A spatial and temporal analysis of the changes in alien macrophyte communities and a baseline assessment of the macroinvertebrates associated with Eurasian watermilfoil, Myriophyllum spicatum L. (Haloragaceae) in the Vaal River
- Authors: Fordham, Colin Justin
- Date: 2012
- Subjects: Water hyacinth -- Control -- South Africa , Aquatic weeds -- Control -- South Africa , Eurasian watermilfoil -- South Africa , Water quality management -- South Africa , Freshwater invertebrates -- Ecology -- South Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5767 , http://hdl.handle.net/10962/d1005455 , Water hyacinth -- Control -- South Africa , Aquatic weeds -- Control -- South Africa , Eurasian watermilfoil -- South Africa , Water quality management -- South Africa , Freshwater invertebrates -- Ecology -- South Africa
- Description: The majority of South Africa’s fresh water (lotic and lentic), is eutrophic and this has resulted in water hyacinth, Eichhornia crassipes (C.Mart.) Solms. (Pontederiaceae) becoming South Africa’s most damaging aquatic macrophyte. Recently however, concerns have also been voiced over the presence of highly invasive submerged macrophyte species, such as Eurasian water-milfoil, Myriophyllum spicatum L. (Haloragaceae) in the Vaal River. Interaction studies between floating and submerged macrophytes have shown that floating macrophyte dominance restricts light penetration into the water column shading out submerged macrophytes while submerged macrophyte dominance reduces nutrient availability in the water column limiting floating macrophyte growth. This cycle ensures that these species cannot coexist in the same habitat for extended periods of time. The aims of this thesis were to: 1. Investigate changes in the historical and current macrophyte dominance in the Vaal River 2. Determine whether these changes could be attributed to stochastic events, such as floods and herbicide control measures. 3. The physio-chemical conditions of the water column, and whether pressure from herbivory by macroinvertebrates had possibly influenced Eurasian water-milfoil’s ability to dominate. Spatial and temporal analysis of satellite imagery revealed that water hyacinth and submerged macrophyte species dominated different regions of the study area over different periods of time from 2006 to 2010. This was significantly correlated with nitrate concentrations of the water column. One of the lower Vaal River Water Management Areas (WMA) had changed from a water hyacinth dominated state in 2006 to an alternative submerged macrophyte dominated stable state in 2008. It was concluded that this change could be attributed to: a stochastic flooding event in 2006; perturbation from integrated control measures implemented against water hyacinth; and low nitrate concentrations of the WMA. The lack of any substantial macroinvertebrate herbivory pressure or control measures implemented against Eurasian water-milfoil, compared to similar surveys conducted in the U.S.A. and its native range in Eurasia was shown to contribute to its dominance. Future successful integrated control programmes, including biological control against Eurasian water-milfoil, could provide the perturbation required to restore the ecosystem. However, without the reduction in nitrate concentration levels, water hyacinth will remain the dominant stable state of the rest of the Vaal River.
- Full Text:
- Date Issued: 2012
- Authors: Fordham, Colin Justin
- Date: 2012
- Subjects: Water hyacinth -- Control -- South Africa , Aquatic weeds -- Control -- South Africa , Eurasian watermilfoil -- South Africa , Water quality management -- South Africa , Freshwater invertebrates -- Ecology -- South Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5767 , http://hdl.handle.net/10962/d1005455 , Water hyacinth -- Control -- South Africa , Aquatic weeds -- Control -- South Africa , Eurasian watermilfoil -- South Africa , Water quality management -- South Africa , Freshwater invertebrates -- Ecology -- South Africa
- Description: The majority of South Africa’s fresh water (lotic and lentic), is eutrophic and this has resulted in water hyacinth, Eichhornia crassipes (C.Mart.) Solms. (Pontederiaceae) becoming South Africa’s most damaging aquatic macrophyte. Recently however, concerns have also been voiced over the presence of highly invasive submerged macrophyte species, such as Eurasian water-milfoil, Myriophyllum spicatum L. (Haloragaceae) in the Vaal River. Interaction studies between floating and submerged macrophytes have shown that floating macrophyte dominance restricts light penetration into the water column shading out submerged macrophytes while submerged macrophyte dominance reduces nutrient availability in the water column limiting floating macrophyte growth. This cycle ensures that these species cannot coexist in the same habitat for extended periods of time. The aims of this thesis were to: 1. Investigate changes in the historical and current macrophyte dominance in the Vaal River 2. Determine whether these changes could be attributed to stochastic events, such as floods and herbicide control measures. 3. The physio-chemical conditions of the water column, and whether pressure from herbivory by macroinvertebrates had possibly influenced Eurasian water-milfoil’s ability to dominate. Spatial and temporal analysis of satellite imagery revealed that water hyacinth and submerged macrophyte species dominated different regions of the study area over different periods of time from 2006 to 2010. This was significantly correlated with nitrate concentrations of the water column. One of the lower Vaal River Water Management Areas (WMA) had changed from a water hyacinth dominated state in 2006 to an alternative submerged macrophyte dominated stable state in 2008. It was concluded that this change could be attributed to: a stochastic flooding event in 2006; perturbation from integrated control measures implemented against water hyacinth; and low nitrate concentrations of the WMA. The lack of any substantial macroinvertebrate herbivory pressure or control measures implemented against Eurasian water-milfoil, compared to similar surveys conducted in the U.S.A. and its native range in Eurasia was shown to contribute to its dominance. Future successful integrated control programmes, including biological control against Eurasian water-milfoil, could provide the perturbation required to restore the ecosystem. However, without the reduction in nitrate concentration levels, water hyacinth will remain the dominant stable state of the rest of the Vaal River.
