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In open-canopied temperate rivers, periphyton plays a pivotal role by converting dissolved nutrients into food for biota. International research suggests that periphyton is particularly responsive to flow and nutrient alterations and therefore ideally suited to aiding the prediction and monitoring of the effects of altered flow regimes. Given that one of South Africa's key focus areas for river management has been the provision of flows to sustain aquatic ecosystems, this study aimed to quantify the relative importance of potential environmental drivers of periphyton, particularly flow, under different nutrient conditions in rivers of the south-western Cape. The study focused on two perennial rivers, the Berg and Molenaars Rivers. Quantitative monthly samples of periphyton biomass were collected from four sites, representative of different flow and nutrient regimes, over a 21-month sampling period between September 2007 and May 2009. The frequency of flood disturbance over the wet season was found to be the single most important driver of periphyton communities. It accounted for almost 75% of the total variation in periphyton biomass under natural flow and nutrient-poor conditions and it was therefore identified as the primary driver of periphyton communities. Its role was smaller under moderately enriched conditions and accounted for 45% of the total variation. These findings suggest that periphyton in south-western Cape rivers has great potential as a tool for predicting and monitoring the effects of altered flow regimes under different nutrient enrichment regimes. Together with some insight into community structure, the next step is to develop periphyton indicators that reflect different aspects of ecosystem integrity, for use in scenario modelling and other management aspects. [ABSTRACT FROM AUTHOR]

This study was conducted to establish the interannual variation in the concentration of metals regarded as toxic to aquatic fauna in the Marico River of South Africa. Five surveys were conducted between 2013 and 2015 at six sites in the river. Water samples were collected and analysed for metals by means of ICP-MS, whereas pH was measured in situ. From these results it is evident that all the metals generally regarded as toxic to macroinvertebrates namely aluminium, titanium, chromium, manganese, iron, cobalt, nickel, copper, zinc, cadmium and lead, were detected at each of the sites, but not during every survey. Significant variations in the mean metal concentrations were demonstrated across all sites and surveys, with the intersurvey coefficient of variance exceeding 80% for all metals, except for Ti, Fe, Co and Ni. These results should be considered in defining the baseline metal concentrations of the Marico River. [ABSTRACT FROM AUTHOR]

Biological control is an effective ways of controlling aquatic plants, especially in South Africa. Release of biological control agents has been limited to Mozambique, where water hyacinth (Eichhornia crassipes (Mart.) Solms-Laubach (Pontederiaceae)), water lettuce (Pistia stratiotes L. (Araceae)), red water ferns (Azolla spp. (Azollaceae)) and salvinia (Salvinia molesta DS Mitch. (Salviniaceae)) are significant weeds in the south of the country. In 2009, we assessed the status of these weeds in seven rivers across southern Mozambique and recorded whether any biocontrol agents were present. The weevils Neochetina eichhorniae Warner (Coleoptera: Curculionidae) and N. bruchi Hustache (Coleoptera: Curculionidae) were on water hyacinth, along with the pathogen Acremonium zonatum (Sawada) W. Gams (Hypocreales) and the mite Orthogalumna terebrantis Wallwork (Acarina: Sarcoptiformes: Galumnidae). Pistia stratiotes supported small numbers of the weevil Neohydronomus affinis Hustache (Coleoptera: Curculionidae). The red water fern in the rivers was A. cristata Kaulfuss (Azollaceae) not the more widely recorded A. filiculoides Lam. (Azollaceae), and it supported small numbers of the weevil Stenopelmus rufinasus Gyllenhal (Coleoptera: Curculionidae). No agents were present on S. molesta. Most of these agents are likely to have dispersed from South Africa, and the rivers of southern Mozambique are likely to be benefitting from the transnational dispersal of these agents. [ABSTRACT FROM AUTHOR]

Steelpoort River has been adversely affected by human activities in the catchment. Water and sediment quality of the river was assessed in 2015. The concentrations of some of the metals in water were found to be high and exceeded the guideline values and the concentrations of metals in sediment were found exceeding the guideline values for Cr, Cu and Zn. The high concentrations of Cu and Zn at Site 1 and Site 2 (upstream) could have originated from anthropogenic sources, such as fertilisers and pesticides from discharge of agricultural wastes, whereas the high concentrations of Cr at Site 3, Site 4 (midstream) and Site 5 (downstream) could have originated from the mine waste, and from domestic/ industrial wastes respectively. The principal component analysis results showed two main components: PC-1 with high positive loading of Cu and Mn, and PC-2 with high positive loading of Zn. These findings indicate the presence of pollution. Therefore, control measures should be implemented to reduce river contamination from anthropogenic sources. [ABSTRACT FROM AUTHOR]

