J.H.J. Van Vuren

Aquatic Invertebrate Communities of Perennial Pans in Mpumalanga, South Africa: A Diversity and Functional Approach

ABSTRACT Perennial pans are a common feature of the Mpumalanga Highveld in South Africa and are increasingly under threat from mining and agricultural activities. Pans are endorheic wetlands that can be perennial or ephemeral in nature. They are widespread in arid and semi-arid regions throughout the world. Although phyllopod crustaceans dominate pan communities in arid regions, the invertebrate communities of perennial pans have not been well studied. The aim of the current research was to characterise the invertebrate communities of several pans (both natural and impaired). A combination of taxonomic and functional approaches was followed to study these communities. The macroinvertebrate species diversity of the pans was comparable to similar ecosystems in southern Africa and other parts of the world. Results indicate large spatial and temporal variations in diversity. This variation became less obvious when the analysis was based on biological traits. It was also evident that both coal mining and agricultural activities had an impact on the aquatic invertebrate community structures. These changes were apparent in both the diversity and the biological traits of the invertebrate communities of adjacent pans.

Sublethal effects of manganese on the carbohydrate metabolism of Oreochromis mossambicus after acute and chronic exposure

Carbohydrate metabolism variables of Oreochromis mossambicus were investigated after acute and chronic sublethal manganese exposure. The sublethal concentrations were determined from the LC50 value of manganese. After the exposures, the fish were carefully netted and blood was drawn from the caudal aorta. The differences in the values of carbohydrate metabolism variables of exposed fish were measured against control values and statistically analysed to prove statistically significant differences in variable values, caused by the metal pollutant (P < 0.05). The results obtained showed changes in the carbohydrate metabolism variables (glucose, lactate, glucose-6-phosphate dehydrogenase and pyruvate kinase concentrations). These alterations are produced as a result of increased levels of Cortisol and catecholamines, as well as hypoxic conditions. The latter induce hyperglycemia and increased lactate levels. Hypoxia may be a result of the damaging effect of manganese on the gills after exposure. The enzymes i...

Concentrations and human health risk assessment of DDT and its metabolites in free-range and commercial chicken products from KwaZulu-Natal, South Africa

ABSTRACT Organochlorine pesticides such as dichlorodiphenyltrichloroethane (DDT) have been used in agriculture and for disease control purposes over many decades. Reports suggest that DDT exposure may result in a number of adverse effects in humans. In the KwaZulu-Natal Province of South Africa, DDT is sprayed annually in homes (indoor residual spraying) to control the mosquito vector of malaria. In the northern part of the Province, samples of free-range chicken meat (n = 48) and eggs (n = 13), and commercially produced chicken meat (n = 6) and eggs (n = 11), were collected and analysed. Of the free-range chicken meat samples, 94% (45/48) contained DDTs (ΣDDTs median 6.1 ng/g wet weight [ww], maximum 79.1 ng/g ww). Chicken egg contents were also contaminated (ΣDDTs in free-range eggs median 9544 ng/g ww, maximum 96.666 ng/g ww; and in commercial eggs median 1.3 ng/g ww, maximum 4.6 ng/g ww). The predominant DDT congener detected was p,pʹ-DDE in both free-range meat (>63%) and eggs (>66%), followed by p,pʹ-DDT and then p,pʹ-DDD. Based on estimated daily intake values, calculated human risk ratio (carcinogenic) values were >1 for DDTs detected in both free-range chicken products. Consumption of free-range eggs poses a particularly high health risk. Graphical Abstract

The case for environmental flow determination for the Phongolo River, South Africa

The construction of Pongolapoort Dam in 1973 on the Phongolo River in KwaZulu-Natal, South Africa, has considerably altered the hydrological behaviour and ecological response of the downstream floodplain. Changes in the flooding regime have had implications for the socio-economic importance of the floodplain and for the structure and functioning of its associated wetlands. Previous studies have recommended annual releases of water from the dam to sustain floodplain ecosystem goods and services. The current artificial water releases are limited by the size of the dams sluices and by the demand for water from the local community. Therefore, water releases do not always follow the original natural flooding regime. To date, the influence of the changed hydrology on the ecology of the Phongolo floodplain system remains poorly known. As a basis for future integrated interdisciplinary research we synthesised the ecological and hydrological work conducted to date on the Phongolo floodplain. We suggest hydro-ecology as an important research direction needed to set environmental flows for the sustainable utilisation and management of the floodplain. Understanding the hydrological behaviour and ecological response of the Phongolo floodplain could help in the implementation of environmental flows by managers at the Department of Water and Sanitation and other stakeholders such as Ezemvelo KZN Wildlife.

Aquatic invertebrate community structure of selected endorheic wetlands (pans) in South Africa

Shallow wetlands, such as pans, are not well studied in South Africa, even though they perform many important functions, such as providing an important food source for migratory birds and habitat to highly specialized fauna. Aquatic invertebrate diversity, abundance, and water quality in pans were analysed seasonally from 3 provinces in South Africa with contrasting climates. Univariate and multivariate statistics were used to assess similarities in aquatic invertebrate communities and water chemistry among pans. Pans inundated for extended periods had greater aquatic invertebrate diversity, and several of these taxa were not adapted to the temporary environment common to pans. The subtropical region had greater aquatic macroinvertebrate diversity than semiarid regions due to more rainfall per annum in the subtropical region. Water temperature was a major driving factor for diversity, with greater diversity occurring in warmer seasons. High water hardness and salinity were found to drive decreased diversity and encourage the presence of hardy and more tolerant species. Understanding the importance of these aforementioned factors (i.e., pan longevity, temperature, water hardness, and salinity) influencing aquatic invertebrate biodiversity in pans provides a baseline for future studies and impact assessments on these important and understudied systems.

Macroinvertebrate variation in endorheic depression wetlands in North West and Mpumalanga provinces, South Africa

Aquatic macroinvertebrates are rarely used in wetland assessments due to their variation. However, in terms of biodiversity, these invertebrates form an important component of wetland fauna. Spatial and temporal variation of macroinvertebrate assemblages in endorheic depressions (locally referred to as pans ) in Mpumalanga and North West provinces were compared in wet and dry seasons in 2012 and 2013. A total of 29 taxa were identified from both provinces, with similarities in the structure of communities, with the exception of one or two species, in perennial endorheic depressions in both provinces. Macroinvertebrates sampled in Mpumalanga endorheic depressions were similar to those reported in previous studies completed in the area, and most macroinvertebrates sampled in Mpumalanga and North West were known to be commonly found in temporary habitats. Long-term studies are required to understand better the ecological functioning of the pans in the North West province.

The sublethal effects of manganese on the differential white blood cell counts of Oreochromis mossambicus

Metal ions have become an increasing source of pollution in the natural waters of South Africa. This phenomenon is related to the increasing industrial, mining and agricultural activity along rivers.