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Novel combinations of climatic conditions due to climate change and prolonged fire seasons have contributed to an increased occurrence of "megafires". Such large-scale fires pose an unknown threat to biodiversity due to the increased extent and severity of burn. Assessments of wildfires often focus on terrestrial ecosystems and effects on aquatic habitats are less documented, particularly in coastal environments. In a novel application of eDNA techniques, we assessed the impacts of the 2019-2020 Australian wildfires on the diversity of estuarine benthic sediment communities in six estuaries in NSW, Australia, before and after the fires. Estuaries differed in area of catchment burnt (0-92%) and amount of vegetative buffer that remained post-fire between burnt areas and waterways. We found greater dissimilarities in the composition and abundance of eukaryotic and bacterial sediment communities in estuaries from burnt catchments with no buffer compared to those with an intact buffer or from unburnt catchments. Shifts in composition in highly burnt catchments were associated with increased concentrations of nutrients, carbon, including fire-derived pyrogenic carbon, and copper, which was representative of multiple highly correlated trace metals. Changes in the relative abundances of certain taxonomic groups, such as sulfate-reducing and nitrifying bacterial groups, in the most impacted estuaries indicate potential consequences for the functioning of sediment communities. These results provide a unique demonstration of the use of eDNA to identify wildfire impacts on ecological communities and emphasize the importance of vegetative buffers in limiting wildfire-associated impacts.

Successful decommissioning of subsea oil and gas infrastructure requires a safe and effective approach to assess and manage waste products. These products, often present as scale on internals of pipelines, include naturally occurring radioactive materials (NORM) and trace metals. Understanding the potential effects of these contaminants on marine fauna is crucial to managing global decommissioning. This review is composed of two aspects: 1) a systematic review was conducted to synthesize literature on all contaminants associated with decommissioned offshore structures and the effects of NORM contaminants on marine organisms; 2) a critical review of current environmental regulations for decommissioning and characterization of petroleum scale and NORM components. Studies defining the chemical and radiological contaminants associated with decommissioned structures were very limited. The main source of contaminants was identified from offshore platforms, with none from subsea structures. Only three studies measured variable chemical effects of radium to organisms from scale materials in subsea oil and gas infrastructure. No studies measured effects on organisms from other NORM, such as lead-210 and polonium-210. Currently, there are no international regulations on subsea pipeline closure, with NORM being underreported and not addressed in environmental impact assessments. This review highlights research gaps from environmental monitoring and characterization of NORM associated with decommissioned structures. Key recommendations for future research include characterizing NORM scale and assessing effects of scale to marine organisms through direct organism exposure experiments. This review emphasizes the need to incorporate ecotoxicology into environmental risk assessment for offshore petroleum decommissioning.

Over the last century, human activities have increased the amount of nutrients inputs to terrestrial and aquatic ecosystems. These activities have altered nitrogen (N) and phosphorus (P) cycling, causing substantial changes in ecosystem function such as provision of clean air and water. Strategies that reduce and remove excess nutrients are urgently needed to remediate impacted systems. Reef-forming shellfish (oysters and mussels) can play a crucial role in nutrient cycling, particularly in N removal from aquatic systems by providing substrate for microbial colonisation and enhancing microbial denitrification in the surrounding sediments. However, the potential for shellfish to enhance nutrient cycling (and denitrification) will likely vary spatially and in response to several environmental factors. Here, we used 1) a qualitative analysis to review nutrient processes occurring on shellfish; and 2) a meta-analysis to evaluate the influence of shellfish on benthic metabolism and nutrient cycling in surrounding sediments, and how that is influenced by environmental factors such as grain size, seasonality, water body type, and tidal position. Overall, we found that shellfish increased oxygen consumption, with consequent release of ammonia (NH

Estuaries are one of the most valuable biomes on earth. Although humans are highly dependent on these ecosystems, anthropogenic activities have impacted estuaries worldwide, altering their ecological functions and ability to provide a variety of important ecosystem services. Many anthropogenic stressors combine to affect the soft sedimentary habitats that dominate estuarine ecosystems. Now, due to climate change, estuaries and other marine areas might be increasingly exposed to the emerging threat of megafires. Here, by sampling estuaries before and after a megafire, we describe impacts of wildfires on estuarine benthic habitats and justify why megafires are a new and concerning threat to coastal ecosystems. We (1) show that wildfires change the fundamental characteristics of estuarine benthic habitat, (2) identify the factors (burnt intensity and proximity to water's edge) that influence the consequences of fires on estuaries, and (3) identify relevant indicators of wildfire impact: metals, nutrients, and pyrogenic carbon. We then discuss how fires can impact estuaries globally, regardless of local variability and differences in catchment. In the first empirical assessment of the impact of wildfires on estuarine condition, our results highlight indicators that may assist waterway managers to empirically detect wildfire impacts in estuaries and identify catchment factors that should be included in fire risk assessments for estuaries. Overall, this study highlights the importance of considering fire threats in current and future estuarine and coastal management.

