Olifants River Research Articles

Blue carbon dynamics across a salt marsh-seagrass ecotone in a cool-temperate estuary

Abstract Background Seagrass and salt marsh ecosystems are recognised for their role in climate change mitigation and adaptation given their carbon storage potential. However, factors driving variability in blue carbon ecosystems are understudied, yet are important to account for. Aims Examine the variability of sediment organic carbon (SOC) and its drivers (seagrass morphometrics and sediment nutrients) at different spatial scales; > 1 km, ~ 150 m and ~ 10 m across the salt marsh-seagrass ecotone. Methods We collected the top 5 cm of sediment in the Olifants River Estuary, a cool-temperate system in South Africa. Using a line transect approach, we sampled across the salt marsh-seagrass ecotone (~ 10 m) in triplicate transects (~ 50 m apart) at three sampling sites (1–3 km) and analysed for SOC and elemental nutrient (nitrogen and phosphorus) content. Seagrass morphometrics (shoot density, leaf length and number per shoot) were measured. Results There was significant (P < 0.05) spatial heterogeneity in SOC stocks between sites (1–3 km) and between salt marshes and seagrass, but low variability at ~150 m. We detected a significant decrease in SOC from salt marsh towards the seagrass edge, with seagrass SOC remaining uniform. Nitrogen content was positively correlated with SOC in seagrass and salt marshes (P < 0.05), but seagrass morphometrics were not significant drivers of SOC. Conclusions The dynamics of blue carbon differ between salt marshes and seagrass, with spatial heterogeneity of SOC at scales > 1 km, suggesting that future BC assessments need to account for spatial heterogeneity to improve the accuracy of carbon removal estimates.

Microplastic Concentrations in Sediments and Waters Do Not Decrease in Two Rivers Flowing Through the Kruger National Park, South Africa

Plastics are manufactured for various purposes but result in microplastic pollution in aquatic ecosystems. Riverine microplastic occurrence, spatial distribution, and impact have been globally documented but not well understood in Africa. We quantified 36 984 microplastics in riverbed sediment and river water along the Olifants and Sabie rivers, Kruger National Park (KNP), South Africa. These rivers have independent catchments. The microplastic profiles (size, polymer, morphotype, and colour) differed significantly between rivers. Riverbed sediment microplastic (mostly beads) concentrations ranged between 2022 to 9971 n/kg dm, and 2237 to 27 259 n/kg dm, for the Olifants and Sabie rivers respectively. Microplastic (mostly fragments) concentrations in river water ranged between 11 to 50 n/L in the Olifants River, and 4.0 n/L to 41 n/L in the Sabie River. Polyethylene terephthalate (PET) was prevalent in sediment (39%) and water (32%). Concentrations varied along both river stretches but the expected concentration decrease downstream was not observed. This raises transboundary concerns, as all the KNP rivers cross into Mozambique and from there into the Indian Ocean. Given the pervasive plastic pollution already present, there is a need for significant upstream and in-park interventions to reduce the concentration of microplastic in rivers flowing through conservation areas.

High conservation importance of range-edge populations of Hooded Vultures (Necrosyrtes monachus)

Critically endangered Hooded Vultures (Necrosyrtes monachus Temminck, 1823), like many vulture species globally, are experiencing rapid population declines due to anthropogenic factors such as poisonings, human persecution, trading for belief-based use, and habitat loss/degradation. The Hooded Vulture is widespread across sub-Saharan Africa. Although it is considered one of the most abundant vultures in West Africa, this vulture species is less common in East and southern Africa, with the population at the southern-most edge of the distribution (in South Africa and Eswatini) estimated at only 100–200 mature individuals. The distribution of Hooded Vultures has contracted dramatically in southern Africa, with breeding populations largely confined to protected areas such as the Greater Kruger National Park. This study aimed to investigate the genetic diversity of the southern African range-edge population and assess if the recent contraction in the distribution has resulted in the population experiencing a genetic bottleneck. Sixteen microsatellite loci were amplified for samples collected along the Olifants River in the Greater Kruger National Park (n = 30). The genetic diversity in the South African population was compared to samples (n = 30) collected in Ghana, where Hooded Vultures are more abundant. Contrary to expectations, the South African peripheral Hooded Vulture population showed higher levels of heterozygosity (HO = 0.495) than the Ghanaian population (HO = 0.315). Neither population showed signs of recent bottleneck events when tested using demographic modelling and Approximate Bayesian computation (ABC). However, both populations showed high levels of inbreeding and relatedness. Our results suggest that despite being a small peripheral population, the South African Hooded Vulture population showed a similar level of genetic diversity as individuals sampled from a core population within the species distribution (in Ghana). This study supports the need for Hooded Vulture conservation efforts in the southern African region and highlights the evolutionary importance of range-edge populations.

