7. EVALUATING THE APPLICATION OF THE STUDY IN WATER RESOURCE MANAGEMENT
7.1 INTRODUCTION
Water is one of the key elements of livelihood in South Africa and hence the appropriate management of water resources is crucial for future economic growth. Water resource management occurs in a changing environment, therefore monitoring techniques and the type of data collected should be aligned with those changes in order to provide the correct assessment of the status of water resources (NWRS 2013). This is important because the South African Constitution (Act No. 108 of 1996) grants all people the right to an environment that is not harmful to their health and well-being, and imposes a duty on the State to protect the environment from ecological degradation and promote conservation through reasonable legislation and other measures. In the context of water resources, protection of our resources from pollution and degradation and the conservation of biodiversity are fundamental to maintaining a healthy functioning aquatic ecosystem. The National Water Act of 1998 (Chapter 3) is critical in promoting the protection of aquatic resources. One of the fundamentals of the NWA is balancing water resource protection with use in a sustainable manner, in order to address basic human needs, achieve ecological sustainability and enable socio-economic prosperity. This study contributes new capacity and results to South African water resource management.
As part of water resource management, regulators have to make decisions regarding the acceptable levels of potentially toxic chemicals or complex effluents that can be discharged into water resources. Toxicity testing is particularly valuable in assessing the biological effects of chemicals and effluents on aquatic ecosystems. Toxicity-based data in conjunction with chemical data can be used to derive acceptable discharge levels for regulatory control (Chapman 1995b). Toxicity testing may play a pro-active or reactive role in water resource management. Reactive tests are those that aim to assess contamination in aquatic ecosystems by confirming the effect of contaminants on species by showing similar effects in the laboratory as those in the field. The aim of pro-active tests is to protect the species in the aquatic ecosystems by assisting in predicting safe levels of contaminants and preventing hazardous effects to aquatic ecosystems (Chapman 1995c).
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This study provides insight to both reactive and pro-active toxicity testing in water resource managements:
Reactively, toxicity tests with locally isolated micro-algae may be used to assess the effects of chemical contamination by effluents, pesticides and other substances that may enter aquatic resources, thereby estimating impacts on the aquatic environment.
Pro-actively, the data obtained from tests with locally isolated micro-algae may contribute to species sensitivity distribution (SSD) curves that may be used to determine water quality guidelines as well as predicting safe levels of effluent and pesticide levels in the environment.
Furthermore, this study demonstrates the importance of toxicity tests in water resource management through:
Deriving water quality guidelines;
Predicting the potential ecological hazard of chemicals and pesticides;
Establishing dilution levels of complex effluents and chemicals into environmental water bodies; and
Determining the cause-effect relationship in impact studies, using selected bio- indicators (Chapman 1995a).
The objective of this chapter is to reflect on the research findings presented in chapters 2 to 6 and to assess the application of the results and data generated from this study to water resource management, particularly in the South African context.
Chapters two and three provided the essential foundational steps for this study to be able to evaluate the role of algae as toxicity test organisms within water resource management. As a developing country, South Africa is lagging behind in implementing certain techniques and methods that have been used for a long time by developed countries. Even though South Africa has a comprehensive water resource policy (National Water Act No. 36 of 1998), implementation is still a problem due to lack of capacity to develop and apply the necessary techniques and methods. Studies such as this one add value and contribute to water resource management by providing tools (e.g. isolation and algal identification) and adding to the existing knowledge and capacity (e.g. refining and adapting the existing micro-algal toxicity test method for the use of indigenous algae).
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Chapter two of this study was dedicated to developing and refining culturing protocols of locally isolated micro-algae for use in toxicity testing. Although culturing micro-algae is not a novel undertaking, in South Africa both isolating and culturing algae for use in toxicity testing is new. Micro-algae have been isolated and cultured for use in studies on growth characteristics, culture methods and taxonomy. What makes isolating and culturing micro- algae for toxicity testing different is that the focus is on specific attributes of the organisms, such as relatively rapid, constant and uniform growth under laboratory conditions, as well as ease with which cells can be counted under a microscope. These traits are essential to ensure compatibility of the culturing protocol with the toxicity test method and desirable test endpoint.
Chapter three built on this and focused on adapting the existing micro-algal toxicity test method so that it is suitable for using the micro-algae isolated and identified in Chapter two.
