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103
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Introduction
My work currently focuses on three core areas:
1) water temperature, climate change and aquatic ecosystems;
2) river health, bioassessment and development of biomonitoring tools in Africa, and
3) the development of biodiversity information systems for conservation, management and decision-making.
Current institution
Additional affiliations
January 1998 - December 2004
Southern Waters Ecological Research & Consulting
Position
- Researcher & Consultant/ Associate
January 1991 - December 2002
March 2012 - present
The Freshwater Research Centre
Position
- Managing Director
Publications
Publications (103)
In South Africa, freshwater habitats are among the most threatened ecosystems, and freshwater fishes are the most threatened species group. Understanding patterns in freshwater fish diversity, threat, invasion, and protection status are vital for their management. However, few studies have undertaken such analyses at ecologically and politically ap...
Freshwater fishes are recognised as South Africa’s most threatened species group. Reliable, long-term data on fish occurrence records are critical for effectively managing and conserving these species. A comprehensive freshwater fish dataset was compiled and uploaded to the Freshwater Biodiversity Information System (FBIS, freshwaterbiodiversity.or...
In South Africa, anthropogenic pressures such as water over-abstraction, invasive species impacts, land-use change, pollution, and climate change have caused widespread deterioration of the health of river ecosystems. This comes at great cost to both people and biodiversity, with freshwater fishes ranked as the country’s most threatened species gro...
Invertebrates are often used as indicators of ecosystem health. In community ecology, the use of organism traits (e.g. behavioural, biological or ecological) can be of value in relation to impact diagnosis and assemblage prediction. It has also been recognised that certain traits are related to ecosystem function, and their use in biological monito...
Identifying thermal resilience hotspots in freshwater systems enables targeted conservation action, and defining relative ecosystem resilience is important for evaluating the potential consequences of climate change for aquatic ecosystems.
The thermal resilience of a river is likely to be affected by variables such as stream order, groundwater dept...
Human activities have cumulatively altered natural thermal regimes, with impacts and occurrences of extreme events amplified and exacerbated by global climate change. This leads to cascading ecological impacts in river systems. This paper translates knowledge generated over more than ten years of thermal research in South Africa into a protocol for...
Access to long-term biodiversity datasets is vital for monitoring, managing and protecting freshwater ecosystems. Detecting critical ecosystem changes, such as losing unique biodiversity and ecosystem services, is dependent on access to data. A wealth of biodiversity data exists for river ecosystems in South Africa, but an operational information s...
Benthic macroinvertebrates are commonly used to assess water quality and ecological condition of aquatic ecosystems and they form the basis of several biotic indices. Many of these biotic indices are based on rapid bioassessment protocols (RBP). The first RBP based on macroinvertebrates, developed in Africa in the early 1990s, was the South Africa...
Compared to other climate regions of the world, Mediterranean regions are likely to experience more severe effects of climate change as rainfall decreases and temperatures increase. Global climate change models predict a reduction in rainfall and rise in the temperature of rivers in South Africa's Cape Fold Ecoregion (CFE) – a Mediterranean region...
Spatial variability in macroinvertebrate assemblages of the Okavango Delta, Botswana, was examined to evaluate differences in assemblages at a regional and habitat scale. Sampling was undertaken six times during a one-year cycle from 2005 to 2006, with 228 macroinvertebrates samples collected from different aquatic habitats in 22 sites in four stud...
The Cape Fold Ecoregion (CFE) is a biodiversity hotspot with high levels of endemism in its freshwater fish fauna. This study examined inter and intra‐specific variation in critical thermal maxima (TCmax) for eight native species of freshwater fish from the CFE. Cape galaxias Galaxias zebratus, Breede River redfin Pseudobarbus burchelli, Berg River...
Understanding the response of aquatic organisms to elevated water temperatures offers insight into the ecological consequences of climate change on riverine species. Upper thermal limits were determined for two riverine invertebrates, the amphipod Paramelita nigroculus (Paramelitidae) and the mayfly Lestagella penicillata (Teloganodidae), in two ri...
An extensive survey of tropical rivers, conducted during 2009–2012 throughout Zambia, collected 151 samples of benthic macroinvertebrates, located on 95 rivers in six of the nine freshwater ecoregions. Associated data for physico-chemistry, human activities and ecosystem stressors were collected. Data were used to develop and test a new Rapid Bioas...
