Search

Aim: Climate change threatens biodiversity in all ecosystems, and major shifts in species distributions are expected. Freshwater ecosystems are considered particularly vulnerable due to the ectothermic physiology of most freshwater species and their limited habitat extent and capacity to track climate trends. In this study, we examined what broad patterns in freshwater riverine species turnover might be expected under climate change across continental Australia and what are the implications of these patterns for aquatic species and the low aquatic biodiversity of some bioregions? Location: Continental Australia. Methods: We built statistical relationships between bioclimatic environments and the occurrence of species of four freshwater taxa (freshwater fish, crayfish, turtles and frogs) and examined trends in projected species turnover for a ‘business as usual’ climate scenario. We used Maxent to model species distributions and present the median projection across 18 global climate models. A recently derived national stream network was used to generate estimates of mean annual river flow and to produce realistic species distributions and migration options by restricting dispersal and migration opportunities usually available to riverine fauna. Results: High species turnover was driven overwhelmingly by potential local extinctions particularly for stream frogs and crayfish where their current biodiversity is largely confined to higher elevation headwater streams. We predicted high turnover for inland regions of Australia, which are arid and generally support fewer freshwater species. Main conclusions: Our analysis indicates that under the most severe emissions pathway, projected climate change is likely to cause substantial changes to the composition of faunal assemblages in Australian rivers well before the end of this century. While freshwater systems globally are subject to immediate and pressing threats from anthropogenic land and water use, management interventions addressing these pressures need to be considered within the context of climate change.

Few freshwater aquatic species have ecological traits that deal with the vagaries of flow in ephemeral tropical rivers. In northern Australia, the tropical freshwater crab, Austrothelphusa transversa (von Martens, 1868) is a conspicuous species that occupies seasonal rivers, where it is thought to estivate in underground burrows while waiting for summer rain. During a survey in seasonal river catchments the first photographic evidence was obtained of an estivating female crab containing 42 crablets under the abdomen plate. Uncovering this female with crablets suggests that egg development progressing to crablets occurs during the dry season estivation when crabs are underground and no water exists in river channels; if this is the case then this female crab may have been waiting for rain, to emerge and successfully continue the life cycle in water. Since 2012 the southern Gulf of Carpentaria has experienced below average rainfall, contributing to no or short flow periods over most of the landscape. In lig...

Coastal managers are increasingly challenged with implementing expensive restoration and on-going maintenance programs to reinstate the services and values of floodplains as important fish nursery areas, but access to long-term data to assist with supporting success is lacking. An environmental levy (funded by farmers, Burdekin Shire Council, a local Natural Resource Management group, and Lower Burdekin Water Board) was enacted in 2003 to fund (approximately $20,000/yr AUD) an ongoing aquatic weed removal program (consisting of an aquatic plant weed harvester that removes floating vegetation to a nearby truck for composting in conjunction with boat weed spraying) designed to maintain the delivery of irrigation water as well as promoting productive fish habitat. We repeated a fish and water quality survey first performed in 2001/2002 (September 2017, May 2018) at 10 lagoons (three clear and seven turbid) on the Burdekin floodplain (north Queensland, Australia) to examine whether these maintenance efforts continue delivering the initial values set nearly 20 years ago. A total of 2267 fish from 24 species were caught, May 2018 (post-wet season) survey yielded more fish (24 species) than the September 2017 (late dry season) survey (19 species) which is close to the results of the 2001/02 survey (post-wet season, 17 species; late dry season, 16 species). A Hydrolab (September 2017) revealed that turbid and clear water lagoons had a similar rhythmic diel temperature cycle that posed no thermal risks to fish. Dissolved oxygen had distinct diel periodicity, with clear lagoons having the widest range, reaching established critical minimum thresholds for some floodplain fish, while turbid lagoons were generally less variable (presumably due to less oxygen demand from biological activity). While as long as sugarcane production occurs, excessive nutrients will necessitate continuance of the aquatic weed program; therefore, the funding model in place must remain. This study advocates the need for long-term maintenance programs facilitated by long-term partnerships, and serves as an exemplar model for managers looking to restore coastal floodplains but are challenged with persistent aquatic weed management issues, not only in Australia but also on floodplains elsewhere.

To test the model that eco-engineering plant boxes on seawalls sustain water temperatures within thermal tolerance to maximize tropical marine biodiversity, we conducted acute thermal effects (AET) experiments using intertidal gastropods (Nerita albicilla and Littoraria articulata). The AET50 (50th percentile) for N. albicilla (39.6 °C) was higher than L. articulata (32.8 °C). Loggers (Hobo) in boxes on a seawall positioned for full exposure to air temperature at mean sea level (

Estuaries are experiencing high rates of modification because of urban development and on-going associated maintenance works which impacts their ecosystem functions and services. This research appraises the fish and crustacean community occupying urbanised estuaries, and whether necessary maintenance works (dredging, mangrove pruning) could be timed to better protect the ecosystem values. Using a range of sampling equipment we collected fish and crustacean assemblages from urban, semi-urban, and non-urban estuaries, in addition to water quality, tidal inundation, and marine plant densities to determine relationships among sites. Seasonal differences in body size distributions of socio-economically important species were also examined to infer timing of juvenile recruitment. Despite common assumptions that urbanised estuaries are degraded and provide little habitat value for coastal species, we found that the species composition of aquatic assemblages was similar between urban and non-urban sites, but differed according to tidal position (i.e. supralittoral vs. lower tidal). Seasonality in body size distributions differed among socio-economically important fisheries species, with some species showing juvenile recruitment during the wet season, dry season, or throughout the year. This study demonstrates that, regardless of urban vs. non-urban context, estuaries provide habitat for many aquatic animals, including socio-economically important fish species. Complexity associated with the dynamism of estuarine ecosystems and variability in constituent species’ life-history patterns makes management decisions regarding timing and delivery of urban waterway maintenance difficult. However, maintenance works that occur during Austral dry season (May to October) would provide the best protection for marine plants (non-flowering season for mangroves), while also reduces downstream movement of sediments and contaminants during wet season rainfall flow. Undertaking necessary maintenance works in the dry season provides grounds for wide scale seascape ecosystem optimism.