Human activities introduce significant contamination into aquatic systems that impact biodiversity and ecosystem function. Many contaminants accumulate, and remediation options are now required worldwide. One method for bioremediation involves the application of macrofauna to stimulate microbial ecosystem processes including contaminant removal. However, if we are to confidently apply such a technique, we need clarity on the effect of bioturbators on different contaminants and how these vary under different environmental scenarios. Here we used a systematic review and meta-analysis to analyse current knowledge on the activities of bioturbating macrofauna in contaminated sediments and quantify how bioturbation-bioremediation changes depend on the taxonomic group, the aquatic ecosystem and important environmental variables. Three common contaminant classes were reviewed and analysed: metals, nutrients (i.e. ammonia and phosphorous) and polycyclic aromatic hydrocarbons (PAH). In addition, meta-regressions were calculated to estimate the effect of environmental and experimental design variables on effect sizes. Meta-analytic results revealed that deeper burrowing and more active sediment surface animals (e.g. polychaetes) increased metal release from sediments, nutrients and oxygen uptake by microbial fractions in comparison to bioturbators that inhabit shallower depths in sediments. In addition, there was a different effect of bioturbators on response variables in different aquatic systems. Finally, bioturbator effects on nutrient and metal release appeared modulated by context-specific variables such as temperature, pH, sediment grain size, animal density and experimental duration. Our findings highlight critical knowledge gaps such as field applications, less studied macrobenthic fauna and the incorporation of molecular approaches. Our results provide the first quantitative synthesis of the effects of bioturbators on contaminant fate and the variables that need to be considered for the optimization of this method as a viable approach for sediment remediation and contaminant management in aquatic systems.

Widespread wastewater pollution is a major barrier to the sustainable management of freshwater and coastal marine ecosystems worldwide. Integrated multi-disciplinary studies are necessary to improve waterway management and protect ecosystem integrity. This study used the Generalised Likelihood Uncertainty Estimation (GLUE) methodology to link microbial community ecotoxicology laboratory data to a mechanistic aquatic ecosystem response model. The generic model provided good predictive skill for major water quality constituents, including heterotrophic bacteria dynamics (r2 = 0.91). The model was validated against observed data across a gradient of effluent concentrations from community whole effluent toxicity (WET) laboratory tests. GLUE analysis revealed that a combined likelihood measure increased confidence in the predictive capability of the model. This study highlights the importance of calibrating aquatic ecosystem response models with net growth rates (i.e., sum of the growth minus loss rate parameter terms) of biological functional groups. The final calibrated net growth rate value of heterotrophic bacteria determined using the GLUE analysis was selected to be 0.58, which was significantly greater than the average literature value of -0.15. This finding demonstrated that use of literature parameter values without a good understanding of the represented processes could create misleading outputs and result in unsatisfactory conclusions. Further, fixed bulk mineralisation rate literature values are typically higher than realistically required in aquatic ecosystem response models. This indicates that explicitly including bacterial mineralisation is crucial to represent microbial ecosystem functioning more accurately. Our study suggests that improved data collection and modelling efforts in real-world management applications are needed to better address nutrients released into the natural environment. Future studies should aim to better understand the sensitivity of aquatic ecosystem response models to bacterial mineralisation rates.

Eutrophication is an increasing problem worldwide and can disrupt ecosystem processes in which macrobenthic bioturbators play an essential role. This study explores how intraspecific variation in body size affects the survival, mobility and impact on sediment organic matter breakdown in enriched sediments of an infaunal bivalve. A mesocosm experiment was conducted in which monocultures and all size combinations of three body sizes (small, medium and large) of the Sydney cockle, Anadara trapezia, were exposed to natural or organically enriched sediments. Results demonstrate that larger body sizes have higher tolerance to enriched conditions and can reduce survival of smaller cockles when grown together. Also, large A. trapezia influenced sediment organic matter breakdown although a direct link to bioturbation activity was not clear. Overall, this study found that intraspecific variation in body size influences survival and performance of bioturbators in eutrophic scenarios.

