Serviços Personalizados
Artigo
Indicadores
Links relacionados
-
Citado por Google
-
Similares em Google
Compartilhar
Water SA
versão On-line ISSN 1816-7950
versão impressa ISSN 0378-4738
Water SA vol.42 no.4 Pretoria Out. 2016
http://dx.doi.org/10.4314/wsa.v42i4.05
REVIEW
Diatom-based water quality monitoring in southern Africa: challenges and future prospects
Tatenda Dalu*; P William Froneman
Zoology and Entomology, Rhodes University, P O Box 94, Grahamstown 6140, South Africa
ABSTRACT
Diatoms are of significant ecological importance in aquatic ecosystems, which stems from their dynamic position at the base of the trophic web as primary producers. Because diatom communities have specific environmental requirements and respond rapidly to changes in environmental conditions they are often employed as a cost-effective method to assess anthropogenic impacts and health statuses of aquatic ecosystems, particularly in Europe and North America. The purpose of this review is to summarise the challenges and future prospects associated with biological water quality monitoring using diatoms with special focus on southern Africa. Much work still needs to be carried out on diatom tolerances, ecological preferences and ecophysiology. It is recommended that past research pertaining to African diatom taxonomy should be made readily accessible to all through electronic media for use as a reference point. Moreover, following the same approach as for macroinvertebrate biomonitoring, African and other developing countries can resort to intermediate diatom taxonomy (i.e. genus), which is easier, less time-consuming and requires less-skilled personnel. While the lack of capacity and baseline information on diatom community composition and ecological requirements represent significant hurdles, diatom biomonitoring potentially holds much promise for understanding the ecological functioning and management of aquatic ecosystems in southern Africa. The application of diatom-based water quality assessment protocols has direct and immediate value for use as an 'added-value' assessment tool in addition to the use of macroinvertebrates and fish indices as these can indicate anthropogenically impacted and pristine sites.
Keywords: application, biomonitoring, ecology, taxonomy, rivers, water quality
INTRODUCTION
Aquatic ecosystems form a fundamental component of global biogeochemical cycles, acting as transport pathways, elemental transformations and storage sites (Wehr and Descy, 1998; Bere and Tundisi, 2010). These systems are characterised by a high degree of interaction and complexity among physical, chemical and biological processes. Aquatic ecosystems, e.g., rivers, often present a continuous gradient of physical, chemical and biological conditions that are frequently predictable (Vannote et al., 1980). An important feature of aquatic ecosystems is that a disturbance at one location, through conversion of landscapes into other uses such as agriculture, urban and industrial developments, often affects the functioning, processes and organisms downstream. This has serious implications for ecosystem functioning and for management of these systems (Ndaragu et al., 2004; Ndiritu et al., 2006).
Agricultural activities, e.g., irrigation and livestock, increase inputs of nutrients and sediments (Leland and Porter, 2000; Bere 2007), and urbanization contributes large quantities of organic wastewater and solids (Lobo et al., 1995; Beyene et al., 2009; Bere and Mangadze, 2014, Dalu et al., 2015), while industries are major sources of inorganic pollution (Beyene et al. 2009). Although information on the impacts of anthropogenic activities in river systems is well documented in developed countries (e.g. Dixit and Smol, 1994; Kelly et al., 2008, 2012; Stevenson, 2014), very little is known from most developing countries, yet such data are important for developing appropriate management practices (Fabricius et al., 2003; De la Rey et al., 2004, 2008; Taylor et al., 2007a; Bere and Tundisi, 2010) necessary to meet Millennium Development Goal 7, on ensuring environmental sustainability.
River systems are characterised by longitudinal differences in the physico-chemical and biotic fauna and flora making it difficult to design and implement management strategies due to their heterogeneous state (Bere and Tundisi, 2010). Ecological principles such as networks, flows and nested systems thus play an important role in determining the best management and policy options for these aquatic ecosystems (De la Rey et al., 2004). The characterisation and management of these dynamic physico-chemical and biological conditions in these heterogeneous systems requires innovative approaches, with many management processes attempting to strike a balance between ecological integrity and human needs (Fig. 1) (De la Rey et al., 2004; Stevenson, 2014).
Currently, two basic approaches to water quality assessment within river ecosystem health assessments are the assessment of physico-chemical variables, and biomonitoring (De la Rey et al., 2004; Bere and Tundisi, 2010). The assessment of physico-chemical variables in river systems to assess water quality allows only for instantaneous measurements, thereby restricting the knowledge of water conditions to the period when the measurements were taken (De la Rey et al., 2004), giving a 'snapshot' result that ignores temporal variation of physico-chemical variables. The monitoring of water chemistry typically also only involves the determination of macronutrient concentrations and measurement of selected physico-chemical variables including pH (De la Rey et al., 2004; Bere et al., 2013).
The second approach, biomonitoring, involves the use of aquatic organisms to assess their response to environmental change. Biomonitoring aims to provide a direct measure of ecological integrity through integration of various stressors. It allows long-term environmental effects to be detected, providing a broad measure of their synergistic impacts (Harding et al., 2004; Stevenson, 2014). Aquatic communities integrate and reflect the effects of environmental disturbances that occur over extended periods of time, thereby providing a holistic and an integrated measure of health (Chutter, 1998; Ndiritu et al., 2006). The main advantage of using a biological approach is that it examines organisms whose exposure to pollutants is continuous and the organisms present in aquatic ecosystems reflect both the past and present water quality history, allowing detection of environmental changes that might otherwise be overlooked using physico-chemical assessments (Pan et al., 1996; De la Rey et al., 2004).
The key to the use of aquatic organisms as reliable indicators of the environmental changes in aquatic ecosystems is untangling the integrated information in species assemblages and the environment (Pan et al., 1996). The use of biomonitoring has, therefore, gained momentum in aquatic ecosystem health management programmes due to the shortcomings in the physico-chemical variables based assessments (De la Rey et al., 2004). Biomonitoring is now viewed as an ideal means by which progress towards integrated water resource management can be monitored in that it provides an overview of environmental conditions (Passy, 2007; Stevenson, 2014; Bere, 2016a). As a consequence, biomonitoring is now viewed as an important branch of applied ecology where the ecological, scientific and economic interests of our society meet in the management of river systems (De la Rey et al., 2004; Passy, 2007; Stevenson, 2014).
The purpose of this review is to summarise the challenges and prospects for employing diatoms as a biomonitoring tool in water quality monitoring, with specific focus on the sub-Saharan African region.
