The relevance of diatoms for water quality assessment in South Africa: A position paper

Abstract

Water quality assessment protocols based on the use of diatoms are now well developed and their value substantiated at an international level. The use of diatoms is not designed or intended to be a "rapid" technology. The detailed level of information generated from the procedure outweighs perceived disadvantages of the additional time required for sample preparation and analysis to species level. The method is applicable across a wide range of aquatic ecosystem types, namely freshwater, brackish, and estuarine, and is inclusive of both lentic and lotic environments, wetlands and their associated damp, marginal and littoral zones. Details provided by diatom assemblages support palaeoecological investigations, historical reconstruction of water quality and the determination of prevailing water quality conditions. Deliberate determination of responses to management strategies or impacts arising from a variety of anthropogenic activities can be achieved via the simple expedient of retrieving living material from introduced artificial substrates. Previous studies in South Africa and elsewhere have shown that on a site-by-site basis the use of diatoms provides a fine level of diagnostic resolution of the causes underlying changes in water quality and environmental condition. The South African Diatom Collection ("the Collection"), a repository of diatom specimens and records that spans the length and breadth of this country, contains an as-yet unutilised wealth of ecological and taxonomic information. More importantly, the historical data analysis records provide an insight into water quality conditions prevailing 40 to 50 years ago-in many cases prior to the "development" of many of our rivers, streams and wetlands. The real value of its existence underpins the great potential for renewed attention to the value of diatom-based approaches to water quality assessments. In addition, the Collection provides a ready-made foundation on which a locally relevant tool for water quality assessment may be established to augment the current use of invertebrate indicators. It is now appropriate that the full potential of the use of diatoms in water quality assessments, and the information contained in the Collection, be developed and utilised for water quality assessment in South Africa.

Bio-écologie des diatomées épilithiques de la rivière Mfoundi (Yaoundé, Cameroun) : diversité, distribution spatiale et influence des pollutions organiques

“…Parmi les organismes utilisés comme « bioindicateurs » de la qualité des eaux, les algues, particulièrement les diatomées, occupent une place de choix pour diagnostiquer l'état de santé des rivières, car elles répondent de manière rapide à l'eutrophisation des eaux ainsi qu'aux diverses pollutions (MORIN, 2006;ROTT et al, 1998;ROUND, 1991). De plus, les diatomées constituent l'élément essentiel de la flore algale des rivières à la base des chaînes alimentaires en milieu aquatique (EULIN, 1997;HARDING et al, 2005). Elles ont une taille microscopique permettant un échantillonnage quantitatif simple et rapide, un cycle de reproduction court, et sont riches en espèces présentant des degrés différenciés de sensibilité à des gammes de paramètres de la qualité des eaux (BLINN et BAILEY, 2001;DE LA REY et al, 2004 …”

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)

“…Diatoms were prepared by oxidising organic material in samples with hydrochloric acid and potassium permanganate (Taylor et al, 2005). Clean diatom frustules were mounted in a synthetic resin with high refraction index (1.73) and counted and identified to the lowest taxonomic level possible (usually species) using a phase-contrast Olympus CX light microscope with 1 000 x magnification.…”

“…Diatoms have been studied extensively for many decades in South African river systems (Giffen, 1963;1970;1971;1973;Schoeman and Archibald, 1976;Schoeman, 1982), and efforts have been made to relate diatom associations to water quality (Bate et al, 2002;Taylor et al, 2005a, b, c;Harding et al, 2005;Taylor et al, 2007). Few studies have been done on diatom colonisation and development patterns in South Africa.…”

Diatom indices in the biological assessment of the water quality based on the example of a small lowland river

“…Diatom indices have also been found useful outside Europe, for example in Africa (Harding et al 2005, Rey et al 2004, Taylor et al 2007.…”