Marine artificial structures such as pilings are replacing natural habitats, and modifying surrounding areas, often resulting in local decreases in species diversity and facilitation of bioinvasion. Most research on the impacts of artificial structures in marine ecosystems has primarily focused on rocky bottom habitats and biodiversity, overlooking the effects of these structures on the functioning of nearby sedimentary habitats. Here we compared, for the first time, benthic metabolism (O

The terrestrial, freshwater and marine realms all provide essential ecosystem services in urban environments. However, the services provided by each realm are often considered independently, which ignores the synergies between them and risks underestimating the benefits derived collectively. Greater research collaboration across these realms, and an integrated approach to management decisions can help to support urban developments and restoration projects in maintaining or enhancing ecosystem services. The aim of this paper is to highlight the synergies and trade-offs among ecosystem services provided by each realm and to offer suggestions on how to improve current practice. We use case studies to illustrate the flow of services across realms. In our call to better integrate research and management across realms, we present a framework that provides a 6-step process for conducting collaborative research and management with an Australian perspective. Our framework considers unifying language, sharing, and understanding of desired outcomes, conducting cost-benefit analyses to minimise trade-offs, using multiple modes of communication for stakeholders, and applying research outcomes to inform regulation. It can be applied to improve collaboration among researchers, managers and planners from all realms, leading to strategic allocation of resources, increased protection of urban natural resources and improved environmental regulation with broad public support.

Artificial structures are agents of change in marine ecosystems. They add novel habitat for hard-substrate organisms and modify the surrounding environment. Most research to date has focused on the communities living directly on artificial structures, and more research is needed on the potential impacts these structures have on nearby communities and the surrounding environment. We compared the sedimentary habitat surrounding two types of artificial structures (pilings and seawalls) to sediments adjacent to rocky reefs using a combination of traditional sediment analyses, stable isotope analysis, and environmental DNA. Artificial and natural shore sediments were best differentiated by sediment variables strongly associated with flow speed. Pilings sediments had significantly finer grain size, higher organic content, and generally lower C:N ratios than sediments adjacent to the other habitat types, suggesting flow is reduced by pilings. Sedimentary assemblages near pilings were also consistent with those predicted under low-flow conditions, with elevated bacterial colonization and increased relative abundances of small deposit feeders compared with other habitat types. Additionally, lumbrinerid polychaetes in pilings sediments had reduced δ15N values, suggesting different detrital resources and fewer trophic linkages compared with lumbrinerids in other habitats. Woody detritus was greater adjacent to seawalls than to natural rocky shores or pilings. Our findings suggest that artificial structures have the potential to influence adjacent soft sediments through changes to sediment properties that affect infaunal and microbial communities, as well as trophic linkages for some consumers. We hypothesize that this is due to a combination of altered flow, differing detrital subsidies, and differing adjacent land-use among habitat types. Managers should consider the potential for changed sediment properties and ecology when deciding where to build different types of artificial structures. Further manipulative experiments are needed to understand mechanisms of change and help manage the impacts of artificial structures on the seafloor.

Coastal waterways are increasingly exposed to multiple stressors, e.g. contaminants that can be delivered via pulse or press exposures. Therefore, it is crucial that ecological impacts can be differentiated among stressors to manage ecosystem threats. We investigated microbial community development in sediments exposed to press and pulse stressors. Press exposures were created with in situ mesocosm sediments containing a range of ‘metal’ concentrations (sediment contaminated with multiple metal(loid)s) and organic enrichment (fertiliser), while the pulse exposure was simulated by a single dose of organic fertiliser. All treatments and exposure concentrations were crossed in a fully factorial field experiment. We used amplicon sequencing to compare the sensitivity of the 1) total (DNA) and active (RNA) component of 2) bacterial (16S rRNA) and eukaryotic (18S rRNA) communities to contaminant exposures. Overall microbial community change was greater when exposed to press than pulse stressors, with the bacterial community responding more strongly than the eukaryotes. The total bacterial community represents a more time-integrated measure of change and proved to be more sensitive to multiple stressors than the active community. Metals and organic enrichment treatments interacted such that the effect of metals was weaker when the sediment was organically enriched. Taxa-level analyses revealed that press enrichment resulted in potential functional changes, mainly involving nitrogen cycling. Furthermore, enrichment generally reduced the abundance of active eukaryotes in the sediment. As well as demonstrating interactive impacts of metals and organic enrichment, this study highlights the sensitivity of next-generation sequencing for ecosystem biomonitoring of interacting stressors and identifies opportunities for more targeted application.