- Full Text:
- Date Issued: 2012
The effects of selected reference toxicants on embryonic development of the freshwater shrimp caridina nilotica (Decapoda: Atyidae)
- Authors: Ketse, Noziphiwo
- Date: 2007
- Subjects: Toxicity testing -- South Africa , Shrimp fisheries -- South Africa , Decapoda , Caridina , Water quality management -- South Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:6025 , http://hdl.handle.net/10962/d1005367 , Toxicity testing -- South Africa , Shrimp fisheries -- South Africa , Decapoda , Caridina , Water quality management -- South Africa
- Description: Aquatic toxicity tests are increasingly being used in water resource management worldwide, and currently in South Africa, policy and legislation are being drafted to reflect this international trend. While standard toxicity test methods and test organisms are being considered to develop and set water quality guidelines and effluent discharge limits, it is not clear whether guidelines and discharge limits set using these standard test organisms will be sufficient to protect South Africa’s scarce water resources. As part of ongoing research to investigate the use of indigenous riverine organisms as toxicity test organisms a number of potential species have been identified, including the freshwater shrimp Caridina nilotica. For much of the history of aquatic toxicological data the bulk of the data has been generated by acute toxicity testing, based on short exposures and using mortality as the response end point. There are relatively few chronic, longterm tests with sub-lethal endpoints. However, it was recognized that information about longer exposure durations and non lethal response endpoints was needed, instead of mortality. Chronic tests can provide a more environmentally realistic measure of chemical toxicity than acute toxicity tests. Caridina nilotica has been identified as a potential standard toxicity test organism, as it is widely distributed, easy to find and it occurs in flowing waters. It is an indigenous species which can be easily cultured and maintained in the laboratory and is also ecologically important. Both adults and juveniles have been used successfully in acute toxicity tests at the Institute for Water Research (Rhodes University) and the ability to rear the organisms under laboratory conditions has allowed the development of chronic toxicity tests using C. nilotica. Chronic early life stage tests include continuous exposure of the early life stages, which are presumed to be the most sensitive for aquatic organisms. This study reports on the embryonic development of C. nilotica at the culture temperature of 24⁰C. Morphological developmental stages were monitored and measured and 7 developmental stages were identified. Based on the measurements of the features that were identified, toxicity tests using the reference chemicals sodium chloride (NaCl), sodium sulphate (Na₂SO₄) and cadmium chloride (CdCl₂) were undertaken to test the suitability of C. nilotica embryonic development for chronic toxicity tests for use in water resource management. The length, width, length:width ratios and area of the features decreased in size when exposed to the chemicals. The Lowest Observed Effect Concentration (LOEC) values were 2000mg/L for Na₂SO₄, 3000mg/L for NaCl and 0.31mg/L for CdCl₂. The No Observed Effect Concentration (NOEC) values were 1000mg/L for Na₂SO₄, 2000mg/L for NaCl and <0.31mg/L for CdCl₂. Further research on the teratogenic effects of single chemicals and industrial effluent on developing C. nilotica embryos needs to be undertaken in order to evaluate the described test protocol for use in water resource management.