Satellite imagery reveals the nature of the Archaean granite-greenstone basement of the Kruger National Park, South Africa, including the newly discovered Olifants River Greenstone Belt

Abstract Archaean greenstone remnants comprising mainly metamorphosed basaltic lavas and lesser metasedimentary interlayers are components of the granite-gneiss-migmatite basement terrane of the central and northern parts of the Kruger National Park (KNP), South Africa’s premier wildlife nature reserve. Most of the greenstone remnants represent extensions into the Kruger Park of better developed and exposed greenstone belts that exist beyond the borders to the west, including the Giyani and Murchison greenstone belts. Geological mapping in the national park presents challenges as exposures are poor and discontinuous, with the dense bush and wildlife adding to the difficulties. Satellite remote sensing provided an ideal solution and in this study Google Earth imagery proved to be especially helpful. The imagery provides a synoptic overview of the terrane making it possible to establish the outline of greenstone remnants irrespective of the dense bush cover. Google Earth imagery furthermore provided a preliminary impression of a hitherto unknown, yet sizeable, greenstone belt remnant in a remote area south of the Olifants River in the central section of the KNP. Referred to as the Olifants River Greenstone Belt in this study the remnant occurs as a major Type 2 interference fold resembling a mushroom-shaped diapir with a broad bulbous core fringed by laterally flattened skirts. Images are presented that illustrate various components of this imposing structure. Google Earth images furthermore display the general character of the Archaean granite-greenstone basement and the Palaeo- and Mesoproterozoic intrusive dyke swarms on the northeastern flank of the Kaapvaal Craton.

Recovery of a subtropical headwater fish community following a large flood, Klaserie River, Limpopo River System, South Africa

AbstractHeadwaters are important refuges for threatened fishes and play an important role in their conservation. The effects of large flooding events on headwater fish assemblages are under studied in southern Africa. In January 2012, heavy rainfall resulted in a large flood in the upper Klaserie River, Olifants River, and Limpopo River System, South Africa. This flood had an estimated return level of 225 years and caused significant ecological and economic damage. This study aimed to explore the impact of a large flood on the fish assemblage and substrate in the headwaters of a subtropical stream. The fish communities and selected substrate variables were collected at 10 sites. Sites were sampled at six monthly intervals thrice before and thrice after the flood. Fish were collected by electrofishing and substrate quantified visually. Changes in habitat resulted from the flood included the scouring of gravel sand and mud, greater exposure of bedrock and boulder substrates, increased stream width, and decreased stream depth in all zones. The fish community showed an increase in abundance for all but three species, colonisation of upstream sites, and colonisation of the study area by six species. The majority of fish species have opportunistic life‐history traits, which could explain the rapid colonisation and increase in abundance. The flood occurred in the middle of the breeding season for most the fish species, and this resulted in an increase of abundance for these species and provided opportunities for upstream colonisation. The impact of late season and aseasonal large floods requires further study.

A rapid and accurate method of mapping invasive Tamarix genotypes using Sentinel-2 images.