Diatom use in biomonitoring
Diatoms comprise the major component of the microphytoben-thos and form an integral part of primary producers in aquatic ecosystem food webs (Dalu et al., 2014a). Diatoms belong to the class Bacillariophyceae and comprise of a ubiquitous, highly successful and distinctive group of mostly unicellular algae, with the most obvious distinguishing characteristic being the presence of siliceous cell walls (frustules; Round et al., 1990). Because diatoms respond directly to growth stimulants such as nutrients (e.g. Lobo et al., 1995; Bere and Mangadze, 2014; Dalu et al., 2014a; Dalu and Froneman, 2014), physical factors such as habitat and elevation (e.g. Ndiritu et al., 2003, 2006; Passy et al., 2006; Dalu et al., 2014b) and/or stressors such as contaminants and habitat alterations (e.g. Lobo et al., 1995; Passy et al., 2006; Stevenson, 2014), they can be employed to monitor changes (natural and anthropogenic) within aquatic systems.
Diatoms have long been employed in ecological assessments for environmental change and pollution around the world (Bere and Tundisi, 2010; Stevenson et al., 2014). Studies by Bate et al. (2002), Bere and Tundisi (2010), Harding et al. (2014) and Stevenson (2014) present a global historical overview of diatom-based monitoring from the time Kolkwitz and Marsson (1908) first used diatoms in water monitoring to the present. Importantly, the global ability to use diatoms to evaluate present (e.g. Ndiritu et al., 2003, 2006; Ndaragu et al., 2004; Bere and Mangadze, 2014; Dalu et al., 2014c) and past conditions (e.g. Haberyn and Hecky, 1987; Stager and Johnson, 2000; Talbot and Lsrdal, 2000; Taylor et al., 2005b; Harding and Taylor, 2014) had increased by the turn of the 21st century.
Biomonitoring programmes across sub-Saharan Africa commonly make use of several aquatic biological indicator organisms including fish (Fish Assemblage Integrity Index, e.g., Kleynhans, 1999; Kadye, 2008), macroinvertebrates (e.g. South African Scoring System (SASS); Chutter, 1998; Gratwicke, 1998; Mbaka et al., 2014; M'Erimba et al., 2014; Bere et al., 2016b) and macrophytes (e.g. Riparian Vegetation Index; Kemper, 2001). Until the turn of the century no biomonitoring method based on autotrophic organisms (diatoms) was routinely being used in African waters (De la Rey et al., 2004; Ndiritu et al., 2004, 2006), despite the fact that earlier African scholars had used diatoms as indicators of water quality (Table 1; e.g. Schoeman et al., 1979; Schoeman and Haworth, 1986; Pieterse and Van Zyl, 1988). Béla Jenö Cholnoky (1899-1972) known as 'the father of South African diatomology, placed little faith in performing only physico-chemical analyses for aquatic ecosystem water quality analysis, arguing that the physico-chemical characteristics of a water body could be determined more reliably and cost effectively through the study of associated diatom communities (Harding et al., 2005). The use of diatom biomonitoring, therefore, formed part of the Department of Water Affairs and Forestry (DWAF) of South Africa's National Aquatic Ecosystem Biomonitoring Programme or River Health Programme (RHP) as it was considered cost effective and accurate, giving comparable data (De la Rey et al., 2004; Harding et al., 2004).
More recently, diatoms have increasingly been used for the assessment of short- and long-term water quality and environmental change (Fabricius et al., 2003; De la Rey et al., 2004; Taylor et al., 2007b; De la Rey et al., 2008; Bere and Tundisi, 2010; Bere et al., 2014) across the African continent. Diatom-based information can be gleaned not only from natural surfaces such as sediments, stones-in-current and marginal vegetation (macrophytes), but also from artificial substrates in aquatic ecosystems (De la Rey et al., 2004; Taylor et al., 2007; Bere and Tundisi, 2011; Dalu et al., 2014a, c; Dalu and Froneman, 2014). The use of artificial substrates has been key in the formulation of stressor-response models (Hirst et al., 2004; Lacoursiêre et al., 2011).
Diatom-based monitoring in southern Africa
Benthic diatom communities are sensitive indicators of environmental pollution, e.g., nutrient status, in aquatic ecosystems, which explains their widespread utilization across North America and Europe for routine determinations of river bio-integrity (Dixit and Smol, 1994; Lang et al., 2012; Stevenson, 2014). In developed countries, various environmental legislation statutory requirements, such as the Water Framework Directive 2000/60/EC in Europe (Kelly et al., 2008, 2012) and Environmental Monitoring and Assessment Program Surface Waters EPA/620/R-94/004F (EMAP-SW) in the United States of America (Dixit and Smol, 1994), have been developed to safeguard these aquatic ecosystems as they seek to evaluate the biotic integrity and trophic conditions.
In sub-Saharan Africa, South Africa (e.g. Schoeman et al., 1979; Schoeman and Haworth, 1986; Pieterse and Van Zyl, 1988; De la Rey et al., 2004, 2006; Harding et al., 2004; Taylor et al., 2007a, b; Taylor and Harding, 2014) has been the leader in environmental protection and the use of benthic diatoms in aquatic ecosystems to monitor biotic integrity, and trophic condition assessments are routinely used in both freshwater and estuarine systems (Taylor et al., 2007). In addition, Kenya has also implemented diatom biomonitoring programmes (e.g. Ndiritu et al., 2003; Ndaragu et al., 2004; Ndiritu et al., 2006; Triest et al., 2012), with other countries such as Zambia (Lang et al., 2012) and Zimbabwe (Bere et al., 2014; Bere and Mangadze, 2014) beginning to embrace the benefits of implementing diatom-based water quality assessments of their aquatic ecosystems. Despite the relative cost effectiveness of this approach, however, the practice of using diatoms to monitor anthropogenic impacts on river health in Africa has largely been ignored (Cocquyt et al., 2013).
In South Africa, Water Research Commission (WRC) funded projects have laid the foundation for the implementation and successful use of diatom-based monitoring programmes in both freshwater and estuarine ecosystems (Bate et al., 2002; Harding, 2004; Taylor et al., 2005a, 2007c, d; DH Environmental Consulting, 2015). In Zambia, the Southern African River Assessment Scheme (SAFRASS) study, funded by African, Caribbean and Pacific countries (ACP) Science and Technology Programme, spearheaded the development of a national diatom biomonitoring protocol, guides and procedures (Dallas et al., 2010; Lang et al., 2012). The importance of the provision of standardized methods has been recognised in Europe and America and has taken the form of recommended standard protocols (CEN, 2003; 2004; Kelly et al., 2012). Although the methods and techniques for diatom preparation for viewing under the microscope existed in Africa before the turn of the century (e.g. Schoeman and Archibald, 1977; Schoeman, 1982; Pieterse and Van Zyl, 1988), these methods often made use of harmful chemicals such as nitric and sulphuric acids (Harding et al., 2004; Taylor et al., 2007c). Consequently, techniques and methods for diatom collection, preparation and enumeration were tested and applied based on methods developed in Europe, for the recommendation of a standard set of procedures in South Africa (Harding et al., 2004; Taylor et al., 2005a; Taylor et al., 2007c, d).
