The South African National Water Act (NWA) (No. 36 of 1998) recognises that in order to sustain the goods and services that are provided by rivers and their associated biological communities, it is necessary to conserve the entire aquatic ecosystem. Conservation and maintenance of ecosystem functioning entails the protection of the biotic components (i.e. fish, macroinvertebrates, riparian vegetation, etc.) and ensuring that the abiotic driver aspects (i.e. required amount and variability of flow, water quality and fluvial geomorphology) are addressed and met (Malan and Day, 2003). According to the Reserve Determination methodology (DWAF, 2003), sustainable utilisation of the river resources requires proper, responsible management and that exploitation without understanding or limits, impacts negatively on the ecological processes, functions and communities, both in the present and the future. Manipulation of the flow regimes of rivers, to provide water when and where people need it, has resulted in a growing deterioration in the condition (health) of riverine ecosystems (King et al., 2000). Stressors on aquatic ecosystems originating from these anthropogenic activities, include point and non-point loadings, land use influences and changes, and stream modification. These are usually defined by the drivers of aquatic ecosystems namely the geomorphology, hydrology and water quality. In turn, the effects on the physical habitat and water quality have both direct and indirect effects on the biotic communities present and are usually defined by biological responses to these changes (Kleynhans et al., 2005). There is currently limited data available to formally propose a methodology to quantify the significance of altered flows in riverine ecosystems brought about by the abstraction or excessive release of water by industrial activities on a reach scale. The aim of this study was to determine the degree and magnitude of habitat-flow alterations caused by pulp and paper mill activities in the Elands and Mvoti Rivers and to link the related biological responses to them. / Prof. V. Wepener

The Reserve concept, introduced in the National Water Act, has led to an increasing use of biomonitoring techniques to assess the current ecological status of rivers in South Africa. The ecological status of a river provides vital information necessary to establish the amount and quality of water needed by the aquatic ecosystem. If the amount and quality of water is inadequate, then the water resource will not be able to provide the necessary goods and services to their respective water users. The biomonitoring of rivers gained impetus with the establishment of the River Health Programme (RHP) and its various objectives. The RHP led to the development and refinement of a range of biomonitoring indices to assess various components of the aquatic ecosystem. The components used to assess the current ecological status of a river include the physical habitat, riparian vegetation, water quality, as well as the macro-invertebrate and fish communities. The Mvoti River, in the vicinity of Stanger, is subjected to extensive water abstraction, which is then utilised for irrigation, industrial use, urban water requirements and various domestic uses by informal settlements. Previous studies on the river indicated that it is in a severely degraded state, especially below the confluences of the Nchaweni and Mbozambo rivers. Thus, this assessment of the current ecological status of the Mvoti River was undertaken to possibly identify the main causes of the degraded state. The study was undertaken during the high (February) and low flow (August) periods in 2005. Selected monitoring sites included sites used in previous studies on the Mvoti River as well as sites on the Nchaweni and Mbozambo tributaries. The methodology for this study was to implement the various indices used in the RHP for the different ecosystem components. The habitat indices implemented in this study were the Habitat Quality Index (HQI) and Integrated Habitat Assessment System (IHAS). Physicochemical water analyses were done during each sampling period to assess the water quality against the South African Water Quality Guidelines. The biotic indices used included the South African Scoring System 5 (SASS5) index to assess the macro-invertebrate community and the Fish Assemblage Integrity Index (FAII) to assess the fish community. Additionally, the newly developed EcoStatus indices for the fish and macro-invertebrate communities were implemented on the available fish and macro-invertebrate data. These indices were developed mainly to be used in Reserve determination assessments, where the assessments are built around the integration of all ecosystem components into a single value for the ecological status. The fish index is termed the Fish Response Assessment Index (FRAI) and the macro-invertebrate index the Macro-invertebrate Assessment Index (MIRAI)…. Multivariate statistical analyses were performed on the water quality as well as the macroinvertebrate and fish communities to establish any temporal and spatial trends together with any dominating water quality variables responsible for species composition at the different sites. PRIMER and CANOCO computer software were used to construct hierarchical clusters and NMDS plots for the biotic communities, while RDA and PCA bi-plots were used to represent the water quality variables and their effects on the biotic community structure. The Mvoti River is in a seriously degraded state and this degradation was particularly evident during the low flow period below the Sappi Stanger mill and the Stanger Sewage works effluent discharge points. The degraded state of the river is caused by the multitude of impacts on the river, which includes the local land-use, upstream land-use