The management of invasive Tamarix genotypes depends on reliable and accurate information of their extent and distribution. This study investigated the utility of the multispectral Sentinel-2 imageries to map infestations of the invasive Tamarix along three riparian ecosystems in the Western Cape Province of South Africa. The Sentinel-2 image was acquired from the GloVis website (http://glovis.usgs.gov/). Random forest (RF) and support vector machine (SVM) algorithms were used to classify and estimate the spatial distribution of invasive Tamarix genotypes and other land-cover types in three riparian zones viz. the Leeu, Swart and Olifants rivers. A total of 888 reference points comprising of actual 86 GPS points and additional 802 points digitized using the Google Earth Pro free software were used to ground-truth the Sentinel-2 image classification. The results showed the random forest classification produced an overall accuracy of 87.83% (with kappa value of 0.85), while SVM achieved an overall accuracy of 86.31% with kappa value of 0.83. The classification results revealed that the Tamarix invasion was more rampant along the Olifants River near De Rust with a spatial distribution of 913.39 and 857.74 ha based on the RF and SVM classifiers, respectively followed by the Swart River with Tamarix coverage of 420.06 ha and 715.46 hectares, respectively. The smallest extent of Tamarix invasion with only 113.52 and 74.27 hectares for SVM and RF, respectively was found in the Leeu River. Considering the overall accuracy of 85% as the lowest benchmark for a robust classification, the results obtained in this study suggests that the SVM and RF classification of the Sentinel-2 imageries were effective and suitable to map invasive Tamarix genotypes and discriminate them from other land-cover types.

Biological and life-history parameters for Labeo rosae Steindachner, 1894 and Oreochromis mossambicus (Peters, 1852) from Flag Boshielo Dam, Olifants River, South Africa

Inland fisheries contribute towards food security for rural communities living close to large aquatic systems. However, sustainable inland fisheries rely on accurate biological information for the target species at the proposed fishery location. In this study, the biological information for Labeo rosae Steindachner, 1894 and Oreochromis mossambicus (Peters, 1852) were determined at Flag Boshielo Dam, Olifants River system, Limpopo province, as part of a larger study to evaluate a small-scale gill net fishery at this impoundment. Nine fish surveys were conducted from February 2016 to April 2017 using mixed sampling gears. Labeo rosae exhibited positive allometric growth (b > 3) while O. mossambicus displayed negative growth (b < 3). For L. rosae, the asymptotic length was 391 mm L ∞, and the length-at-50% sexual maturity 165.8 mm. For O. mossambicus, the asymptotic length was 420 mm L ∞, and the length-at-50% sexual maturity 166.5 mm. Both species population stocks showed signs of exploitation. Total mortality for L. rosae was 0.57 yr−1 with a fishing exploitation of 0.21 yr−1, while total mortality of 0.78 yr−1 and fishing exploitation of 0.50 yr–1 were estimated for O. mossambicus. The biological data collected, apart from the length–weight parameters for O. mossambicus, are suitable for conducting a fisheries assessment for these species at Flag Boshielo Dam.

Revealing salient aquatic ecosystem services bundles in the Olifants River catchment, South Africa

Revealing salient aquatic ecosystem services bundles in the Olifants River catchment, South Africa

Effects of trace elements on benthic macroinvertebrate distribution in the sediments of two rivers in the Olifants River Basin, South Africa

Many freshwater ecosystems are facing ecological challenges such as influx of trace elements from human activities, and sediments behave as a sink for trace elements in these environments. Trace element contamination in river sediments is a major environmental concern due to its devastating effect on benthic organisms. The aim of this study was to assess the effect of trace elements in sediments on the distribution of benthic macroinvertebrates in the Blyde and Mohlapitsi rivers of the Olifants River Basin, South Africa. Sediment samples and benthic macroinvertebrates were collected from six sites along each river. The results showed variations in the concentration of the trace elements in the sediment and the distribution of benthic macroinvertebrates among the different sites and between the two rivers. Both rivers recorded high taxa richness and sensitive taxa were well represented in most parts of the rivers, an indication that the rivers are not highly disturbed. There were insignificant correlations between most of the trace elements and the abundance of the benthic macroinvertebrates, though some taxa showed significant correlations with the trace elements. Despite the low impact of the trace elements on the distribution and diversity of benthic macroinvertebrates, ecological health of the rivers and structural distribution of macroinvertebrates may be affected in the future due to increasing human activities in the catchments. It is therefore recommended that effluents from human activities should be controlled to prevent a further degradation of the rivers to protect macroinvertebrates and other aquatic biota.

