Oxidative stress biomarkers in Oreochromis niloticus as early warning signals in assessing pollution from acid mine drainage and diffuse sources of pollutants in a subtropical river

Abstract

This study investigated the use of an exotic fish species Oreochromis niloticus as a bio-indicator organism in active biomonitoring of Yellow Jacket and Mazowe rivers, Zimbabwe, receiving acid mine drainage from Iron Duke Mine. The Yellow Jacket River flows through Iron Duke Pyrite Mine while the Mazowe River passes through the Mazowe factory and estate shop that receives runoff from intensive agricultural activities. Active biomonitoring (ABM) exposures were conducted for 6 weeks in effluent-contaminated sections of the rivers during high flow, from February to March 2013. A set of biomarkers of exposure and effect (glutathione S-transferase, catalase and metallothioneins) were selected and their responses determined in O. niloticus liver, gills and muscle. We hypothesized that the increase in activities of GST, CAT and MT in exposed fish, in comparison to control fish, can be used to assess river water quality using O. niloticus . Biomarker expression was measured after 4 and 6 weeks and compared against control fish kept under laboratory conditions without contaminants.

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