The standard algal toxicity test method, the growth inhibition assay is an internationally recognised toxicity test method (US EPA 1978, OECD 1984, ISO 1989). This assay, developed in the mid-1960s as the Algal Assay Procedure Bottle Test, has been modified and accepted by various regulatory agencies as a standard toxicity test assay with Pseudokirchneriella subcapitata as the standard species (U.S. EPA 1969, US EPA 1978, OECD 1984, Slabbert et al 1998, Slabbert 2004). It is in the list of a battery of single species toxicity tests recommended for use in the implementation of programmes designed to be used to manage effluent discharges into surface waters and monitoring surfaces waters in South Africa (Slabbert et al 1998, Slabbert 2004).
Chapters four, five and six used these foundational steps to evaluate the newly isolated taxa and to assess their relative sensitivity to the following range of carefully selected toxicants, based on their relative importance in the South African context:
Internationally recognised reference toxicants (K2Cr2O7 and CdCl2),
Inorganic salts (NaCl and Na2SO4) selected for the important role they play in South African water resource management,
Effluents from industries (power generation and petro-chemical) of significant function in the country, and
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A glyphosate-based herbicide (Roundup®) important for its common use in agriculture, and its role in controlling invasive alien species.
The reference toxicants (K2Cr2O7 and CdCl2) were selected for their common use, especially for test with micro-algae, particularly the standard species P. subcapitata. They are the most commonly used reference toxicants locally and internationally for micro-algae and have been used in inter-laboratory evaluation of toxicity tests to ensure adequate standardization for routine use (Wang 1987, Slabbert et al. 1998, ISO 2004, Slabbert 2004, Chapman et al.
2011a). Using these two reference toxicants enabled the comparison of the toxicity data generated in this study with available internationally generated data, contributing to the validity of the subsequent tests with other toxicants and mixtures. This step also enabled the comparison of the sensitivity of the locally isolated species Chlorella sorokiniana and Chlorella vulgaris with that of the standard toxicity test species P. subcapitata, and Chlorella protothecoides (from a commercial culture collection). Furthermore the sensitivity of the local isolates C. sorokiniana and C. vulgaris to the reference toxicants was compared to that of other micro-algal species using species sensitivity distribution (SSD) curves. The data used in SSDs was obtained from international and local databases to ensure that the sensitivity of these local isolates is compared to a broader list of freshwater micro-algal species and that data are more representative of the local natural communities.
The inorganic salts NaCl and Na2SO4 were selected for the important role they play as indicators of the country’s two main land-use activities, mining and agriculture. In-stream levels of Na2SO4 are monitored in national programmes as an indicator of mining activity, while levels of NaCl indicate agricultural activity. The response of the locally isolated algae, C. vulgaris and C. sorokiniana, to the salts was assessed and compared to that of the standard species P. subcapitata as well as the commercial species C. protothecoides.This step also enabled the comparison of the sensitivity of the locally isolated micro-algae with that of macro-invertebrates using SSDs. This would enable an indication of the potential effect of the organisms’ sensitivity to salts on the algae-herbivore relationship as an important part of the aquatic food chain. Substances that affect micro-algae at the base of the food chain could threaten the ecosystem function at the higher levels of organisation.
Effluents were selected from coal-based industries of significant importance in the country (power generation and petro-chemical). Coal mining is one of the growing industries in this
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country as it plays a vital role in power generation as well as fuel and chemical production.
Coal-based power generation and its effects on the environment, as well as acid mine drainage from coal mines have recently become points of concern and discussion in South Africa. The use of these effluents contributed to the applicability, site-specificity and environmental realism of the study. The response and sensitivity of these local species to the effluents was compared to that of the standard toxicity test species P. subcapitata and C.
protothecoides from a culture collection in order to consider the potential of using of the selected local micro-algae in addition to the standard species in routine toxicity testing to determine industrial effluent impacts on local aquatic resources. Furthermore, the sensitivity of the locally isolated micro-algae to a commonly used herbicide Roundup was assessed. This herbicide was selected for the important role it plays in controlling weeds and alien vegetation. This herbicide is used by commercial farmers in the agricultural sector as well as in formal national programmes that are designed to control invasive alien species. The use of the herbicide in this study further contributed to the environmental realism and applicability of the study to the country’s water resource management as the use of this herbicide may negatively impact on non-target organisms such as micro-algae in the aquatic ecosystem.