and effluent discharges in the vicinity of Stanger. The water quality in the vicinity of Stanger was in a poor state during the low flow, while the high flow was only slightly better. The upstream site is in a fair condition but, after the Nchaweni and Mbozambo rivers enter the Mvoti River, the water quality decreases. The variables found to be problematic included microbiological variables, chlorides and electrical conductivity in the Mvoti River. High nutrient values were found together with very high electrical conductivity in especially the Nchaweni River tributary. The lower Mvoti River contains very little habitat of good quality to support the biotic communities. The habitat is generally degraded due to the destruction of the riparian zone and the dominance of alien vegetation in the form of reeds. This, together with land-use and water abstraction activities, has caused high sediment loads in the lower Mvoti River which are continually moving. The IHAS and HQI results indicated the habitat in the lower Mvoti River is in a modified condition. The statistical analysis of the macro-invertebrate data showed that a definite spatial variation existed while no significant temporal variation was identified. There is a difference in the community structure between the Mvoti River and its tributaries, with the tributaries containing a very poor diversity. This lowered species diversity was attributed to the effects of, specifically, chlorides on the community structure but the origin of the chlorides could not be linked specifically to the Sappi Stanger mill’s activities. The SASS5 was similar with the Mvoti River sites having slightly higher scores, placing it in either a B or C class while most of the tributaries had a Class D. The community structure in the tributaries responded to nutrients and chlorides and these variables reduced the numbers of sensitive species and allowed hardy taxa to flourish. The results of the MIRAI index provided the same categories as identified by the SASS5 index. The fish community structure showed the same spatial differences identified in the macroinvertebrate communities, with the tributary sites containing different community structures than those found in the Mvoti River. The Mvoti River fish community is in a modified state with the majority of fish sampled being tolerant with very few sensitive species present. The FAII scores for the Mvoti River was a Category C, while the tributary sites scored a Category D or lower. The fish community is affected by the poor water quality, habitat and flow modifications in the lower Mvoti River. The FRAI index provided the lower Mvoti River and its tributaries with the same categories as identified with FAII. Overall, the Mvoti River is in a seriously degraded state with even the reference site being subjected to impacts that could potentially be harmful to the ecosystem. The ecological state of the river decreases as it moves past Stanger and is subjected to the impacts from the Nchaweni and Mbozambo rivers in the form of nutrients and salinity concentrations. The impacts on the Mvoti River have a multitude of different sources and if the aquatic ecosystem is to improve, only a collective effort will be of any value. / Prof. V. Wepener

M.Sc. / The Mvoti River is referred to as a ‘working river’ in that it is highly utilized and developed. It is also, however, in a severely degraded state according to recent ecological assessments that were carried out on the Lower Mvoti River in 2000 and 2005. Previously, this was mostly attributed to the specific activities related to a pulp and paper mill. However, findings of the abovementioned studies indicated that there are multiple stressors present in the system and to derive the combined effect of stressors in an environment affected by multiple activities, a characterization of the different contributing activities is required. Thus, this assessment was undertaken to determine the impact of one of the contributing stressors, i.e. sugar milling activities on the ecological integrity of the Mvoti River. The survey assessments, incorporating local and international accredited methods and techniques, were carried out over a high and low flow period during 2006. A BACI (before-after controlled impact)-research design was applied in this study. Four sites were selected on the Mvoti River, up and downstream of the Glendale Distillery (GDR and GDS) and the Ushukela Milling Company (USR and USS). The former sites were selected to assess the impact of a sugar mill alone and the latter to determine the combined effects of sugar milling and pulp and paper activities. Additionally, 2 sites were selected on the Amatikulu River, up and downstream of the Amatikulu Mill (AR and AS), to assess the effect of the sugar milling activities alone. This study consists of two components, namely the abiotic driver component and the biotic response component. The abiotic driver component involved the analysis of water quality, sediment and habitat quality in which physico-chemical variables of water and sediment were carried out during high and low flow periods and the habitat indices, Habitat Quality Index (HQI) and Integrated Habitat Assessment System (IHAS) were implemented. The biotic response component involved the assessment of the macroinvertebrate and fish community structures, as well as the determination of acute and chronic toxicity and mutagenicity resulting from exposure to mill effluent. The macroinvertebrate communities were assessed using the South African Scoring System Version 5 (SASS5) index and the fish communities were assessed using the Fish Assemblage Integrity Index (FAII). The toxicological assessments were carried out via the use of the Direct Estimation of Ecological Effect Potential, or DEEEP, methodology, and biomarkers.