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Indigenous Research Methodologies (IRMs) for considering cultural values of water are a missing component of water and wetlands management in Australia. On this dry, flat and ancient continent Traditional Knowledge has been passed on from generation to generation for millennia. The profound knowledge of surface and groundwater has been critical to ensuring the survival of Indigenous peoples in the driest inhabited continent, through finding, re-finding and protecting water. Indigenous Research Methodologies can provide a basis for the exploration of this knowledge in a way that that is culturally appropriate, and which generates a culturally safe space for Indigenous researchers and communities. The development of IRMs has been and continues to be limited in Australia in the water context, primarily due to the lack of Indigenous water practitioners, with non-Indigenous researchers dominating the sector. The intention of the paper is to shift and decolonise the research paradigm from studying Indigenous peoples through non-Indigenous research methodologies, to partnering in developing methods appropriate to Indigenous knowledge systems. Indigenous Research Methodologies are rooted in Indigenous epistemologies and ontologies and represent a radical departure from more positivist forms of research (Wilson, Can J Native Educ 25:2, 2001). This allows the Indigenous researcher to derive the terms, questions, and priorities of what is being researched, how the community is engaged, and how the research is delivered. This paper provides an overview of Indigenous engagement in water management in Australia and Aotearoa (New Zealand), with reference to case studies. These more general models are used as the basis for developing an IRM appropriate to the Kamilaroi people in the Gwydir Wetlands of northern NSW, Australia.

Social-ecological networks (SENs) represent the complex relationships between ecological and social systems and are a useful tool for analyzing and managing ecosystem services. However, mainstreaming the application of SENs in ecosystem service research has been hindered by a lack of clarity about how to match research questions to ecosystem service conceptualizations in SEN (i.e., as nodes, links, attributes, or emergent properties). Building from different disciplines, we propose a typology to represent ecosystem service in SENs and identify opportunities and challenges of using SENs in ecosystem service research. Our typology provides guidance for this growing field to improve research design and increase the breadth of questions that can be addressed with SEN to understand human-nature interdependencies in a changing world.

Salinity is increasing in many naturally fresh waters because of human activities, and there are concerns about the ecological effects of these increases. Salinity, as with any stressor, can affect organisms both directly and indirectly. In a previous study (Bray et al. 2019), we evaluated the relative importance of direct and indirect effects of increased salinity on stream invertebrates. Chessman (2021) criticised that study, claiming that the biotic treatments were confounded and did not directly test the hypotheses. Chessman (2021) also conducted a reanalysis of the data. We show through the analysis of new data that our biotic treatments were not confounded and that the conclusions made by Chessman (2021) were probably a consequence of the low statistical power of his analysis. Consequently, we argue that Chessman’s (2021) comments do not substantively alter the conclusions of our study, and we provide more evidence to support the conclusions of our previous publication. The study of biota–stressor interactions is increasingly relevant to a wide range of global ecosystems. There is a need to develop tractable experimental and survey designs that address these problems, and we identify further avenues for study of these complex issues.

Describing the hydrogeomorphic character of rivers in a holistic way is essential to understanding the processes whereby freshwater ecosystems maintain patterns of biodiversity and ecosystem processes. A key question in carrying out this characterisation is the temporal and spatial scales which best represent differences and similarities between habitats. The purpose of this study is to describe the hydrological and geomorphological character of a large river-floodplain system (the Upper Mississippi River, USA) at multiple spatial and temporal scales in order to holistically determine the physical template influencing the riverine ecosystem. Seventeen variables are used to describe the hydrogeomorphic character of 99 backwaters and floodplain lakes along a 100 km reach of the river. At the landscape scale (10 s of km), position in the landscape and proximity to neighbouring habitats contributed most to variability in hydrogeomorphic character. At the smaller patch scale (10–100 s of m), the shape of entry to the patch and water depth were distinguishing variables. In relation to temporal variables, habitats are distinguished by decadal scale variables describing the historic nature of the rise and fall of connection events, and mean peak and duration of connection over long periods. In contrast, the interplay of magnitude and duration of individual connection events produced unique patterns at the short-term temporal scale (intra-annual). Analysis of all variables across all scales showed that no variable from one scale of observation was dominant, rather variables from multiple scales are contributing to hydrogeomorphic character to varying degrees. This work demonstrates how an interdisciplinary, multi-scale approach is critical in detecting unique patterns in hydrogeomorphic character across different spatial and temporal scales. This approach enables a holistic view of spatio-temporal heterogeneity of a system and provides a firm basis for investigating how the physical template influences and helps to maintain patterns of biodiversity and ecosystem processes in complex and dynamics systems.

Water is a critical issue for governments and community in an Australian context, and internationally. First Peoples of Australia, its Indigenous peoples, have over 65,000 years of connection and u...

Water places have been critical to central Australian Indigenous peoples for thousands of years. However, many waterhole communities have been degraded by factors including invasion by large feral ...

Many water scientists aim for their work to inform water policy and management, and in pursuit of this objective, they often work alongside government water agencies to ensure their research is relevant, timely and communicated effectively. A paper in this issue, examining 'Science integrity, public policy and water governance in the Murray-Darling Basin, Australia���, suggests that a large group of scientists, who work on water management in the Murray-Darling Basin (MDB) including the Basin Plan, have been subject to possible ���administrative capture'. Specifically, it is suggested that they have advocated for policies favoured by government agencies with the objective of gaining personal benefit, such as increased research funding. We examine evidence for this claim and conclude that it is not justified. The efforts of scientists working alongside government water agencies appear to have been misinterpreted as possible administrative capture. Although unsubstantiated, this claim does indicate that the science used in basin water planning is increasingly caught up in the politics of water management. We suggest actions to improve science-policy engagement in basin planning, to promote constructive debate over contested views and avoid the over-politicisation of basin science.

