Abstract
MSc. (Zoology)
The use of parasites in aquatic monitoring studies has increased over the last two decades, due to the remarkable ability to accumulate metals to higher concentrations than their hosts. Studies utilizing parasitic organisms have primarily focused on the use of endoparasites, resulting in limited knowledge on the potential of ectoparasitic organisms.
The present study was undertaken in April 2013 at UJ Island (26°52.249‟S; 20°10.249‟E) in the Vaal Dam where 22 Labeo capensis Smith, 1841 were collected with the aid of gill nets. All Argulus japonicus Thiele, 1900 specimens were collected off of each host upon host collection, and kept alive for 24 hours prior to being frozen, to allow for digestion of intestinum content. Water and sediment samples were collected on site, and water quality data was received from Rand Water Analytical Facility in Vereeniging for the sampling period, as this organisation routinely monitors the physico-chemical parameters and metal concentrations of the Vaal Dam. The fish were sacrificed by severing the spinal cord, and blood, gill arch, gill filament, kidney, liver, muscle and skin tissues were collected from each fish for metal analysis. All samples were frozen and transported to the University of Johannesburg for analysis. Water, fish tissue, parasite and sediment samples underwent acid digestion utilizing closed vessel microwave digestion techniques, and analysis was performed utilizing both Inductively Coupled Plasma-Mass Spectrometry (ICP-MS) and Inductively Coupled Plasma-Optical Emission Spectrometry (ICP-OES). Fish muscle tissue underwent further Cold Vapour Atomic Absorption Spectrometry (CVAAS) analysis. Selected A. japonicus specimens were prepared for fluorescence microscopy. These specimens underwent photo irradiation and were treated with Phen Green FL cell permeate diacetate stain to visually locate regions where the metals were being accumulated. The results from the metal analysis indicated that metals present within the Vaal Dam water are all at trace levels. The comparison of metal concentrations between the water, sediment and fish tissues revealed that sediment contains the highest concentrations for metals, followed by fish tissues and water at the lowest concentrations. This trend exists as a result of the underlying geological morphology of the Vaal Dam, the physiological and biological characteristics of L. capensis, and the physico-chemical variables of the water. The risk assessment performed on the muscle tissue revealed that the levels of arsenic, cadmium and selenium were above the safety threshold values for human consumption. The analysis of the A. japonicus specimens revealed that the selected techniques were not adequate for the analysis of individual specimens, as specimens were too small...