Biochemical responses revealed in an amphibian species after exposure to a forgotten contaminant: An integrated biomarker assessment

Vanadium is a metal whose toxicity towards terrestrial and aquatic species has been under-reported to date.. The biochemical responses of vanadium in amphibian species have not been determined. To establish the effects of vanadium (V) on exposed adult Xenopus laevis, acute and chronic exposures were conducted, and biomarker analyses were performed on liver and muscle tissues from exposed frogs. Biomarkers of exposure, such as acetylcholinesterase (AChE) and metallothioneins (MT), were analysed. Biomarkers of effect were also analysed to determine possible increases in reactive oxygen species (ROS), and the effect of the exposure on the energy balance in the organisms. These included superoxide dismutase (SOD), catalase (CAT), reduced glutathione (GSH), protein carbonyls (PC), malondialdehyde (MDA), and cellular energy allocation (CEA) (energy available, energy consumption, lipids, proteins and glucose). In acute exposures, the energy balances in organisms were distinctly affected, possibly due to insulin mimetic properties of V. In chronic exposures, MT, AChE, SOD, CAT and GSH responses were more pronounced. Although AChE is generally inhibited by pollutant exposure, in this study, it was stimulated. There were significant inhibitions of SOD and CAT, previously observed in frog species. PC levels increased in the highest acute exposure concentration, indicating protein damage. The IBR.v2 revealed the biochemical responses of V more effectively than traditional statistical analysis.

Baseline bio-accumulation concentrations and resulting oxidative stress in Synodontis zambezensis after an acute laboratory exposure to 4,4'-DDT

The use of 1,1'-(2,2,2-Trichloro-1,1-ethanediyl)bis(4-chlorobenzene) (DDT) as a pesticide for the control of insects vectors responsible for the spread of many life threatening diseases was officially banned in 1972 by the United States Environmental Protection Agency (USEPA). It was banned throughout the world, in most developed countries, because of the toxic effects it causes in wildlife, including birds and fish. However, DDT is still used in approximately 43 African countries, including South Africa, to control the spread of malaria. The lipophilic nature of DDT and therefore its persistence in the environment makes it extremely important for laboratory based studies to be conducted in an effort to evaluate the accumulation potential and possible physiological effects of DDT in aquatic organisms under controlled conditions. The aim of this study was to establish baseline bioaccumulation concentrations within Synodontis zambezensis following an acute exposure to 4,4'-DDT. The three metabolites analysed were 4,4'-DDE, 4,4'-DDD and 4,4'-DDT. None of the 2,4'-isomers were analysed in this study since the acute exposure used a solution of 98.7% pure 4,4'-DDT (Sigma-Aldrich PESTANAL®, Analytical Standard, CAS-No 50-29-3, Batch number SZBE057XV) and not a mixture of 4,4'-DDT and 2,4'-DDT as found in technical grade DDT. Soxhlet extraction of tissue samples and liquid/liquid extraction of water samples followed by analysis through Gas-chromatography mass-spectrophotometry was completed. Mean 4,4'-DDE, 4,4'-DDD and 4,4'-DDT concentrations ranged from 15.34 ng/g to 45.34 ng/g, 28.16 ng/g to 63.25 ng/g and 28.64 ng/g to 96.21 ng/g respectively. All of the accumulated concentrations fell within environmentally relevant concentrations with no input through the food web. The accumulated concentrations of 4,4'-DDT and its three metabolites resulted in oxidative stress responses within the gills and the liver tissue of S. zambezensis. Significant differences (p ≤ .05) were observed between malondialdehyde (MDA) and reduced glutathione (GSH) within the liver and in superoxide dismutase (SOD), catalase (CAT) and reduced glutathione (GSH) in the gills.