This research was funded by the Australian Commonwealth Department of Environment and Energy under the Environmental Watering Knowledge and Research program. We thank John Pengelly from the Commonwealth Scientific and Industrial Research Organization for dissolved organic carbon and Chl a analyses. We thank Douglas Ford from University of Western Australia for stable isotope analyses and David Francis from Deakin University is thanked for analyses of fatty acids. We thank Michael Shackleton of La Trobe University for production of Fig. 1. We also thank three anonymous reviewers and the editor Bob Hall whose insightful comments improved our manuscript.

Studying food webs across contrasting abiotic conditions is an important tool in understanding how environmental variability impacts community structure and ecosystem dynamics. The study of extreme environments provides insight into community‐wide level responses to environmental pressures with relevance to the future management of aquatic ecosystems. In the western Lake Eyre Basin of arid Australia, there are two characteristic and contrasting aquatic habitats: springs and rivers. Permanent isolated Great Artesian Basin springs represent hydrologically persistent environments in an arid desert landscape. In contrast, hydrologically variable river waterholes are ephemeral in space and time. We comprehensively sampled aquatic assemblages in contrasting ecosystem types to assess patterns in community composition and to quantify food web attributes with stable isotopes. Springs and rivers were found to have markedly different invertebrate communities, with rivers dominated by more dispersive species and springs associated with species that show high local endemism. Qualitative assessment of basal resources shows autochthonous carbon appears to be a key basal resource in both types of habitat, although the particular sources differed between habitats. Food‐web variables such as trophic length, trophic breadth, and community isotopic niche size were relatively similar in the two habitat types. The basis for the similarity in food‐web structure despite differences in community composition appears to be broader isotopic niches for predatory invertebrates and fish in springs as compared with rivers. In contrast to published theory, our findings suggest that the food webs of the hydrologically variable river sites may show less dietary generalization and more compact food‐web modules than in springs., We analyzed aquatic assemblages in the western Lake Eyre Basin of arid Australia, using stable isotope analysis and measures of community composition across two characteristic and contrasting aquatic habitats: springs and rivers. Springs and rivers were found to have markedly different invertebrate communities, but general food‐web variables such as trophic length, trophic breadth, and community isotopic niche size were relatively similar in the two habitat types despite some subtle differences in the isotopic niche of specific functional groups and basal carbon sources.

In the face of mounting environmental problems, it is essential that accurate and timely scientific information is available to inform policy development and guide management. Scientists have specialised knowledge necessary for evidenced-based decision making, but despite extensive literature on the interface between science and policy, there is little guidance on achieving policy relevance while maintaining high standards of scientific integrity. Here, we provide a set of principles for environmental scientists to engage with policy makers and environmental water managers. We propose the adoption of a contemporary pluralistic approach using a diversity of modes of engagement between scientists, policy makers, and managers. We define a set of ‘roles’ for environmental scientists to engage effectively with policy and management, and discuss the advantages and pitfalls of each. We illustrate the breadth of modes of engagement at the science-policy-management interface using an example from Australia’s largest river system, the Murray-Darling Basin. We challenge the anachronistic, yet persistent concept that engaging with industry or government compromises the objectivity of involved scientists. We argue that there are multiple assurance processes in place to protect scientific integrity. Society needs scientists to be actively involved in finding solutions to the many urgent environmental issues we are facing, and if our principles are followed there are opportunities for healthy interaction between science, policy, and management.

Australia is the driest inhabited continent on Earth and has an acute need to manage its water resources effectively. Australian Aboriginal peoples have a profound knowledge of surface wate...

1.Pesticide concentrations are correlated with regional declines in stream invertebrate diversity. Experimental studies have identified that pesticides can have strong and persistent negative effects on aquatic ecosystems. These effects may occur at concentrations orders of magnitude lower than laboratory toxicity studies predict. Synergism among stressors is one explanation for observed laboratory‐field differences. However, the true effect of pesticides on stream invertebrates remains uncertain, given interactions between stressors and natural environmental conditions. 2.We experimentally examined multiple‐stressor effects on stream invertebrate assemblages and leaf‐litter breakdown using 24 independent ~900L re‐circulating outdoor mesocosms in a semi‐orthogonal design. Two pulses of the pesticide malathion (C10H19O6PS2) were delivered at low and high concentrations (Pulse 1: low at 0.1 and high at 1 μg L−1; Pulse 2: at 2.5 and 25 μg L−1). These were crossed with a treatment combining stressors commonly associated with agricultural development; nitrogen, phosphorus and sediment (kaolinite). 3.Malathion degradation was rapid (

The biomass of organisms of different sizes is increasingly being used to explore macroscale variation in food-web and community structure. Here we examine how invasive species and river flow regulation affect native fish biomass and fish community log10biomass – body mass scaling relationships in Australia’s largest river system, the Murray–Darling. The log10biomass – body mass scaling exponent (scaling B) of invasive fishes (95% CI: −0.14 to −0.18) was less negative than for native fishes (95% CI: −0.20 to −0.25), meaning that invasive species attained a higher biomass in larger size-classes compared to native species. Flow alteration and invasive common carp (Cyprinus carpio) biomass were correlated with severe reductions in native fish biomass ranging from −47% to −68% (95% CI). Our study provides novel evidence suggesting that invasive and native communities have different biomass – body mass scaling patterns, which likely depend on differences in their trophic ecology and body size distributions. Our results suggest that restoration efforts using environmental flows and common carp control has potential to boost native fish biomass to more than double the current level.

Fluoxetine, a selective serotonin reuptake inhibitor (SSRI), is frequently detected in surface waters globally, yet the effects of SSRIs on ecological processes at environmentally realistic concentrations are not currently known. We used a controlled, replicated artificial stream experiment to expose biofilm, algal and stream insect communities to two different concentrations of fluoxetine: 20 ng/L (typical concentration detected in surface waters) and 20 µg/L (concentration shown to influence insect emergence and algal productivity). We quantified a range of community and ecosystem response metrics over the course of the 21d experiment including; algal biomass (chl-a), net ecosystem production (NEP), gross primary production (GPP), ecosystem respiration (ER) and invertebrate emergence. At 20 ng/L, fluoxetine significantly suppressed algal colonization on rocks, and reduced GPP after 13 days, but by day 21 chl-a, NEP and GPP did not differ between treatments and control. Fluoxetine increased ER on leaves where invertebrates were excluded, but had no effect on leaves accessible to invertebrates. Streams receiving 20 ng/L of fluoxetine had adult insects from the order Diptera emerge sooner and at a greater rate than control streams. Our results suggest that ecosystem function, including primary production and respiration, and invertebrate population dynamics are sensitive to SSRIs and that fluoxetine may alter these key processes concentrations found in the environment.