Introduced rainbow trout Oncorhynchus mykiss have invaded many headwater streams in South Africa’s Cape Fold Ecoregion (CFE) and pose arguably the greatest threat to several species of threatened native fishes. Trout impacts in these systems appear to be density-dependent; we hypothesized that temperature is a key factor determining trout density a...
Non-native vegetation in the riparian zone impacts on water temperatures, flow patterns, degree of shading, channel modification, and changes to natural sediment loads. Freshwater ecosystems in the Garden Route Initiative planning domain are of particular conservation value, because of the rich Gondwanaland relict aquatic macroinvertebrate fauna fo...
The thermal regime of rivers plays an important role in the overall health and composition of aquatic ecosystems, and together with flow, is recognised as one of the most influential abiotic drivers of aquatic ecosystem processes affecting species distribution. Changes in thermal conditions in aquatic systems are driven by on-going human-induced cl...
Native freshwater fish populations throughout South Africa's Cape Fold Ecoregion (CFE) are in decline as a result of human impacts on aquatic habitats, including the introduction of non‐native freshwater fishes. Climate change may be further accelerating declines of many species, although this has not yet been studied in the CFE. This situation pre...
1. The sub-lethal effects of water temperature on the egg development was investigated in three syntopic mountain stream insects, viz. Lestagella penicillata (Ephemeroptera: Teloganodidae), Aphanicercella scutata (Plecoptera: Notonemouridae) and Chimarra ambulans (Trichoptera: Philopotamidae) from the winter rainfall Western Cape Province, South Af...
Invasions by non‐native species can compromise the conservation value of otherwise pristine headwater streams. While both developed and developing countries recognize this threat, few of the latter have suitable budgets to implement control programmes.
This study assessed the effectiveness of a mechanical project to remove non‐native rainbow trout...
The study tested the hypothesis that measurement, using multivariate Principal Components Analysis (PCA), of the niche-breadth of river macrophyte species in southern tropical Africa, may predict their larger-scale biogeographical range. Two measures of niche-breadth were calculated for 44 riverine macrophyte species, from 20 families commonly occu...
The upper thermal limits of two cold-water stenotherms: the mayfly, Lestagella penicillata (Teloganodidae), and the stonefly, Aphanicerca capensis (Notonemouridae), were determined from six rivers in the Western Cape, South Africa. Limits were estimated using the Critical Thermal Method (expressed as Critical Thermal maximum) and the Incipient Leth...
Ecological processes in freshwater lotic systems are disrupted when upstream–downstream connectivity is broken. Changes in catchment land use, catchment density of small dams, and instream impoundments result in changes to thermal and flow regimes, which in turn affect natural biological turnover patterns and rates, as well as organism exchange and...
The Zambian Macrophyte Trophic Ranking system (ZMTR) is a new bioassessment scheme to indicate the trophic status of tropical southern African river systems. It was developed using a dataset of 218 samples of macrophytes and water chemistry, collected during 2009–2012, from river sites located in five world freshwater ecoregions primarily represent...
Water temperature is a key variable affecting aquatic organisms. Understanding their response to elevated water temperatures is important for estimating upper thermal limits, and ultimately for assisting with setting defendable, biologically-relevant water temperature guidelines for lotic systems. Sublethal effects impacting on an individual organi...
The first-ever extensive macrophyte survey of Zambian rivers and associated floodplain waterbodies, conducted during 2006 – 2012, collected 271 samples from 228 sites, mainly located in five freshwater ecoregions of the world primarily represented in Zambia. The results supported the hypothesis that variation in macrophyte community structure (meas...
The biological assessment of rivers using aquatic macroinvertebrates is an internationally recognised approach for
the determination of riverine ecological conditions. In this study a Tanzanian macroinvertebrate-based biotic method,
Tanzania River Scoring System (TARISS), was developed in 2012, based on the South African Scoring System (SASS).
Macr...
Freshwater ecosystems are amongst the most vulnerable in the world with respect to global
climate change. Southern Africa has been identified as a ‘critical region’ of water stress.
Existing anthropogenic stresses on freshwater ecosystems are substantial and global climate
change exacerbates this stress. Water temperature is a key component of aqua...
Blackfly along the middle and lower reaches of the Orange River contribute to losses to the meat industry calculated to exceed R300 million per annum,(based on 2012 meat prices). The problem is attributed mainly to the Simulium chutteri, following winter high flows, although there are times when other species are problematic. Following worsening ou...