There is growing public concern about the global expansion of harmful algal bloom species (HABs), with dinoflagellate microalgae comprising the major portion of the harmful taxa. These motile, unicellular organisms have a lifecycle involving sexual reproduction and resting cyst formation whereby cysts can germinate from sediments and 'seed' planktonic populations. Thus, investigation of dinoflagellate cyst (dinocyst) distribution in sediments can provide significant insights into HAB dynamics and contribute to indices of habitat quality. Species composition and abundance of dinocysts in relation to sediment characteristics were studied at 18 stations in two densely populated temperate Australian estuaries, Sydney Harbour (Parramatta River/Port Jackson; PS) and Botany Bay (including Georges River; GB). Eighteen dinocyst taxa were identified, dominated by Protoceratium reticulatum and Gonyaulax sp.1 in the PS estuary, together with Archaeperidinium minutum and Gonyaulax sp.1 in the GB estuary. Cysts of Alexandrium catenella, which is one of the causative species of paralytic shellfish poisoning (PSP), were also detected in both estuaries. Out of the measured sediment characteristics (TOC, Cd, Cr, Cu, Fe, Pb, Mn, Ni, Zn and polycyclic aromatic hydrocarbons), TOC was the parameter explaining most of the variation in dinocyst assemblages and was positively correlated to most of the heavy metals. Given the significant relationship between sediment TOC and dinocyst abundance and heavy metal concentrations, this study suggests that sediment TOC could be broadly used in risk management for potential development of algal blooms and sediment contamination in these estuaries.

Widespread wastewater pollution is one of the greatest challenges threatening the sustainable management of rivers globally. Understanding microbial responses to gradients in environmental stressors, such as wastewater pollution, is crucial to identify thresholds of community change and to develop management strategies that protect ecosystem integrity. This study used multiple lines of empirical evidence, including a novel combination of microbial ecotoxicology methods in the laboratory and field to link pressure-stressor-response relationships. Specifically, community-based whole effluent toxicity (WET) testing and environmental genomics were integrated to determine real-world community interactions, shifts and functional change in response to wastewater pollution. Here we show that wastewater effluents above moderate (>10%) concentrations caused consistent significant shifts in bacterial community structure and function. These thresholds of community shifts were also linked to changes in the trophic state of receiving waters in terms of nutrient concentrations. Differences in the community responses along the effluent concentration gradient were primarily driven by two globally relevant bacterial indicator taxa, namely Malikia spp. (Burkholderiales) and hgcI_clade (Frankiales). Species replacement occurred above moderate effluent concentrations with abundances of Malikia spp. increasing, while abundances of hgcI_clade decreased. The responses of Malikia spp. and hgcI_clade matched gene patterns associated with globally important nitrogen cycling pathways, such as denitrification and nitrogen fixation, which linked the core individual taxa to putative function and ecosystem processes, rarely achieved in previous studies. This study has identified potential indicators of change in trophic status and the functional consequences of wastewater pollution. These findings have immediate implications for both the management of environmental stressors and protection of aquatic ecosystems.

Infrastructure associated with coastal communities is likely to not only directly displace natural systems, but also leave environmental footprints' that stretch over multiple scales. Some coastal infrastructure will, there- fore, generate a hidden layer of habitat heterogeneity in sediment systems that is not immediately observable in classical impact assessment frameworks. We examine the hidden heterogeneity associated with one of the most ubiquitous coastal modifications; dense swing moorings fields. Using a model based geo-statistical framework we highlight the variation in sedimentology throughout mooring fields and reference locations. Moorings were correlated with patches of sediment with larger particle sizes, and associated metal(loid) concentrations in these patches were depressed. Our work highlights two important ideas i) mooring fields create a mosaic of habitat in which contamination decreases and grain sizes increase close to moorings, and ii) model- based frameworks provide an information rich, easy-to-interpret way to communicate complex analyses to stakeholders.

© 2019 Elsevier B.V. Natural systems are threatened by a variety of anthropogenic stressors and so understanding the interactive threats posed by multiple stressors is essential. In this study we focused on urban stressors that are ubiquitous to urban estuarine systems worldwide: elevated nutrients, toxic chemical contaminants, built infrastructure and non-indigenous species (NIS). We investigated structural (abundance, diversity and species richness) and functional endpoints (productivity, primary production (chlorophyll-a) and metabolism) commonly used to determine responses to these selected stressors. Through a systematic review of global literature, we found 579 studies of our selected stressors; 93% measured responses to a single stressor, with few assessing the effects of multiple stressors (7%). Structural endpoints were commonly used to measure the effects of stressors (49% of the total 579 studies). Whereas, functional endpoints were rarely assessed alone (10%) but rather in combination with structural endpoints (41%). Elevated nutrients followed by NIS were the most studied single stressors (43% and 16% of the 541 single stressor studies), while elevated nutrients and toxic contaminants were overwhelmingly the most common stressor combination (79% of the 38 multiple stressor studies); with NIS and built infrastructure representing major gaps in multi-stressor research. In the meta-analysis, structural endpoints tended to decrease, while functional endpoints increased and/or decreased in response to different types of organisms or groups. We predicted an antagonistic effect of elevated nutrients and toxic contaminants based on the opposing enriching versus toxic effects of this stressor combination. Of note, biodiversity was the only endpoint that revealed such an antagonistic response. Our results highlight the continuing paucity of multiple stressor studies and provide evidence for opposing patterns in the responses to single and interacting stressors depending on the measured endpoint. The latter is of significant consequence to understanding relevant impacts of stressors in coastal monitoring and management.

