The Spatial and Temporal Variations of Ichythyofauna and Water Quality in the Crocodile River (East), Mpumalanga, South Africa

The Crocodile River is situated in the north east of the Republic of South Africa. It is a large river basin with a total length of 320 km and draining a catchment of 10,450 km2. The water quality of this river is of high importance in sustaining the people and businesses relying on the sustainability of the river. The aim of the study was to use fish and water quality data to determine the present ecological state of the river and identifying the possible sources of pollution in the river. Multivariate statistical analysis was used to identify the main contaminants in the river at the various sections of the river. The results obtained indicated that species richness and diversity are high during low flow condition and the lower reaches had high species richness and diversity compared to the middle and upper reaches. The Fish Response Assessment Index indicated that the Ecological Class for the Crocodile River is mostly at C class beginning from the Kwena Dam downstream. Water quality constituents such as total dissolved solids and electrical conductivity increase with the increase in river distance in the downstream reaches. It was evident from this study that anthropogenic activities along the Crocodile River play a role in water quality deterioration and the subsequent distribution of fish during high and low flow conditions. The main sources of the pollution are believed to be agricultural activities in the upper reaches and a combination of industrial, domestic and agricultural activities in the middle and lower reaches of the Crocodile River.

The Loading Capacity of the Elands River: A Case Study of the Waterval Boven Wastewater Treatment Works, Mpumalanga Province, South Africa

Nutrient loads into water resources continues to be a major problem in Southern Africa. This has resulted in significant compromises in the ecological integrity of freshwater resources. The study aimed to assess the pollution load into the Elands River in terms of nitrates and orthophosphates. These variables were compared against the Crocodile Catchment Interim Resource Quality Objectives to determine compliances or non-compliance of the Waterval Boven wastewater treatment plant. Generally upstream nitrate levels did not exceed the ideal limit of 0.5 mg·l-1 as indicated in the 2015 to 2016 samples where values ranged between 0.32 mg·l -1 and 0.27 mg·l-1, respectively. Similarly, observed upstream orthophosphates levels were below the ideal limit of 0.03 mg·l-1. However, downstream values of both nutrients exceeded the respective set limits. The nutrient load contribution from the sewage plant was characterised by a simple point-source model. Patterns of the loads into the river were demonstrated on a load duration curve based on the river which equalled or exceed 0.18 m3/s upstream and 1.31 m3/s downstream at 90% of the time. However, the flows were regarded as significantly low to deal with uncontrolled pollution loads. Most of the observed loads fell below the ideal limit of 0.05 mg·l-1 for nitrates both upstream and downstream of the sewage plant. For orthophosphates, most of the upstream loads were below the tolerable limit of 0.1 mg·l-1 whilst the downstream loads were exceeding the tolerable limits. The higher loads downstream in the river were attributed to the sewage discharge from the Waterval Boven wastewater treatment plant and the low river flows. Hence it could be concluded that river water quality should be interpreted based on the river flow regime in a given season.

Free-Living Nematodes as Pollution Indicator in Incomati River Estuary, Mozambique

Four sites following the salinity gradient of the Incomati River Estuary E1 (0-3NST), E2 (3-5NST), E3 (6-18NST) and E4 (19-27NST) were selected for the study. The aim of the study was to use free-living marine nematodes as pollution indicators in an area strongly affected by anthropogenic activities. Multivariate statistical analyses were used to determine the relationship between different environmental factors and with free-living marine nematodes. Metals such Cadmium, Colbat, Chromium, Copper, Iron, Manganese, Nickel, Vadium, Zinc and Aluminium influenced the diversity and density of free-living nematodes. Shannon-Wiener Diversity, Maturity Index and colonize-persisters percentage (c% - p%) were found to be good tools for use as pollution indicators in the study. Nematode genera such as Terschellingia, Theristus and Halalaimus were found to be dominant at a site strongly impacted by both metals concentration and organic matters. The three genera are believed to be good indicators of pollution in the Incomati River Estuary. It is recommended that further studies are done along the Mozambican Coast to identify nematodes that can be used as pollution indicators.