Microbial and nutrient pollution in the coastal bathing waters of Dar es Salaam

Authors

  • Thomas J. Lyimo

    Corresponding author
    1. Department of Molecular Biology and Biotechnology, Faculty of Science, University of Dar es Salaam, P.O. Box 35179, Dar es Salaam, Tanzania
    • Department of Molecular Biology and Biotechnology, Faculty of Science, University of Dar es Salaam, P.O. Box 35179, Dar es Salaam, Tanzania
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Abstract

  • 1.The objective of the present study was to assess the microbial and nutrient quality of coastal beach waters used for bathing in the city of Dar es Salaam, Tanzania. Concentrations of traditional and alternative microbial indicators of faecal pollution and nutrients were assessed over a 1 year period (August 2005 to August 2006) using standard methods and the results were compared with the WHO water quality guidelines.
  • 2.Faecal indicator bacteria values varied in a consistent fashion and correlated significantly with eachother, reflecting the presumed human faecal pollution.
  • 3.The maximum counts (MPN per 100 mL) were observed on the site close to the city centre (Ocean Road) throughout the sampling period where values ranged from 1700 to>240 000 total coliform (TC), 200 to 92000 faecal coliform (FC) and 11 to 4900 enterococci (ENT). Other sites showed less predictable results with a range of values from 0–920, 0–540 and 0–46 for TC, FC and ENT, respectively. Furthermore, the faecal indicator bacteria concentration varied significantly with sampling time (P<0.05) and between sampling points (P<0.05).
  • 4.Similarly, nutrients were significantly higher (P<0.05) at Ocean Road where concentration (µmolL−1) ranges were 0.2–54 (NO3), 0.0–20 (NO2) and 0.3–45 (PO4).
  • 5.The levels of faecal indicator bacteria and nutrients were higher during the rainy seasons than the dry seasons, showing the inclusion of rain run-off as a source of contamination. The faecal indicator bacteria correlated positively with nutrients in both 1 year and daily data sets (P<0.01). Positive relationships were also observed among faecal indicators. This strongly suggests that an important role is played by sewage contamination in the extent of microbial pollution at the studied urbanized coastal beaches.

Copyright © 2009 John Wiley & Sons, Ltd.

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