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Aim: To test the ability of biological traits to predict climate-related changes in geographical ranges of running-water invertebrates. Location: The Australian state of New South Wales and the Australian Capital Territory. Methods: I analysed data from 8928 biomonitoring samples collected during a 16-year period of generally rising air temperatures and declining precipitation. I used quantile regression to test for expansions and contractions on the climatically cooler, warmer, drier and wetter edges of the ranges of 120 invertebrate taxa, and correlated these shifts with the traits of thermophily (degree of preference for high versus low temperature) and rheophily (preference for flowing versus still water). Results: The most commonly inferred range shifts were cool-edge expansion plus warm-edge contraction (71 taxa) and wet-edge expansion plus dry-edge contraction (71), but contractions from both cool and warm extremes (36) and from both dry and wet extremes (28) were also frequent. High-temperature preference was associated with cool-edge expansion and low-temperature preference with wet-edge expansion and contraction from all other extremes. A preference for flow was associated with wet-edge expansion and dry-edge contraction. Main conclusions: Trait analysis has potential for predicting which species will expand their ranges and which will contract, but needs to be coupled with assessment of how the landscape provides each species with opportunities to track or avoid climate change. Improved quantification of climatically relevant traits and integration of trait analysis with species distribution modelling are likely to be beneficial.

Anthropogenic salinisation of inland waters worldwide causes diverse social, economic and ecological impacts, including shifts in the composition of biological communities. I used published data on occurrence of aquatic invertebrate taxa in relation to salinity to develop a novel Invertebrate-Based Salinity Index (IBSI) suitable for purposes such as indicating the ecological impact of anthropogenic salinisation and charting faunal recovery after salinity mitigation. Testing of the index with data independent of those used in its derivation showed a stronger association with salinity than prior Australian salinity indices based on macroinvertebrates. IBSI is applicable to both running and standing inland waters across Australia, and could be extended to other countries. Potential limitations of IBSI and its underlying salinity tolerance values are discussed, and suggestions are made for future index refinement and testing.

Constructed wetlands may compensate to some degree for the impact of the loss of natural wetlands on aquatic biodiversity. However, information is lacking on the relative value of artificial wetlands and comparable natural wetlands for freshwater turtles. I contrasted the population structure, diet and body growth of Australian eastern long-necked turtles (Chelodina longicollis) in artificial and natural ponds in farmland settings. Turtle populations in the artificial ponds had a more even distribution of body size, and a much larger proportion of young individuals, than those in the natural ponds, suggesting that the artificial ponds were important recruitment sites. Diet differed little between the two types of ponds, being greatly dominated by aquatic insects in both cases. However, body growth of juvenile turtles was on average more rapid in the artificial ponds, possibly because they were generally permanent, unlike the natural ponds. These findings suggest that artificial farm ponds are valuable habitats for C. longicollis, which may foster population recruitment that counters the effects of introduced nest predators and road mortality.

1. Assessment of the performance of protected areas in conserving freshwater biodiversity has been limited, has mostly involved small-scale studies and has produced mixed findings. 2. I analysed monitoring data from Australia's Murray–Darling Basin (> 10⁶ km² and mostly arid or semi-arid) to compare fish assemblages between rivers inside and outside of protected areas. 3. The average richness and abundance of native species were significantly lower at sites within protected areas, but these sites were weighted towards steeper terrain and colder climates. 4. When analysis was confined to a subset of geographically and environmentally matched sites, the richness and abundance of native species did not differ significantly between protected and unprotected areas, and only two native species were significantly more abundant within protected areas, whereas another two were significantly more abundant outside. 5. Synthesis and applications. Protected status probably has little effect on native fish in the Murray–Darling Basin because it does not, by itself, exclude threats such as alien fish and alteration of water regimes. My findings therefore support the view that reserves need to be designed and managed specifically for freshwater species if they are to be most effective in their conservation. In the Murray–Darling Basin, and in similar regions around the world, actions such as greater control of alien species and allocation of adequate environmental flows will likely be critical to enabling protected areas to realize their potential for aquatic conservation.

Diatom blooms in the middle reaches of the shallow, freshwater, Hunter River, Australia, are a frequent nuisance to river users. During a 4-year study, blooms of Cyclotella meneghiniana and Nitzschia spp. coincided with water temperatures above 23°C and flows below 400 Ml d-¹ that lasted for more than 12 days. Redundancy analysis showed that water temperature was positively related, and antecedent flow was negatively related, to the abundance of both taxa. Addition experiments indicated that nutrients are seldom limiting to growth. It is suggested that a combination of faster growth rates at higher temperatures and longer retention times at low flows allows bloom populations to develop. Simulation modelling showed that flow regulation and water extraction have decreased flows in the river during summer, and consequently have probably increased the number of diatom blooms. Environmental flows have been provided to the river, but are not sufficient to prevent blooms. Discharges required for bloom suppression are described.