Despite concerted surveys, the Maloti minnowPseudobarbus quathlambae(Barnard 1938) had not been recorded in South African waters for almost eighty years since the original collections were made at the type locality in the upper uMkhomazana River in 1938. The species was therefore declared extinct in South Africa, whereas extant populations were considered confined to various rivers in the Lesotho highlands. In April 2017, however, this species was rediscovered in the Mzimkhulu River system in KwaZulu-Natal. The rediscovery of a species that was considered locally extinct supports the need for extensive surveys to determine its distribution range, estimate population sizes, assess conservation status and implement effective strategies to ensure its continued existence in KwaZulu-Natal. [ABSTRACT FROM PUBLISHER]

Rapid biomonitoring protocols, using biotic indices based on macroinvertebrate diversity to assess river ecosystem health, are widely used globally. Such quick assessment techniques are lauded for the rapid results obtained and the relatively easy protocol used to achieve an answer. However, do such quick assessments of water quality give enough information about ecosystems? Are important details being overlooked? When should a full faunal survey be used in preference? Important research programmes, including environmental impact studies, often misuse biomonitoring techniques, making influential management decisions using superficial, low-level data obtained using biomonitoring tools, inappropriate to address those management objectives. The value of using biomonitoring as a quick tool, versus a more detailed faunal assessment, is considered here. The assessment of teloganodid mayfly fauna occurring in South African rivers provides an example of the value of detailed studies versus superficial family level investigations, showing that a rapid biomonitoring approach should not be used as a shortcut when a more detailed survey is needed. Each situation should be assessed for its own merit in a given set of project circumstances. A checklist of criteria is presented, giving guidance on when rapid biomonitoring alone is valuable and when more detailed assessments would give a more relevant result. [ABSTRACT FROM PUBLISHER]

The Mfolozi–Msunduzi estuarine system is subject to periodic dry and wet cycles, with subsequent changes in the abiotic and biotic characteristics of the system. The aim of the current study was to compare its mesozooplankton composition during relatively dry and wet periods. Mesozooplankton samples were collected between 2007 and 2010 in both the Mfolozi and the Msunduzi, covering a dry period between 2007 and 2008 and a period of relatively high freshwater inputs during 2009 and 2010. High flows during the wet period reduced the densities of most of the dominant estuarine mesozooplankton taxa in the Mfolozi Estuary, such as estuarine calanoidsPseudodiaptomus stuhlmanni(Poppe & Mrázek, 1895) andAcartiella natalensis(Connell & Grindley, 1974). The Msunduzi Estuary functioned as a reservoir from which recolonisation by estuarine taxa would quickly take place after the Mfolozi was scoured by floodwaters. Densities of dominant meroplankton taxa, such as zoeae of the crabParatylodiplax blephariskiosandMacrobrachiumspp., were not noticeably different in the Mfolozi–Msunduzi system between the low- and high-flow periods. [ABSTRACT FROM PUBLISHER]

Diel movements of Orange–Vaal smallmouth yellowfishLabeobarbus aeneus(Burchell, 1822) in the Vaal River, South Africa, were determined by externally attaching radio transmitters to 11 adult fish and manually tracking them between March and May 2012. Twenty-four radio telemetry monitoring surveys produced 2 304 diel tracks. At night, yellowfish displayed a preference for slow shallow (<0.3 m s−1, <0.5 m) and fast shallow habitats (>0.3 m s−1, <0.3 m), whereas by day they avoided these habitats, preferring fast deep areas (>0.3 m s−1, >0.3 m). The average total distance of 272 m moved per 24-hour period was three times greater than the diel range, and the average maximum displacement per minute was significantly higher in daytime (4 m) than at night (1.5 m). These findings suggest thatL. aeneusis active primarily during the day in fast-flowing, deeper waters, and relatively inactive at night, when it occupies shallower habitats. This behaviour should be further explored to identify causal mechanisms underlying the diel habitat shifts in this species such as water temperature, foraging tactics and/or predator avoidance. [ABSTRACT FROM PUBLISHER]