Terrestrial Diet Dependence in an Unprotected Nile Crocodile (Crocodylus niloticus) Population

Nile Crocodile (Crocodylus niloticus) populations that exist outside of protected areas are under threat in South Africa. They are believed to predominantly feed on fish, but they also take prey from the terrestrial system, which brings them into conflict with humans and hampers their management. Here, we use stable light isotope analysis to explore the diet of an unprotected Nile Crocodile population in the Olifants River, Mpumalanga and Limpopo Provinces. Nitrogen stable isotope ratios were obtained from fish and crocodile populations along the length (±430 km) of the river. The catchment is severely polluted with elevated d15N values at nutrient hotspots, which provides a basis for tracking the trophic response of crocodiles to the longitudinal profile of fish d15N values. Crocodiles did not respond to changes in the d15N values of fish populations and dietary predictions based on size-specific diet to tissue discrimination factors suggests a nonaquatic food base. These results suggest terrestrial diet dependence in one of the few viable Nile Crocodile populations from outside protected areas, posing unique challenges to their conservation.

A Faceless Compass: Johannesburg's haunted streets

A Faceless CompassJohannesburg's haunted streets Ivan Vladislavić (bio) Like dogs we circle back to old territory. On the first Sunday after the lockdown has been shifted to Level 2, we drive across Johannesburg to walk on Van Buuren Road. When Minky and I lived in Troyeville we walked this route regularly, but we haven't been here for the better part of a decade. The last six months under lockdown have stretched the distance between our new neighborhood and the old. Everything looks emptier, bleaker, more faded in the wan sunlight. It's the end of winter and the place is as brittle as an old print under a film of dust. [End Page 17] We park as usual (if one can claim familiarity after so long an absence) in the retail strip off Nicol and then walk east on Van Buuren. No one would call this scenic—it's not the Sea Point Promenade—but it has its virtues, and Joburg walkers count those where they can. There are broad paths in fairly good shape set well back from the road, few cross streets to break your stride, just enough passing traffic to feel safe. There is shade in the summer too, although the oaks and planes are bare now. The paths were swept not long ago, and leaves are piled haystack-high against garden walls or stuffed into garbage bags, squashed together under the trees like enormous black berries. The plots here are large, and some of the houses are grand, but many of them are neglected. The Penny Farthing Guesthouse still promises "Try Us—You'll Come Back Again!!!" but there is only one car in the drive and the bicycle mural is flaking. The traffic on Van Buuren has got busier over the years, and the road is now lined with more cluster developments and businesses than freestanding houses. The bigger, flashier homes, the nouveau-riche palaces that define this suburb, are to the south, down side streets that have been closed off by booms or palisades. It feels good to stretch our legs, so after a kilometer or so, we follow the curve into Harper Road past the Health Club. Although the restrictions were eased a week ago, the gates of the Club are still chained and a Covid-19 notice is wired to the bars. The football field used by the Sunday league is empty. At the end of Harper, where it bumps into the R24, we go right. Since we were last here, more houses have been turned into businesses or demolished to make way for small office buildings. We laugh about the Longevity Lounge, a skin-rejuvenation salon, and we laugh even more about the Happily Ever Laughter restaurant. On the Corobrik apron outside the New Delhi Indian Restaurant two glossy starlings hop and glitter, while a blacksmith plover stilts around, pecking at the joints between paving stones, keeping an eye on us. The last plover we came across was standing on a rock in the water beside a low-level [End Page 18] bridge across the Olifants River, where he belonged. What's this one doing here in the suburbs? We wait for him to call, but he's tight-beaked and wary, and only when we walk on does he send three quick anvil-clinks after us. Construction is going on against the odds. The Tzu Chi Foundation, a Taiwanese Buddhist NGO that does charity work and disaster relief around the world, is putting up a hall on the site of its old, more modest headquarters. Only half built, the Jing Si Hall already looks uncannily like the artist's impression on an immense billboard. Perhaps the builders consult the picture from time to time, like jigsaw-puzzlers consulting the lid of the box. The stocky pillars and front-porch eaves (Dr. Google informs me later) are shaped like the Chinese character for "human." We turn back into Van Buuren and enter a stretch of old-school Tuscany. Twin goddesses in togas, gossamer rendered lightly in chocolate-brown concrete, hold cornucopias on either side of a motorized gate. The slots tell me they are letter boxes. The...

