Cyanobacteria and cyanotoxins in the source water from Lake Chivero, Harare, Zimbabwe, and the presence of cyanotoxins in drinking water

  • Lindah Mhlanga University of Zimbabwe, Lake Kariba Research Station, PO Box 48, Kariba, Zimbabwe; Freshwater Research Unit, Department of Zoology, University of Cape Town, Rondebosch 7701, South Africa
  • Jenny Day Freshwater Research Unit, Department of Zoology, University of Cape Town, Rondebosch 7701, South Africa
  • Gertrud Cronberg Department of Ecology/Limnology, University of Lund, SE-223 62 Lund, Sweden
  • Moses Chimbari University of Zimbabwe, Lake Kariba Research Station, PO Box 48, Kariba, Zimbabwe
  • Nqobizitha Siziba Lake Kariba Fisheries Research Institute, PO Box 75, Kariba, Zimbabwe
  • Heléne Annadotter Department of Ecology/Limnology, University of Lund, SE-223 62 Lund, Sweden

Abstract

The phytoplankton community and cyanotoxins in Lake Chivero (formerly Lake McIlwaine) and the presence of cyanotoxins in treated drinking water were investigated between 2003 and 2004. A typical seasonal succession of Cyanobacteria species occurred from January to April, Bacillariophyta from May to July, and Cryptophyta and Chlorophyta from August to December. Microcystis aeruginosa and M. wesenbergii, known producers of the toxin microcystin, and the non-toxic cyanobacterium M. novacekii dominated during summer. The highest concentrations of microcystins and lipopolysaccharide endotoxins occurred when cyanobacterial biomass was highest. Lipopolysaccharide endotoxin concentrations in the lake ranged between 8 and 3 200 Endotoxin Units (EU) ml–1. Microcystin concentrations in treated water were below the recommended safe limit for drinking water. Lipopolysaccharide endotoxin concentrations in treated water ranged from 0.15 to 11 EU ml–1. The phytoplankton community comprised non-microcystin-producing species for the greater part of the study period.

Keywords: cyanotoxins; dominant organisms; endotoxins; LPS; microcystins; phytoplankton

African Journal of Aquatic Science 2006, 31(2): 165–173
Published
2006-12-04
Section
Articles

Journal Identifiers


eISSN: 1727-9364
print ISSN: 1608-5914