Present legislation, e.g., the water and environmental acts, governing water resource management in many African countries (e.g. Botswana, Kenya, South Africa, Zambia, Zimbabwe) requires that river health, and aquatic ecosystem health, be assessed in order to determine user strategies and impacts of new developments on the environment (Harding et al., 2004). In support of these requirements, river health assessment protocols have been developed in South Africa (Harding et al., 2004; Taylor et al., 2007c, d; DH Environmental Consulting, 2015) and, more recently, in Zambia methodological recommendations have been developed (Dallas et al., 2010; Lang et al., 2012). The protocols need to be constantly refined as part of the river health policy implementation based on diatom monitoring as new diatoms are identified and ecological tolerances/preferences determined. Other African countries, e.g., Zimbabwe, have adapted diatom protocols and methods and procedures developed in South Africa for use in river health monitoring (Bere and Mangadze, 2014; Bere et al., 2014).
Recently, diatom-based indices such as the Specific Pollution Index (SPI) and Biological Diatom Index (BDI) have come into the spotlight as potential additions to more established biological indicators such as SASS (De la Rey et al., 2008), with several studies being carried out over the past few years exploring the potential use of diatoms as biological indicators (De la Rey et al., 2004; Harding et al., 2005; Taylor et al., 2007a, b). A standard protocol for assessment using diatoms has also been published (Taylor et al., 2005a) to facilitate comparability of diatom index results. The value of diatoms as biological indicators has been recognized and formed part of the state of the rivers report for the Crocodile West-Marico Water Management Area in South Africa (River Health Programme, 2005; Taylor et al., 2007b; De la Rey et al., 2008).
Challenges and prospects in diatom-based monitoring in Africa
Round (1993) and De la Rey et al. (2004) have highlighted the benefits of using diatom-based biomonitoring programmes which bear special relevance to South Africa, Kenya and Zimbabwe. These include cost effectiveness, rapidity and accuracy of data collection, and that non-specialists with a biological background can do identifications and counts if they are provided with illustrated guides.
Concerns have, however, been raised by scholars on the confidence in results produced by non-specialists in diatom identification (Kociolek and Stoermer, 2001). The difficulties with diatom taxonomy and nomenclature can now, however, be addressed through recent technology advances enabling comparison of images with electronic keys and rapid e-mail communication with experts (De la Rey et al., 2004; Kociolek and Stoermer, 2001). Indeed, Kociolek and Stoermer (2001) propose that studies on the taxonomy and ecology of diatoms in the 21st Century must be linked through integrated research programmes, facilitated by technological advances that support both accurate taxonomy and improved ecological interpretation, such as through the use of powerful microscopes (i.e. electron microscopes). The authors' personal experience from using the most recent and powerful electron microscopes, supported by good identification guides, along with recently published literature, confirms in the possibility of a marked reduction in the time required for identification (taxonomy) and high confidence in the results obtained.
One major problem that has led to diatom-based biological monitoring not being widely employed is the lack of capacity and the training of diatom taxonomists due to limiting funding and job opportunities. Taxonomists tend to restrict themselves to identifying and naming species and often fail to consider the ecological context (i.e. species tolerances) of the different species. Such an approach limits funding and employment opportunities. The study of diatoms in southern Africa initially attracted a number of investigators who produced large volumes of published research (Harding et al., 2004). However, relatively few students were trained to extend their work. Moreover, the decision to focus on biomonitoring using macroinvertebrates in the 1980s further contributed to limited job opportunities for diatom specialists. As a consequence, South Africa now only has a handful of diatom experts (< 10). A select group of individuals with limited skills and training are attempting to continue diatom biomonitoring and ecology studies within the region. In South Africa, for example, the bulk of the diatom taxonomic work appears in the grey literature (formerly housed at the Council for Scientific and Industrial Research (CSIR) but now housed at the South African Institute for Aquatic Biodiversity (SAIAB) National Diatom Collection at North-West University, South Africa) and is not readily available to researchers using internet search engines. These data can, however, be accessed on request, but this can often be time consuming (Fig. 2, Table 2; see Harding et al. (2004) for further details). Furthermore, only a handful of papers and books relate to water quality assessment using diatoms. Moreover, most African research institutions and universities do not have the necessary facilities (such as powerful electron microscopes) and expertise to conduct routine diatom analyses. All these challenges have contributed to the difficulty of implementing diatom-based biological monitoring programmes in most sub-Saharan countries. Hence the field of diatoms has gained the reputation of being one of the most technically difficult within the region (Kociolek and Stoermer, 2001; Kelly et al., 2012; Bere, 2016a).
A further challenge that has been highlighted is the use of species data and ecological requirements of diatoms species between the northern and southern hemisphere. Questions remain concerning the range of ecological tolerances of widespread/introduced species due to various physico-chemical factors, distance and climate (Round, 1991). This view is supported by Mann and Droop (1996) and Kelly et al. (2012), who argued that a considerable number of diatoms are endemic and/or show a regionally restricted distribution due to specific physico-chemical factors at specific locations that determine this distribution, with geographic location being the determining factor in the distribution of diatom species and the composition of communities.
Besides the abovementioned logistical challenges, there is also a general perception that diatom biomonitoring is onerous and that the sample preparation is time consuming and requires high levels of expertise and taxonomic skills. In South Africa, unlike in other African countries, diatom ecologists are fortunate in that the majority of the taxonomic work had already been undertaken by Cholnoky (1950-1970) in Harding et al. (2004), with more work still to be done in unexplored environments. Benthic diatom taxonomy in the majority of sub-Saharan African countries, excluding countries such as South Africa, Sierra Leone, Gambia, Ghana and Malawi, warrants re-investigation as highlighted by the discovery of several new diatom species in Democratic Republic of Congo (DRC) (Cocquyt et al., 2013; Cocquyt and Taylor, 2015)and Zambia (Cocquyt et al. 2014; Taylor et al. 2014a, b). There is a strong reliance on the published diatom literature from European and American sources in the identification of species.