A workshop was held in Wageningen, The Netherlands, in September 2017 to collate data and literature on three aquatic ecosystem types (agricultural drainage ditches, urban floodplains, and urban estuaries), and develop a general framework for the assessment of multiple stressors on the structure and functioning of these systems. An assessment framework considering multiple stressors is crucial for our understanding of ecosystem responses within a multiply stressed environment, and to inform appropriate environmental management strategies. The framework consists of two components: (i) problem identification and (ii) impact assessment. Both assessments together proceed through the following steps: 1) ecosystem selection; 2) identification of stressors and quantification of their intensity; 3) identification of receptors or sensitive groups for each stressor; 4) identification of stressor-response relationships and their potential interactions; 5) construction of an ecological model that includes relevant functional groups and endpoints; 6) prediction of impacts of multiple stressors, 7) confirmation of these predictions with experimental and monitoring data, and 8) potential adjustment of the ecological model. Steps 7 and 8 allow the assessment to be adaptive and can be repeated until a satisfactory match between model predictions and experimental and monitoring data has been obtained. This paper is the preface of the MAEGA (Making Aquatic Ecosystems Great Again) special section that includes three associated papers which are also published in this volume, which present applications of the framework for each of the three aquatic systems.

The marine environment is being increasingly modified by the construction of artificial structures, the impacts of which may be mitigated through eco-engineering. To date, eco-engineering has predominantly aimed to increase biodiversity, but enhancing other ecological functions is arguably of equal importance for artificial structures. Here, we manipulated complexity through habitat structure (flat, and 2.5 cm, 5 cm deep vertical and 5 cm deep horizontal crevices) and seeding with the native oyster (Saccostrea glomerata, unseeded and seeded) on concrete tiles (0.25 m × 0.25 m) affixed to seawalls to investigate whether complexity (both orientation and depth of crevices) influences particle removal rates by suspension feeders and colonisation by different functional groups, and whether there are any ecological trade-offs between these functions. After 12 months, complex seeded tiles generally supported a greater abundance of suspension feeding taxa and had higher particle removal rates than flat tiles or unseeded tiles. The richness and diversity of taxa also increased with complexity. The effect of seeding was, however, generally weaker on tiles with complex habitat structure. However, the orientation of habitat complexity and the depth of the crevices did not influence particle removal rates or colonising taxa. Colonisation by non-native taxa was low compared to total taxa richness. We did not detect negative ecological trade-offs between increased particle removal rates and diversity and abundance of key functional groups. Our results suggest that the addition of complexity to marine artificial structures could potentially be used to enhance both biodiversity and particle removal rates. Consequently, complexity should be incorporated into future eco-engineering projects to provide a range of ecological functions in urbanised estuaries.

The supply and fate of wrack (dead organic matter) is a critical determinant of the structure and function of shoreline ecosystems, and their role as carbon repositories. The increasingly common practise of armouring urbanised shorelines with seawalls impacts wrack deposits of unvegetated estuarine and coastal shorelines by truncating the intertidal zone and/or by modifying the physical and biological processes that deliver and remove wrack. This study tested whether such effects also extend to mangrove forests. A survey of wrack deposits in mangrove forests with and without seawalls along the Parramatta River, Sydney, Australia, revealed that at sites with seawalls placed at a mid-intertidal elevation wrack deposits were shifted from the high- to mid-intertidal but were otherwise of similar cover and composition. Experiments tracking the fate of wrack determined that, as compared to the mid-intertidal zone of unarmoured shorelines, wrack deposits at sites with seawalls were more readily mobilised. This was in some instances countered by the reduction in Casuarina glauca litter on armoured shorelines, as experiments revealed that Avicennia marina leaf decomposition was slower in the absence than the presence of C. glauca. Overall, the results suggest that effects of armouring on wrack composition and dynamics may be weaker in mangrove forests than on unvegetated shorelines. This could reflect the predominantly autochthonous source of wrack in mangrove forests, the habitat structure of forests minimizing hydrodynamic impacts of seawalls, and/or the differing reasons for which hard structures are constructed in low hydrodynamic energy vegetated as opposed to high hydrodynamic energy unvegetated settings.