Mechanisms linked to demographic, biogeographic, and food-web processes thought to underpin community stability could be affected by habitat size, but the effects of habitat size on community stability remain relatively unknown. We investigated whether those habitat-size-dependent properties influenced community instability and vulnerability to perturbations caused by disturbance. This is particularly important given that human exploitation is contracting ecosystems, and abiotic perturbations are becoming more severe and frequent. We used a perturbation experiment in which 10 streams, spanning three orders of magnitude in habitat size, were subjected to simulated bed movement akin to a major flood disturbance event. We measured the resistance, resilience, and variability of basal resources, and population and community-level responses across the stream habitat-size gradient immediately before, and at 0.5, 5, 10, 20, and 40 d post-disturbance. Resistance to disturbance consistently increased with stream size in all response variables. In contrast, resilience was significantly higher in smaller streams for some response variables. However, this higher resilience of small ecosystems was insufficient to compensate for their lower resistance, and communities of smaller streams were thus more variable over time than those of larger streams. Compensatory dynamics of populations, especially for predators, stabilized some aspects of communities, but these mechanisms were unrelated to habitat size. Together, our results provide compelling evidence for the links between habitat size and community stability, and should motivate ecologists and managers to consider how changes in the size of habitats will alter the vulnerability of ecosystems to perturbations caused by environmental disturbance.

Valuing, managing and conserving marine biodiversity and a full range of ecosystem services is at the forefront of research and policy agendas. However, biodiversity is being lost at up to a thousand times the average background rate. Traditional disciplinary and siloed conservation approaches are not able to tackle this massive loss of biodiversity because they generally ignore or overlook the interactive and dynamic nature of ecosystems processes, limiting their predictability. To conserve marine biodiversity, we must assess the interactions and impacts among biodiversity and ecosystem services (BD-ES). The scaling up in complexity from single species to entire communities is necessary, albeit challenging, for a deeper understanding of how ecosystem services relate to biodiversity and the roles species have in ecosystem service provision. These interactions are challenging to map, let alone fully assess, but network and system-based approaches provide a powerful way to progress beyond those limitations. Here, we introduce a conceptual multi-layered network approach to understanding how ecosystem services supported by biodiversity drive the total service provision, how different stressors impact BD-ES and where conservation efforts should be placed to optimize the delivery of ecosystem services and protection of biodiversity. This article is part of the theme issue Integrative research perspectives on marine conservation. Funding Agencies|HIFMB; Ministry for Science and Culture of Lower Saxony (MWK); Volkswagen Foundation through the Niedersachsisches Vorab grant program [ZN3285]; NERCNERC Natural Environment Research Council [NE/S001395/1]

Within human modified ecosystems the effects of individual stressors are difficult to establish amid co-occurring biological processes, environmental gradients and other stressors. Coupled examination of several endpoints across different levels of organisation may help elucidate the individual and combined effects of stressors and interactions. Malathion is a commonly used organophosphate pesticide that contaminates freshwaters and has strong negative effects on aquatic biota. However, both other stressors (e.g. increased sediment) and common ecosystem components (e.g. macrophytes and variable pH) can reduce the aqueous concentrations of malathion, reducing its toxic effects. We conducted a fully orthogonal bioassay to examine how pH (at 7 and 7.8) and sorptive processes (across two levels of kaoline clay 0 and 24 g L−1) affected aqueous malathion concentrations and toxicity in an aquatic invertebrate genus. Survival and acetylcholinesterase activity as a sub-organism response were examined in the mayfly Coloburiscoides spp. (Ephemeroptera; Coluburiscidae). Measured aqueous malathion concentrations decreased with increased pH and in the presence of kaolin clay. Survival declined with increasing malathion concentrations and exposure period. Results further identify that antagonism of malathion toxicity was associated with both pH (alkaline hydrolysis) and effects associated with sediment independent of pH (driven by sorptive processes). However, model predictions varied associated with target and measured concentrations and concentrations examined. Antagonistic effects were most apparent using subset target malathion concentrations because of the dominant effect of malathion at high concentrations. Acetylcholinesterase activity, identified repression occurred across all treatments and did not identify antagonistic interactions, but these results were similar to survival responses at the time points examined (i.e. 120 h). Examination of chemistry, acetylcholinesterase, and survival, affords greater understanding of stressor effects and their interactions. Measured malathion concentrations may underestimate effects on aquatic biota; not because of synergism among stressors, but because of strong effects despite antagonism.

Freshwater ecosystems and their associated biota have been negatively impacted by the human development of water resources. Fundamental to restoration activities for target species is an understanding of the factors affecting population decline or recovery. Within Australia&rsquo, s Murray&ndash, Darling Basin, recovery efforts to address the population decline of native freshwater fish include stock enhancement, habitat restoration, and the delivery of environmental water. Essential to guiding future management actions is information to assess the efficacy of these efforts. We undertook a study to investigate whether natural spawning and recruitment, stock enhancement, or a combination of the two is contributing to sustaining populations of golden perch (Macquaria ambigua) in the highly regulated Lachlan River, Australia. Otolith microchemistry and genetic analyses were used as complementary tools to determine the source (hatchery origin or wild-spawned) of existing populations in the catchment. We identified that natural spawning and recruitment was contributing to riverine populations in some years but that populations were heavily reliant on stocking. It was not possible to distinguish hatchery and wild-born fish using genetic tools, highlighting the value of using multiple lines of evidence to establish causal mechanisms contributing to population recovery.

