Summary Climate extremes and their physical impacts – including droughts, fires, floods, heat waves, storm surges and tropical cyclones – are important structuring forces in riverine ecosystems. Climate change is expected to increase the future occurrence of extremes, with potentially devastating effects on rivers and streams. We synthesise knowledge of extremes and their impacts on riverine ecosystems in Australia, a country for which projected changes in event characteristics reflect global trends. Hydrologic extremes play a major structuring role in river ecology across Australia. Droughts alter water quality and reduce habitat availability, driving organisms to refugia. Extreme floods increase hydrological connectivity and trigger booms in productivity, but can also alter channel morphology and cause disturbances such as hypoxic blackwater events. Tropical cyclones and post‐cyclonic floods damage riparian vegetation, erode stream banks and alter water quality. Cyclone‐induced delivery of large woody debris provides important instream habitat, although the wider ecological consequences of tropical cyclones are uncertain. Wildfires destroy catchment vegetation and expose soils, increasing inputs of fine sediment and nutrients to streams, particularly when followed by heavy rains. Research on the impacts of heat waves and storm surges is scarce, but data on temperature and salinity tolerances, respectively, may provide some insight into ecological responses. We identify research gaps and hypotheses to guide future research on the ecology of extreme climate events in Australia and beyond. A range of phenomenological, experimental and modelling approaches is needed to develop a mechanistic understanding of the ecological impact of extreme events and inform prediction of responses to future change.

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Gambusia holbrooki is an invasive predatory poeciliid fish in wetlands of south-eastern Australia, where it coexists with the native waterbug Anisops thienemanni (Notonectidae). Gambusia has been shown to produce trophic cascades, leading to increased algal biomass following invasion, whereas these effects relative to the often-dominant invertebrate predator Anisops are unknown. Given its flexible diet, we predicted that Gambusia would feed more broadly than Anisops, thereby reducing the abundance of zooplankton grazers, and increasing chlorophyll a. We tested this hypothesis in experimental 110-L wetland mesocosms, using Gambusia and Anisops alone and in combination, in addition to no-predator treatments. We ran two experiments lasting 91 and 35 days, respectively. Both fish and macroinvertebrates generated weak trophic cascades, resulting in minor increases in chlorophyll a above concentrations in control treatments. Gambusia, in lowering total zooplankton abundances, triggered a larger, although still relatively small, algal response relative to Anisops. Impacts of both predators on dominant invertebrate grazers (e.g. Simocephalus spp., copepod nauplii) were similar, although Anisops was associated with an increase in ostracod (Newnhamia sp.) numbers. The similar trophic role of the two predators on algae was unexpected, given their different effects on planktonic communities and their very different taxonomic positions and zoogeographic origins.

Summary 1. The factors that promote coexistence of global invaders and native species are poorly understood. The role of abiotic factors in determining the dominance of invasive species is also an area of increasing interest. Gambusia holbrooki (Eastern Mosquitofish) is an important global invader, displacing endemic fish and frogs on four continents. However, Gambusia co‐occurs with a similar‐sized fish (Hypseleotris spp.) in dynamic floodplain wetland pools of south‐eastern Australia. 2. We examined the relative abundance of Gambusia and Hypseleotris in regularly flooded and irregularly flooded pools to determine whether seasonal hydrological disturbance may be advantageous to the native species. We aimed to determine whether Gambusia and Hypseleotris populations respond differently to regular seasonal flooding and whether this could reduce the ability of Gambusia to dominate numerically the native species. We tested this by sampling fish bi‐monthly in 15 floodplain pools over 2.5 years. 3. We found that the relative abundance of the two species differed between regularly and irregularly flooded pools, while both pool types persisted (over a period of a year). Hypseleotris were numerically dominant in regularly flooded pools from spring through to autumn, following a major spring flood. In contrast, Gambusia were more abundant than Hypseleotris in irregularly flooded pools from summer until pools dried completely. 4. Due to the higher reproductive response of Hypseleotris to a spring flood, and the timing of its breeding season, we suggest that Hypseleotris may have a reproductive advantage over Gambusia during productive post‐flood spring/summer conditions. While the abundances of both species were usually within a similar range, variation in hydrologic habitats and the inter‐play between life‐history traits and hydrologic disturbance may nonetheless give the native fish an edge.

Purpose The purpose of this paper is to explore undergraduate student attitudes towards the inclusion of social media training within higher education pedagogy, student perceptions of social media proficiency as professional expertise and its impact on graduate employability. Design/methodology/approach In all, 81 undergraduate students studying medicine, law, science and arts volunteered to complete an online survey. Questions examined student attitudes towards the delivery of social media pedagogy at university and the perceived benefits of social media proficiency. Findings Participants stated that social media skills should be taught in optional classes (85 per cent) covering generic competencies (56 per cent). The majority (91 per cent) of respondents reported that social media skills and training were valuable for employability. Research limitations/implications This was a pilot study and was therefore limited by the self-selection of participants, sample size and geographic location. Practical implications This study identifies that undergraduates across a range of disciplines are receptive to developing professionally relevant social media skills within higher education pedagogy and identify a link between social media proficiency and graduate employability. Originality/value Despite the increasing necessity for social media skills in professional environments, few studies have examined the teaching of social media skills as a core competency in higher education. Instead, social media is largely examined in relation to curriculum delivery and student engagement. This study explores attitudes towards the delivery of social media pedagogy at university and the perceived benefits of social media proficiency exclusively from the viewpoint of undergraduate students, to provide an alternative insight rarely explored in the literature.