The dataset (Data File S1; DOI: 10.6084/m9.figshare.8863721) and the R code used to generate the results (Code S1; DOI: 10.6084/m9.figshare.8863655), including step by step explanations of the statistical tests, have been deposited in Figshare Digital Repository (https://figshare.com/projects/Sediment_Respiration_Pulses_in_Intermittent_Rivers_and_Ephemeral_Streams/66104)., Intermittent rivers and ephemeral streams (IRES) may represent over half the global stream network, but their contribution to respiration and carbon dioxide (CO2) emissions is largely undetermined. In particular, little is known about the variability and drivers of respiration in IRES sediments upon rewetting, which could result in large pulses of CO2. We present a global study examining sediments from 200 dry IRES reaches spanning multiple biomes. Results from standardized assays show that mean respiration increased 32–66-fold upon sediment rewetting. Structural equation modelling indicates that this response was driven by sediment texture and organic matter quantity and quality, which, in turn, were influenced by climate, land use and riparian plant cover. Our estimates suggest that respiration pulses resulting from rewetting of IRES sediments could contribute significantly to annual CO2 emissions from the global stream network, with a single respiration pulse potentially increasing emission by 0.2–0.7%. As the spatial and temporal extent of IRES increases globally, our results highlight the importance of recognizing the influence of wetting-drying cycles on respiration and CO2 emissions in stream networks., We thank Y. Etxeberria, L. Sánchez, C. Gutiérrez, G. LeGoff and B. Launay for laboratory support. DvS was supported by a Short-Term Scientific Mission of the COST Action CA15113 (SMIRES, Science and Management of Intermittent Rivers and Ephemeral Streams, www.smires.eu), supported by COST (European Cooperation in Science and Technology) and received additional funding from the EU’s 7th Framework Programme for research, technological development and demonstration under grant agreement No. 603629 (GLOBAQUA) and a Grant for Research Groups of the Basque University System (IT-951-16) funded by the Basque Government. RM and BO were supported by the Spanish Ministry of Science, Innovation and Universities through project C-HYDROCHANGE (CGL2017-86788-C3-2-P and CGL2017-86788-C3-3-P). FA was funded by the Swiss National Science Foundation grants No. PP00P3_150698 and PP00P3_179089. NC was supported by the EU project LIFE+ TRivers (LIFE13 ENV/ES/000341). SDL received funding from the EU’s Horizon 2020 research and innovation programme under the Marie Sklodowska-Curie grant agreement No 748625. PP and MP were supported by INTER-COST project LTC17017. The authors declare that they have no competing interests.

Estuaries provide important environmental, social, cultural, and economic services. The provision of these services is often negatively impacted by urban development within the catchment and along shorelines, most notably through habitat loss and alteration of hydrological and sedimentation regimes influencing system structure and function. Mitigating the effects of urban development on estuaries provides a great challenge for managers, particularly when considering the diversity of estuaries and catchment characteristics. The management of urban stormwater is a challenging issue where no single solution is apparent but requires varied approaches. Using three distinctly different Australian estuaries, this chapter presents an account of combined management plans, restoration, monitoring/research, and education efforts used in addressing and managing the issues of urban pressures on water quality surrounding Port Jackson, Gold Coast Broadwater, and the Ross River estuary. Although the case study estuaries significantly vary according to rainfall seasonality and intensity, population density, and catchment size, a survey of implemented protection and management initiatives, illustrates a consistent theme of management practices across the case studies: (1) catchment/estuary management policies and plans including stormwater quality improvement device initiative practices; (2) low impact and purpose-designed development options including water-sensitive urban design options, including specific design adaptations required for effective operation in varying climatic zones and catchment conditions; (3) restoration programs; (4) water quality monitoring programs; (5) research activities; and (6) stakeholder and community education campaigns. The best management outcomes for urbanized estuaries require implementation of catchment-based management plans that are supported by clear objectives regarding ecosystem services and regional challenges.