Black fly along the Orange River are major pests of livestock and labour-intensive agriculture, causing annual estimated industry losses in excess of US$30 million. The problem is attributed to winter high flows, with the main pest species being Simulium chutteri Lewis, 1965, although Simulium damnosum Theobald, 1903 and Simulium impukane de Meillo...
Freshwater resources in South Africa are under severe pressure from existing anthropogenic impacts and global climate change is likely to exacerbate this stress. This review outlines the abiotic drivers of climate change, focusing on predicted changes in temperature and precipitation. The consequences of global climate change for freshwater ecosyst...
The water resources of Zambia are likely to experience increasing multiple pressures in the future as a result of
very high predicted population growth, industrial development, land use change, and potentially, altered regional rainfall patterns. It is well known that rivers in tropical regions typically have a rich biodiversity, controlled in part...
Thermal alteration is associated with ecological change in freshwater systems. Global climate change is likely to amplify thermal stresses on aquatic systems. We used cumulative daily heat units to examine potential impacts of temperature changes on selected aquatic organisms using scenario analyses. We selected two species of aquatic macroinverteb...
A Zâmbia é um dos países menos desenvolvidos do mundo e consequentemente dos mais pobres. Os sectores da agricultura, indústria e florestas estão a expandir, mas é o sector terciário, sobretudo com o ecoturismo, que tem impulsionado a criação de postos de trabalho, facto derivado de um terço do país ser ocupado por áreas protegidas e parques nacion...
Pressure on water resources in Zambia is likely to increase in future decades as a result of exceptionally high predicted population growth. To underpin sustainable water management, an international group of scientists and practitioners has been involved in the development of protocols to assess the ecological status of Zambian rivers. This paper...
Hydrology is a major factor controlling the structure and function of river ecosystems. In contrast to perennial rivers, temporary rivers have periods where surface flow ceases resulting in a highly variable flow regime. Existing bioassessment methods in South Africa are designed for use in perennial rivers, and thus the potential application of th...
Rivers in mediterranean regions are subject to hydrological extremes. They range from highly stable, perennial ground- or snow-fed systems to highly ephemeral, unpredictable ones in semi-arid environments. Spatial and temporal complexity inherent in these systems presents challenges for ecological status assessment and defining reference conditions...
Key aspects of a river’s temperature regime are described by magnitudes, timing and durations of thermal events, and frequencies of extreme exceedance events. To understand alterations to thermal regimes, it is necessary to describe thermal time series based on these statistics. Classification of sites based on their thermal metrics, and understand...
Water temperature is an important abiotic driver of aquatic ecosystems. It influences many aspects of an organism’s existence
including its growth, feeding and metabolic rates; emergence; fecundity; behaviour and ultimately survival. All organisms
have an optimum temperature range within which they survive and are able to thrive. Determining upper...
A large body of scientific literature has highlighted the importance of water temperature as a primary abiotic driver of lotic systems, particularly those regulated by impoundments. In South Africa the river flow regulation is mainly based on reserve determinations. In literature there are no clear guidelines on how to incorporate thermal aspects i...
Micro-scale heterogeneity in water temperature was examined in 6 upland sites in the Western Cape, South Africa. Hourly water temperature data converted to daily data showed that greatest differences were apparent in daily maximum temperatures between shallow- and deep-water biotopes during the warmest period of the year. Pool depth affected water...
Water temperature is an important abiotic driver of aquatic ecosystems. It influences many aspects
of an organism’s existence including its metabolic, growth and feeding rates; fecundity; emergence;
behaviour and ultimately survival. This study determined the upper thermal limits of a range of aquatic
macroinvertebrates from rivers in the south-wes...
Detailed information on viewing and querying data in the Biobase has been provided, together with screen dumps of the actual database. These include the four key viewing components, namely Sites, Biological & Physico-Chemical Data, Taxonomic Data, and Study Reference Information. The Query Master is described and steps for extracting data listed. T...
In order to manage water resources it is necessary to take into account not just the amount of water that is used but also its quality. What is usually meant by the term ‘water quality’ is the magnitudes of the physical attributes (like temperature and conductivity) and the concentrations of chemical constituents (like nitrogen, calcium, or alumini...
Seasonal variability of macroinvertebrate assemblages was examined in two regions of South Africa: Western Cape and Mpumalanga. Sampling was undertaken at reference sites using the rapid bioassessment method SASS4 (South African Scoring System, Version 4). This study examined the influence of sampling season on the occurrence of taxa, macroinverteb...
