This study was aimed at investigating and comparing the

The study was aimed at assessing techniques, which would provide an accurate indication of the planktonic bacterial pollution load in the Berg River, Western Cape, South Africa. Sampling of sites started in June 2004 and continued for a period of 1 year until June 2005. The most probable number (MPN) technique was used to determine the level of faecal coliforms and E. coli, while the heterotrophic plate count method was used to determine the amount of culturable microorganisms in planktonic samples. The flow cytometry (FCM) and direct acridine orange count (DAOC) (epifluorescence microscopy) techniques were employed to evaluate total bacterial counts in planktonic (water) samples. The highest MPN and heterotrophic plate counts were recorded in Week 37 at site B2 at 1.7 x 10 7 micro-organisms/100 mℓ and 1.04 x 10 6 microorganisms/mℓ, respectively. In comparison, the viable FCM counts, were significantly higher (p < 0.05) for that period at 1.7 x 10 7 micro-organisms/mℓ. The highest total FCM count of 3.7 x 10 7 micro-organisms/mℓ was recorded in Week 41 at Site B2. In comparison the highest DAOC of 8.3 x 10 6 micro-organisms/mℓ was obtained in Week 29 at Site B2. Results showed that on average the heterotrophic plate count represented a fraction (< 3.65%) of the total FCM counts. The total DAOC count also represented a fraction (< 43.08%) of the total FCM count for most of the sampling period. Results therefore showed that the FCM proved to be more effective in evaluating microbial pollution in water samples.

No abstract

A recent decline in water quality of the Berg River, Western Cape, South Africa, has led to the investigation into the degree of metal pollution in the river system. This study was conducted over a period of one year, from May 2004 to May 2005. The nitric acid digestion technique was used to extract metals from water, sediment and biofilm samples collected at various points (Site A-agricultural area, Site B-informal settlement and Site C-Newton pumping station) along the Berg River. Metal concentrations were determined using inductively coupled plasma atomic emission spectrometry (ICP-AES). The highest mean metal concentrations recorded were as follows; water samples, 6 mg•ℓ-1 for Al, 14.6 mg•ℓ-1 for Fe and 18.8 mg.ℓ-1 for Mn; sediment samples, 17 448.8 mg•kg-1 for Al and 26 473.3 mg•kg-1 for Fe; biofilm samples, 876.8 mg•ℓ-1 for Al and 1 017.5 mg•ℓ-1 for Fe. The increased availability, or noteworthy incidence of Al and Fe, could be due to the leaching of metals into the river water from waste and household products associated with the informal settlement and the subsequent settling on sediment. No guidelines were available for metals in biofilms. The highest recorded concentrations in water were for Site C (agricultural area). Recorded concentrations in water fluctuated throughout the study period for most of the metals analysed, but Al and Fe were consistently above the recommended guidelines as stipulated by the Department of Water Affairs and Forestry and the Canadian Council of Ministers of the Environment.

Bacterial species present in the Berg and Plankenburg Rivers (Western Cape, South Africa) were isolated from water and biofilm samples and population shifts between sampling sites were phylogenetically identified. Deoxyribonucleic acid (DNA) extraction of representative isolates was performed and amplified using 2 different primer sets. Various Enterobacteriaceae species were present at all of the sites, confirming faecal contamination. Phylogenetic analyses also showed that, in general, Gram-negative micro-organisms dominated at all of the sites sampled in both the Berg and Plankenburg river systems. Pathogens and opportunistic pathogens, such as Pseudomonas aeruginosa, Staphylococcus sp., and Bacillus cereus, were isolated from the Berg River. Similarly, in the Plankenburg River system, Aeromonas sp., Acinetobacter sp., Stenotrophomonas sp. and Yersinia enterocolitica were also isolated. This raises major health concerns as human population densities along both rivers are high, thus resulting in increased human exposure to these organisms.