The absence of diatom experts and lack of necessary resources (e.g. microscopes, identification guides) in most African countries, represent significant obstacles in ensuring that diatom-based biomonitoring programmes are included as part of national policy, as is the case of South Africa which included diatoms in the River Health Programme and regular biomonitoring assessments. In Europe and the United States, all water systems are protected under one policy, such as the water quality European standards EN 14407:2004 and EN 13946:2003 and the EMAP-SW EPA/620/R-94/004F, which are constantly being amended in line with changing environments and research. In Africa, different regions can develop different policies that ensure that all aquatic ecosystems are properly conserved, managed and protected for future generations.
CONCLUSIONS AND RECOMMENDATIONS
Diatom-based biomonitoring programmes have been implemented with some success in Kenya, South Africa, Zambia and Zimbabwe. This approach has been incorporated into the national river health programme of South Africa (Dallas et al., 2010), now part of the National Aquatic Ecosystem Health Monitoring Programme (DWS, 2016);). It is anticipated that this approach will be adopted by several other African countries in the near future. The standardization of methodology has laid the foundation for the continued and meaningful collection and analysis of diatom samples in South Africa (Taylor et al., 2007a). It is anticipated to yield similar results in Kenya, Zambia, Zimbabwe and many other African countries that are currently in the process of standardizing their diatom methodology, although these protocols must consider endemic diatom taxa (see Bere (2016a), for Zimbabwean experiences).
In terms of diatom tolerances, ecological preferences and ecophysiology, much work still has to be done (Bate et al., 2002). All past research pertaining to African diatom taxonomy should be made readily accessible to all for use as a reference point, such as the work by Giffen (1963), Cholnoky (1968), Schoeman and Archibald (1977) and Taylor et al (2007c) highlighting the diatom flora of South Africa. On this point, the SAIAB National Diatom Collection is a commendable effort which making much of the grey literature readily accessible to other African researchers. The collection of diatom samples from different African countries, e.g. DRC, Zambia and Zimbabwe, for water quality determination should be complemented with sound taxonomical investigations to update knowledge of Africa's diatom flora (e.g. in Zambia, a new diatom species has been recently discovered (see Cocquyt et al., 2014; Taylor et al., 2014a, b) and also in DRC (see Cocquyt et al., 2013; Cocquyt and Taylor, 2015)). Cholnoky (1950-1970), and Giffen (1960-1980), amongst other authors, only produced diatom line diagrams which are open to misinterpretation, so the digitisation of the images of African and South African type specimens needs to be considered (Harding et al., 2004). Additionally, aquatic ecologists should work in conjunction with diatom taxonomists (see Kociolek and Stoermer, 2001). As this information becomes available it may then be resolved into numerical diatom indices. Finally attention should be paid to both the biology and ecology of diatoms occurring in moderate to high water quality environments, as several studies (e.g. Taylor et al., 2007; Bere et al., 2013; Mangedze et al., 2014; Bere 2016a) have highlighted that cosmopolitan species are found in a variety of habitats impacted by different types of pollutants.
One of the most important approaches that African and other countries around the world can adopt, which has also been observed with other biomonitoring methods such as macroinvertebrates (Chutter, 1998; Dickens and Graham, 2002; Metzeling et al., 2006), is to resort to intermediate diatom taxonomy, which is easier, less time consuming and requires less-skilled personnel. Development of a diatom biomonitoring method based on intermediate taxonomy, i.e., genus level, will make the process faster and easier. However, care must be taken to ensure that ecological information is not lost when taxonomic resolution is decreased, as this may compromise diatom model inferences. Several studies (e.g. Raunio and Soininen, 2007; Rimet and Bouchez, 2012; Keck et al., 2015) have highlighted that taxonomic resolution has little effect on diatom community structure description, suggesting that little ecological information is lost as a result of a decrease in diatom taxonomic resolution from species to genus level (see Kelly et al., 2016 for detailed information). However, Bowman and Bailey (1997) and Jones (2008) highlighted that information content increases with diatom taxonomic resolution. Taxonomic identifications become less certain at finer resolutions and data noise increases with increasing taxonomic resolution (Rimet and Bouchez, 2012). Therefore, we advocate for the use of genus level identification for water quality assessments and the development of appropriate indices based on genus level identification.
While the lack of capacity and baseline information on diatom community composition and ecological requirements represent significant hurdles, diatom biomonitoring potentially holds much promise for understanding the ecological functioning and informing the management of aquatic ecosystems in sub-Saharan Africa. Interdisciplinary research that will result in the union of environmental management, biogeography, conservation biology, diatom ecology and systematics could result in significantly more funding, if the relevance of diatom studies and biomonitoring is to be further developed. Results from such a multidisciplinary and integrative approach would also likely yield publications with a greater impact. There is a compelling need for diatom systematics research to be undertaken within multi-interdisciplinary projects, rather than focusing on the taxonomic identification, as such an approach will help in addressing challenging ecological problems.
African countries, like many European countries, should consider introducing ring tests to maintain the skills of the analysts, whereby they take part in identification of specific slides and pool the results to look for problem taxa and resolve prevailing issues (Hedden, 2010; Kelly, 2013). These tests can routinely be conducted, similar to the SASS training for mac-roinvertebrates which is conducted at approximately 6-monthly intervals by GroundTruth (GroundTruth, 2016). In this way, less experienced individuals can familiarize themselves with the various diatom taxa and acquire the necessary skills set to analyse diatom data, while at the same time providing an opportunity to recruit new researchers into the field. This approach might prevent the profession from collapse and enhance collaboration amongst diatom analysts and taxonomists from different regions of Africa. Across the world, identification is moving towards the use of molecular tools such that eventually identifying species using their basic morphology may become redundant. However, it is recognized that in many countries in Africa, the traditional identification techniques will still be required in the foreseeable future, as well as to interpret the research conducted by phyloge-neticists and continue describing new species.
In conclusion, the use of diatom biomonitoring has importance in providing information relevant to common concerns about ecological condition and can be employed for short- and long-term monitoring of aquatic ecosystem function and health. Diatom monitoring programmes can provide results that are readily accessible to water managers and non-specialists. Regional examples from Kenya, South Africa, Zambia and Zimbabwe clearly indicate the importance and robustness of this protocol as a scientific biomonitoring tool (e.g. Stevenson, 2014).
ACKNOWLEDGEMENTS
This review article is part of a study into the use of diatoms for biomonitoring in the Eastern Cape, South Africa. The financial support for the study is from Rhodes University and the first author is a recipient of the Rhodes University Postdoctoral Fellowship grant.