Increasing demand for freshwater during the last century has so severely degraded many wetland ecosystems that they are some of the most seriously impacted environments in the world. Environmental flows are used as a management tool to restore parts of the hydrological regime altered by human water use, to rehabilitate these wetlands. Research and monitoring to date has focused on understanding ‘flow-ecology’ relationships, without investigating the mechanisms underlying them. We sought to understand how different basal food sources are incorporated into fish tissue in temporary wetland systems. This study provides a necessary first step toward the development of mechanistic research that investigates the effects of variation in fatty acids (FA) within the food and prey base on top predators. We added different sources of fatty acids to wetland mesocosms by adding extra food sources including redgum leachate to increase planktonic bacteria populations, cyanobacteria, green algae and biofilm matrix to observe how they were incorporated into secondary consumers. Wetland soil and water was added to replicate mesocosms, left for 28 days to produce zooplankton and then Western carp gudgeons added. There was a clear shift in the invertebrate assemblage structure following the introduction of the gudgeons. There was also a clear difference in assemblage structure and nutritional value between benthic and planktonic invertebrates. However, the addition of extra food sources did not generate differing FA profiles between treatments in the substratum fractions, invertebrates or fish after 14 days. We suggest that food sources generated within the mesocosms themselves may have outweighed any treatment effects. Using flooded wetland mesocosms potentially would have provided more realistic knowledge of the food web mechanisms of wetland inundation rather than feeding zooplankton fed specific primary food sources to fish. However, future experiments attempting to identify the mechanisms of the transfer of basal food sources in wetlands to secondary consumers may wish to directly feed fish primary consumers raised on specific basal food sources.

This research addressed the question of whether invertebrate food web structure varied between a native and an invasive macrophyte leaf species in the littoral zone of a tropical reservoir. We compared macroinvertebrate herbivore functional trait diversity composition with food web structure on the two macrophyte leaves, the invasive white ginger lily (Hedichium coronarium—Zingiberaceae) and the native pickerelweed (Pontederia cordata—Pontederiaceae). We predicted that the herbivore macroinvertebrate trait indices would decrease with macrophyte leaf species due to a lower resource quality with the flow-on effects in the food web structure. We calculated the number of functionally singular species (sing.sp) and herbivore functional trait richness (FRic) indices. For the macroinvertebrate food webs, we calculated the total number of trophic links (L), link density (L/S), connectance (C) and predator–prey ratios using a predator–prey matrix. We analysed the relationship between chemical traits of the macrophyte species’ leaves herbivore traits and food web indices using multivariate regression and Pearson’s correlation. Hedichium coronarium leaves had higher biomass and higher nitrogen content than the native P. cordata, which had higher phosphorus and carbohydrate content. Pontederia cordata leaves were associated with specialist macroinvertebrate species which primarily feed on biofilms (e.g. Ulmeritrus and Scirtidae) and plant leaves (e.g. Beardius). Food webs on P. cordata had lower numbers of trophic links (L), links per species (L/S) and predator–prey ratios. Connectance, which represents food web complexity, was similar between macroinvertebrate assemblages on the two leaf types. Our study suggests that chemical compounds of macrophyte leaves quality may have potential flow-on effects on food web structure.

Aim: Ecological models that do not account for interactions among stressors, if interactions are important, could be inaccurate and lead to inefficient conservation strategies. Conversely, if interactions are not important (i.e., stressors operate largely independently), then actions concentrating on a stressor-by- stressor basis would be warranted. Here, we investigated whether interactions among multiple stressors affected widely used indices of freshwater macroinvertebrate biodiversity, which are sensitive to environmental change at management-relevant scales (i.e., reaches and catchments). Location: State of Victoria, south-eastern Australia. Methods: We used a 7,418-sample dataset for stream macroinvertebrates from 2,165 sites distributed over 237,630 km2 for 20 years. We calculated the interactive effects on stream macroinvertebrates of stressors operating at different scales, namely vegetation loss at the catchment and reach scales and hydrological change and salinization at the local scale. The importance of interactions among multiple stressors was assessed by comparing the cross-validated predictive performance of models with and without multiple stressor interaction terms. Results: Cross-validated models explained 31%–63% of the variation in the macroinvertebrate responses. The most important stressors were catchment vegetation loss (the proportion of remaining native vegetation cover) and salinity. The inclusion of interaction terms did not increase cross-validated predictive performance, which indicates that there was little evidence that interactions among stressors were important for explaining variation in commonly used freshwater macroinvertebrate condition indices. Main conclusions: Interactions among vegetation, salinity and hydrological change stressors may not always be of importance for determining patterns of stream macroinvertebrate biodiversity, so that such interactions may not necessarily be critical considerations for catchment and reach scale management, at least if based on these or comparable condition indices. The mitigation of the impacts of vegetation loss, salinization and hydrological change stressors one-by- one probably is sufficient to guide conservation activities and might be advantageous if socio-political contexts make it difficult to address interactions among stressors.

Globally, large river systems have been extensively modified and are increasingly managed for a range of purposes including ecosystem services and ecological values. Key to managing rivers effectively are developing approaches that deal with uncertainty, are adaptive in nature, and can incorporate multiple stakeholders with dynamic feedbacks. Australia's largest river system, the Murray–Darling Basin (MDB), has been extensively developed for shipping passage, irrigation, hydroelectric development, and water supply. Water development in the MDB over the last century resulted in overallocation of water resources and large‐scale environmental degradation throughout the Basin. Under the pressure of a significant drought, there was insufficient water to supply critical human, environmental, and agricultural needs. In response, a massive programme of water reform was enacted that resulted in considerable institutional, social, and economic change. The underlying policy was required to be enacted in an absence of certainty around the scientific basis, with an adaptive management focus to incorporate new knowledge. The resulting institutional arrangements were challenged by a need to generate new governance arrangements within the constraints of existing state and national structures. The ongoing reform and management of the MDB continues to challenge all parties to achieve optimization for multiple outcomes, and to communicate that effectively. As large‐scale water reform gains pace globally, the MDB provides a window of insight into the types of systems that may emerge and the challenges in working within them. Most particularly, it illustrates the need for much more sophisticated systems thinking that runs counter to the much more linear approaches often adopted in government.