- Full Text:
- Date Issued: 2007
- Authors: Ketse, Noziphiwo
- Date: 2007
- Subjects: Toxicity testing -- South Africa , Shrimp fisheries -- South Africa , Decapoda , Caridina , Water quality management -- South Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:6025 , http://hdl.handle.net/10962/d1005367 , Toxicity testing -- South Africa , Shrimp fisheries -- South Africa , Decapoda , Caridina , Water quality management -- South Africa
- Description: Aquatic toxicity tests are increasingly being used in water resource management worldwide, and currently in South Africa, policy and legislation are being drafted to reflect this international trend. While standard toxicity test methods and test organisms are being considered to develop and set water quality guidelines and effluent discharge limits, it is not clear whether guidelines and discharge limits set using these standard test organisms will be sufficient to protect South Africa’s scarce water resources. As part of ongoing research to investigate the use of indigenous riverine organisms as toxicity test organisms a number of potential species have been identified, including the freshwater shrimp Caridina nilotica. For much of the history of aquatic toxicological data the bulk of the data has been generated by acute toxicity testing, based on short exposures and using mortality as the response end point. There are relatively few chronic, longterm tests with sub-lethal endpoints. However, it was recognized that information about longer exposure durations and non lethal response endpoints was needed, instead of mortality. Chronic tests can provide a more environmentally realistic measure of chemical toxicity than acute toxicity tests. Caridina nilotica has been identified as a potential standard toxicity test organism, as it is widely distributed, easy to find and it occurs in flowing waters. It is an indigenous species which can be easily cultured and maintained in the laboratory and is also ecologically important. Both adults and juveniles have been used successfully in acute toxicity tests at the Institute for Water Research (Rhodes University) and the ability to rear the organisms under laboratory conditions has allowed the development of chronic toxicity tests using C. nilotica. Chronic early life stage tests include continuous exposure of the early life stages, which are presumed to be the most sensitive for aquatic organisms. This study reports on the embryonic development of C. nilotica at the culture temperature of 24⁰C. Morphological developmental stages were monitored and measured and 7 developmental stages were identified. Based on the measurements of the features that were identified, toxicity tests using the reference chemicals sodium chloride (NaCl), sodium sulphate (Na₂SO₄) and cadmium chloride (CdCl₂) were undertaken to test the suitability of C. nilotica embryonic development for chronic toxicity tests for use in water resource management. The length, width, length:width ratios and area of the features decreased in size when exposed to the chemicals. The Lowest Observed Effect Concentration (LOEC) values were 2000mg/L for Na₂SO₄, 3000mg/L for NaCl and 0.31mg/L for CdCl₂. The No Observed Effect Concentration (NOEC) values were 1000mg/L for Na₂SO₄, 2000mg/L for NaCl and <0.31mg/L for CdCl₂. Further research on the teratogenic effects of single chemicals and industrial effluent on developing C. nilotica embryos needs to be undertaken in order to evaluate the described test protocol for use in water resource management.
- Full Text:
- Date Issued: 2007
Biomonitoring in two contrasting catchments
- Authors: Maseti, Pumza Penelope
- Date: 2006
- Subjects: Water quality biological assessment -- South Africa , Water quality management -- South Africa , Rivers -- South Africa , Freshwater fishes -- South Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:6034 , http://hdl.handle.net/10962/d1006175 , Water quality biological assessment -- South Africa , Water quality management -- South Africa , Rivers -- South Africa , Freshwater fishes -- South Africa
- Description: The introduction of instream biological monitoring to water resources management has been an increasing trend world-wide. This monitoring uses biological field assessments of instream biota such as macroinvertebrates, fish and riparian vegetation as an integrated and sensitive tool for diagnosing the condition of the ecosystems and assessing ecological impacts. Biomonitoring information has become an important component in the overall assessment of water resources and is used to drive and direct processes of decision-making and management of water resources. The River Health Programme (RHP) was initiated in South Africa to serve as a source of information regarding the ecological status of river systems, in order to support rational management of these natural resources. In this study, biomonitoring indices (SASS5 and FAII) were used to assess the present ecological status of two rivers located in contrasting catchments of the Eastern Cape. The first river is the Buffalo River located in an urban and industrialized catchment. The second river is the Inxu River draining a rural and afforested catchment. SASS5 was used successfully in both rivers and the results based on water quality and SASS5 indicated that most sites selected on the upper catchment of the Buffalo River have a fair water quality with most sites selected on the lower catchment having a poor water quality. The Inxu River sites (both upper and lower catchment) based on SASS5 and water quality results have a good to fair water quality. The majority of sites sampled on both rivers systems had very low FAII scores and fell within a critically modified water quality category. This result may be due to the fact that these rivers have low fish diversities (either low natural diversity or low diversity due to the presence of alien fish species), poor water quality or inadequate sampling methods. Observations from this study suggest that this index may not be suitable for rivers with low fish diversity. A fish index that is usable to all ecoregions of South Africa with minor adaptations to suit local conditions is still needed, as the present FAII index does not meet these requirements.
