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). Macroinvertebrate samples were collected from 101 sites, including both reference and test sites, in the Pangani, Rufiji and Wami-Ruvu basins in the Pangani highlands and central eastern Africa ecoregions. TARISS modification involved adjustments of the list of taxa and the assigning of sensitivity weightings to three new families. Six SASS taxa were excluded and three new taxa were included, resulting in a total of 96 TARISS taxa. Assigned sensitivity weightings of the new taxa were: 10 for Dicercomyzidae, 9 for Ephemerythidae and 4 for Neritidae. Through validation, TARISS proved to be reliable in distinguishing reference from test sites, based on macroinvertebrate assemblages and TARISS metrics. The degree of reliability in distinguishing reference from test sites was higher when river types were used. TARISS scores and average score per taxon (ASPT) showed stronger correlations with the disturbance gradient, and were more reliable in distinguishing between reference and test sites than the number of taxa.

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 ecosystems are reviewed, with effects grouped into those related to water quantity, water quality, habitat and aquatic biological assemblages. Several guiding principles aimed at minimising the potential impact of climate change on freshwater ecosystems are discussed. These guidelines include those focused on water quantity and the maintenance of appropriate environmental flows, integration of global climate change into water quality management, conservation planning for freshwater biodiversity, the promotion of ecosystem resilience, and extending climate change science into policy and public discourse. Proactive assessment and monitoring are seen as key as these will allow for the identification of ecological triggers and thresholds, including thresholds of vulnerability, which may be used to monitor and inform decisions, as well as to improve the ability to forecast based on this knowledge. Setting the stage-abiotic drivers of global climate change General circulation models (GCMs) are a class of computer-driven models for weather forecasting; those that project climate change are commonly called global climate models. GCMs are the core tool for simulating the coupled climate system using physical representations of the atmosphere, land and ocean surface. 6 GCMs simulate the most important features of the climate (i.e. air temperature and rainfall) reliably at a large scale, although, as uncertainties are inherent in CGMs, predictions for rainfall intensity, frequency and spatial distribution have a lower

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 thermal limits provides insight into the relative sensitivity of organisms to elevated temperatures. Thermally sensitive taxa may be useful as bioindicators of thermal alteration and used in the generation of target thermal thresholds for aquatic systems. This study determined the upper thermal limit (CTmax) of a range of aquatic macroinvertebrates from rivers in the south-western Cape, South Africa, using the dynamic Critical Thermal Method. The study focused on the taxonomic level of family as an initial screening tool for ranking thermal sensitivity. Of the 27 families examined, four were both thermally sensitive and highly suitable as test organisms, including Paramelitidae, Notonemouridae, Teloganodidae and Philopotamidae. Five families were moderately sensitive and highly suitable, including Palaemonidae, Heptageniidae, Leptophlebiidae, Corydalidae and Aeshnidae. Preliminary experiments to determine potential sources of variation in CTmax revealed that thermal sensitivity was relatively uniform within families, but that acclimation temperature influenced CTmax. Further investigation of the influence of thermal history, acclimation temperature and rate of temperature change on CTmax is necessary. Target water temperatures for river management will be derived using CTmax data, in addition to longer duration experimental data, which will be linked to in situ temperature data.

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 small scales, and international comparisons should be focussed at multiple scales. 2. Mediterranean-climate regions (MCRs) are characterized by remarkable seasonal variability in precipitation and temperature. Accordingly, rivers in these regions have seasonal and predictable floods and droughts, and temporary reaches are frequent. Present in six geographical regions of the world, MCRs have similar environmental constraints and are ideal for testing intercontinental similarities between macroinvertebrate communities. 3. We examined aquatic macroinvertebrate taxon richness and composition in MCRs at three scales: regional, reach and macrohabitat. At the regional scale, the Mediterranean Basin had the highest taxon richness at family level, and southwestern Australia the lowest. Taxonomic composition showed c. 85% similarity between the northern hemisphere MCRs of California and the Mediterranean Basin, which were followed in similarity by South Africa. The two Australian MCRs (South west and South) showed a similarity to each other of about 70% whereas the Chilean fauna was the most distinct. 4. At the reach scale, taxon richness was not significantly different between permanent and temporary reaches in any MCR, whereas taxonomic composition was significantly different among northern hemisphere MCRs. At the macrohabitat scale, taxon richness was not significantly different between lotic and lentic macrohabitats within any of the MCRs, but differences in macroinvertebrate communities were found between macrohabitats when considering regions. 5. Our results show that the strength of similarity between distant but climatically similar regions is scale-dependent, being highest at the macrohabitat scale. Although the similarities in richness and composition at the macrohabitat scale are presumed to be universal, the seasonal predictability of drought in MCRs is expected to result in characteristic macroinvertebrate responses at the reach scale. We suggest, however, that regional evolutionary history and environmental characteristics may override this general pattern of a similar response of MCRs at different scales. The Mediterranean Basin and

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