Water quality studies conducted in the recent past in the Lower Fraser River Basin indicated that locally some high pollution levels exist. With further urbanization and industrialization of the Vancouver region an increase in waste loadings and a degradation of water quality can be expected if no strict pollution control is applied. Of particular concern are biologically undegradable substances such as heavy metals and poly-chlorinated hydrocarbons. They accumulate in the sediments of the river and the estuary and become concentrated in organisms of the food chain. Pollution is a gradually occurring process. Anticipation of potential problems is important for the decision maker responsible for water quality management. The Fraser River supports one of the largest salmon runs of the world and is abundant with other commercially and recreationally valuable fish. Salmon are very sensitive to pollution and could disappear from the Fraser river system as they already have from many other major rivers if pollution levels become too high. The Fraser River estuary has the function of a bottleneck. Adult salmon enter the river to migrate upstream to their spawning grounds, and juvenile salmon stay in the estuary for a while to acclimatize themselves to the saline environment. In this thesis a method is presented to simulate the effects of potential pollution on the size of a salmon stock. A model which uses data from various life stages of a particular sockeye salmon run in the Fraser system is developed. Uncertainties due to environmental fluctuations are accounted for. Using this model the effects of an increase in mortality rate in two stages of the sockeye salmon life cycle on adult return numbers are studied. The analysis showed that at a certain mortality rate chances are that the stock might not be able to recover. In light of a planned salmon enhancement program to increase salmon stocks in various Pacific rivers, the fact that decreasing water quality could counteract all enhancement efforts should be a warning signal to the decision makers. The development of a water quality index to predict future conditions is recommended and a possible procedure to relate water quality parameters to an increase in mortality rate is sketched out. / Applied Science, Faculty of / Civil Engineering, Department of / Graduate

An investigation to determine the factors responsible for the distribution of a population of Maaoma balthica (L.) on a mudflat receiving sewage effluent was carried out in the Fraser River estuary of British Columbia. The factors examined were those suggested by previous studies to be controlling the distribution of the macro-invertebrate community. They included reduced salinity, low levels of dissolved oxygen, effluent toxicity, toxicity due to chlorination, substrate grain size, and the effects of metal contaminated sediments. Results of the study showed that salinity, dissolved oxygen levels and sediment grain size did not satisfactorily explain the distribution of M. balthica. Both unchlorinated and chlorinated sewage effluent were shown to be non-toxic to the clam in laboratory tests, and these results were confirmed by 7 day in situ bioassays. The factor which appeared to be responsible for the distribution of M. balthica was the degree of contamination of the substrate which affected the settling and survival of larval and juvenile clams. Heavy metals occurred in high concentrations in the contaminated sediments and were considered to be the most likely controlling factor. / Science, Faculty of / Earth, Ocean and Atmospheric Sciences, Department of / Graduate

M.Sc. / This study was initiated after a clear need to test and establish a more userfriendly fish species for use in routine laboratory bioassays was identified. This led to a literature review of current toxicity testing species of fish being used, internationally as well as nationally, and identifying which species could possibly be the most suited for use in South African laboratories. From this literature review, it was evident that much emphasis is placed on the practicability of the chosen fish species, and the fact that it can easily be bred within the laboratory, as well as the particular fish specie’s general sensitivity to various toxicants over a wide range of concentrations. The objective of this study is therefore to profile various species of fish to determine which species would be most suited to routine toxicity testing under South African laboratory conditions. This will be done through assimilation of available literature as well as personal communications with people with various expertise and experience in working with the particular fish species. This choice will then be based on the ability of the particular species of fish to ‘balance’ amenability to laboratory conditions with general sensitivity to toxicants. Various indigenous as well as exotic species were therefore selected and tested for suitability for routine testing. Exotic species included Poecilia reticulata and Danio rerio, while the indigenous species tested were Barbus trimaculatus, Barbus argenteus, Tilapia sparrmanii, Oreochromis mossambicus and Pseudocrenilabrus philander philander. Breeding experiments were conducted with all of the abovementioned species and, based on these results; recommendations are made as to which species of fish showed the highest degree of amenability to maintenance within the laboratory.