Of all ecosystems, freshwaters support the most dynamic and highly concentrated biodiversity on Earth. These attributes of freshwater biodiversity along with increasing demand for water mean that these systems serve as significant models to understand drivers of global biodiversity change. Freshwater biodiversity changes are often attributed to hydrological alteration by water-resource development and climate change owing to the role of the hydrological regime of rivers, wetlands and floodplains affecting patterns of biodiversity. However, a major gap remains in conceptualising how the hydrological regime determines patterns in biodiversity's multiple spatial components and facets (taxonomic, functional and phylogenetic). We synthesised primary evidence of freshwater biodiversity responses to natural hydrological regimes to determine how distinct ecohydrological mechanisms affect freshwater biodiversity at local, landscape and regional spatial scales. Hydrological connectivity influences local and landscape biodiversity, yet responses vary depending on spatial scale. Biodiversity at local scales is generally positively associated with increasing connectivity whereas landscape-scale biodiversity is greater with increasing fragmentation among locations. The effects of hydrological disturbance on freshwater biodiversity are variable at separate spatial scales and depend on disturbance frequency and history and organism characteristics. The role of hydrology in determining habitat for freshwater biodiversity also depends on spatial scaling. At local scales, persistence, stability and size of habitat each contribute to patterns of freshwater biodiversity yet the responses are variable across the organism groups that constitute overall freshwater biodiversity. We present a conceptual model to unite the effects of different ecohydrological mechanisms on freshwater biodiversity across spatial scales, and develop four principles for applying a multi-scaled understanding of freshwater biodiversity responses to hydrological regimes. The protection and restoration of freshwater biodiversity is both a fundamental justification and a central goal of environmental water allocation worldwide. Clearer integration of concepts of spatial scaling in the context of understanding impacts of hydrological regimes on biodiversity will increase uptake of evidence into environmental flow implementation, identify suitable biodiversity targets responsive to hydrological change or restoration, and identify and manage risks of environmental flows contributing to biodiversity decline.

Environmental flows are designed to enhance aquatic ecosystems through a variety of mechanisms; however, to date most attention has been paid to the effects on habitat quality and life-history triggers, especially for fish and vegetation. The effects of environmental flows on food webs have so far received little attention, despite food-web thinking being fundamental to understanding of river ecosystems. Understanding environmental flows in a food-web context can help scientists and policy-makers better understand and manage outcomes of flow alteration and restoration. In this paper, we consider mechanisms by which flow variability can influence and alter food webs, and place these within a conceptual and numerical modelling framework. We also review the strengths and weaknesses of various approaches to modelling the effects of hydrological management on food webs. Although classic bioenergetic models such as Ecopath with Ecosim capture many of the key features required, other approaches, such as biogeochemical ecosystem modelling, end-to-end modelling, population dynamic models, individual-based models, graph theory models, and stock assessment models are also relevant. In many cases, a combination of approaches will be useful. We identify current challenges and new directions in modelling food-web responses to hydrological variability and environmental flow management. These include better integration of food-web and hydraulic models, taking physiologically-based approaches to food quality effects, and better representation of variations in space and time that may create ecosystem control points.

Human impacts on natural ecosystems are pervasive and will play out more severely as human populations and per capita resource use increase. Freshwater ecosystems are critical for human well-being and experience a diverse range of human-induced pressures. Most river systems throughout the world have much-altered flow regimes. The Murray–Darling Basin in southeastern Australian has been the focus of an extensive water reform process to address the over-allocation of water for human uses. This has included many scientific investigations, hydrological modelling and the development of institutional and market structures to reallocate water. Substantial recovery of water has been achieved, which has been used to restore aspects of the natural flow regime. We reviewed recent papers on responses to flow restoration in the Murray–Darling Basin and complemented this with inferences from the global literature. Ecological responses to flow restoration are often inconsistent, site and taxon specific and difficult to detect. By combining ideas from mainstream thinking in restoration ecology with the insights from our review, we propose a conceptual model for understanding responses to flow restoration. This model incorporates key factors that influence the size of ecological responses to restoration, including existing ecological condition, legacy impacts of past change, interactions with other variables, life-history traits of taxa and broad-scale and long-term trends due to climate or land-use change.

Pesticides are increasingly recognised as a threat to freshwater biodiversity, but their specific ecological effects remain difficult to distinguish from those of co-occurring stressors and environmental gradients. Using mesocosms we examined the effects of an organophosphate insecticide (malathion) on stream macroinvertebrate communities concurrently exposed to a suite of stressors typical of streams in agricultural catchments. We assessed the specificity of the SPEcies At Risk index designed to determine pesticide effects in mesocosm trials (SPEARmesocosm). This index determines the log abundance proportion of taxa that are considered physiologically sensitive to pesticides. Geographic variation in pesticide sensitivity within taxa, coupled with variation between pesticides and the effects of co-occurring stressors may decrease the accuracy of SPEARmesocosm. To examine this, we used local pesticide sensitivity assessments based on rapid toxicity tests to develop two new SPEAR versions to compare to the original SPEARmesocosms index using mesocosm results. We further compared these results to multivariate analyses and community indices (e.g. richness, abundance, Simpson's diversity) commonly used to assess stressor effects on biota. To assess the implications of misclassifying species sensitivity on SPEAR indices we used a series of simulations using artificial data. The impacts of malathion were detectable using SPEARmesocosm, and one of two new SPEAR indices. All three of the SPEAR indices also increased when exposed to other agricultural non-pesticide stressors, and this change increased with greater pesticide concentrations. Our results support that interactions between other non-pesticide stressors with pesticides can affect SPEAR performance. Multivariate analysis and the other indices used here identified a significant effect of malathion especially at high concentrations, with little or no evidence of effects from the other agricultural stressors.