REFERENCES
ARCHIBALD RM (1972) Diversity in some South African diatom associations and its relation to water quality. Water Res. 6 1229-1238. [ Links ]
BATE G, SMAILES P and ADAMS J (2004) A water quality index for use with diatoms in the assessment of rivers. Water SA 30 493-449. [ Links ]
BATE GC and SMAILES PA (2008) The response of the diatom flora of St Lucia Lake and estuary, South Africa, to a severe drought. Afr. J. Aquat. Sci. 33 1-16. [ Links ]
BATE GC, ADAMS JB and VAN DER MOLEN JS (2002) Diatoms as indicators of water quality in South African river systems. WRC Report No. 814/1/02. Water Research Commission, Pretoria. [ Links ]
BELLINGER BJ, COCQUYT C and O'REILLY CM (2006) Benthic diatoms as indicators of eutrophication in tropical streams. Hydrobiologia 573 75-87. [ Links ]
BERE T (2007) The assessment of nutrient loading and retention in the upper segment of the Chinyika River, Harare; Implications for eutrophication control. Water SA. 33 279-284. [ Links ]
BERE T (2016a) Challenges of diatom-based biological monitoring and assessment of streams in developing countries. Environ. Sci. Pollut. Res. 23 5477-5486. [ Links ]
BERE T (2016b) Are diatom-based biotic indices developed in eutrophic, organically enriched waters reliable monitoring metrics in clean waters? Ecol. Indic. 62 312-316. [ Links ]
BERE T, DALU T and MWEDZI T (2016) Detecting the impact of heavy metal contaminated sediment on benthic macroinvertebrate communities in tropical streams. Sci. Total Environ. 572 147-156. [ Links ]
BERE T and MANGADZE T (2014) Diatom communities in streams draining urban areas: community structure in relation to environmental variables. Trop. Ecol. 55 271-281. [ Links ]
BERE T and TUNDISI JG (2010) Biological monitoring of lotic ecosystems: the role of diatoms. Braz. J. Biol. 70 493-502. [ Links ]
BERE T and TUNDISI JG (2011) The effects of substrate type on diatom-based multivariate water quality assessment in a tropical river (Monjolinho), Säo Carlos, SP, Brazil. Water Air Soil Pollut. 216 391-409. [ Links ]
BERE T, MANGADZE T and MWEDZI T (2014) The application and testing of diatom-based indices of stream water quality in Chinhoyi Town, Zimbabwe. Water SA 40 530-512. [ Links ]
BERE T, PHIRI P, KADYE WT and UTETE B (2013) Benthic diatom assemblages in mountain streams: community structure in relation to environmental and human pressures. Afr. J. Ecol. 51 625-634. [ Links ]
BEYENE A, ADDIS T, KIFLE D, LEGESSE W, KLOOS H and TRIEST L (2009) Comparative study of diatoms and macroinvertebrates as indicators of severe water pollution: Case study of the Kebena and Akaki Rivers in Addis Ababa, Ethiopia. Ecol. Indic. 9 381-392. [ Links ]
CHOLNOKY BJ (1958) Hydrobiologische Untersuchungen in Transvaal II. Selbstreinigung im Jukskei-2647Crocodile Flusssystem. Hydrobiologia 11 205-266. [ Links ]
CHOLNOKY BJ (1968) Die Ökologie der Diatomeen in Binnengewässern. J Cramer, Lehre. [ Links ]
CHUTTER FM (1998) Research on the rapid biological assessment of water quality impacts in streams and rivers. WRC Report No. 422/1/98. Water Research Commission, Pretoria. [ Links ]
COCQUYT C and TAYLOR JC (2015) New and interesting Surirella taxa (Surirellaceae, Bacillariophyta) from the Congo Basin (DR Congo). Euro. J. Taxon. 133 1-15. [ Links ]
COCQUYT C, DE HAAN M and TAYLOR JC (2013) Cavinulalilande (Bacillariophyta) a new diatom species from the Congo Basin, Central Africa. Diatom Res. 28 157-163. [ Links ]
COCQUYT C, TAYLOR JC and WETZEL CE (2014) Stenopterobia cataractarum sp. nov. (Bacillariophyta), a new benthic diatom from a waterfall in Zambia, Africa. Phytotaxa 158 76-84. [ Links ]
COMITÉ EUROPÉEN DE NORMALISATION (CEN) (2003) Water quality - Guidance standard for the routine sampling and pre- treatment of benthic diatoms from rivers. European Standard. EN13946:2003. [ Links ]
COMITÉ EUROPÉEN DE NORMALISATION (CEN) (2004) Water quality - Guidance for the identification and enumeration of ben- thic diatom samples from rivers, and their interpretation. European Standard. EN 14407:2004. [ Links ]
DALLAS H, KENNEDY M, TAYLOR J, LOWE S and MURPHY K (2010) WP4: Review of existing biomonitoring methodologies and appropriateness for adaptation to river quality assessment proto cols for use in southern tropical Africa. Southern African River Assessment Scheme (SAFRASS). AFS/2009/219013. ACP Science and Technology Programme, Cape Town. [ Links ]
DALU T and FRONEMAN PW (2014) Can stable isotopes (δ15N, δ13C) and fatty acid signatures be employed to observe changes in phyto- benthos composition on artificial substrates? Afr. J. Aquat. Sci. 39 425-433. [ Links ]
DALU T, BERE T and FRONEMAN PW (2016) Assessment of water quality based on diatom indices in a small temperate river system: a case of the Kowie River, South Africa. Water SA 42 183-193. [ Links ]
DALU T, BERE T, RICHOUX NB and FRONEMAN PW (2015) Assessment of the spatial and temporal variations in periphyton communities along a small temperate river system: A multimetric and stable isotope analysis approach. S. Afr. J. Bot. 100 203-212. [ Links ]
DALU T, FRONEMAN PW and RICHOUX NB (2014b) Phytoplankton community diversity along a river-estuary continuum. Trans. R. Soc. S. Afr. 69 107-116. [ Links ]
DALU T, FRONEMAN PW, CHARI LD and RICHOUX NB (2014a) Colonisation and community structure of benthic diatoms on artificial substrates following a major flood event: A case of the Kowie River (Eastern Cape, South Africa). Water SA 40 471-480. [ Links ]
DALU T, RICHOUX NB and FRONEMAN PW (2014c) An assessment, using multivariate analysis and stable isotopes, of the effects of substrate type on phytobenthos communities. Inland Waters 4 397-412. [ Links ]
