Lateral hydrological connectivity differentially affects the community characteristics of multiple groups of aquatic invertebrates in tropical wetland pans in South Africa

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A Conceptual Framework for Using Mussels as Biomonitors in Whole Effluent Toxicity

As a main source of direct and continuous input of pollutants in the aquatic ecosystem, studying the effects of effluents on receiving ecosystems has a high ecological relevance. While ecological risk assessment procedures are usually based on a chemical-based single component approach, their application for complex mixtures and effluents is less straightforward. A chemical-based approach has to rely on the knowledge of what chemicals are present in effluents, their potential toxicity, how all of these individual chemicals interact and what their individual and combined contribution to the mixture is. Whole effluent toxicity (WET) testing, however, is an integrative tool that measures the toxic effect of an effluent as a whole and accounts for uncharacterized sources of toxicity and for interactions. This paper addresses the use of transplanted bivalves, i.e., caged mussels, as a biomonitoring tool in WET testing with special reference to field situations in both freshwater and marine environments. We indicate how endpoints at different levels of biological organization within exposed mussels can give an integrative overview of effects. Finally, we will provide a framework for future research using mussels and discuss a multitude of instream responses for routine, efficient and cost-effective active biomonitoring applications.     

The effect of acid mine drainage on the hatching success of branchiopod egg banks from endorheic wetlands in South Africa

Endorheic wetlands are abundant in South Africa, and are more commonly referred to as pans. The pan environment experiences daily and seasonal fluctuations in physico-chemical conditions, caused by variable hydroperiods. Branchiopod crustaceans are a unique group of fauna which are able to survive this variability through the production of dormant egg banks. The endorheic nature of these wetlands makes them more vulnerable to anthropogenic activities. A decrease in the hatching success of branchiopods could be detrimental to the biodiversity and ecosystem functioning of these wetlands. Pans were selected from regions where increasing mining activities are a potential risk. The sediment collected from selected pans was inundated with two saline solutions of 1,000 and 1,500 mg/l, respectively, which served as controls. A third solution of decanted acid mine drainage (AMD) was used to determine hatching success with exposure to AMD. Findings showed that AMD had a negative effect on the hatching success from egg banks. Recovery experiments were performed to assess whether egg banks could recover from AMD exposure upon first inundation. Recovery rates were low and support the concern that affected wetlands will suffer a loss of biodiversity.     

Temporal dynamics of a subtropical floodplain pool after 2 years of supra-seasonal drought: a mesocosm study

Hydrobiologia - A need exists to understand how drought and its linked consequences threaten aquatic ecosystems and their associated biota in semi-arid countries, as climate change is predicted to...     

Temporal movement of free-swimming fishes and their response to environmental variables in some of the rivers of Kruger National Park,South Africa

Environmental Biology of Fishes - The increase in anthropogenic stress on river ecosystems is of growing concern globally as demand for water increases and freshwater ecosystem degradation occurs....     

COMMENTS ON THE WATER QUALITY OF THE MHLATHUZE ESTUARY IN RELATION TO DETERMINING THE ECOLOGICAL INTEGRITY CLASS

Summary

Water quality forms an integral component of the determination of the Ecological Reserve of a water resource. This paper presents the available historical and current information on the water quality of the Mhlathuze estuary, The data were assessed in order to determine the forcing factors that characterise the water quality of Mhlathuze estuary. These factors were used in conjunction with a previously-developed water quality indexing system to assign a water quality integrity class to the Mhlathuze estuary. Three reaches of the estuary were classified as being largely natural with few modifications. Major issues relating to water quality data gaps were identified. By addressing these issues an integrity class could in future be assigned with greater confidence.