Climate change and human pressures are changing the global distribution and the extent of intermittent rivers and ephemeral streams (IRES), which comprise half of the global river network area. IRES are characterized by periods of flow cessation, during which channel substrates accumulate and undergo physico‐chemical changes (preconditioning), and periods of flow resumption, when these substrates are rewetted and release pulses of dissolved nutrients and organic matter (OM). However, there are no estimates of the amounts and quality of leached substances, nor is there information on the underlying environmental constraints operating at the global scale. We experimentally simulated, under standard laboratory conditions, rewetting of leaves, riverbed sediments, and epilithic biofilms collected during the dry phase across 205 IRES from five major climate zones. We determined the amounts and qualitative characteristics of the leached nutrients and OM, and estimated their areal fluxes from riverbeds. In addition, we evaluated the variance in leachate characteristics in relation to selected environmental variables and substrate characteristics. We found that sediments, due to their large quantities within riverbeds, contribute most to the overall flux of dissolved substances during rewetting events (56%–98%), and that flux rates distinctly differ among climate zones. Dissolved organic carbon, phenolics, and nitrate contributed most to the areal fluxes. The largest amounts of leached substances were found in the continental climate zone, coinciding with the lowest potential bioavailability of the leached OM. The opposite pattern was found in the arid zone. Environmental variables expected to be modified under climate change (i.e. potential evapotranspiration, aridity, dry period duration, land use) were correlated with the amount of leached substances, with the strongest relationship found for sediments. These results show that the role of IRES should be accounted for in global biogeochemical cycles, especially because prevalence of IRES will increase due to increasing severity of drying events., In this study we experimentally simulated under laboratory conditions rewetting of leaves, riverbed sediments, and epilithic biofilms collected during the dry phase from intermittent rivers and ephemeral streams covering global spatial scale. We determined the amounts and quality of the leached nutrients and dissolved organic matter, assessed their inter‐substrate and cross‐climate differences, and estimated areal fluxes from 1 m2 of riverbeds. In addition, we evaluated the variance in leachate characteristics related to selected environmental variables and substrate characteristics.

Mangrove forests are important habitats for fish. However, their utilisation by fish, and the specific values they confer, are still not fully understood. This study describes how fish use mangrove forests in an Indo-Pacific mangrove-coral reef seascape. Sampling was conducted using underwater video cameras (UVCs) to describe spatial and temporal variations in fish assemblages across a small-scale (~ 2.5 km2) system, and over the tidal and lunar cycle. UVCs were deployed in the two main component habitats of mangrove forests: at the mangrove forest edge, and inside the forest (5 m from the forest edge), to establish patterns of utilisation of fish across the tidal and lunar cycle. Proximity to coral reefs had a strong influence on the mangrove fish community, as most fish recorded were reef-associated. Juveniles of 12 reef species were observed, including two species classified as vulnerable on the IUCN list, and one endemic species. Fish assemblages on the mangrove edge differed significantly from those inside the forest. Most fish utilised the forest edge, with few species making regular use of in-forest habitats, supporting the contention that most fish species remain on the edge and potentially retreat into the forest for opportunistic feeding, or when threatened by larger predators. Species-specific patterns of utilisation varied across the tidal and lunar cycle. Small differences in depth profiles and substrate across the small-scale system had a significant effect on fish assemblages, highlighting the importance of accounting for spatial heterogeneity in these factors. These data provide important information for managers to implement adequate conservation strategies that include broader interconnected habitat mosaics.

Tethering experiments are one of the few approaches available to ecologists to assess predation rates in aquatic environments, and they have provided important insights into the processes driving observed patterns in aquatic communities. The potential for experimental artefacts to arise when tethering mobile prey has been well recognised and was vigorously discussed in the literature around 20 years ago. However, we reviewed 128 published studies that tethered fish and mobile crustaceans and found a growing number since that time that we believe do not adequately consider these potential issues. The majority of studies recognise that tethering mobile prey can only provide a relative rather than absolute estimate of predation rates, yet 16% present and interpret their results as if they reflect absolute natural predation rates. Two thirds of published studies at least acknowledge other potential artefacts, less than half test for them, while one third seemingly give no consideration to potential artefacts or biases of the method. Our review also revealed the potential for a lack of independence between individual replicates. More than two thirds of studies deployed replicate tethered prey a minimum of no>5m apart, with more than one quarter deploying them no>1m apart. Eighty-five percent of studies considered missing prey to represent predation. We deployed 104 tethered fish prey in field trials and monitored them using remote underwater video to determine the causes of prey loss. These trials reinforced the simple but important point that prey missing from tether lines at the end of an experiment can be missing for a variety of reasons other than reflecting predation. They also highlight the potential for underwater video, where it is practical to use, to overcome many of the issues confronting field tethering experiments. Carefully designed tethering studies will continue to be an important tool for ecologists studying patterns of predation in aquatic systems. However, our findings suggest a re-emerging need for researchers to recognise and test for potential biases and artefacts inherent with the technique.

Acute thermal and asphyxia exposure risks for freshwater fish occupying three tropical wetland typologies were examined. Field water‐quality data revealed that fish in wetlands grazed by pigs had the highest exposure risks, because they are shallow and heavily damaged by pig activities. In contrast, with the exception is dissolved oxygen (which still reached critical conditions because of aquatic vegetation respiration), deeper permanent and pig‐managed wetlands provides the best opportunity for the same fish species to survive in a heavily pig‐modified tropical landscape.

The unique values of Australia's Great Barrier Reef (GBR) are under threat from environmental change and the unforeseen, cumulative consequences of coastal development. Development decisions are underpinned by Environmental Impact Assessments (EIAs) but these are plagued by inconsistent methods and a lack of independent evaluation, leading to perceptions of inadequate scientific rigor. To be credible and effective, EIAs should be subject to independent peer review, the yardstick applied in the normal process of science. Without it, decisions based on EIA are at best contestable and potentially invalid. Peer review should be applied to the whole EIA process from project development to reporting and auditing approval requirements. It should be based on rigorous, standard protocols, and produce standardized and publicly available data. Securing the future of the GBR and other global natural assets requires refocusing EIA so it becomes a tool for strategic environmental protection rather than ad hoc permitting of development.