M.Sc. / The occurrence of invertebrates in drinking water supplies is a common consumer complaint with studies showing that very few drinking water distribution networks are totally free of organisms. A detailed investigation of different types of metazoan animals in the drinking water supply networks of South Africa has not been undertaken. In limited worldwide studies, invertebrates (mainly Amphipoda, Chironomidae, Cladocera, Copepoda and Ostracoda) have been detected in produced drinking water. In countries that have started monitoring these organisms, the quality of the produced water has improved due to the improved methods of filtering. The occurrence of “worms” (Nematodes and Diptera) and Crustaceans decreases the aesthetic value of the drinking water, and pathogenic organisms, which may also be associated with them, can affect human health. Limited reference works have been compiled during the conducted studies on drinking water distribution networks throughout the world. All fresh water invertebrates have the potential to be passed into the drinking water supply network (Rising mains, pipelines, reservoirs, and consumer taps). There are few complete reference works available for fresh water invertebrates occurring in the fresh water sources and those of Southern Africa. Therefore, there are no reference works regarding fresh water invertebrates that can be used to monitor drinking water supply networks in South Africa. / Prof. J.H.J. van Vuren

Dry bean breeding programs have made significant advances in combating both abiotic and biotic stresses as well as improving plant architectural traits via selective breeding. Flooding can cause complete crop loss in dry bean. On the other hand, breeding for an upright architecture in dry bean has been a breeding target in several programs. However, the stem cell wall components underlying this change have yet to be studied. This research focused on analyzing the cell wall components that might be involved in dry bean architecture as well as pre-germination flooding tolerance in dry bean. For the plant architecture study, two significant genomic regions were identified on Pv07 and Pv08 associated with lignin accumulation in dry bean. For the pre-germination flooding study, one unpigmented seed coat genotype (Verano) and three pigmented seed coat genotypes (Indeterminate Jamaica Red, Durango, and Midnight) had germination rates similar to that of the tolerant check.

Thesis (M.Sc. (Zoology)) -- University of Limpopo, 2020 / The present study was carried out in the Kwena Dam, with the aim of determining selected water quality parameters, parasite diversity and condition factor (K) of Clarias gariepinus (sharptooth catfish), Cyprinus carpio (common carp) and Oreochromis mossambicus (Mozambique tilapia). This study was conducted in autumn (April 2016), winter (July 2016), spring (October 2016) and summer (February 2017). The present study was the first to investigate the parasite composition of these three fish species in the Kwena Dam. A total number of 26 Clarias gariepinus, 21 Cyprinus carpio and 57 O. mossambicus specimens were collected using gill nets of different mesh sizes (30 mm – 120 mm). Each fish was weighed, measured and euthanised by severing the spinal cord. Mucus smears from the skin, fins and gills were examined for ectoparasites using a stereo-microscope. The fish were then dissected and all organs examined for endoparasites. All parasites were fixed and preserved according to standard methods for each parasite group. In situ water parameters were determined using a handheld multi-parameter instrument for each sampling season. In addition, water samples were collected seasonally and sent to an accredited laboratory where they were analysed for selected metals and nutrients. Water quality parameters and the presence of metals in water are of importance in determining the water quality of an aquatic environment. Most water quality parameters were within the Target Water Quality Range (TWQR) for aquatic ecosystems. Aluminium, selenium and zinc had concentrations above the TWQR for aquatic ecosystems. Nutrient concentrations were within the TQWR during all sampling seasons. The water quality did not differ significantly between seasons during the present study. Four parasite groups were reported infecting Cyprinus carpio and these included Monogenea (Dactylogyrus extensus and Dactylogyrus minutus), Digenea (Diplostomum sp.), Cestoda (Atractolytocestus huronensis), Branchiura (Argulus japonicus) and Copepoda (Neoergasilus japonicus). Parasites collected from Clarias gariepinus belonged to four groups, namely Protozoa (Trypanosoma sp.), Monogenea (Quadriacanthus sp. and Gyrodactylus sp.), Nematoda (Paracamallanus cyathopharynx and Contracaecum sp.) and Branchiura (Dolops ranarum). Parasites collected from O. mossambicus belonged to five groups, namely Monogenea (Cichlidogyrus halli, Cichlidogyrus sclerosus, Cichlidogyrus tilapiae and Enterogyrus conoratus), Nematoda (Contracaecum sp.), Cestoda (Neogryporhynchus sp.), Acanthocephala (Acanthogyrus tilapiae) and Branchiura (Dolops ranarum). iv The number of parasite species for the four seasons were as follows: summer (13) > autumn and winter (12) > spring (11). From the Shannon-Wiener index results, O. mossambicus had a higher parasite diversity than Clarias gariepinus and Cyprinus carpio. The Parasite Index (IP) and Inverted Parasite Index (IPI) of the three fish species indicated that the water from the dam is not polluted. The condition factor (K) for all fish species indicated that fish collected from the dam during all sampling seasons were in a good condition and parasite load had little effect on K for all fish species. The use of PI and IPI in conjunction with the fish K can be regarded as a useful tool in freshwater and fish health monitoring. The present results report new geographical records of the parasites of Clarias gariepinus, Cyprinus carpio and Oreochromis mossambicus. Since no parasitological research was done before the present study at the Kwena Dam, the results of the present study form baseline data for future parasitology studies and can consequently be useful in the management and conservation of the Kwena Dam. / DSI–NRF SARChI Chair (Ecosystem Health) of the University of Limpopo and the Limpopo Department of Economic Development and Tourism (LEDET)