- Full Text:
- Date Issued: 2006
- Authors: Maseti, Pumza Penelope
- Date: 2006
- Subjects: Water quality biological assessment -- South Africa , Water quality management -- South Africa , Rivers -- South Africa , Freshwater fishes -- South Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:6034 , http://hdl.handle.net/10962/d1006175 , Water quality biological assessment -- South Africa , Water quality management -- South Africa , Rivers -- South Africa , Freshwater fishes -- South Africa
- Description: The introduction of instream biological monitoring to water resources management has been an increasing trend world-wide. This monitoring uses biological field assessments of instream biota such as macroinvertebrates, fish and riparian vegetation as an integrated and sensitive tool for diagnosing the condition of the ecosystems and assessing ecological impacts. Biomonitoring information has become an important component in the overall assessment of water resources and is used to drive and direct processes of decision-making and management of water resources. The River Health Programme (RHP) was initiated in South Africa to serve as a source of information regarding the ecological status of river systems, in order to support rational management of these natural resources. In this study, biomonitoring indices (SASS5 and FAII) were used to assess the present ecological status of two rivers located in contrasting catchments of the Eastern Cape. The first river is the Buffalo River located in an urban and industrialized catchment. The second river is the Inxu River draining a rural and afforested catchment. SASS5 was used successfully in both rivers and the results based on water quality and SASS5 indicated that most sites selected on the upper catchment of the Buffalo River have a fair water quality with most sites selected on the lower catchment having a poor water quality. The Inxu River sites (both upper and lower catchment) based on SASS5 and water quality results have a good to fair water quality. The majority of sites sampled on both rivers systems had very low FAII scores and fell within a critically modified water quality category. This result may be due to the fact that these rivers have low fish diversities (either low natural diversity or low diversity due to the presence of alien fish species), poor water quality or inadequate sampling methods. Observations from this study suggest that this index may not be suitable for rivers with low fish diversity. A fish index that is usable to all ecoregions of South Africa with minor adaptations to suit local conditions is still needed, as the present FAII index does not meet these requirements.
- Full Text:
- Date Issued: 2006
Nutrient dynamics in and offshore of two permanently open South African estuaries with contrasting fresh water inflow
- Authors: Jennings, Michael Evan
- Date: 2006
- Subjects: Estuaries -- South Africa -- Great Fish River , Estuaries -- South Africa -- Kariega River , Marine ecology -- South Africa , Freshwater ecology -- South Africa , Rivers -- Environmental aspects , Water quality management -- South Africa , Water -- Analysis
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5735 , http://hdl.handle.net/10962/d1005421 , Estuaries -- South Africa -- Great Fish River , Estuaries -- South Africa -- Kariega River , Marine ecology -- South Africa , Freshwater ecology -- South Africa , Rivers -- Environmental aspects , Water quality management -- South Africa , Water -- Analysis
- Description: The nutrient dynamics in two contrasting estuaries and in the adjacent nearshore environment along the south-east coast of South Africa was investigated seasonally. Due to an inter-basin transfer of water from the Gariep Dam to the Great Fish River, the Great Fish estuary is a fresh water dominated, terrestrially driven system with an annual fresh water inflow of 250 – 650 x 10⁶ m³ per year. In contrast, the Kariega estuary is a fresh water deprived, marine dominated system with a fresh water inflow estimated at 2.5 – 35 x 10⁶ m³per year. The reduced fresh water inflow into the estuary is attributed to regular impoundments along the Kariega River. Water samples were collected from surface and subsurface layers along the length of the estuaries as well as from a series of transects occupied in the nearshore environment. Samples were analysed for nitrate, nitrite, ammonium, phosphate and silicate. Temperature and salinity were recorded at each station. A Land-Ocean Interactions in the Coastal Zone (LOICZ) budget was constructed for each estuary to describe the role of ecosystem-level metabolism as either a sink or a source of phosphorus, nitrogen and carbon. Seasonal variation in physico-chemical properties and nutrient concentrations in the Kariega estuary was minimal due to constant low inflow, while in the Great Fish estuary, concentrations varied in response to changes in flow rate. Nutrient concentrations were consistently higher in the Great Fish estuary than in the Kariega estuary, largely reflecting differences in fresh water inflow. During periods of high flow (32.92 m³.s⁻¹in the Great Fish River) dissolved inorganic nitrogen (DIN) concentrations in the Great Fish estuary were an order of magnitude higher than those recorded in the Kariega estuary. Results of the LOICZ budgeting procedures revealed that in spite of the contrasting hydrodynamic features, the estuaries behave in largely the same manner – both predominantly sources of nutrients with heterotrophic processes dominating over autotrophic actions and both were net denitrifyers during all surveys. This was, however, due to different sets of processes operating in the two estuaries, namely low nutrient concentrations resulting in microbial activity in the Kariega estuary, and riverine influx of nutrients and phytoplankton combined with a short residence time of the water in the Great Fish estuary. In the marine nearshore environment, higher nutrient concentrations were recorded adjacent to the Great Fish estuary than offshore of the Kariega estuary. This was due to a surface plume of less saline water leaving the Great Fish estuary, which acted as an ‘outweller’ of nutrients. Offshore of the Kariega estuary, on the other hand, the nutrient concentrations were characteristic of marine waters due to a lack of fresh water outflow from the estuary. Nutrient concentrations in the marine environment adjacent to the Kariega estuary were, at times, higher than those recorded within the estuary. This observation supports previous statements which suggest that the Kariega estuary is not an ‘outweller’ of dissolved nutrients and particulate material, but rather an extension of the marine environment.