DE LA REY PA, ROUX H, VAN RENSBURG L and VOSLOO A (2008) On the use of diatom-based biological monitoring Part 2: A comparison of the response of SASS 5 and diatom indices to water quality and habitat variation. Water SA 34 61-70. [ Links ]
DE LA REY PA, TAYLOR JC, LAAS A, VAN RENSBURG L and VOSLOO A (2004) Determining the possible application value of diatoms as indicators of general water quality: A comparison with SASS 5. Water SA 30 325-332. [ Links ]
DH ENVIRONMENTAL CONSULTING 2015). THE USE OF DIA TOMS FOR WATER QUALITY DETERMINATION AND BIOMONITORING IN SOUTH AFRICA. URL: WWW.DHEC.CO.ZA/DIATOMS (Accessed 13 January 2015). [ Links ]
DICKENS CWS and GRAHAM PM (2002) The South African Scoring System (SASS) version 5 rapid bioassessment method for rivers. Afr. J. Aquat. Sci. 27 1-10. [ Links ]
DIXIT SS and SMOL JR (1994) Diatoms as indicators in the environmen tal monitoring and assessment program-surface waters (EMAP-SW). Environ. Monit. Assess. 31 275-306. [ Links ]
DWS (Department of Water and Sanitation) (2016) National Aquatic Ecosystem Health Monitoring Programme. URL: https://www.dwa.gov.za/iwqs/rhp/naehmp.aspx (Accessed 22 May 2016). [ Links ]
FABRICIUS ALM, MAIDANA N, GOMEZ MN and SABATER S (2003) Distribution pattern of benthic diatoms in a Pampean river exposed to seasonal floods: the Cuarto River (Argentina). Biodiv. Conserv. 12 2443-2454. [ Links ]
GARCÍA-RODRÍGUEZ F, BATE GC, SMAILES P, ADAMS JB and METZELTIN D (2007) Multivariate analysis of the dominant and sub-dominant epipelic diatoms and water quality data from South African rivers. Water SA 33 653-658. [ Links ]
GIFFEN MH (1963) Contributions to the diatom flora of South Africa. Hydrobiologia. 21 201-265. [ Links ]
GRATWICKE B (1998) The effect of season on a biotic water quality index: A case study of the Yellow Jacket and Mazowe Rivers, Zimbabwe. S. Afr J. Aquat. Sci. 24 24-35. [ Links ]
GROUNDTRUTH (2016) SASS, miniSASS and Aquatic Ecology Training. URL: http://www.groundtruth.co.za/services/training.html (Accessed 6 September 2016). [ Links ]
HABERYAN KA and HECKY RE (1987) The late Pleistocene and Holocene stratigraphy and paleolimnology of Lakes Kivu and Tanganyika. Palaeogeo. Palaeoclim. Palaeoecol. 61 169-197. [ Links ]
HARDING WR and TAYLOR JC (2014) Diatoms as indicators of historical water quality: A comparison of samples taken in the Wemmershoek catchment (Western Cape Province, South Africa) in 1960 and 2008. Water SA 40 601-606. [ Links ]
HARDING WR, ARCHIBALD CGM and TAYLOR J (2005) Diatomology in South African biomonitoring: the South African Diatom Collection. Afr. J. Aquat. Sci. 30 221-221. [ Links ]
HARDING WR, ARCHIBALD CGM, TAYLOR JC and MUNDREE S (2004) The South African diatom collection: An appraisal and over view of needs and opportunities. WRC Report no.TT 242/04. Water Research Commission, Pretoria. [ Links ]
HARRISON TD, COOPER JAG and RAMM AEL (2000) Geomorphology, ichthyofauna, water quality and aesthetics of South African estuaries. ENV-DC 2000-01. Department of Environmental Affairs and Tourism, Pretoria, South Africa. [ Links ]
HECKY RE, KLING HJ, JOHNSON TC, BOOTSMA HA and WILKINSON P (1999) Algal and sedimentary evidence for recent changes in the water quality and limnology of Lake Malawi/ Nyasa. Victoria. 1 1-2. [ Links ]
HEDDEN H (2010) The Accidental Taxonomist. Information Today, Medford, New Jersey [ Links ]
HIGGINS SN, KLING HJ, HECKY RE, TAYLOR WD and BOOTSMA HA (2003) The community composition, distribution, and nutrient status of epilithic periphyton at five rocky littoral zone sites in Lake Malawi, Africa. J. Great Lakes Res. 29 181-189. [ Links ]
HIRST H, CHAUD F, DELABIE C, JÜTTNER I and ORMEROD SJ (2004) Assessing the short-term response of stream diatoms to acidity using inter-basin transplantations and chemical diffusing substrates. Freshwat. Biol. 49 1072-1088. [ Links ]
HOLMES M and TAYLOR JC (2015) Diatoms as water quality indicators in the upper reaches of the Great Fish River, Eastern Cape, South Africa. Afr. J. Aquat. Sci. 40 321-338. [ Links ]
JANSE VAN VUUREN S and TAYLOR JC (2015) Changes in the algal composition and water quality of the Sundays River, Karoo, South Africa, from source to estuary. Afr. J. Aquat. Sci. 40 339-357. [ Links ]
JONES FC (2008) Taxonomic sufficiency: the influence of taxonomic resolution on freshwater bioassessments using benthic macroinverte- brates. Environ. Rev. 16 45-69. [ Links ]
KADYE WT (2008) The application of a Fish Assemblage Integrity Index (FAII) in a Southern African river system. Water SA 34 25-31. [ Links ]
KAONGA CC and MONJEREZI M (2012) Periphyton and earthworms as biological indicators of metal pollution in streams of Blantyre City, Malawi. In: Balkis N (ed) Water Pollution. INTECH Open Access Publisher, DOI: 10.5772/28781. URL: http://www.intechopen.com/books/water-pollution/periphyton-and-earthworms-as-biological-indicators-of-heavy-metal-pollution-in-streams-of-blantyre-m (Accessed 15 January 2015). [ Links ]
KELLY MG, KROKOWSKI J and HARDING JP (2016) RAPPER: A new method for rapid assessment of macroalgae as a complement to diatom-based assessments of ecological status. Sci. Total Environ. DOI: 10.1016/j.scitotenv.2015.12.068. [ Links ]
KELLY M (2013) Building capacity for ecological assessment using diatoms in UK rivers. J. Ecol. Environ. 36 89-94. [ Links ]