Globally the coastal zone is suffering the collateral damage from continuing urban development and construction, expanding resource sectors, increasing population, regulation to river flow, and on-going land change and degradation. While protection of natural coastal habitat is recommended, balancing conservation with human services is now the challenge for managers. Marine infrastructure such as seawalls, marinas and offshore platforms is increasingly used to support and provide services, but has primarily been designed for engineering purposes without consideration of the ecological consequences. Increasingly developments are seeking alternatives to hard engineering and a range of ecological solutions has begun to replace or be incorporated into marine and coastal infrastructure. But too often, hard engineering remains the primary strategy because the tools for managers to implement ecological solutions are either lacking or not supported by policy and stakeholders. Here we outline critical research needs for marine urban development and emerging strategies that seek to mitigate the impacts of marine infrastructure. We present case studies to highlight the strategic direction necessary to support management decisions internationally.

Coastal freshwater and tidal wetland habitats are being transformed as a result of increasing demand for commercial, residential and tourism activities. The consequence is a habitat seascape complex, comprising a mosaic of natural and engineered coastal features. This study used the freely available mapping tool (Google Earth) to define the extent of coastal engineering structures in the Great Barrier Reef World Heritage Area (GBR; Australia), a marine ecosystem of global biodiversity and cultural significance. Continuing threats to the heritage estate concomitant with expanding urban and industrial developments has raised concerns directed at the future conservation and resilience of the reef ecosystems, along with maintaining expected human lifestyles and livelihoods it provides. The data here shows that break walls and pontoons/jetties dominate development, contributing to approximately 10% (equivalent) of the coastline linear length. Most (60%) development occurs along the coastline or within the first few kilometres upstream along estuaries. While conservation and protection of natural coastal habitats is still preferred for the objective of fisheries production and biodiversity, managers must consider seascape implication/benefits more broadly when approving new marine infrastructure rather than a case-by-case approach which further contributes to an ad hoc mosaic seascape of natural and engineered habitats. Not only within the GBR heritage estate, but more broadly, coastal managers need to regard wider seascape connectivity processes during the assessment of any new development. There is an urgent need for policy and planning instrument reform that is inclusive of accumulative impacts of urban and industrial development in this heritage estate. Opportunities to include eco-friendly (green engineering) solutions, in the repair and revitalisation of existing artificial structures, is necessary in any new proposed urban and industrial development and expansion.

The ephemeral rivers in northern Australia break up into a series of waterholes during the long, dry summer season. These in-stream waterholes provide vital habitat for the survival of aquatic biota during this period. We describe how high-time-resolution (20 min) waterhole temperature measurements made in the Flinders and Gilbert Rivers in tropical northern Australia were used to derive thermal frequency curves that show how often waterhole temperature exceeded any given temperature threshold. During the summer period, temperatures near the surfaces of waterholes were often above that suitable for the optimum growth of some tropical fish (31°C). At the bottom of waterholes, this exceedance occurred less often, and in turbid waterholes that were stratified, temperatures rarely exceeded this threshold. Temperatures that could be lethal to some fish (34°C) also were exceeded at the surface of waterholes, but rarely, if ever, at the bottom of waterholes. An energy-balance model was used to estimate d...

International audience; Perennial rivers and streams make a disproportionate contribution to global carbon (C) cycling. However, the contribution of intermittent rivers and ephemeral streams (IRES), which sometimes cease to flow and can dry completely, is largely ignored although they represent over half the global river network. Substantial amounts of terrestrial plant litter (TPL) accumulate in dry riverbeds and, upon rewetting, this material can undergo rapid microbial processing. We present the results of a global research collaboration that collected and analysed TPL from 212 dry riverbeds across major environmental gradients and climate zones. We assessed litter decomposability by quantifying the litter carbon-to-nitrogen ratio and oxygen (O2) consumption in standardized assays and estimated the potential short-term CO2 emissions during rewetting events. Aridity, cover of riparian vegetation, channel width and dry-phase duration explained most variability in the quantity and decomposability of plant litter in IRES. Our estimates indicate that a single pulse of CO2 emission upon litter rewetting contributes up to 10% of the daily CO2 emission from perennial rivers and stream, particularly in temperate climates. This indicates that the contributions of IRES should be included in global C-cycling assessments.

The shallow tidal and freshwater coastal wetlands adjacent to the Great Barrier Reef lagoon provide a vital nursery and feeding complex that supports the life cycles of marine and freshwater fish, important native vegetation and vital bird habitat. Urban and agricultural development threaten these wetlands, with many of the coastal wetlands becoming lost or changed due to the construction of artificial barriers (e.g. bunds, roads, culverts and floodgates). Infestation by weeds has become a major issue within many of the wetlands modified (bunded) for ponded pasture growth last century. A range of expensive chemical and mechanical control methods have been used in an attempt to restore some of these coastal wetlands, with limited success. This study describes an alternative approach to those methods, investigating the impact of tidal reinstatement after bund removal on weed infestation, associated changes in water quality, and fish biodiversity, in the Boolgooroo lagoon region of the Mungalla wetlands, East of Ingham in North Queensland. High resolution remote sensing, electrofishing and in-water logging was used to track changes over time- 1 year before and 4 years after removal of an earth bund. With tides only penetrating the wetland a few times yearly, gross changes towards a more natural system occurred within a relatively short timeframe, leading to a major reduction in infestation of olive hymenachne, water hyacinth and salvina, reappearance of native vegetation, improvements in water quality, and a tripling of fish diversity. Weed abundance and water quality does appear to oscillate however, dependent on summer rainfall, as changes in hydraulic pressure stops or allows tidal ingress (fresh/saline cycling). With an estimated 30% of coastal wetlands bunded in the Great Barrier Reef region, a passive remediation method such as reintroduction of tidal flow by removal of an earth bund or levee could provide a more cost effective and sustainable means of controlling freshwater weeds and improving coastal water quality into the future.