The spatial distribution of aquatic macroinvertebrates in the Okavango River Delta, Botswana, was investigated during the low-water period in February 2003. This complements an earlier study undertaken during high-water in June 2000. Seventy-five samples were taken in a range of aquatic habitats at 29 georeference points in four focal areas: Upper...
Available information pertaining to water temperature in riverine ecosystems is examined and consolidated into an overview that describes the spatial and temporal variation in water temperature, the importance of water temperature in lotic ecosystems , the measurement and modelling of water temperature, anthropogenic factors that modify water tempe...
Available information pertaining to water temperature in riverine ecosystems is examined and consolidated into an overview that describes the spatial and temporal variation in water temperature, the importance of water temperature in lotic ecosys-tems, the measurement and modelling of water temperature, anthropogenic factors that modify water tempe...
1. Similar constraints in distant, but climatically comparable, regions may be expected to yield biotic assemblages with similar attributes. Environmental factors that constrain communities at smaller scales, however, may be different between climatically similar regions. Thus, patterns observed at large scales may differ from those detected at sma...
The variability of macroinvertebrate assemblages was investigated at 27 upland reference sites in the south-western Cape,
South Africa. Multivariate analyses showed that sites did not group on the basis of geomorphological zonation, i.e. mountain
stream and foothill-cobble bed. When separate analyses were undertaken for mountain stream (n=21) and f...
The classification of reference sites based on macroinvertebrate assemblages sampled in different aquatic biotopes in Mpumalanga, South Africa, was examined. Environmental variables that best predicted group membership for each of four classi-fications (stones, vegetation, sand and these three biotopes combined) were identified. Variables at severa...
1. Macroinvertebrate biotope preferences and the influence of differences in the availability of biotopes on individual taxa, macroinvertebrate assemblages and a biotic index, the South African Scoring System (SASS), were investigated in two regions of South Africa.
2. Among biotope differences in individual taxa and macroinvertebrate assemblages r...
An overview is given of the bioassessment of the ecological integrity of river ecosystems using aquatic macroinvertebrates, focussing on the South African situation within a global context. Biotic indices and their use in aquatic bioassessment are covered, and comparative descriptions of the more important and/or widely used macroinvertebrate-based...
The ability of 2 Rapid Bioassessment Protocols (RBPs) to assess stream water quality was compared in 2 Mediterranean-climate regions. The most commonly used RBPs in South Africa (SA-protocol) and the Iberian Peninsula (IB-protocol) are both multihabitat, field-based methods that use macroinvertebrates. Both methods use preassigned sensitivity weigh...
Preliminary testing of the Integrated Habitat Assessment System (IHAS), a widely-used aquatic macroinvertebrate habitat assessment method in South Africa, was undertaken. Based on the sensitivity of the South African Scoring System (SASS) to biotope availability and assuming that SASS Scores at minimally-impacted reference sites are the highest Sco...
Spatial variability in macroinvertebrate assemblages was examined with the aim of evaluating the utility of regional classification systems in aquatic bioassessment. Sampling was undertaken at reference sites in the Western Cape and Mpumalanga, South Africa, using the rapid bioassessment method SASS4 (South African Scoring System Version 4). Multiv...
Summary in English. Word processed copy. Thesis (Ph. D. (Zoology))--University of Cape Town, 2001. Includes bibliographical references (leaves 195-210).
South Africa's new water law recognises that basic human and environmental needs should be met and that the exploitation of water in all aspects (quality, quantity and reliability of supply) must be sustainable in the long term. Protecting the needs of the environment requires tools that can be used to monitor environmental conditions as well as fo...
A database has been developed comprising biological (macroinvertebrate) and chemical data derived from documented studies of riverine ecosystems within South Africa. The intrinsic variability of biotic and chemical components of these ecosystems has necessitated the adoption of a three-level hierarchical framework within which the biological and ch...
The rivers of South Africa differ in water chemistry because of differences in geology and climate, and in the nature of the terrestrial vegetation. Thus the riverine biotas also differ in their water quality requirements. This paper describes the use of multivariate analytical techniques on a large inorganic chemical database as a means of dividin...
The rivers of South Africa differ in water chemistry because of differences in geology and climate, and in the nature of the terrestrial vegetation. Thus the riverine biotas also differ in their water quality requirements. This paper describes the use of multivariate analytical techniques on a large inorganic chemical database as a means of dividin...