The most appropriate and widely used source of drinking water for the rural populations of South Africa is groundwater. Pilot studies and surveys conducted by the Department of Water Affairs and Forestry (DW AF) indicated that there are a number of boreholes across the country that contain apart from fluoride, levels of nitrate, some heavy metals, total dissolved solids, sulphates and faecal coliform (in isolated regions) that could pose a health risk if the water is used for drinking purposes. Very few boreholes have been tested for heavy metals or toxic organic substances. However considering the levels of fluoride, in general, groundwater is of acceptable quality except for some provinces in which elevated levels of natural groundwater fluoride occurs. Very high levels of fluoride, >4 mg/l occur in some groundwater sources in all nine provinces of South Africa, especially in the Limpopo, North-West, Eastern Cape, Northern Cape, Western Cape and KwaZulu Natal provinces. A superficial inspection reveals that most of the local people in those areas suffer from dental fluorosis at varying degrees. The main aim of this study is to determine the distribution of the fluoride ion concentration levels in South African groundwater and the impacts thereof on dental health. The available data is used to assess the distribution of the various fluoride ion concentration levels in some national groundwater sources. Areas of particularly high or low fluoride levels are identified. Results from an epidemiological survey carried out by the National Department of Health (NDOH) are used concurrently with the fluoride data to determine the percentage morbidity of dental fluorosis in each area The results are compared in order to determine if any relationship exists between the occurrence of fluoride in drinking water and the incidences of dental fluorosis. Vegter's lithostratigraphy and the simplified geology of South Africa are used to interpret the results and assess the role of surface geology in the release and distribution of fluorides in groundwater. The role of other factors such as climate and the interactions of the fluoride ion and other water quality parameters in aqueous media are also assessed. / Dissertation (MSc (Water Utilization))--University of Pretoria, 2006. / Chemical Engineering / unrestricted

A behavioral model for acute responses in bivalves, was developed using time series analysis for use in a real-time biomonitoring unit. Stressed bivalves closed their shell and waited for the stressful conditions to pass. Baseline data showed that group behavior of fifteen bivalves was periodic, however, individuals behaved independently. Group behavior did not change over a period of 20 minutes more than 30 percent, however, following toxic exposures the group behavior changed by more than 30 percent within 20 minutes. Behavior was mathematically modeled using autoregression to compare current and past behavior. A logical alarm applied to the behavior model determined when organisms were stressed. The ability to disseminate data collected in real time via the Internet was demonstrated.

Growth of mussels under laboratory conditions was examined under various food regimes in different water types and temperatures. Growth was less than would be useful as an indicator and comparisons with field exposures were of minimal value. The effects of organophosphates on bivalves were examined via toxicity tests, tissue concentration, and by controlling exposure through the use of physical constraints. Upper temperature tolerance of both bivalve species was examined with respect to different acclimation temperatures and organophosphate exposures. Deviations from control exposures occurred at some temperatures. Copper effectively lowered the mean heat coma temperatures of C. fluminea at some concentrations, however, chlorine exposures did not alter heat coma temperature.

Several species of the diatom genus Thalassiosira Cleve, were observed in freshwater phytoplankton samples collected from a fifty-two kilometer reach of the San Joaquin River in the vicinity of Stockton, California, USA. The study was conducted between the South Airport Way bridge near Vernalis and the Stockton Deep Water Ship Channel during fall and summer of both 2005 and 2006. The entire reach is freshwater habitat with the lower twenty-eight km strongly influenced by tidal flow reversals driven by the San Francisco Estuary. Ninety four whole water samples were collected from surface waters during the months of July, August, September and October in 2005 and the months of July and August in 2006. Six species of Thalassiosira were identified using scanning electron and light microscopy: T. weissjlogii (Grunow), T. gessneri Hustedt, T. lacustris (Grunow), T. visurgis (Grunow), T. decipiens (Grunow), and T. incerta (Makarova). Of the species observed, only T. weissjlogii has been previously reported in the freshwater portion of the San Joaquin River. The other five species have been previously reported from sites in the San Joaquin- San Francisco Estuary characterized as brackish, suggesting they are distributed in waters of various salinities ranging from freshwater to brackish within the river and estuary.