Jhj van Vuren

Anthropogenic spatial and temporal changes in the aquatic macro invertebrate assemblages of the lower Mvoti River, KwaZulu-Natal, South Africa

Industrial and urban impacts on the lower reaches of the Mvoti River were studied using changes in macroinvertebrate community structures as indicators of environmental change. Macroinvertebrates were sampled during high- and low-flows in 2005 in the lower Mvoti River and its tributaries. Uni- and multivariate analyses revealed significant spatial differences between sites on the Mvoti River and those on the tributaries, as well as between sites on the Mvoti above and below the confluences of these tributaries. No significant trends in temporal distributions were recorded. Spatial differentiation was attributed to the abundance of insensitive taxa such as chironimids and oligochaetes at impacted sites. Increased salts and chemical oxygen demand, with lower dissolved oxygen concentrations, were identified as the driving water quality parameters affecting macroinvertebrate community structures. Comparison of macroinvertebrate structures in the Mvoti River with those in the biogeographically similar Mhlathuze River indicated the absence of sensitive taxa such as Atyidae, Naucoridae, Gomphidae and Leptoceridae from the Mvoti.

Heavy metal concentrations in the water of the Nyl River system, South Africa

The Nyl River floodplain, a Ramsar site that provides habitat for a number of endangered species, is one of the jewels in the arid Limpopo province and thus its conservation and protection are vitally important. Very little work has been done on assessing its water quality and no data have been published on the metal concentrations found in this valuable system. The aim of this project was thus to provide baseline data for metal concentrations in the Nyl River floodplain system and to determine whether there were any point sources of pollution or if its metal levels were natural. Eighteen localities along the course of the Nyl River were selected as sampling sites. Water samples were collected quarterly, between August 2001 and July 2002, and analysed using ICP-MS to determine metal content. Zinc, copper, iron, selenium, cadmium, lead, aluminium, arsenic, chromium and manganese concentrations were determined. Although metal concentrations in the water were greater than target water quality range (TWQR) values for aquatic ecosystems, they remained relatively constant throughout the system and posed little or no potential threat to the system. The results suggest that the metal content originates from natural sources.

Health of sharptooth catfish Clarias gariepinus in Pongolapoort Dam, South Africa: a comprehensive study

A histology-based fish health assessment protocol was used in 2009–2010 to assess the health status of Clarias gariepinus from Pongolapoort Dam, South Africa. Nineteen fish were collected by angling. The histology of liver, kidney, gills and testes or ovaries was semi-quantitatively assessed and compared to that of fish from a reference site in the Okavango Panhandle, Botswana. Necropsy observations indicated that C. gariepinus from Pongolapoort Dam were in poorer condition than those from the Okavango Panhandle. Microscopic analysis showed that the mean liver index (I L), gill index (I G), testis index (I T) and ovary index (I O) were higher, although not statistically significant, in fish from the Okavango Panhandle. The difference in the results between the necropsy-based observations and semi-quantitative histological results was due to the external abnormalities detected in the necropsy analysis, including parasites and skin lesions, not expressing as changes to cell and tissue structure. According to the parameters measured, C. gariepinus from Pongolapoort Dam were in a healthy state.

Bacterial levels in the Nyl River system, Limpopo province, South Africa

Because water quantity and quality are of great importance in the arid Limpopo province, the bacterial content of water in the Nyl River System and its possible origins were assessed at five sites. Quarterly surveys took place between April 2001 and July 2002 and the water was analysed for bacterial counts using standard procedures. Heterotrophic plate counts, faecal coliform counts and total coliform counts indicated that the system was stressed. The Modimolle sewage treatment works and local agricultural activities were found to be the point and diffuse sources of bacterial contamination, respectively.

Spatial and temporal variation in the macroinvertebrate community structure of the lower Elands River, Mpumalanga, South Africa

The Elands River, Mpumalanga, is an ecologically sensitive river that is constantly threatened by a variety of human activities. The influence of a pulp and paper mill on the rivers macroinvertebrate assemblages was studied in March and June 2005, representing high- and low-flow seasons, respectively. Macroinvertebrates were collected from various biotopes using a standard sampling net, and were preserved and identified to family level. A range of multivariate and univariate statistical analyses was applied to assess the spatial and temporal variations in the macroinvertebrate communities. Diversity loss and dominance by a single taxon, Melanoides tuberculata, were noted directly below the mill. Other sites did not appear to be affected. Macroinvertebrate communities at all sites showed a strong seasonal variation.