KELLY MG, GÓMEZ-RODRÍGUEZ C, KAHLERT M, ALMEIDA SFP, BENNETT C, BOTTIN M, DELMAS F, DESCY J-P, DÖRFLINGER G, KENNEDY B, MARVAN P, OPATRILOVA L, PARDO I, PFISTER P, ROSEBURY J, SCHNEIDER S and VILBASTE S (2012) Establishing expectations for pan-European diatom based ecological assessments. Ecol. Indic. 20 177-186. [ Links ]
KELLY MG, JUGGINS S, GUTHRIE R, PRITCHARD S, JAMIESON J, RIPPEY B, HIRST H and YALLOP M (2008) Assessment of ecological status in UK rivers using diatoms. Freshwater Biol. 53 403-422. [ Links ]
KEMPER NP (2001) RVI: Riparian Vegetation Index. WRC Report No. 850/3/01. Water Research Commission, Pretoria. [ Links ]
KLEE R and CASPER SJ (1992) New centric diatoms (Thalassiosirales) of Lake Malawi (formerly Lake Nyassa; Malawi, East Africa). Arch. Protistenkunde 142 179-192. [ Links ]
KLEYNHANS CJ (1999) The development of a fish index to assess the biological integrity of South African rivers. Water SA 25 265-270. [ Links ]
KOCIOLEK JP and STOERMER EF (2001) Taxonomy and ecology: A marriage of necessity. Diatom Res. 16 433-442. [ Links ]
KOLKWITZ R and MARSSON M (1908) Ökologie der pflanzlicheSaprobien. Ber. Deut. Bot. Ges. 26 505-519. [ Links ]
KOTSEDI D, ADAMS JB and SNOW GC (2012) The response of micro- algal biomass and community composition to environmental factors in the Sundays Estuary. Water SA 38 177-190. [ Links ]
LACOURSIËRE S, LAVOIE I, RODRÍGUEZ MA and CAMPEAU S (2011) Modeling the response time of diatom assemblages to simulated water quality improvement and degradation in running waters. Can. J. Fish. Aquat. Sci. 68 487-497. [ Links ]
LANG P, TAYLOR JC, BERTOLLI L, LOWE S, DALLAS H, KENNEDY MP, GIBBINS C, SICHINGABULA H, SAILI K, DAY J, WILLEMS F, BRIGGS JA and MURPHY KJ (2012) Proposed procedure for the sampling, preparation and analysis of benthic diatoms from Zambian rivers: a bioassessment and decision support tool applicable to fresh water ecoregions in tropical southern Africa. Southern African River Assessment Scheme (SAFRASS). AFS/2009/219013. ACP Science and Technology Programme, Cape Town. [ Links ]
LELAND HV and PORTER SD (2000) Distribution of benthic algae in the upper Illinois River basin in relation to geology and land use. Freshwater. Biol. 44 279-301. [ Links ]
LOBO EA, KATOH K and ARUGA Y (1995) Response of epilithic diatom assemblages to water pollution in rivers in the Tokyo Metropolitan area, Japan. Freshwater Biol. 34 191-204. [ Links ]
MANGADZE T, BERE T and MWEDZI T (2015) Epilithic diatom flora in contrasting land-use settings in tropical streams, Manyame Catchment, Zimbabwe. Hydrobiologia 753 163-173. [ Links ]
MANGADZE T, BERE T and MWEDZI T (2016) Choice of biota in stream assessment and monitoring programs in tropical streams: A comparison of diatoms, macroinvertebrates and fish. Ecol. Indic. 63 128-143. [ Links ]
MANN DG and DROOP JM (1996) Biodiversity, biogeography and conservation of diatoms. Hydrobiologia 336 19-32. [ Links ]
MBAKA JG, M'ERIMBA CM, THIONGO HK and MATHOOKO JM (2014) Water and habitat quality assessment in the Honi and Naro Moru rivers, Kenya, using benthic macroinvertebrate assemblages and qualitative habitat scores. Afr. J. Aquat. Sci. 39 361-368. [ Links ]
M'ERIMBA CM, MATHOOKO JM and OUMA KO (2014) Macroinvertebrate distributions in relation to human and animal- induced physical disturbance of the sediment surface in two Kenyan tropical Rift Valley streams. Afr. J. Aquat. Sci. 39 337-346. [ Links ]
METZELING L, PERRISS S and ROBINSON D (2006) Can the detection of salinity and habitat simplification gradients using rapid bioassess- ment of benthic macroinvertebrtes be improved through finer taxonomic resolution or alternative indices? Hydrobiologia 572 235-252. [ Links ]
NDARUGA AM, NDIRITU GG, GICHUKI NN and WAMICHA WN (2004) Impact of water quality on macroinvertebrates assemblages along a tropical stream in Kenya. Afr. J. Ecol. 42 208-216. [ Links ]
NDIRITU GG, GICHUKI NN and TRIEST L (2006) Distribution of epilithic diatoms in response to environmental conditions in an urban tropical stream, Central Kenya. Biodiv. Conserv. 15 3267-3293. [ Links ]
NDIRITU GG, GICHUKI NN, KAUR P AND TRIEST L (2003) Characterization of environmental gradients using physico-chemical measurements and diatom densities in Nairobi River, Kenya. Aquat. Ecosyst. Health Manag. 6 343-354. [ Links ]
PAN Y, STEVENSON RJ, HILL BH, HERLIHY AT and COLLINS GB (1996) Using diatoms as indicators of ecological conditions in lotic systems: a regional assessment. J. N. Am. Benthol. Soc. 15 481-495. [ Links ]
PASSY SI (2007) Community analysis in stream biological monitoring: what must we measure and what we don't. Environ. Monit. Assess. 127 409-417. [ Links ]
PERISSINOTTO R, IYER K and NOZAIS C (2006) Response of micro- phytobenthos to flow and trophic variation in two South African temporarily open/closed estuaries. Bot. Mar. 49 10-22. [ Links ]
PHIRI C, DAY J, CHIMBARI M and DHLOMO E (2007) Epiphytic diatoms associated with a submerged macrophyte Vallisnera aethi- opica, in the shallow marginal areas of Sanyati Basin (Lake Kariba): a preliminary assessment of their use as biomonitoring tools. Aquat. Ecol. 41 169-181. [ Links ]
PIETERSE AJH and VAN ZYL JM (1988) Observations on the relation between phytoplankton diversity and environmental factors in the Vaal River at Balkfontein, South Africa. Hydrobiologia 169 199-207. [ Links ]
RIATO L, VAN GINKEL C and TAYLOR JC (2014) Zooplankton and diatoms of temporary and permanent freshwater pans in the Mpumalanga Highveld region, South Africa. Afr. Zool. 49 113-127. [ Links ]
RIMET F (2012) Recent views on river pollution and diatoms. Hydrobiologia 683 1-24. [ Links ]