Offshore oil and gas activities can result in the discharge of large amounts of drilling muds. While these materials have generally been regarded as non-toxic to marine organisms, recent studies have demonstrated negative impacts to suspension feeding organisms. We exposed the arctic-boreal sponge Geodia barretti to the primary particulate components of two water-based drilling muds; barite and bentonite. Sponges were exposed to barite, bentonite and a natural reference sediment at a range of total suspended solid concentrations (TSS = 0, 10, 50 or 100 mg/L) for 12 h after which we measured a suite of biomarker responses (lysosomal membrane stability, lipid peroxidation and glutathione). In addition, we compared biomarker responses, organic energy content and metal accumulation in sponges, which had been continuously or intermittently exposed to suspended barite and natural sediment for 14 d at relevant concentrations (10 and 30 mg TSS/L). Lysosomal membrane stability was reduced in the sponges exposed to barite at 50 and 100 mg TSS/L after just 12 h and at 30 mg TSS/L for both continuous and intermittent exposures over 14 d. Evidence of compromised cellular viability was accompanied by barite analysis revealing concentrations of Cu and Pb well above reference sediments and Norwegian sediment quality guidelines. Metal bioaccumulation in sponge tissues was low and the total organic energy content (determined by the elemental composition of organic tissue) was not affected. Intermittent exposures to barite resulted in less toxicity than continuous exposure to barite. Short term exposures to bentonite did not alter any biomarker responses. This is the first time that these biomarkers have been used to indicate contaminant exposure in an arctic-boreal sponge. Our results illustrate the potential toxicity of barite and the importance of assessments that reflect the ways in which these contaminants are delivered under environmentally realistic conditions.

Burgeoning populations and the increasing concentration of humans in urban areas have resulted in extensive and increasing degradation and destruction of natural ecosystems. The multitude of impacts and their drivers in urban areas across realms are often studied at local scales, but there is regularly a mismatch between the spatial extent of the impacts and that of the pressures driving those impacts. For example, most human activities occur on land and therefore disturb terrestrial habitats (intrinsic impacts), but their impacts can also extend to the atmosphere and aquatic realms (extrinsic impacts). Management of urban impacts is often designed at local scales and aims to control local pressures, mostly overlooking pressures originating outside the 'managed' area. This is often due to jurisdictional barriers but can also result from the lack of knowledge and recognition among scientists and managers of larger scale pressures. With the aim to highlight the importance of ameliorating extrinsic impacts for holistic management of urban areas, this paper discusses the range and extent of extrinsic impacts produced by the most common pressures in urban environments. We discuss that the terrestrial realm is a 'net-donor' of impacts, as most human activities occur on land and the resulting impacts are transferred to aquatic and atmospheric realms. However, activities in aquatic realms can result in impacts on land. We conclude that, to achieve effective management strategies, greater collaboration is needed between scientists and managers focussing on different realms and regions and we present suggestions for approaches to achieve this.

Assessments of human impacts on natural habitats often focus on the abundance of component species, yet physiological and/or sub-lethal effects of stressors on functional attributes may be equally important to consider. Here we evaluated how artificial structures, an integral part of urbanisation in the marine environment, affects key functional properties of the habitat-forming kelp Ecklonia radiata. Given that stressors rarely occur in isolation, we assessed the effects of infrastructure across an urbanised estuary. Estuaries are ideal for studying how multiple anthropogenic and natural stressors influence potential impacts of infrastructure on habitat-forming species because these habitats usually face a wide range and levels of stressors. Here, we compared the abundance of habitat-forming macro-algae as well as the growth, erosion and photosynthetic activity of kelp in artificial and natural habitats across one of the largest urbanised estuaries in the word - Sydney Harbour. We predicted that effects of artificial structures on functional attributes of kelps would be stronger in the inner area of the Harbour, characterised by higher levels of human impacts and low flushing. Contrary to our predictions, we found that effects of infrastructure were consistent across the estuary, regardless of the ecological footprint caused by human activities or natural environmental gradients. When differences were observed between areas of the estuary, they mostly occurred independently of impacts of substrate type. Importantly, we found lower erosion rates of kelp on pilings than on reefs, likely resulting in lower production of detritus in estuaries where natural reefs are degraded or lost and pilings added. Such impacts have important implications for the connectivity among coastal habitats and secondary productivity in adjacent and remote habitats, which are highly dependent on the exportation of kelp detritus. Our study is the first to assess potential functional consequences of urbanisation through physiological and/or biomechanical effects on habitat-formers, an often overlooked mechanism of environmental impact on ecosystem functioning.