A comparison of water quality and macroinvertebrate community structure in endorheic depression wetlands and a salt pan in the Gauteng province, South Africa

Depression wetlands (colloquially referred to in South Africa (SA) as pans) are found worldwide and primarily occur in arid regions including North and South America, southern and central Africa and southern and western Australia. Surface water resources in SA, and specifically in Gauteng, are under pressure from urbanisation, poor agricultural practices and untreated mining and industrial effluent. Research of these wetlands will benefit the development of health assessment tools for these unique aquatic resources. The aim of this project was to determine the water quality and macroinvertebrate community structure for each perennial pan during consecutive dry and wet seasons and to establish a possible comparison between these pans that can be used as a baseline for future research on pans. The sampled pans in Gauteng presented higher TDS, Cl and Mg results compared to other South African studies, and similar SO₄ results to pans in the Mpumalanga province. Ammonia, Al and Zn results of all pans through all sampling events exceed the Target Water Quality Range (TWQR) for aquatic ecosystems of the Water Quality Guidelines (WQG) from the Department of Water and Sanitation (DWS). The water quality from selected systems is suitable for livestock watering based on the DWS TWQR. Macroinvertebrate species of all sampled pans were mostly low water quality tolerant species with a predator dominant community structure. Seasonal variation of species was evident. Macroinvertebrate families found in the wet season include Hydrophilidae, Aeshnidae, Pleiidae, Ephemeroptera, Belostomatidae and Notonectidae. Families found in the dry season include Planaridae, Dysticidae, Hirudinidae and Daphnidae. Graphical representation of ordination analyses with Canoco version 5 (Ter Braak and Šmilauer 2012) indicated that TDS, temperature, pH, sulphates and hardness are strong drivers of the existing macroinvertebrate community in most of the pans.

Histological changes in the liver of Oreochromis mossambicus (Cichlidae) after exposure to cadmium and zinc

The toxic effects, of two heavy metals, cadmium (Cd) and zinc (Zn), on the histology of the liver of the southern African freshwater fish Oreochromis mossambicus, were investigated. The goal was to identify whether metal concentrations and exposure period influence the degree and nature of histological changes in the liver of exposed fish. Selected fish were exposed to a mixture of 5% concentrations of the LC(50) of cadmium and zinc and to a mixture of 10% concentrations of the LC(50) of cadmium and zinc, over both short- and long-term exposure periods. Similar histological changes occurred in the livers of specimens exposed to both 5% and 10% concentrations, indicating a definite toxic response to both the metal concentrations. These histological changes included hyalinization, hepatocyte vacuolation, cellular swelling, and congestion of blood vessels. The intensity of these histological changes was, however, influenced by the extent of the exposure period.

Histological evidence of intersex in feral sharptooth catfish (Clarias gariepinus) from an estrogen-polluted water source in Gauteng, South Africa

This is the first histological evidence of intersex in a fish species inhabiting a South African water source. One hundred catfish (Clarias gariepinus) were collected randomly from the Marais Dam (MD) and the Rietvlei Dam (RVD) in the Rietvlei Nature Reserve (RNR), South Africa. These dams drain water from a stream that receives effluent from industrial sites, agricultural activities, informal settlements, and municipal treatment plants. Each fish was evaluated macroscopically and had blood drawn, and its gonads were macroscopically and histologically examined to verify intersex potentially related to endocrine disruption. Gonadal histology of several fish showed primary oocytes scattered in testicular tissue, indicative of intersex. The results showed intersexuality in 20% of fish from both the dams. The GSI value for intersex fish was closer to male GSI values, suggesting that the sampled intersex fish were more likely to have occurred from the feminization of male catfish. Target chemical analyses showed that the water, sediment, and serum samples tested positive for p-nonylphenol (p-NP). The p-NP level in water and sediment at MD was 6360 and 4.0 microg/kg, respectively, whereas in sediment at RVD it was 113 microg/kg. Commonly found in the effluent from sewage treatment plants, p-NP in water and sediment indicates estrogenic water pollution, which might affect wildlife and humans dependent on these sources.

The use of different enzymes in feral freshwater fish as a tool for the assessment of water pollution in South Africa

Selected enzymes in the organs/tissues of two fish species (Oreochromis mossambicus and Labeo umbratus) were evaluated as biomarkers of water pollution in warm- and cold-water systems. The fish were caught using standard techniques during two high-flow and two low-flow surveys. The results indicated that the fluctuating enzyme activities measured were not a result of pollution but could be initiated as a result of (1) no or too little pollution, (2) handling of the fish, and (3) struggling in the nets. Furthermore, most of the enzymes are nonspecific for the specific pollutants present. It is concluded that the selected enzymes could not be successfully employed as biomarkers of water pollution when the organisms are sampled from a polluted water source.