In-situ multi-mode extraction (iMME) sampler for a wide-scope analysis of chemical and biological targets in water in urbanized and remote (off-the-grid) locations

Chemical pollution (including chemicals of emerging concern – CECs) continues to gain increasing attention as a global threat to human health and the environment, with numerous reports on the adverse and sometimes devastating effects upon ecosystems the presence of these chemicals can have. Whilst many studies have investigated presence of CECs in aquatic environments, these studies have been often focused on higher income countries, leaving significant knowledge gaps for many low-middle income countries. This study proposes a new integrated powerless, in-situ multi-mode extraction (iMME) sampler for the analysis of chemicals (105 CECs) and biological (5 genes) markers in water in contrasting settings: an urbanized Avon River in the UK and remote Olifants River in Kruger National Park in South Africa. The overarching goal was to develop a sampling device that maintains integrity of a diverse range of analytes via analyte immobilization using polymeric and glass fibre materials, without access to power supply or cold chain (continuous chilled storage) for sample transportation. Chemical analysis was achieved using ultra-performance liquid chromatography coupled with tandem mass spectrometry. Several mobile CECs showed low stability in river water, at room temperature and typical 24 h sampling/transport time. It is therefore recommended that, in the absence of cooling, environmental water samples are spiked with internal standards on site, immediately after collection and analyte immobilization option is considered, in order to allow fully quantitative analysis. iMME has proven effective in immobilization, concentration and increased stability of CECs at room temperature (and at least 7 days storage) allowing for sample collection at remote locations. The results from the River Avon and Olifants River sampling indicate that the pristine environment of Olifants catchment is largely unaffected by CECs common in the urbanized River Avon in the UK with a few exceptions: lifestyle chemicals (e.g., caffeine, nicotine and their metabolites), paracetamol and UV filters due to tourism and carbamazepine due to its persistent nature. iMME equipped with an additional gene extraction capability provides an exciting new opportunity of comprehensive biochemical profiling of aqueous samples with one powerless in-situ device. Further work is required to provide full integration of the device and comprehensive assessment of performance in both chemical and biological targets.

Flow patterns and chemical loads in the middle Olifants River, Limpopo River System, South Africa

Historical data (July 1998 – June 2018) for the middle Olifants River, Limpopo River system, were compiled to evaluate the dynamics of selected water physico-chemical parameters with river discharge. The concentration of most water quality parameters increased over time. However, these concentrations are rapidly decreased, or reset, by the rapid filling, or spilling, of Loskop and/or Flag Boshielo Dams during a high-flow event. The flow-duration curves for stations below impoundments in the middle catchment on the Olifants River are typical of highly regulated rivers, although releases from Flag Boshielo Dam were more consistent through the 20 years. No outflow from Loskop Dam was recorded for 5.4% of the 20 years. The load-duration curves for gauging weirs on the Olifants and Elands rivers immediately upstream of Flag Boshielo Dam showed that the ‘tolerable’ concentrations were exceeded for total dissolved solids at the 60th and 20th percentiles of the flow, respectively. In addition, records for electrical conductivity, sodium, chloride, and alkalinity frequently exceeded the ‘tolerable’ concentrations at these sites. The results for Loskop and Flag Boshielo dams are generally lower than the tolerable concentrations for the parameters evaluated. Management of the flow regulation of the Olifants River should be aimed at meeting the water quality stipulations for all users in the agricultural, domestic, industrial, and recreational sectors.

Dragonflies and Damselflies of the Lower Olifants River Valley: Citrusdal to the sea

This paper contains a list of the 38 species of dragonflies and damselflies recorded to date on the section of the Olifants River between Citrusdal and the sea at Papendorp. It is designed to be used as a guide for residents and visitors. To help with the identification of species, links to the species texts in the online Atlas of the Dragonflies and Damselflies of South Africa, Lesotho and Eswatini are provided. These contain comprehensive species information and annotated photographs. We also set out priorities for further observations.

