Abstract
Aquatic ecosystem biomonitoring tools are largely lacking for many developing countries, resulting in adoption of tools developed from other countries/regions. In many instances, however, the applicability of adopted tools to the new system has not been explicitly evaluated. The objective of this study was to test the applicability of foreign diatom-based water quality assessment indices to urban streams in Zimbabwe, with the view of stimulating research to develop improved approaches for assessing ecological integrity of lotic systems in the country. The study evaluated the relationship between measured water quality variables and diatom index scores. The study found a high degree of concordance between water quality variables and diatom index scores. Thus, the indices proved useful in providing an indication of the quality of the investigated waters. This could be attributed to the occurrence of many widely distributed diatom species that have similar environmental tolerances to those recorded elsewhere. Diatom indices which exhibited consistent classifications and strong correlations with water quality variables such as Trophic Index, Saprobic Index, Pampean Diatom Index, Biological Index of Water Quality and Leclercq Index are recommended for use in the country. However, ecological requirements of some diatom species from Zimbabwe need to be clarified and incorporated in a diatom-based water quality assessment protocol unique to the country. Keywords : biological monitoring, pollution, benthic diatoms, biotic indices
Highlights
The relation between diatom communities and environmental variables in aquatic systems is robust and quantifiable (Wehr and Sheath, 2003; Azim et al, 2005; Bere and Tundisi, 2010a, 2010b; 2011a)
There were no significant differences in temperature among sampling sites (ANOVA, p > 0.05) for all of the sampling periods, though Sites 3, 4 and 8, with significantly high vegetation cover (ANOVA, p < 0.05), generally tended to be cooler compared to the rest of the sites
No significant differences were observed in conductivity, dissolved oxygen (DO), pH, turbidity, nitrite, ammonia, phosphate, calcium, iron and manganese levels among the sampling periods
Summary
The relation between diatom communities and environmental variables in aquatic systems is robust and quantifiable (Wehr and Sheath, 2003; Azim et al, 2005; Bere and Tundisi, 2010a, 2010b; 2011a). Each particular species requires different structural, physical and chemical characteristics intrinsic to its habitat Whenever these characteristics are subject to slight variations, due to natural or anthropogenic activities, associated diatom communities respond rapidly, often changing in both taxonomic composition and biomass (Wehr and Sheath, 2003; Azim et al, 2005; Bere and Tundisi, 2009; Lavoie et al, 2008; Smucker and Vis, 2011; Stenger-Kovacs et al 2013). There is evidence that diatom metrics or indices developed in one geographic area are less successful when applied in other areas (Pipp, 2002) This is due to the floristic differences among regions (Potapova and Charles, 2002; Rimet et al, 2004; Taylor et al, 2007a; Chessman and Townsend, 2010), and to the environmental differences that modify species responses to water-quality characteristics (Potapova and Charles, 2007). Strict testing of these borrowed indices is required to ensure that diatom index scores give a realistic reflection of the specific type of environmental pollution being tested (Taylor et al, 2007a)
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