Summary Arid landscapes pose arguably one of the greatest challenges to dispersal of aquatic insects, and may drive speciation in taxa with low dispersal potential. We investigated genetic divergence in aquatic insects with high and low dispersal potential between two regions within the Australian arid zone. We used two dragonfly species to infer patterns for strong-dispersing species, and mayfly species from two genera to represent weak-dispersing species. Based on dispersal-related traits of the taxa, we predicted that dragonflies would show little divergence between and within the two geographical regions, while mayflies would show evidence of genetic isolation, with divergence timing associated with aridification in Australia. Samples were collected from perennial pools in ephemeral stream networks in central and western Australia. The two study regions are separated by approximately 1,500 km of predominantly dune desert. Collected insects were sequenced for one mitochondrial and one nuclear marker. We investigated spatial distribution of haplotypes, estimated divergence dates for identified mayfly lineages, and performed phylogenetic reconstruction to investigate relationships with known congeners. Both dragonfly species showed evidence of recent or ongoing gene flow between the central and western Australian study regions. In contrast, mayflies showed evidence of ancient, but not recent, gene flow between regions, with species-level CO1 divergence within regions. We found 11 previously unknown putative mayfly species, that if confirmed could double the known diversity within these genera in Australia. Timing of divergence events for mayflies coincided with the development of the Australian arid zone, and phylogenetic relationships are similar to divergence patterns found in other Australian arid taxa. The findings of this study suggest that aridification is more likely to be a driver of diversification in taxa with low dispersal potential than in those with high dispersal potential. This is because effective aerial dispersal is integral for maintaining gene flow when aquatic connections are lost between distant populations, and reduced gene flow can promote genetic divergence.

Managing and restoring faunal diversity across large areas requires an understanding of the roles of connectivity and dispersal in driving community patterns. We sought to determine the influence of connectivity, water regime, water source, geographical location, and dispersal traits on patterns of aquatic invertebrate diversity across a continent-wide arid biome. We compiled data on freshwater invertebrate assemblages from sites spanning the breadth of arid Australia. Univariate analyses (analysis of variance and rarefaction) revealed that alpha and gamma diversity across sites decreased as latitude increased. Multivariate analyses (ordination and analysis of similarity) revealed that community composition had considerable fidelity to geographic regions. Hydrological connectivity was strongly associated with riverine community composition although water rarely flowed (often less than annually). Hydrologically isolated sites (springs and rockholes) supported communities that were markedly dissimilar to hydrologically connected sites, and to each other. We investigated the influence of dispersal on diversity patterns by examining Distance Decay Relationships for each of four dispersal trait groups (obligate aquatic and passive, weak, and strong aerial dispersers) on the basis of geodesic (shortest path) distances between pairs of sites and Mantel tests. We did not detect clear differences between dispersal traits and distance decay relationships at the continental scale, even for the two groups with the lowest dispersal ability (obligate aquatics and passive dispersers.) Our results suggest that the loss of hydrological connectivity from water developments in arid lands (for example, the impoundment of intermittent rivers) is likely to affect macroinvertebrates. However, the exact flow mechanisms underlying such changes remain to be determined. This article is protected by copyright. All rights reserved.

Constructed stormwater wetlands are one strategy for mitigating the negative effects of urbanization on aquatic ecosystems. However, the biotic community in these wetlands generally is dominated by organisms able to tolerate poor water quality. Reduced macroinvertebrate diversity and abundance in comparison to natural wetlands, and prevalence of invasive species, such as Gambusia, can influence the flow of energy through food webs. We used stable-isotope analysis (δ13C and δ15N) of food webs to assess whether the amount of catchment urbanization (total imperviousness [imperviousness] = % catchment covered in impervious surfaces) influenced basal resources and trophic relationships in constructed wetlands in Melbourne, Australia. As imperviousness increased, the abundance and diversity of macroinvertebrates decreased significantly and the values of δ13C and δ15N recorded for fishes and macroinvertebrates increased significantly. An increase in imperviousness was associated with a decrease in the me...

Managing ecosystems to provide ecosystem services in the face of global change is a pressing challenge for policy and science. Predicting how alternative management actions and changing future conditions will alter services is complicated by interactions among components in ecological and socioeconomic systems. Failure to understand those interactions can lead to detrimental outcomes from management decisions. Network theory that integrates ecological and socioeconomic systems may provide a path to meeting this challenge. While network theory offers promising approaches to examine ecosystem services, few studies have identified how to operationalize networks for managing and assessing diverse ecosystem services. We propose a framework for how to use networks to assess how drivers and management actions will directly and indirectly alter ecosystem services.

Investigating how environmental factors influence within-species trait variability is critical to understanding the evolution and maintenance of individual behavioural differences (i.e. temperament or personality), and their integration into wider ecological theory. Populations of Australian desert gobies, Chlamydogobius eremius , from starkly contrasting aquatic environments in arid Australia were used to investigate how environmental differences influence temperament traits. Focusing on boldness and exploration, fish were assessed using novel environment, dispersal and novel food item assays under laboratory conditions. The results of these experiments were analysed for repeatability and for patterns of divergence within and between populations. We found consistent within-species differences in novel environment and novel food item assays, with refuge emergence and inspection latency of a novel food item both strongly repeatable behavioural axes. Although both traits can be considered measures of boldness, refuge emergence significantly diverged according to sex, while inspection latency was predicted by habitat differences. This suggests that multiple measures of boldness are diverging independently according to different ecological drivers. Specifically, we found that fish caught from environments without predators and with probable intense intraspecific competition are less active and bolder in a novel food item context. Further analysis demonstrated how extreme habitat differences are driving behavioural divergence on multiple axes, relating to boldness and dispersal behaviours. This provides valuable insights into how the environment and behaviour interact and how we define temperament traits, as well as highlighting the importance of studying temperament within a community ecology context.