Optimizing the utility of constructed waterways as residential development with water-frontage, along with a productive and functional habitat for wildlife is of considerable interest to managers. This study examines Lake Hugh Muntz, a large (17 ha) freshwater lake built in Gold Coast City, Australia. A ten year water quality monitoring programme shows that the lake has increasing nutrient concentrations, and together with summer algal blooms, the lake amenity as a popular recreational swimming and triathlon training location is at risk. A survey of fish and aquatic plant communities showed that the lake supports a sub-set of species found in adjacent natural wetlands. Sediment contaminants were below the lower Australian trigger values, except As, Hg, Pb and Zn, probably a function of untreated and uncontrolled stormwater runoff from nearby urban roads. Sediment biogeochemistry showed early signs of oxygen depletion, and an increase in benthic organic matter decomposition and oxygen consumption will result in more nitrogen recycled to the water column as NH4(+) (increasing the intensity of summer algal blooms) and less nitrogen lost to the atmosphere as N2 gas via denitrification. A series of catchment restoration initiatives were modeled and the optimal stormwater runoff restoration effort needed for lake protection will be costly, particularly retrospective, as is the case here. Overall, balancing the lifestyles and livelihoods of residents along with ecosystem protection are possible, but require considerable trade-offs between ecosystem services and human use.

The construction of artificial, residential waterways to increase the opportunities for coastal properties with waterfrontage is a common and widespread practice. We describe the fish community from the world's largest aggregation of artificial, estuarine lakes, the Burleigh Lake system that covers 280 ha on the Gold Coast in Queensland, Australia. Fish were collected from 30 sites in winter and spring of one year, and water salinity was measured 3-monthly for a 10 year period. Fish are not present in deep, bottom waters and the intensive sampling focussed on the shallow waters around lake margins. The fish fauna consisted of 33 species. All but three species are marine species that can tolerate some brackishness. The other three are freshwater species, normally found in rivers but also occurring in the upper reaches of estuaries. Fish communities differed among the lakes, reflecting a weak gradient in salinity in lakes at different distances from the single connection to the natural estuary and thus marine waters. Overall, the deeper (to 28 m), wider (700 m) characteristics of lake estates, and their incorporation of partial barriers to tidal exchange with natural reaches of estuaries, remove some of the hydrological concerns with very extensive canal estates. The shallow lake margins are habitat for a subset of fish species inhabiting adjacent natural wetlands. Where the lakes occupy space that was formerly land, this is novel habitat for fish. In place, however, where lakes have replaced natural wetlands, further comparisons of fish in lake and adjacent natural wetlands will be useful.

Understanding the effects of sediment disturbances on nutrient loadings is important for the management of estuarine settings. This study investigated the initial influence of sediment disturbance on water column nutrient concentrations in a shallow estuarine setting within the Gold Coast Broadwater, using a laboratory-based approach. Undisturbed sediment cores (200 mm Ø × 330 mm length, plexiglass) were incubated before and after being subjected to a disturbance event, to investigate the effect on the immediate and subsequent short-term water column nutrient concentrations. Sediment NH4+bio and PO43-bio concentrations ranged from 150 to 478 and 1.50 to 8.56 nmol g-1dry wt, respectively. Water column NH4+concentrations underwent the greatest increase (>1000% or approx. 14 times greater) immediately following disturbance, with mean effluxes increasing by >300%. Thereafter, water column NH4+concentrations and efflux rates declined to near initial pre-disturbance concentrations. Water column NH4+concentrations accounted for 0.58%-5.50% of the depth-integrated sediment NH4+bio concentration, indicating mobilization of the sediment bound exchangeable NH4+. The observed changes in PO43-concentrations and fluxes were much lower in comparison to those observed for N-species. Following disturbance, increases in the water column PO43-concentration accounted for 7.16%-8.22% depth-integrated sediment bioavailable PO43-at +1 and +2 hours, and 5.65% at +7 hours, respectively. These results provide important insight into the potential implications of disturbance events, such as vessel activities and dredging operations, within the case study region, providing information for potential management options and relevant water quality concerns. Refereed/Peer-reviewed

Artificial residential waterways are now widespread in the world’s estuaries. We used the global mapping tool, Google Earth, to determine that there are nearly 4000 linear km of artificial waterways globally, covering an area of 270 km 2 . Residential waterways constructed as open, flow-through canal estates are at their greatest extent in North America (77% of global linear extent), where systems are typically longer and narrower, with more openings and dead-ends than systems elsewhere. The remaining canal estates are spread across all other continents except Antarctica: Asia (7%), Europe (7%), Oceania (7%), South America (0.9%), and Africa (0.6%). A relatively recent design change from open canals to artificial estuarine lakes with tidal barriers has occurred on all continents except Africa, most extensively in Australia (14 km 2 area, 57 independent systems). The extremely large expansion in artificial residential waterways aimed at increasing opportunities for waterfront living by humans has also modified and expanded estuarine habitat available to aquatic biota. Research can best underpin planning and management of these types of waterways by focussing on their value as habitat and their provision of other goods and services.