Accumulation of hepatic Hsp70 and plasma cortisol in Oreochromis mossambicus following sublethal metal and DDT exposure

Heat shock response in Oreochromis mossambicus livers was measured, using antibodies specific to Hsp70 family members, by an immunoblotting protocol. The hepatic isoforms Hsp70, Hsp74 and Hsp76 were identified and quantified from copper exposures. Long-term DDT exposure did not result in significant induction of hepatic Hsp70. An increase in plasma cortisol concentration was associated with a decrease in heat shock protein accumulation after cadmium exposure, but this negative correlation was not statistically significant. A positive correlation between Hsp70 accumulation and plasma cortisol concentration was observed after chromium and nickel exposures. The induction of cortisol as a stress response may be metal-specific. No statistically significant relationship between cortisol and Hsp70 synthesis was found. The quantification of three hepatic Hsp70 isoforms demonstrates the feasibility of applying heat shock response in O. mossambicus as a biomarker of exposure to pollutants in the aquatic environment.

Do aquatic macroinvertebrate communities respond to land-use effects in the Wilge River, Mpumalanga, South Africa?

Aquatic macroinvertebrate community responses to the effects of various land uses were investigated in 2010–2013 in the Wilge River, a tributary of the Olifants River, South Africa. The catchment area is characterised by agricultural, mining and industrial activities, which potentially contribute to the rivers deteriorating water quality and poor in-stream habitat conditions. Agricultural activities comprise the predominant land use, causing major nutrient input into the Wilge River, resulting in eutrophic conditions. Thus it was expected that the functional feeding group (FFG) scraper/grazer populations would be the most abundant as they consume algae, but this was not the case. The primary FFGs present were predators and gathering collector populations, whilst shredders were the least abundant. The primary drivers responsible for separating the monitoring sites and their aquatic macroinvertebrate communities were differing in situ water quality, season and habitat availability. Therefore, land use was not a driving variable, probably owing to limited organic and inorganic water quality data.

A comparison of methods for incubating zooplankton diapausing eggs from sediment of endorheic pans in the Free State, South Africa

Determining the composition of zooplankton in endorheic pans can be challenging, and live sampling of these microcrustaceans does not give a true indication of their species diversity and abundance. The incubation of zooplankton diapausing eggs can assist in determining their diversity and abundance. In this study the efficacy of two incubation methods – isolation and non-isolation – was tested using samples taken in 2013 from five endorheic pans in the Free State province, South Africa. The non-isolation incubation method made use of distilled water in the hatching experiments, whereas the Onbé–Marcus isolation incubation method, using 1:5 v/v ADAM medium/water, was adapted and applied to samples to isolate the diapausing eggs. The isolation method provided hatchlings at a higher rate than that of the non-isolation method, but subsequent removal and identification of the hatchlings was challenging. In particular, the success of the isolation method was putatively related to sediment grain size composition. Some difficulties were also noted in using the non-isolation method in the hatching and growing of anostracans.

Exfoliative liver cytology in Oreochromis mossambicus as a bio-assessment tool for aquatic pollution

The use of exfoliative cytology as a bio-assessment tool was evaluated to (1) identify and describe different cell types of normal liver cytology of Oreochromis mossambicus, (2) identify and describe changes in the cell types after exposure to cadmium and zinc, and (3) determine if non-imaging-guided fine-needle aspiration (FNA) cytology can be performed without sacrificing the fish. All fish used in the aspiration experiment recovered and survived. Livers of O. mossambicus exposed to cadmium and zinc showed excess numbers of exfoliated red blood cells, loss of cellular cohesion, regenerative hyperplasia, pale and weak cytoplasm staining, pronounced vacuolation and degeneration. Cadmium and zinc exposure induced pathological cellular changes. Exfoliative cytology is thus a safe, cost-effective and reliable bio-assessment tool.