Observed trends and projections of temperature and precipitation in the Olifants River Catchment in South Africa.

Among the projected effects of climate change, water resources are at the center of the matrix. Certainly, the southern African climate is changing, consequently, localized studies are needed to determine the magnitude of anticipated changes for effective adaptation. Utilizing historical observation data over the Olifants River Catchment, we examined trends in temperature and rainfall for the period 1976-2019. In addition, future climate change projections under the RCP 4.5 and RCP 8.5 scenarios for two time periods of 2036-2065 (near future) and 2066-2095 (far future) were analysed using an ensemble of eight regional climate model (RCA4) simulations of the CORDEX Africa initiative. A modified Mann-Kendall test was used to determine trends and the statistical significance of annual and seasonal rainfall and temperature. The characteristics of extreme dry conditions were assessed by computing the Standardized Precipitation Index (SPI). The results suggest that the catchment has witnessed an increase in temperatures and an overall decline in rainfall, although no significant changes have been detected in the distribution of rainfall over time. Furthermore, the surface temperature is expected to rise significantly, continuing a trend already evident in historical developments. The results further indicate that the minimum temperatures over the Catchment are getting warmer than the maximum temperatures. Seasonally, the minimum temperature warms more frequently in the summer season from December to February (DJF) and the spring season from September to November (SON) than in the winter season from June to August (JJA) and in the autumn season from March to May (MAM). The results of the SPI affirm the persistent drought conditions over the Catchment. In the context of the current global warming, this study provides an insight into the changing characteristics of temperatures and rainfall in a local context. The information in this study can provide policymakers with useful information to help them make informed decisions regarding the Olifants River Catchment and its resources.

Modelling water temperature in the lower Olifants River and the implications for climate change

Freshwater systems in southern Africa are under threat of climate change, not only from altered flow regimes as rainfall patterns change, but also from biologically significant increases in water temperature. Statistical models can predict water temperatures from air temperatures, and air temperatures may rise by up to 7 °C by 2100. Statistical water temperature models require less data input than physical models, which is particularly useful in data deficient regions. We validated a statistical water temperature model in the lower Olifants River, South Africa, and verified its spatial applicability in the upper Klaserie River. Monthly and daily temporal scale calibrations and validations were conducted. The results show that simulated water temperatures in all cases closely mimicked those of the observed data for both temporal resolutions and across sites (NSE&gt;0.75 for the Olifants River and NSE&gt;0.8 for the Klaserie). Overall, the model performed better at a monthly than a daily scale, while generally underestimating from the observed (indicated by negative percentage bias values). The statistical models can be used to predict water temperature variance using air temperature and this use can have implications for future climate projections and the effects climate change will have on aquatic species. Significance: Statistical modelling can be used to simulate water temperature variance from observed air temperature, which has implications for future projections and climate change scenarios. While there are many other factors affecting water temperature, air temperature accounts for up to 95% of water temperature variance. The model used can successfully simulate water temperature variance for different rivers.

Comparative Spatial Assessment of Trace Metal(loid) Pollution in the Sediments of the Lower Olifants River Basin in South Africa

Globally, many freshwater ecosystems are facing chemical pollution from both natural and anthropogenic sources. The Olifants River Basin in South Africa is experiencing degradation due to mining, industrial, agricultural, and domestic activities. The impacts of these activities coupled with climate change is likely to shift the hydrological cycle that may increase accumulation of toxic chemicals in the sediments. The aim of the study was to assess the contamination of As, Cr, Cu, Fe, Mn, Ni, Pb, and Zn in the sediments collected at the upstream, midstream and downstream of four rivers of the Lower Olifants River Basin; the Blyde, Mohalpitsi, Ga-Selati, and Steelpoort rivers. The highest concentrations of most of the trace metal (loid)s assessed were from the Steelpoort River followed by the Blyde River. Significant differences in metal concentrations were found across study sites and rivers. The overall assessment of the sub-catchment, which is characterised mainly by mining and agricultural activities shows significantly elevated levels of As, Cr, Mn, and Ni in the sediments and may cause secondary pollution in the water. Using enrichment factor (EF) and geo-accumulation index (Igeo), some of the sediments were severely enriched and extremely contaminated respectively with As, Cr, and Ni. This may risk the lives of aquatic biota and humans, especially rural communities that rely on these rivers for drinking water. The findings provide baseline information for effective management control of metal(loid) pollution in the Olifants River Basin.

