Abstract
Ph.D. (Aquatic Health)
Acid mine drainage (AMD), characterised by low pH and increased bioavailability of metals, is a widespread problem that affects water quality. Metals are considered to be some of the most serious potential pollutants of aquatic ecosystems due to their toxicity, resistance to biodegradation, long duration in the environment, and trophic-level enrichment. The aims of this study were to (1) determine the spatial and temporal biomarker responses using Oreochromis niloticus, (2) determine macro-invertebrate and fish diversity and abundance, (3) assess metal trophic-level enrichment in the Yellow Jacket and Mazowe Rivers, and (4) to provide a framework for the management of the two rivers. The management plan was developed to ensure that existing and potential environmental impact caused by pyrite mining and processing are mitigated.
To achieve this, a study was done to assess changes in critical aquatic macro-invertebrate and fish community distributions, and how they related to measured environmental factors. Six sites were selected; three sites along the Yellow Jacket River as it flows through Iron Duke Mine (IDM), two sites along the Mazowe River, and an additional site below the confluence of the two rivers. Standard techniques for water, sediment, macrophytes, macro-invertebrate, and fish sampling were used. The sampled macro-invertebrates were identified to family level whereas fish were identified to species level. Active biomonitoring (ABM) exposures were conducted at the selected sites for four weeks during high flow (April 2014 and April 2015) and low flow (October 2013 and October 2014). Biomarker response analyses of the liver, gills, and muscle tissues of O. niloticus were applied to investigate the biochemical response of the organism to possible toxicant exposure and to infer water quality at selected sites. A set of biomarkers of exposure and effect (metallothioneins (MT), glutathione S-transferase (GST), and catalase (CAT)) were selected and their responses determined. The antioxidant enzymes CAT, GST and MT were selected in this study because of their sensitivity to pesticides and metals which are the major pollutants in the Yellow Jacket and Mazowe Rivers and are known to modulate defence systems and cause oxidative stress in aquatic organisms. Biomarker expression was measured after four weeks and compared against control fish kept...