Ecosystems modified by human activities are generally predicted to be biologically impoverished. However, much pollution impact theory stems from laboratory or small-scale field studies, and few studies replicate at the level of estuary. Furthermore, assessments are often based on sediment contamination and infauna, and impacts to epibiota (sessile invertebrates and algae) are seldom considered. We surveyed epibiota in six estuaries in south-east Australia. Half the estuaries were relatively pristine, and half were subject to internationally high levels of contamination, urbanisation, and industrialisation. Contrary to predictions, epibiota in modified estuaries had greater coverage and were similarly diverse as those in unmodified estuaries. Change in epibiota community structure was linearly correlated with sediment-bound copper, and the tubeworm Hydroides elegans showed a strong positive correlation with sediment metals. Stressors such as metal contamination can reduce biodiversity and productivity, but others such as nutrient enrichment and resource provision may obscure signals of impact.

An ‘underwater elevator’ takes research 10,000 m under the sea and reveals a pollution legacy in remote oceanic trenches.

Cost-effective and sensitive measures of anthropogenic stress are necessary tools in any environmental monitoring program. When implementing new monitoring tools in a region, rigorous laboratory and field studies are essential for characterizing the sensitivity and efficacy of the approach. We exposed the oyster Saccostrea glomerata to various individual contaminants through multiple exposure pathways (water- and food-borne) in the laboratory and measured two biomarker responses, lysosomal membrane stability (LMS) and lipid peroxidation (LPO). LMS was sensitive to both contaminant exposure pathways. We subsequently measured this biomarker in oysters which had been experimentally deployed at multiple sites in each of ten estuaries with varying levels of contamination associated with re-suspended sediments. There was a strong association between LMS and metal exposure, despite substantial natural variation in water quality parameters. Our results illustrate the potential use of LMS as a pragmatic indicator of biotic injury in environmental monitoring programs for re-suspended contaminated sediments.

Intermittently Closed and Open Lakes and Lagoons (ICOLLS) are important coastal systems that are periodically separated from the ocean by a sand barrier or a berm. In urban ICOLLs, continuous inputs of organic material and nutrients into coastal lagoons are contributing to eutrophic conditions that, together with natural environmental factors have implications for the resident sediment bacterial communities. We used molecular tools to investigate the ecological communities of four ICOLLs; Narrabeen, Dee Why, Curl Curl and Manly in Sydney, Australia, which have been subjected to increasing pressure from anthropogenic activities over the last century. We used targeted gene sequencing of the prokaryotic 16S ribosomal RNA gene to describe the bacterial diversity and community structure and discuss differences with respect to environmental factors at the ICOLL scale (e.g. size, shape, normalised N loading) and site scale (e.g. water and sediment quality) within each lagoon. Due to differences in hydrological patterns, we expected that sediment bacterial communities would be more heterogenous in displacement-dominated lagoons (Curl Curl and Manly) than the mixing-dominated lagoons (Narrabeen and Dee Why). Interestingly, we did not find strong relationships between the main bacterial groups and distance from the lagoon entrance (used as a proxy for salinity and silt) in the displacement-dominated lagoons. Moreover, we found that α diversity was highest in Narrabeen and Manly lagoons despite differences in lagoon size and shape. Furthermore, while bacterial community structure was similar in Curl Curl and Dee Why, communities in Manly and Narrabeen differed along temperature/TOC and salinity/silt gradients respectively. In Manly lagoon, we found relatively more anaerobic bacteria such as Epsilonbactereota which is involved in the oxidation and reduction of sulfur compounds. Moreover, we identified several bacterial taxa (including sulfur metabolising Chlorobiaceae) related to increasing TOC that could be investigated further as potential indicators of excess enrichment.

Urban land and seascapes are increasingly exposed to artificial lighting at night (ALAN), which is a significant source of light pollution. A broad range of ecological effects are associated with ALAN, but the changes to ecological processes remain largely unstudied. Predation is a key ecological process that structures assemblages and responds to natural cycles of light and dark. We investigated the effect of ALAN on fish predatory behaviour, and sessile invertebrate prey assemblages. Over 21days fish and sessile assemblages were exposed to 3 light treatments (Day, Night and ALAN). An array of LED spotlights was installed under a wharf to create the ALAN treatments. We used GoPro cameras to film during the day and ALAN treatments, and a Dual frequency IDentification SONar (DIDSON) to film during the night treatments. Fish were most abundant during unlit nights, but were also relatively sedentary. Predatory behaviour was greatest during the day and under ALAN than at night, suggesting that fish are using structures for non-feeding purposes (e.g. shelter) at night, but artificial light dramatically increases their predatory behaviour. Altered predator behaviour corresponded with structural changes to sessile prey assemblages among the experimental lighting treatments. We demonstrate the direct effects of artificial lighting on fish behaviour and the concomitant indirect effects on sessile assemblage structure. Current and future projected use of artificial lights has the potential to significantly affect predator-prey interactions in marine systems by altering habitat use for both predators and prey. However, developments in lighting technology are a promising avenue for mitigation. This is among the first empirical evidence from the marine system on how ALAN can directly alter predation, a fundamental ecosystem process, and have indirect trophic consequences.