Karyotypic data from Australian native freshwater fishes are scarce, having been described from relatively few species. Golden perch (Macquaria ambigua) and Murray cod (Maccullochella peelii) are two large-bodied freshwater fish species native to Australia with significant indigenous, cultural, recreational and commercial value. The arid landscape over much of these fishes’ range, coupled with the boom and bust hydrology of their habitat, means that these species have potential to provide useful evolutionary insights, such as karyotypes and sex chromosome evolution in vertebrates. Here we applied standard and molecular cytogenetic techniques to characterise karyotypes for golden perch and Murray cod. Both species have a diploid chromosome number 2n = 48 and a male heterogametic sex chromosome system (XX/XY). While the karyotype of golden perch is composed exclusively of acrocentric chromosomes, the karyotype of Murray cod consists of two submetacentric and 46 subtelocentric/acrocentric chromosomes. We have identified variable accumulation of repetitive sequences (AAT)10 and (CGG)10 along with diverse methylation patterns, especially on the sex chromosomes in both species. Our study provides a baseline for future cytogenetic analyses of other Australian freshwater fishes, especially species from the family Percichthyidae, to better understand their genome and sex chromosome evolution.

International audience; Predator-prey interactions in natural ecosystems generate complex food webs that have a simple universal body-size architecture where predators are systematically larger than their prey. Food-web theory shows that the highest predator-prey body-mass ratios found in natural food webs may be especially important as they create weak interactions with slow dynamics that stabilize communities against perturbations and maintain ecosystem functioning. Identifying these vital interactions in real communities typically requires arduous identification of interactions in complex food webs. Here, we overcome this obstacle by developing predator-trait models to predict average body-mass ratios based on a database comprising 290 food webs from freshwater, marine and terrestrial ecosystems across all continents. We analyzed how species traits constrain body-size architecture by changing the slope of the predator-prey body-mass scaling. Across ecosystems, we found high body-mass ratios for predator groups with specific trait combinations including (1) small vertebrates and (2) large swimming or flying predators. Including the metabolic and movement types of predators increased the accuracy of predicting which species are engaged in high body-mass ratio interactions. We demonstrate that species traits explain striking patterns in the body-size architecture of natural food webs that underpin the stability and functioning of ecosystems, paving the way for community-level management of the most complex natural ecosystems.

Toxicants have both sub-lethal and lethal effects on aquatic biota, influencing organism fitness and community composition. However, toxicant effects within ecosystems may be altered by interactions with abiotic and biotic ecosystem components, including biological interactions. Collectively, this generates the potential for toxicant sensitivity to be highly context dependent, with significantly different outcomes in ecosystems than laboratory toxicity tests predict. We experimentally manipulated stream macroinvertebrate communities in 32 mesocosms to examine how communities from a low-salinity site were influenced by interactions with those from a high-salinity site along a gradient of salinity. Relative to those from the low-salinity site, organisms from the high-salinity site were expected to have greater tolerance and fitness at higher salinities. This created the potential for both salinity and tolerant-sensitive organism interactions to influence communities. We found that community composition was influenced by both direct toxicity and tolerant-sensitive organism interactions. Taxon and context-dependent responses included: (i) direct toxicity effects, irrespective of biotic interactions; (ii) effects that were owing to the addition of tolerant taxa, irrespective of salinity; (iii) toxicity dependent on sensitive-tolerant taxa interactions; and (iv) toxic effects that were increased by interactions. Our results reinforce that ecological processes require consideration when examining toxicant effects within ecosystems. This article is part of the theme issue ‘Salt in freshwaters: causes, ecological consequences and future prospects’.

The effects of pharmaceuticals on aquatic ecosystems are the subject of increasing environmental concern. Of particular interest are a suite of drugs known as selective serotonin reuptake inhibitors (SSRIs), commonly prescribed to treat depression. SSRIs are now detected in the environment worldwide, but their effects on ecosystems are not well understood. We conducted replicated experiments testing for an ecosystem effect of SSRIs in streams. We used artificial stream mesocosms to expose natural biofilms and aquatic insect communities to concentrations (20 µg/L) of fluoxetine or citalopram or a mix of both (totaling 40 µg/L). These concentrations are the lowest found to have an effect on aquatic invertebrates in other studies. Treatments suppressed gross primary production by 29% and community respiration by ≥43% on rock biofilms but did not affect algal biomass or whole-stream metabolism. A common group of dipteran midges emerged earlier in all SSRI treated streams compared with the controls. To...

Constructed wetlands are commonly used to remove contaminants such as heavy metals from stormwater. However, metals can become bioavailable and be transferred into and along wetland food chains. Our study sought to establish whether urbanisation affected concentrations of metals in water, wetland sediments, freshwater crayfish and fish tissues. Samples were taken from constructed wetlands in western Melbourne. There was no relationship between catchment total imperviousness (TI, an index of urbanisation) and water column and sediment concentrations of metals with the exception of Zn, which was higher in more urbanised catchments. Concentrations of metals in fish tissues were highest in benthic species but declined with increasing body size and trophic level. This suggests that metals are not bioaccumulating or biomagnifying along food chains in these systems. Metabolic activity can differ between smaller and larger fish, or smaller fish may also be feeding on different food sources. Our results suggest that there is not a major human health risk associated with accumulation of metals in large-bodied fish in these wetlands, and that most of the metal load is retained in sediments, or the lowest trophic levels.

We used highly realistic temperature treatments based on down-scaled global circulation models for 1990–2000 (control) and 2100 (warming treatment) to experimentally assess the impacts of altered temperature regimes on the emerging adults of aquatic insect communities. Experiments were run for 6 weeks and emerging adults of insects were identified and measured for length. There were clear responses to the warming treatment, but responses were taxa- and gender-specific. Males of mayfly Ulmerophlebia pipinna Suter 1986 (Leptophlebiidae) emerged faster under 2100 temperatures. This resulted in a change in the sex ratio that could compromise populations. Mean body size of some insects decreased under warming conditions, which is in agreement with the general hypothesis of reduced body size in response to climate change. However, the degree to which organism size was affected by temperature varied within and between taxa. These changes show the potential for changed temperature regimes to impact ecological systems at individual, population, and community levels. Changes in body size and species composition of emerging insects are likely to impact different levels in both the aquatic and terrestrial communities, for example through disruption of interactions between emerging insects and riparian predators which rely on those resources.

