe human developmental endeavours. In South Africa, more than 30% of the population lives along the 3000 kilometer coastline. The Durban bay is no exception especially with the existing Durban harbour taking up the natural expanse of the bay. The bay is burdened with a diversity of anthropogenic endeavours, from port operations to industrial activities, to storm water drainage outlets, through to various recreational ventures. These activities have over the years caused a reduction of the bay‘s mangrove forest, reduced the population of some biota and caused extinction of some indigenous species. Five areas were selected based on the specific activities and infrastructure that occurred there. Samples of water from these pre-selected sites were collected routinely and analysed for their water quality status. The overall water quality within the bay compared with the DWAF water quality guidelines for South Africa was identified as below stipulated standards. The dissolved oxygen contents as well as nutrients in the form of nitrogen content in its assorted forms are some of the most affected water quality indicators. The majority of the sub standard water quality levels, indicators which are critical to the proper functioning, growth and reproduction of biota within the ecosystems of the bay obtained could be linked directly or indirectly to the activities within the area of sampling. The resultant chemical and physical conditions in water quality created as a result of the ongoing activities within the bay are not suitable for proper feeding, growth and reproduction of ecosystems. This has caused many species within the bay to migrate or adapt to the adverse conditions and such situations are likely to worsen if stringent measures are not taken in the near future. It appears that the some species are exhibiting some degree of resilience and are at the moment surviving the relatively harsh conditions within the bay. The long term effect of the ever expanding anthropogenic disturbances on the ecosystems are unpredictable and it is therefore imperative that more stringent environmental management plans, programs and policies, legally binding, are formulated to serve as a check on all who benefit from the bay‘s resources. / Thesis (M.Sc.)-University of KwaZulu-Natal, Westville, 2010.

The zooplankton communities of the Mdloti and Mhlanga estuaries were studied over a 13-month period (March 2002-March 2003). Monthly daytime samples were collected from both estuaries at the lower, middle and upper reaches using a WP-2 net and a hyperbenthic sled. Throughout the study period, the Mdloti Estuary experienced nine breachings, while the Mhlanga experienced 16 such events. Significant differences in zooplankton abundance were observed between the two estuaries (F I, 73 = 5.2; P<0.05), with the Mdloti consistently exhibiting higher values than the Mhlanga. No significant differences were, however, observed in zooplankton biomass between the two estuaries (U = 634; P>0.05). At the Mdloti, zooplankton abundance ranged from 20 ind.m-3 to 5.4 x 106 ind.m-3 , while at the Mhlanga this ranged from 76 ind.m-3 to 2.0 x 105 ind.m-3 • Zooplankton biomass ranged from 0.08 mg.m-3 (OW) to 2010 mg.m-3 (OW) at the Mdloti, and from 0.18 mg.m-3 (OW) to 1210 mg.m-3 (OW) at the Mhlanga. A one-way ANOV A revealed significant differences in zooplankton abundance between the open and the closed phase, both at the Mdloti (FI, 30 = 59; P<0.05) 'and the Mhlanga (FI, 38 = 7.3; P<0.05), with the closed phase exhibiting consistently higher values than the open. Similarly, biomass was significantly higher during the closed than the open phase, both at the Mdloti (U= 16.5; P<O.OI) and the Mhlanga (U= 88, P<O.O 1). This pattern may be attributed to the stability achieved by these systems during periods of mouth closure, when the estuaries exhibit less freshwater input and a restricted exchange of water with the sea. At the Mdloti, zooplankton biomass (OW) was positively correlated to both phytoplankton (r= 0.36) and microphytobenthos biomass (r = 0.41). At the Mhlanga, zooplankton biomass (OW) was only positively correlated to phytoplankton biomass (r = 0.45) The most abundant taxa at the Mdloti during the open phase were Pseudodiaptomus hessei and copepod nauplii, each contributing 38% and 32% of the total stock, respectively. During the closed phase, however, rotifers were by far the dominant taxon, contributing 82% of the total zooplankton abundance. These were followed by cope pod nauplii with 16%. At the Mhlanga, the most abundant groups during the open phase were again the copepod nauplii (89%) and P. hessei (7 %), while the closed phase was dominated mainly by caridean larvae (39%) and copepod nauplii (26%). The dominance of P. hessei during the open phase of both estuaries may be attributed to the pioneering nature of this species. The dominance of rotifers at the Mdloti during the closed phase may have been due to the freshwater conditions that prevailed in this estuary as a result of prolonged mouth closure. The concentration of copepod nauplii increased dramatically 2-4 weeks after major rain events, possibly due to the hatching of dormant eggs in response to freshwater pulses. / Thesis (M.Sc.)-University of KwaZulu-Natal, 2005.