ContextA core theme in ecohydrology is understanding how hydrology affects spatial variation in the composition of species assemblages (i.e., beta diversity). However, most empirical evidence is from research in upland rivers spanning small spatial extents. Relatively little is known of the consequences of hydrological variation for beta diversity across multiple spatial scales in lowland rivers.ObjectivesWe sought to examine how spatial variation in hydrology and fish beta diversity within and among rivers changed over time in response to intensification and cessation of hydrological drought.MethodsWe used monitoring data of fish assemblages, coupled with hydrological and biophysical data, to test how spatial variation in hydrology and multiple components of fish beta diversity in lowland rivers of the Murray—Darling Basin (Australia) varied across spatial scales during contrasting hydrological phases.ResultsSpatial variation in hydrology among rivers declined with increasing duration of drought before increasing during a return to above-average flows. Spatial variation in hydrology within rivers did not show consistent changes between hydrological phases. Beta diversity among and within rivers showed variable, river-specific changes among hydrological phases for both incidence- and abundance-based components of assemblage composition.ConclusionsInconsistent hydrology—beta diversity patterns found here suggest that mechanisms and outcomes of drought and flooding impacts to beta diversity are context-dependent and not broadly generalisable. Our findings indicate that hydrological fluctuations occurring in the Murray—Darling Basin in the period analysed here did not cause significant or consistent homogenisation or differentiation of freshwater fish assemblages.

The status of biological assemblages is often inferred by comparing observational assemblage data with reference data generated by a predictive model. Limiting environmental difference analysis (LEDA) applies the ecological concepts of distance decay of similarity and limiting factor theory to model reference data by extrapolation from samples collected at reference sites. I applied LEDA modeling to data sets from the Australian Capital Territory (ACT), Laurentian Great Lakes (GL), and Canadian Yukon Territory (YT) to test its accuracy and precision in predicting the composition of benthic macroinvertebrate samples from reference sites, and its specificity and sensitivity in detecting mathematically simulated human impacts on sample composition. LEDA models were significantly and substantially more accurate than null models for all 3 data sets, but not significantly more precise. They mostly assessed unimpacted samples correctly but seldom detected mild simulated impacts. However, they often detected moderate and usually detected severe impacts. Model performance for the test data sets probably was constrained by limitations of the environmental predictor variables and low taxonomic richness in many samples. The simulated impacts provided insight into model behavior but were limited in their scope and realism. I suggest that future simulations should separately test detection of different kinds of assemblage change, not only different intensities, and should address the consequences of human alteration of predictor variables.

Geomorphic change, water resources development and climate change can alter the timing, frequency, magnitude and duration of replenishment of floodplain wetlands via overbank flows. If we understand the ecological consequences of these hydrological changes, environmental water allocations can be used more effectively to sustain wetland biodiversity and associated ecosystem processes. We analysed long-term monitoring data for 13 wetlands on the floodplain of the Murrumbidgee River in south-eastern Australia to determine how aquatic macroinvertebrate assemblages related to the proportion of time during which a wetland contained water. The more temporary wetlands had significantly different and poorer assemblages than the more permanent ones, with frequency of occurrence significantly negatively related to permanence for eight invertebrate genera and positively related for 17. The invertebrates most strongly associated with more temporary wetlands were mainly crustaceans whose resting stages withstand drying, together with highly mobile insects. Those associated with more permanent wetlands included a prawn, molluscs and less mobile insects. These findings suggest that maintaining a broad spectrum of hydrological regimes at the local scale is necessary if macroinvertebrate diversity on the Murrumbidgee River floodplain is to be sustained.

We present the concept of assemblage tolerance profiles (ATPs) as an aid to freshwater bioassessment, and illustrate it with a practical example. An ATP describes the proportion of taxa in an observed assemblage that is estimated to tolerate each level of a specific stressor within a defined range. We used an extensive compilation of biomonitoring field data to estimate the lower tolerances for pH and dissolved oxygen (DO) of common families of macroinvertebrates in rivers of south-eastern Australia. These limits were then used to establish ATPs for macroinvertebrate assemblages at 30 sites across six river systems with varying levels of exposure to drainage from disused mines and discharges from sewage treatment plants. We hypothesised that sites with more exposure to mine drainage would have ATPs indicating greater tolerance of low pH, whereas sites with more exposure to sewage discharges would have ATPs indicating greater tolerance of low DO, and found that these hypotheses were confirmed for five of the six river systems. We suggest that stressor-specific ATPs, based on tolerances derived from either field distributions or laboratory tests, can help to verify or eliminate candidate causes of inferred human impacts on aquatic ecosystems.

Stable isotope signatures (δ¹³C and δ¹⁵N) were used to compare trophic linkages between epilithic periphyton and three families of macroinvertebrates (Baetidae, Leptophlebiidae and Gripopterygidae) in riffles of two rivers with developed catchments (including agriculture, urbanization, impoundment and flow regulation) and two with undeveloped catchments (native forest with no major impoundments) in the Murrumbidgee River system, New South Wales, Australia. Periphyton had much higher average δ¹⁵N values and lower average C:N ratios in the developed rivers than in the undeveloped rivers, probably because of the combined effects of nutrient enrichment, upstream impoundment and alteration of riparian vegetation. The invertebrates were generally slightly depleted in ¹³C and ¹⁵N relative to expected values if they were assimilating whole periphyton alone, which suggests that they were assimilating periphyton components selectively or also consuming other foods. The match in isotope signatures between periphyton and invertebrates was only slightly weaker in the developed than in the undeveloped rivers, suggesting that development did not greatly disrupt trophic linkages between periphyton and these invertebrates.