Excess nitrogen (N) leading to the eutrophication of water and impacts on ecosystems is a serious environmental challenge. Wetlands can remove significant amounts of N from the water, primarily through the process of denitrification. Most of our knowledge on wetland denitrification is from temperate climates; studies in natural tropical wetlands are very scarce. We measured denitrification rates during a dry and a wet season in five floodplain forests dominated by Melaleuca spp., a coastal freshwater wetland of tropical Australia. We hypothesised that the denitrification potential of these wetlands would be high throughout the year and would be limited by N and carbon (C) availability. Mean potential denitrification rates (Dt) were 5.0±1.7mgm2h–1, and were within the reported ranges for other tropical and temperate wetlands. The rates of Dt were similar between the dry and the wet seasons. From the total unamended denitrification rates (Dw, 3.1±1.7mgm2h–1), 64% was derived from NO3– of the water column and the rest from coupled nitrification–denitrification. The factor most closely associated with denitrification was background water NO3–-N concentrations. Improved management and protection of wetlands could play an important role in improving water quality in tropical catchments.

Correction to: Nature Geoscience https://doi.org/10.1038/s41561-018-0134-4, published online 21 May 2018. In the version of this Article originally published, the affiliation for M. I. Arce was incorrect; it should have been: 5Leibniz Institute of Freshwater Ecology and Inland Fisheries (IGB), Berlin, Germany. This has now been corrected in the online versions of the Article.

Fishes were collected from residential canal estates leading directly off natural estuaries and artificial lakes with control tidal exchange in south-east Queensland, Australia, to test the model that the difference in artificial waterway design affects fish assemblages. A total of 17 779 fish representing 52 species was caught, including 23 species of economic importance (45% of the catch). Total fish abundance and species richness differed little among sites within or between the two artificial habitats (canals and lakes) in either of the seasons sampled (winter and spring). Multivariate analysis showed, however, that assemblages differed among sites within the same artificial habitat. The differences were best explained by the distance sites were from open water, while salinity, water temperature and dissolved oxygen explained little of the variability. Most species were found in canals and lakes, but there were enough differences in composition between the habitats to detect a difference in both seasons (significant ANOSIM tests). Salinity was lower in lakes because of the tidal restrictions, and while this was only weakly correlated with differences in fish assemblages, it had the most explanatory power of any environmental variable. New recruits arrived later in lakes than canals, perhaps because of the barriers to tidal flow. A survey the following year showed that differences among individual lakes were consistent through time, offering insights into the influence of different tidal barriers on fish assemblages. The design change from canals to lakes has a minor influence on fish assemblages and alters the timing of recruitment.

[Extract] The coastal zone functions as an interconnected habitat complex that provides critical nursery and feeding services for the health and longevity of fisheries production. Protection of this habitat complex is always preferred for biodiversity protection and conservation. The World Wildlife Fund recently (2014) finalized the "Living Planet Report" (http://wwf.panda. org/about_our_earth/all_publications/living_planet_report/), and outlined that the collateral damage of human population growth and development, in addition to climate change, continues to threaten the utility of freshwater and coastal wetlands as critical habitats (Figure 1). These threats are most apparent in the tropics (N 23.4378°, S 23.4378°) where biodiversity is greatest, but also where most of the population growth and development is anticipated over the next few decades. In reaction to these conclusions, we advocate that protection of tropical coastal ecosystems under a business-asusual approach is impracticable. Resilience and protection of coastal services necessitates targeted scientific research on the full range of created habitats. In addition, all new development approvals need eco-friendly engineering designs. Climate change and rising sea level need to be also considered as part of marine spatial planning initiatives. This more inclusive approach would enhance the resilience of tropical coastal systems leading to more robust ecology that is better able to accommodate expected future landscape scenarios.

We used carbon stable isotope and stomach content analyses to test whether snub-nosed garfish, Arrhamphus sclerolepis (Hemiramphidae), in the extensive artificial urban waterways of southeast Queensland, Australia, rely on autotrophic sources different to those in natural wetlands. Carbon isotope values of A. sclerolepis were similar to those in previous investigations, with enriched values in natural habitat (mean = −13.9‰, SE=0.6) and depleted values (−19.1‰, 0.1) in artificial habitat. A. sclerolepis in natural habitat consumed large amounts of seagrass during the day and night, and at night also ingested small quantities of crustacean prey. In artificial habitat, A. sclerolepis consumed macroalgae during the night and switched to invertebrates (terrestrial ants) in the day. Values of δ15 N in all the fish were 3–8‰ more enriched than sources. Mathematical modelling of feasible source mixtures showed that in natural habitat the bulk of the dietary carbon is obtained from seagrass, but the nitrogen is obtained from animal prey. In artificial habitat, carbon is obtained from a mixture of macroalgae and animals. We could not determine the nitrogen sources in artificial habitat of A. sclerolepis since, even after accounting for trophic fractionation of δ15 N, the values were outside the range of potential sources. If the types of animals ingested vary over time, perhaps one or more types of animal important in the provision of nitrogen was not sampled during the study. This study demonstrates that not only does A. sclerolepis occur in both artificial and natural habitats, but it uses the same strategy of bulk herbivory with the inclusion of smaller amounts of animal prey. This understanding of how ecological processes support fisheries production in artificial habitat improves the overall understanding of the effects of urbanisation on coastal food webs.

The Gold Coast Broadwater, a large shallow estuarine water body, is a central feature of the Gold Coast City in Southeast Queensland (Australia) and forms the southern part of Moreton Bay. The Broadwater has undergone dramatic changes over the past few decades, including the construction of an extensive number and network of artificial waterways that account for up to 90 % of Australia’s canal estates. Positioned in one of the fastest growing regions in the developed world, urbanisation surrounding the Broadwater will continue. The region has important biodiversity values that have led to areas of the Broadwater being listed as an international Ramsar site and inclusion to international migratory bird agreements. The Broadwater provides a vital function in the provision of feeding, spawning and nursery sites for recreationally and commercially important finfish species. Key to the protection of the Broadwater is a reduction of pollutant loads from urban and agricultural stormwater run-off, golf courses and industrial infrastructure/areas and replacement of natural habitats with urban development. Collectively, initiatives undertaken by regulatory authorities have been successful to date and demonstrate that future conservation requires the integration of multidisciplinary science and proactive management driven by the high ecological, economical and community values placed on the Broadwater and adjoining waterways.