Ecological assessments over large spatial scales require that anthropogenic impacts be distinguishable above natural variation, and that monitoring tools are implemented to maximise impact detection and minimise cost. For three heavily modified and four relatively 'pristine' estuaries (disturbance category), chemical indicators (metals and PAHs) of anthropogenic stress were measured in benthic sediments, suspended sediments and deployed oysters, together with other environmental variables. These were compared with infaunal and hard-substrate invertebrate communities. Univariate analyses were useful for comparing contaminant loads between different monitoring tools and identified the strongest relationships between benthic and suspended sediments. However, multivariate analyses were necessary to distinguish ecological response to anthropogenic stressors from environmental "noise" over a large spatial scale and to identify sites that were being impacted by contaminants. These analyses provide evidence that suspended sediments are a useful alternative monitoring tool to detect potential anthropogenic impacts on benthic (infaunal and hard-substrate) communities. © 2011 Elsevier Ltd. All rights reserved.

Biofouling increases drag on marine vessels resulting in higher fuel consumption and can also facilitate the transport of harmful non-indigenous species (NIS). Antifouling technologies incorporating biocides (e.g., copper and tributyltin) have been developed to prevent settlement of organisms on vessels, but their widespread use has introduced high levels of contamination into the environment and raised concerns about their toxic effects on marine communities. The recent global ban on tributyltin (1 January 2008) and increasing regulation of copper have prompted research and development of non-toxic paints. This review synthesises existing information regarding the ecological impact of biocides in a wide range of organisms and highlights directions for the management of antifouling paints. We focus particularly on representatives of the recent past (copper and tributyltin) and present (copper and 'booster') biocides. We identify knowledge gaps in antifouling research and provide recommendations relating to the regulation and phasing-out of copper.

With many environments worldwide experiencing at least some degree of anthropogenic modification, there is great urgency to identify sensitive indicators of ecosystem stress. Estuarine organisms are particularly vulnerable to anthropogenic contaminants. This study presents bacterial communities as sensitive indicators of contaminant stress. Sediments were collected from multiple sites within inner and outer zones of three heavily modified and three relatively unmodified estuaries. Bacterial communities were censused using Automated Ribosomal Intergenic Spacer Analysis and analysed for a suite of metal and PAH contaminants. Shifts in both bacterial community composition and diversity showed strong associations with sediment contaminant concentrations, particularly with metals. Importantly, these changes are discernable from environmental variation inherent to highly complex estuarine environments. Moreover, variation in bacterial communities within sites was limited. This allowed for differences between sites, zones and estuaries to be explained by variables of interest such as contaminants that vary between, but not within individual sites.

While contaminants are predicted to have measurable impacts on fish assemblages, studies have rarely assessed this potential in the context of natural variability in physico-chemical conditions within and between estuaries. We investigated links between the distribution of sediment contamination (metals and PAHs), physico-chemical variables (pH, salinity, temperature, turbidity) and beach fish assemblages in estuarine environments. Fish communities were sampled using a beach seine within the inner and outer zones of six estuaries that were either heavily modified or relatively unmodified by urbanization and industrial activity. All sampling was replicated over two years with two periods sampled each year. Shannon diversity, biomass and abundance were all significantly higher in the inner zone of estuaries while fish were larger on average in the outer zone. Strong differences in community composition were also detected between the inner and outer zones. Few differences were detected between fish assemblages in heavily modified versus relatively unmodified estuaries despite high concentrations of sediment contaminants in the inner zones of modified estuaries that exceeded recognized sediment quality guidelines. Trends in species distributions, community composition, abundance, Shannon diversity, and average fish weight were strongly correlated to physico-chemical variables and showed a weaker relationship to sediment metal contamination. Sediment PAH concentrations were not significantly related to the fish assemblage. These findings suggest that variation in some physico-chemical factors (salinity, temperature, pH) or variables that co-vary with these factors (e.g., wave activity or grain size) have a much greater influence on this fish assemblage than anthropogenic stressors such as contamination.