RIVER HEALTH PROGRAMME (2005) State-of-Rivers Report: Monitoring and Managing the Ecological State of Rivers in the Crocodile (West) Marico Water Management Area. Department of Environmental Affairs and Tourism, Pretoria. [ Links ]
ROUND FE, CRAWFORD RM and MANN DG (1990) Diatoms: Biology and Morphology of the Genera. Cambridge University Press, Cambridge. [ Links ]
ROUND FE (1991) Diatoms in river water-monitoring studies. J. Appl. Phycol. 3 129-145. [ Links ]
ROUND FE (1993) A Review and Methods for the Use of Epilithic Diatoms for Detecting and Monitoring Changes in River Water Quality. Methods for the Examination of Water and Associated Materials. HMSO Publications, London. [ Links ]
SCHOEMAN FR (1973) A Systematical and Ecological Study of the Diatom Flora of Lesotho with Special Reference to the Water Quality. V & R Printers, Pretoria [ Links ]
SCHOEMAN FR (1976) Diatom indicator groups in the assessment of water quality in the Jukskei-Crocodile river system (Transvaal, Republic of South Africa). J. Limnol. Soc. S. Afr. 2 21-24. [ Links ]
SCHOEMAN FR (1979). Diatoms as indicators of water quality in the upper Hennops River. J. Limnol. Soc. South. Afr. 5 73-78. [ Links ]
SCHOEMAN FR (1982) The diatoms of the Jukskei-Crocodile River system (Transvaal, Republic of South Africa): a preliminary check-list. J. S. Afr. Bot. 48 295-310. [ Links ]
SCHOEMAN FR and ARCHIBALD REM (1977) The diatom flora of Southern Africa. Special report WT50. National Institute for Water Research. Council for Scientific and Industrial Research, Pretoria. [ Links ]
SCHOEMAN FR and HAWORTH EY (1986) Diatom as indicator of pollution. Proceedings of the 8thInternational Diatom Symposium. Koeltz Scientific Books, Koenigstein. 757-766. [ Links ]
SNOW GC (2007) Contributions to the use of microalgae in estuarine freshwater reserve determinations. PhD thesis, Nelson Mandela Metropolitan University. South Africa. [ Links ]
STAGER JC and JOHNSON TC (2000) A 12,400 14c yr. offshore diatom record from east central Lake Victoria, East Africa. J. Paleolimnol. 23 373-383. [ Links ]
STEVENSON J (2014) Ecological assessments with algae: a review and synthesis. J. Phycol. 50 437-461. [ Links ]
TALBOT MR and LvERDAL T (2000) The late Pleistocene-Holocene paleolimnology of Lake Victoria, East Africa, based upon elemental and isotopic analyses of sedimentary organic matter. J. Paleolimnol. 23 141-164. [ Links ]
TAYLOR JC, DE LA REY PA and VAN RENSBURG L (2005a) Recommendations for the collection, preparation and enumeration of diatoms from riverine habitats for water quality monitoring in South Africa. Afr. J. Aquat. Sci. 30 65-75. [ Links ]
TAYLOR JC, HARDING WR and ARCHIBALD CGM (2007c) An illustrated guide to some common diatom species from South Africa. Report TT 282/07. Water Research Commission, Pretoria. [ Links ]
TAYLOR JC, HARDING WR and ARCHIBALD CGM (2007d). A methods manual for the collection, preparation and analysis of diatom samples. Version 1.0. WRC Report No. TT 281/07. Water Research Commission, Pretoria. [ Links ]
TAYLOR JC, HARDING WR, ARCHIBALD CGM and VAN RENSBURG L (2005) Diatoms as indicators of water quality in the Jukskei-Crocodile River system in 1956 and 1957, a re-analysis of diatom count data generated by BJ Cholnoky. Water SA 31 237-246. [ Links ]
TAYLOR JC, HARDING WR, ARCHIBALD CGM and VAN RENSBURG L (2005b) Diatoms as indicators of water quality in the Jukskei-Crocodile river system in 1956 and 1957, a re-analysis of diatom count data generated by BJ Cholnoky. Water SA 31 237-246. [ Links ]
TAYLOR JC, JANSE VAN VUUREN MS and PIETERSE AJH (2007e) The application and testing of diatom-based indices in the Vaal and Wilge Rivers, South Africa. Water SA 33 51-60. [ Links ]
TAYLOR JC, JANSE VAN VUUREN MS and PIETERSE AJH (2007a) The application and testing of diatom-based indices in the Vaal and Wilge rivers, South Africa. Water SA 33 51-60. [ Links ]
TAYLOR JC, KARTHICK B, COCQUYT C and LANG P (2014a) Diploneis fenestrata sp. nov. (Bacillariophyta), a new aerophilic diatom species from Zambia, Africa. Phytotaxa 167 79-88. [ Links ]
TAYLOR JC, KARTHICK B, KOCIOLEK JP, WETZEL CE and COCQUYT C (2014b) Actinellopsis murphyigen. et spec. nov.: A new small celled freshwater diatom (Bacillariophyta, Eunotiales) from Zambia. Phytotaxa 178 128-137. [ Links ]
TAYLOR JC, POPE N and VAN RENSBURG L (2009) Community participation in river monitoring using diatoms: a case study from the Buffelspoort Valley. Afr. J. Aquat. Sci. 34 173-182. [ Links ]
TAYLOR JC, PRYGIEL J, VOSLOO A, DE LA REY PA and VAN RENSBURG L (2007b) Can diatom-based pollution indices be used for biomonitoring in South Africa? A case study of the Crocodile West and Marico water management area. Hydrobiologia 592 455-464. [ Links ]
TRIEST L, LUNG'AYIA H, NDIRITU G and BEYENE A (2012) Epilithic diatoms as indicators in tropical African rivers (Lake Victoria catchment). Hydrobiologia 695 343-360. [ Links ]
VANNOTE RL, MINSHALL GW, CUMMIS KW, SEDELL JR and CUSHING C (1980) The river continuum concept 1. Can. J. Fish. Aquat. Sci. 37 130-137. [ Links ]
VERITY P and BORKMAN D (2010) A decade of change in the Skidaway River Estuary. III. Plankton. Estuar. Coasts 33 513-540. [ Links ]
WALSH G and WEPENER V (2009) The influence of land use on water quality and diatom community structures in urban and agriculturally stressed rivers. Water SA 35 579-594. [ Links ]
WEHR JD and DESCY J (1998) Use of phytoplankton in large river management. J. Phycol. 36 741-749. [ Links ]
Received 29 March 2015
Accepted in revised form 6 September 2016
* To whom all correspondence should be addressed. s +27 83 3087633; e-mail: dalutatenda@yahoo.co.uk