The Gold Coast City is the tourist center of Australia and has undergone rapid and massive urban expansion over the past few decades. The Broadwater estuary, in the heart of the City, not only offers an array of ecosystems services for many important aquatic wildlife species, but also supports the livelihood and lifestyles of residents. Not surprisingly, there have been signs of imbalance between these two major services. This study combined a waterway hydraulic and pollutant transport model to simulate diffuse nutrient and sediment loads under past and future proposed land-use changes. A series of catchment restoration initiatives were modeled in an attempt to define optimal catchment scale restoration efforts necessary to protect and enhance the City’s waterways. The modeling revealed that for future proposed development, a business as usual approach to catchment management will not reduce nutrient and sediment loading sufficiently to protect the community values. Considerable restoration of upper catchment tributaries is imperative, combined with treatment of stormwater flow from intensively developed sub-catchment areas. Collectively, initiatives undertaken by regulatory authorities to date have successfully reduced nutrient and sediment loading reaching adjoining waterways, although these programs have been ad hoc without strategic systematic planning and vision. Future conservation requires integration of multidisciplinary science and proactive management driven by the high ecological, economical, and community values placed on the City’s waterways. Long-term catchment restoration and conservation planning requires an extensive budget (including political and societal support) to handle ongoing maintenance issues associated with scale of restoration determined here.

Dry-season waterholes in ephemeral rivers provide vital habitat for aquatic biota, whose survival is dependent on the waterholes lasting throughout the dry season with temperatures that are not lethal. To examine this in the Flinders and Gilbert Rivers, 20-min temperature measurements were taken during the 2012–2013 dry season in 10 waterholes in each catchment. These data were used to derive thermal-frequency curves that quantify how often waterhole temperature exceeds thresholds for (1) the optimum growth of tropical fish and (2) their lethal temperature. Waterholes that remained deeper than ~0.5m throughout the dry season provided thermally suitable fish refugia, especially if they were turbid, because this decreased the risk of exposure to undesirable temperatures at the bottom of the waterhole. However, surface temperatures in these waterholes often exceeded optimal and even potentially lethal temperatures, so fish may have had to move to cooler water at the bottom of these waterholes. The risk to aquatic species in waterhole refugia is, therefore, primarily determined by depth, with shallow waterholes presenting the greatest risk because they become thermally unsuitable well before (1–2 months) they fully dry out.

Water hyacinth (Eichhornia crassipes) is an aquatic weed degrading tropical floodplains everywhere. On the Burdekin floodplain, northern Australia, it is widespread and contributes to poor water quality, specifically hypoxia which contributes to voluminous wetland fish kills each summer. Removing weeds have focused on applying herbicides using aerial spraying, though restoration success is not monitored. Here, we investigated four aerial spray applications scheduled between November 2013 (Year 1, November 2013 to November 2014) and November 2015 (Year 2, November 2014 to November 2015) in Lochinvah wetland (35 ha wetland, Burdekin floodplain). Using high-frequency (20 min) loggers, dissolved oxygen (DO%) was tracked, which revealed that concentrations were similar before and several weeks after a spray application (independent t test, p > 0.01, except spray application 2, p = 0.06). More interestingly, aquatic weed coverage was low (5% of wetland) during Year 1 and DO had a typical diurnal cycle (20% to 130%). In contrast, low wetland flushing in Year 2 and high weed coverage (80% coverage) combined to increase DO hypoxia exposure risks for fish, with nearly 100% of the logging time failing acute and chronic values known for local fish. The Year 2 weed cover also increased water temperature exposure risk (twofold increase), which was unexpected and which means that fish probably could access cool, deeper, water refugia more frequently compared with Year 1. Controlling aquatic weeds using aerial spraying seems to have minimal risk for fish when cover is low; however, the proliferation of aquatic weeds and spraying has deleterious impact on available oxygen for fish.

Benthic oxygen and nutrient fluxes and nitrate reduction rates were determined seasonally under light and dark conditions at three sites in a micro-tidal creek within an urbanised catchment (Saltwater Creek, Australia). It was hypothesized that stormwater inputs of organic matter and inorganic nitrogen would stimulate rates of benthic metabolism and nutrient recycling and preferentially stimulate dissimilatory nitrate reduction to ammonium (DNRA) over denitrification as a pathway for nitrate reduction. Stormwaters greatly influenced water column dissolved inorganic nitrogen (DIN) and suspended solids concentrations with values following a large rainfall event being 5–20-fold greater than during the preceding dry period. Seasonally, maximum and minimum water column total dissolved nitrogen (TDN) and DIN concentrations occurred in the summer (wet) and winter (dry) seasons. Creek sediments were highly heterotrophic throughout the year, and strong sinks for oxygen, and large sources of dissolved organic and inorganic nitrogen during both light and dark incubations, although micro-phytobenthos (MPB) significantly decreased oxygen consumption and N-effluxes during light incubations due to photosynthetic oxygen production and photoassimilation of nutrients. Benthic denitrification rates ranged from 3.5 to 17.7 μmol N m2 h−1, denitrification efficiencies were low (

