Application of a direct toxicity assessment approach to assess the hazard of potential pesticide exposure at selected sites on the Crocodile and Magalies rivers, South Africa

  • TM Ansara-Ross
  • V Wepener
  • PJ van den Brink
  • MJ Ross

Abstract

The potentially hazardous effects of agricultural pesticide usage in the Crocodile (west) Marico catchment were evaluated using the Danio rerio and Daphnia pulex lethality, Selenastrum capricornutum growth inhibition and the Ames mutagenicity plate incorporation assays. Hazard assessment categories are proposed to standardise the output of the different toxicity assessments. Sites were categorised according to the toxicity hazard indicated and were related to the gradients of agricultural land-use intensity at each site. Intensive agricultural sites showed the highest effects to all tested biota. Receiving water at urban sites associated with increased nutrients and lowest pesticide usage showed few adverse effects, while the relatively unimpacted site indicated no hazard to any organism, and only a slight stimulation to algal growth. Weighted hazard scores indicated that the unimpacted sites were least hazardous, falling within a B category, the urban sites were moderately hazardous (C category), and the agricultural sites (D category) had the highest potential impacts on aquatic organisms. This study demonstrated the usefulness of using the hazard assessment approach and the role it could play in assessing site-specific potential toxicity hazards of river water impacted by agrochemicals. It can be used together with other assessment methods, such as biological indices, in a tiered approach.

Keywords: agricultural impacts, algal growth inhibition, classification, fish, hazard assessment, invertebrates, mutagenicity test

African Journal of Aquatic Science 2009, 34(3): 207–217

Author Biographies

TM Ansara-Ross
Centre for Aquatic Research, Department of Zoology, University of Johannesburg, Auckland Park, PO Box 524, Johannesburg 2006, South Africa
V Wepener
Centre for Aquatic Research, Department of Zoology, University of Johannesburg, Auckland Park, PO Box 524, Johannesburg 2006, South Africa
PJ van den Brink
Department of Aquatic Ecology and Water Quality Management, Wageningen University and Research Centre, PO Box 47, 6700 AA Wageningen, The Netherlands; Alterra, Wageningen University and Research Centre, PO Box 47, 6700 AA Wageningen, The Netherlands
MJ Ross
Centre for Aquatic Research, Department of Zoology, University of Johannesburg, Auckland Park, PO Box 524, Johannesburg 2006, South Africa
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Articles

Journal Identifiers


eISSN: 1727-9364
print ISSN: 1608-5914