- Full Text:
- Date Issued: 2006
- Authors: Jennings, Michael Evan
- Date: 2006
- Subjects: Estuaries -- South Africa -- Great Fish River , Estuaries -- South Africa -- Kariega River , Marine ecology -- South Africa , Freshwater ecology -- South Africa , Rivers -- Environmental aspects , Water quality management -- South Africa , Water -- Analysis
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5735 , http://hdl.handle.net/10962/d1005421 , Estuaries -- South Africa -- Great Fish River , Estuaries -- South Africa -- Kariega River , Marine ecology -- South Africa , Freshwater ecology -- South Africa , Rivers -- Environmental aspects , Water quality management -- South Africa , Water -- Analysis
- Description: The nutrient dynamics in two contrasting estuaries and in the adjacent nearshore environment along the south-east coast of South Africa was investigated seasonally. Due to an inter-basin transfer of water from the Gariep Dam to the Great Fish River, the Great Fish estuary is a fresh water dominated, terrestrially driven system with an annual fresh water inflow of 250 – 650 x 10⁶ m³ per year. In contrast, the Kariega estuary is a fresh water deprived, marine dominated system with a fresh water inflow estimated at 2.5 – 35 x 10⁶ m³per year. The reduced fresh water inflow into the estuary is attributed to regular impoundments along the Kariega River. Water samples were collected from surface and subsurface layers along the length of the estuaries as well as from a series of transects occupied in the nearshore environment. Samples were analysed for nitrate, nitrite, ammonium, phosphate and silicate. Temperature and salinity were recorded at each station. A Land-Ocean Interactions in the Coastal Zone (LOICZ) budget was constructed for each estuary to describe the role of ecosystem-level metabolism as either a sink or a source of phosphorus, nitrogen and carbon. Seasonal variation in physico-chemical properties and nutrient concentrations in the Kariega estuary was minimal due to constant low inflow, while in the Great Fish estuary, concentrations varied in response to changes in flow rate. Nutrient concentrations were consistently higher in the Great Fish estuary than in the Kariega estuary, largely reflecting differences in fresh water inflow. During periods of high flow (32.92 m³.s⁻¹in the Great Fish River) dissolved inorganic nitrogen (DIN) concentrations in the Great Fish estuary were an order of magnitude higher than those recorded in the Kariega estuary. Results of the LOICZ budgeting procedures revealed that in spite of the contrasting hydrodynamic features, the estuaries behave in largely the same manner – both predominantly sources of nutrients with heterotrophic processes dominating over autotrophic actions and both were net denitrifyers during all surveys. This was, however, due to different sets of processes operating in the two estuaries, namely low nutrient concentrations resulting in microbial activity in the Kariega estuary, and riverine influx of nutrients and phytoplankton combined with a short residence time of the water in the Great Fish estuary. In the marine nearshore environment, higher nutrient concentrations were recorded adjacent to the Great Fish estuary than offshore of the Kariega estuary. This was due to a surface plume of less saline water leaving the Great Fish estuary, which acted as an ‘outweller’ of nutrients. Offshore of the Kariega estuary, on the other hand, the nutrient concentrations were characteristic of marine waters due to a lack of fresh water outflow from the estuary. Nutrient concentrations in the marine environment adjacent to the Kariega estuary were, at times, higher than those recorded within the estuary. This observation supports previous statements which suggest that the Kariega estuary is not an ‘outweller’ of dissolved nutrients and particulate material, but rather an extension of the marine environment.
- Full Text:
- Date Issued: 2006
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