Invasive species are an important contributor to global biodiversity loss. This is particularly true in freshwater ecosystems, where introduced species have contributed to native fish extinctions, altered native fish communities and modified aquatic ecosystem structure and function. Native species can potentially mitigate the impact of invasive predators and competitors by altering their behaviour, for example by reducing activity such as foraging or by increasing their use of shelter. This study investigated interactions between an introduced salmonid, the rainbow trout (Oncorhynchus mykiss), and a native fish, the riffle galaxiid (Galaxias arcanus), that currently co-inhabit streams in parts of south-eastern Australia. We used three separate sets of behavioural experiments to test whether riffle galaxiids avoided trout under different substrate conditions. We hypothesised that habitat selection in the presence of a predator could be an important factor in facilitating galaxiid and trout co-existence. We found that interactions between the two fish differed depending on substrate. Galaxiids avoided trout when only sand substrate was available, but did not avoid trout when cobble substrate was available. The complex structure of cobbles may afford riffle galaxiids protection from trout, thereby facilitating their current existence in trout-inhabited streams.

There is a global need for management of river flows to be informed by science to protect and restore biodiversity and ecological function while maintaining water supply for human needs. However, a lack of data at large scales presents a substantial challenge to developing a scientifically robust approach to flow management that can be applied at a basin and valley scale. In most large systems, only a small number of aquatic ecosystems have been well enough studied to reliably describe their environmental water requirements. The umbrella environmental asset (UEA) approach uses environmental water requirements developed for information-rich areas to represent the water requirements of a broader river reach or valley. We illustrate this approach in the Murray–Darling Basin (MDB) in eastern Australia, which was recently subject to a substantial revision of water management arrangements. The MDB is more than 1 million km2 with 18 main river valleys and many thousands of aquatic ecosystems. Detailed eco-hydrologic assessments of environmental water requirements that focused on the overbank, bankfull and fresh components of the flow regime were undertaken at a total of 24 UEA sites across the MDB. Flow needs (e.g. flow magnitude, duration, frequency and timing) were established for each UEA to meet the needs of key ecosystem components (e.g. vegetation, birds and fish). Those flow needs were then combined with other analyses to determine sustainable diversion limits across the basin. The UEA approach to identifying environmental water requirements is a robust, science-based and fit-for-purpose approach to determining water requirements for large river basins in the absence of complete ecological knowledge. © 2015 The Authors. River Research and Applications published by John Wiley & Sons, Ltd.

Freshwater ecosystems in arid regions range from highly fragmented to highly connected, and connectivity has been assumed to be a major factor in the persistence of aquatic biota in arid environments. This review sought to synthesize existing research on genetic estimation of population connectivity in desert freshwaters, identify knowledge gaps, and set priorities for future studies of connectivity in these environments. From an extensive literature search, we synthesized the approaches applied, systems studied, and conclusions about connectivity reached in population genetic research concerning desert freshwater connectivity globally. We restrict our scope to obligate aquatic fauna that disperse largely via freshwaters and exclude those with active aerial dispersal abilities. We examined 92 papers, comprising 133 studies, published from 1987 to 2014. Most described studies of fishes and invertebrates in the deserts of Australia and North America. Connectivity declined with increasing scale, but did not differ significantly among arid regions or taxonomic classes. There were significant differences in connectivity patterns between species with different dispersal abilities, and between spring and riverine habitats at local scales. Population connectivity in desert freshwaters is typically most influenced by the ecology of the species concerned and hydrological connectivity. Most studies did not assess predefined models of connectivity, but described gene flow and/or genetic structure. Climate change and anthropogenic impacts worldwide are likely to increase the incidence and impact of habitat fragmentation in already threatened desert freshwaters. To reduce this risk, biodiversity conservation and environmental management must address connectivity, but often the required information does not exist. Researchers can provide this by explicitly considering the effects of hydrology and species’ ecology on connectivity, and incorporating these into connectivity models, which are vital for understanding connectivity in desert freshwaters.

Traits provide key ecological information that can be applied to understanding the mechanisms which drive community assembly and persistence. In recent years, trait information has provided important insights into the responses of communities to stressors including pollutants and climatic extremes. Outside of Europe and North America, the use of stream macroinvertebrate traits has generally been hindered by the lack of a national database assigning traits to taxa. Here, we present an integrated database for Australian stream macroinvertebrates, which for the first time brings together data from multiple jurisdictions to facilitate the use of traits in both theoretical and applied studies. We describe the database and discuss its applications as well as challenges and limitations of this and other trait databases. The Australian trait database provides new opportunities for research and application in freshwater management.

Bi-allelic Single Nucleotide Polymorphism (SNP) markers are widely used in population genetic studies. In most studies, sequences either side of the SNPs remain unused, although these sequences contain information beyond that used in population genetic studies. In this study, we show how these sequence tags either side of a single nucleotide polymorphism can be used for comparative genome analysis. We used DArTseq (Diversity Array Technology) derived SNP data for a non-model Australian native freshwater fish, Macquaria ambigua, to identify genes linked to SNP associated sequence tags, and to discover homologies with evolutionarily conserved genes and genomic regions. We concatenated 6,776 SNP sequence tags to create a hypothetical genome (representing 0.1-0.3% of the actual genome), which we used to find sequence homologies with 12 model fish species using the Ensembl genome browser with stringent filtering parameters. We identified sequence homologies for 17 evolutionarily conserved genes (cd9b, plk2b, rhot1b, sh3pxd2aa, si:ch211-148f13.1, si:dkey-166d12.2, zgc:66447, atp8a2, clvs2, lyst, mkln1, mnd1, piga, pik3ca, plagl2, rnf6, sec63) along with an ancestral evolutionarily conserved syntenic block (euteleostomi Block_210). Our analysis also revealed repetitive sequences covering approximately 12% of the hypothetical genome where DNA transposon, LTR and non-LTR retrotransposons were most abundant. A hierarchical pattern of the number of sequence homologies with phylogenetically close species validated the approach for repeatability. This new approach of using SNP associated sequence tags for comparative genome analysis may provide insight into the genome evolution of non-model species where whole genome sequences are unavailable.