There has been a widespread world-wide use of flathead mullet, Mugil cephalus, in fish biomonitor studies within the coastal zone. This review summarises this research field, focusing on heavy metals, and considers the implications of the accumulated data. Differences in sampling methodology, tissues analysed and units of reported data provide challenges in assessing and benchmarking these biomonitor studies. The benthic feeding strategy of M. cephalus invariably increases exposure risk relative to middle or upper water column feeders, nevertheless contaminant accumulation via direct and indirect pathways was regulated sufficiently such that toxicants were below food guidelines in most coastal regions (32 of the 49 examined). Human health issues can arise if fish are consumed from heavily industrialised regions. Recommendations are provided for future biomonitoring studies, based on the results for M. cephalus but relevant for fish species more broadly, to provide more comparable data so that managers can benchmark against local conditions. Refereed/Peer-reviewed

Benthic oxygen and nutrient fluxes, and rates of nitrate reduction, were determined seasonally under light and dark conditions at four sites within a sub-tropical coastal lagoon (Coombabah Lake, Australia). Sediments at all sites were strongly heterotrophic acting as strong oxygen sinks and sources of dissolved inorganic nitrogen (DIN) in all seasons during both light and dark incubations. Sediment oxygen demand (SOD) and DIN effluxes were greatest during summer, but showed only a relatively small degree of seasonal variation. In contrast, there was a strong spatial trend in SOD and DIN effluxes, which were consistently greater at the sites with fine grained compared to the coarser sediments. Microphytobenthos (MPB) directly influenced SOD and DIN effluxes, with lower SOD and DIN effluxes measured during all light incubations. Strong correlations were found between sediment chlorophylla content and light-dark shifts in oxygen and ammonium fluxes (Delta O-2 and Delta NH4+), and between Delta O-2 and Delta NH4+. Rates of total nitrate reduction were relatively low ranging from 3 to 26 mu mol N m(-2) h(-1) and exhibited only minor seasonal variations. Dissimilatory nitrate reduction to ammonium (DNRA) was the dominant pathway for nitrate reduction, accounting for on average, 65 and 68% of total nitrate reduction during light and dark incubations. respectively. Nitrification was the dominant source of nitrate fuelling nitrate reduction processes, accounting for approximately 90% of total nitrate supply. In contrast to typical MPB colonised sediments, rates of nitrification and, as a consequence, nitrate reduction rates were consistently stimulated in the light, indicating that MPB primarily influenced these processes through photosynthetic oxygen evolution rather than through competition for inorganic N-species. Refereed/Peer-reviewed

Despite the widespread use of carbon stable isotopes to distinguish among potential energy pathways in food webs, their usefulness is limited where potential basal carbon sources are numerous and diverse. We measured carbon isotope values of the major fisheries species, the mostly carnivorous Scylla serrata (giant mud crab), and potential basal, autotrophic sources supporting the food web. Conventional mixing modelling of autotroph and crab isotope data could not differentiate contributions from different sources. Pooling of modelled contributions from sources with similar isotope values indicated a role for organic matter from seagrass meadows or saltmarshes, but still did not define contributions well. Crab isotope data from a subsequent, spatially explicit survey of 14 sites, selected to represent different distances from key habitats, were analyzed using multiple regression. Crab isotope values showed a significant relationship with distance from seagrass (R^2 = 0.87), but not with distance from mangroves or saltmarsh grass. Alongside seagrass meadows, crabs had very enriched isotope values, demonstrating their reliance on sources with enriched isotope values (seagrass and algae epiphytic on seagrass, 65–90% of their energy intake). At the site furthest from seagrass (21 km), crabs assimilated carbon primarily from depleted sources such as mangroves and terrestrial organic matter from coastal catchments (70–85%). Explicit spatial analysis of isotope data following a comprehensive survey revealed energy pathways not evident in conventional analyses.

Metal and pesticide contaminants were measured in water, sediment and fish species in various Gold Coast waterways, Queensland. With the exception of Cu, metal concentrations in water, measured using the diffuse gradients in a thin film (DGT) technique, complied with relevant Australian guidelines. Cu concentrations in these waterways have been related to recreational vessel activities previously. All sediment metal concentrations measured were below the national guidelines, although Cu, Zn and Pb were found to vary significantly between habitat types. Evidence of spikes in sediment pesticide concentrations (some banned over 50 years ago) was observed in some artificial residential waterways. Heavy metals and pesticides were measured in the tissue (muscle, gills and liver) of three economically important species of fish, with different feeding strategies (partly herbivore Arrhamphus sclerolepis, carnivore Acanthopagrus australis, detritivore Mugil cephalus). We tested the hypothesis that fish accumulate different amounts of contaminants from wetland habitats affected by different intensities of anthropogenic activities (i.e., marinas, artificial residential canals, artificial residential lakes, estuaries and natural, vegetated waterways). Significantly higher concentrations of Cu were found in the gills of each fish species from marinas compared to fish caught in other waterways. Furthermore, fish caught in canals had the second highest Cu and natural waterways the lowest. These results support the stated hypothesis for Cu and furthermore indicate that these fish species are suitable as biomonitors in estuarine waterways. Metal and pesticide concentrations in the edible muscle tissue of all fish complied with the Australian Food Standard Code recommended limits for human consumption, apart from As which is likely to be due to bioconcentration of lower toxicity organo-As species. These results indicate a low health risk for humans consuming fish, in terms of contaminant levels. The accumulated body of evidence on contaminants within Gold Coast waterways generally suggests that there are no major threats of metal or pesticide contamination, except for marina facilities which are a major source of Cu which also accumulates in fish. Water quality threats are also highlighted in residential canals, presumably as a consequence of their hydrological design. Refereed/Peer-reviewed