In February 2012 the Rondegat River, in the Cape Floristic Region, was the first river in South Africa where the piscicide rotenone was used to remove an alien invasive fish, smallmouth bassMicropterus dolomieu. In preparation for this treatment, the sensitivity of smallmouth bass to various concentrations of the rotenone formulation CFT Legumine (5% active rotenone) was evaluated a week prior to treatment using standard toxicity tests to determine the minimum effective dose (MED) that would result in 100% mortality after exposure for 4 h. The MED was 0.0125 mg l-1rotenone. Adverse effects, including erratic swimming, loss of equilibrium and death, occurred in a dose-dependent manner with smaller fish responding faster than larger ones. Standard operating procedures for the use of rotenone recommend treatment at a minimum of twice the calculated MED. Given the uncertainty associated with rotenone losses through hydrolysis and photolysis under field conditions, and the possible occurrence of smallmouth bass more tolerant than those tested, a concentration of twice the recommended treatment dose (0.050 mg l-1rotenone) was finally used to treat the Rondegat River for a duration of 6 h. [ABSTRACT FROM PUBLISHER]

Variable seasonal stream temperatures are a critical factor in maintaining aquatic invertebrate community patterns. We investigated whether the degree of predictability in a stream's water temperature profile provides insights into the structure and functional predictability of macroinvertebrate communities. Quarterly macroinvertebrate sampling over 11 months at five paired sites along the longitudinal axes of the Keurbooms River, Western Cape, and the Kowie/Bloukrans River, Eastern Cape, was undertaken in conjunction with collection of hourly water temperatures. Macroinvertebrate taxonomic turnover across seasons was higher for sites having lower water temperature predictability values than for sites with higher predictability, while temporal partitioning was greater at sites with greater temperature variability. Macroinvertebrate taxa responded in a predictable manner to changes in their environment. Specialist taxa preferred sites with greater temperature variability, and generalist taxa those with less temperature variability. Water temperature is an important abiotic driver of stream ecosystems, and should be expressed in terms of predictability metrics, as mean values do not adequately measure the components of water temperature that are important for biotic communities. Water temperature predictability provided an indication of the structure, functional predictability and seasonal turnover in macroinvertebrate communities. These findings have implications for streams experiencing temperature modifications due to the onset of climate change. [ABSTRACT FROM AUTHOR]

Fish predation is one of the driving forces of freshwater invertebrate community structures, with alien predators having a pronounced effect. A quantitative assessment of aquatic invertebrates in the Wit River, Sundays River catchment, Eastern Cape, South Africa, was undertaken to assess the impact of the alien fish Micropterus salmoides on their relative abundance and community structure. Communities in the stones-in-current and marginal vegetation biotopes were sampled in the presence and absence of M. salmoides in late summer (February-April) 2008. Results suggest that the presence of M. salmoides does have an impact on indigenous macroinvertebrate fauna and communities. Community structure in the stones-in-current biotopes did not differ significantly between sections of the river with or without fish. However, there was a significant difference in community structure in marginal vegetation between sections of river. In sections with M. salmoides several large or conspicuous taxa (Odonata, Hemiptera and Coleoptera) were significantly reduced (p < 0.05) or even absent, while cryptic/inconspicuous taxa (Trichoptera, Leptoceridae and Mollusca, Physidae) were significantly more abundant (p < 0.05). [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

To provide the foundation for a freshwater conservation plan for KwaZulu-Natal, three-level hierarchical river and wetland type classifications, based on spatio-temporal scaling relationships, are proposed. This resolution of classification is appropriate for regional- or provincial-scale conservation planning. The hierarchical structure of the classifications provides scope for finer resolution, by the addition of further levels, for application at a sub-regional or municipal scale. The proposed classifications include 74 river and 16 wetland types. River typing incorporating a classification based on intra-annual flow patterns from 40 gauging weirs could not be accurately represented spatially. Research on testing the strengths of the relationships among environmental surrogates for biotic diversity is proposed. [ABSTRACT FROM AUTHOR]

Water quality, macroinvertebrate diversity (using SASS5) and fish diversity (using the fish response assessment index) of the Shingwedzi River system were monitored in 2007/2008 to determine the present status of the system. Possible water pollution sources were identified by aerial survey. Water quality parameters frequently exceeded the threshold of potential concern values set by SANParks. SASS scores were generally low, due mainly to organic pollution as a result of the lack of infrastructure in the catchment. Fish responses indicated a general ecological decline to a 'category C' river: moderately modified. Of concern was the absence of some fish species that historically occurred in this system. Sources of pollution such as acid mine drainage from abandoned mines, inadequate sewerage infrastructure and habitat destruction due to siltation and sand mining are discussed. [ABSTRACT FROM AUTHOR]