Distribution and diversity of benthic macroinvertebrates in the Mohlapitsi River, South Africa

Freshwater ecosystems are facing degradation from human activities in the form of alterations of flow regimes, changes in land-use, and intensive water abstraction, in turn generating adverse effects on biodiversity and ecological functionality. Efficient assessment of river/stream ecosystem response to such anthropogenic changes is urgently needed. Many human activities that have an effect on water quality and river health are increasing along the Mohlapitsi River, which used to be one of the rivers with good water quality in South Africa. The aim of the study was to assess spatial variation in macroinvertebrate assemblages in relation to water quality of the Mohlapitsi River. A combination of canonical correspondence analysis and univariate analyses were used to examine the macroinvertebrate assemblages at six different sites of the Mohlapitsi River. The spatial difference in macroinvertebrate abundance was mostly related to changes in water quality. The number of taxa and the diversity of macroinvertebrates remained relatively high across the river as compared to other rivers in the Olifants River System. The midstream and downstream sites were mostly dominated by macroinvertebrates tolerant to disturbance/pollution. The most abundant family was the Thiaridae (about 60%) and mainly occurred in the midstream and downstream sites of the river (more disturbed sites). The study showed a higher evenness index in the upstream than the midstream and downstream sites which is an indication of good water quality at the upstream sites of the river. The results suggest that the river is being subjected to a moderate environmental pollution, which requires continuous assessment and monitoring to determine causes and initiate remedial measures.

Responses of evapotranspiration to changing climate for the past six decades in the upper catchment of the Olifants River basin

In river basins such as the Olifants, the evapotranspiration has been documented as the biggest water user and therefore one of the most important hydrological processes in the basin. Thus, using the Soil and Water Assessment Tool (SWAT) model, this study attempted to assess the hydrological responses of evapotranspiration (ET) to climate change in the Olifants River basin over a period of six decades, focusing mainly on the upper catchment (UC) of the basin. The study showed, on average, a general decline of seasonal ET with a decrease of 10.5% in spring, 29.8% in summer and 17.3% in winter. However, autumn ET showed an average increase of 12.5%. With (1960 – 1970) decade considered as the baseline, the study also found that annual ET in the UC, has been on the decline consistently since the 1960s with the most recent decade (2010 – 2018) taking the biggest share of the drop (12.8%). Here, the average annual decline of ET of 1.75 mm/yr was observed with most of the decline happening in the last decade. This general decadal trend of annual ET mortality in the area coincides with the temperature rise and precipitation decrease of the area, signifying the impact climate change may have had on the evapotranspiration for the past six decades.

‘I fish because I am a fisher’: Exploring livelihood and fishing practices to justify claims for access to small-scale fisheries resources in South Africa

In South Africa, claims for and access to natural resources are deeply embedded in people’s histories, identities and livelihood experiences. As in the case of land, access to and rights over fisheries resources is a highly contested issue where individuals and communities have equated such rights with human rights. This article considers the role of cultural and livelihood experiences of fishers in articulating claims for accessing fisheries resources. Individual and oral history interviews conducted with fishers and community members demonstrate how historical (and contemporary) organisation of the fishery contributes to local livelihoods and social cohesion and how formal management practices have not considered these rights. This study discusses how fishers as a community have endured systematic dispossession and exclusion, framings of fisher identity, livelihood activities and how cultural significance of the fishery takes centre stage when claims for access to fisheries resources were made. This article concludes by highlighting how fisher activities, identity and social relations, which are embedded in this system have challenged formal management approaches and altered a trajectory in fisheries management and conservation planning.Contribution: This research draws inspiration from the Ebenhaeser community on the Olifants River estuary to demonstrate the intrinsic value of this traditional small-scale fishery to this community. This study contributes to the discourses on complex social-ecological systems and how social values underpin these systems.