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[Display omitted] • Biomarkers to identify and quantify carbon contributors to sequestration are needed. • Use of complete sets of fatty acid (FA) profiles are novel to biomarker discovery. • XGBoost models of FA profiles discriminated seaweed carbon from other sources. • High predictive accuracies of this biomarker approach may facilitate quantification. • Quantifying seaweed contributions to blue carbon sequestration may soon be feasible. Differentiating between carbon contributors in marine environments is crucial to gaining a deeper understanding of marine carbon sequestration, and some efforts have been made through the application of various approaches. This study proposed a new approach through the use of fatty acid (FA) profiles of six marine macrophytes within three macroalgal lineages, and three coastal angiosperms (mangrove, saltmarsh, and seagrass). We compiled FA profiles (consisting of 84 individuals and 9 classes/groups of FAs) of 544 Australian coastal macrophyte species identified in published reports. The data were gradually screened into three different datasets (full-84FA, reduced-57FA, and reduced-48FA) for analysis to minimise the effects of imbalanced distributions of data on analysis. XGBoost (eXtreme Gradient Boosting) multiclass classification modelling with hyperparameter tuning was applied to reveal the specific FA signatures of each macrophyte lineage. The XGBoost models run across the three datasets generated high model-performance metrics including precision, recall, F-score, and multiclass-AUC, indicating similar performance between the three models with predictive accuracies of 94%, 85%, and 95%, respectively. At the class level, the three models also demonstrated high performance with precision, recall, and F-score values for each lineage above 0.95, except for Rhodophyta, which ranged from around 0.80 to 0.89. Overall, our findings suggest that the XGBoost classifier can reveal the lineage-specific patterns of FAs (carbon-based molecules) that can be implemented to predict and potentially quantify the carbon contributors to marine sediments, and more specifically, to discern macroalgal carbon contributions from those of other coastal macrophytes. [ABSTRACT FROM AUTHOR]

For thousands of years humankind has sought to explore our oceans. Evidence of this early intrigue dates back to 130,000 BCE, but the advent of remotely operated vehicles (ROVs) in the 1950s introduced technology that has had significant impact on ocean exploration. Today, ROVs play a critical role in both military (e.g. retrieving torpedoes and mines) and salvage operations (e.g. locating historic shipwrecks such as the RMS Titanic), and are crucial for oil and gas (O&G) exploration and operations. Industrial ROVs collect millions of observations of our oceans each year, fueling scientific discoveries. Herein, we assembled a group of international ROV experts from both academia and industry to reflect on these discoveries and, more importantly, to identify key questions relating to our oceans that can be supported using industry ROVs. From a long list, we narrowed down to the 10 most important questions in ocean science that we feel can be supported (whole or in part) by increasing access to industry ROVs, and collaborations with the companies that use them. The questions covered opportunity (e.g. what is the resource value of the oceans?) to the impacts of global change (e.g. which marine ecosystems are most sensitive to anthropogenic impact?). Looking ahead, we provide recommendations for how data collected by ROVs can be maximised by higher levels of collaboration between academia and industry, resulting in win-win outcomes. What is clear from this work is that the potential of industrial ROV technology in unravelling the mysteries of our oceans is only just beginning to be realised. This is particularly important as the oceans are subject to increasing impacts from global change and industrial exploitation. The coming decades will represent an important time for scientists to partner with industry that use ROVs in order to make the most of these ‘eyes in the sea’. [ABSTRACT FROM AUTHOR]

Excessive accumulation of plant ‘wrack’ on beaches as a result of coastal development and beach modification (e.g. groin installation) is a global problem. This study investigated the potential for converting beach-cast seagrass wrack into biochar as a ‘climate-friendly’ disposal option for resource managers. Wrack samples from 11 seagrass species around Australia were initially screened for their biochar potential using pyrolysis techniques, and then two species – Posidonia australis and Zostera muelleri – underwent detailed analyses. Both species had high levels of refractory materials and high conversion efficiency (48–57%) of plant carbon into biochar carbon, which is comparable to high-quality terrestrial biochar products. P. australis wrack gave higher biochar yields than Z. muelleri consistent with its higher initial carbon content. According to 13 C NMR, wrack predominantly comprised carbohydrates, protein, and lignin. Aryl carbon typical of pyrogenic materials dominated the spectrum of the thermally-altered organic materials. Overall, this study provides the first data on the feasibility of generating biochar from seagrass wrack, showing that biocharring offers a promising climate-friendly alternative to disposal of beach wrack in landfill by avoiding a portion of the greenhouse gas emissions that would otherwise occur if wrack was left to decompose. [ABSTRACT FROM AUTHOR]

Seagrass ecosystems, considered among the most efficient carbon sinks worldwide, encompass a wide variety of spatial configurations in the coastal landscape. Here we evaluated the influence of the spatial configuration of seagrass meadows at small scales (metres) on carbon storage in seagrass sediments. We intensively sampled carbon stocks and other geochemical properties (δ 13 C, particle size, depositional fluxes) across seagrass–sand edges in a Zostera muelleri patchy seagrass landscape. Carbon stocks were significantly higher (ca. 20%) inside seagrass patches than at seagrass–sand edges and bare sediments. Deposition was similar among all positions and most of the carbon was from allochthonous sources. Patch level attributes (e.g. edge distance) represent important determinants of the spatial heterogeneity of carbon stocks within seagrass ecosystems. Our findings indicate that carbon stocks of seagrass areas have likely been overestimated by not considering the influence of meadow landscapes, and have important relevance for the design of seagrass carbon stock assessments. [ABSTRACT FROM AUTHOR]

The seafood industry has become increasingly interconnected at a global scale, with fish the most traded commodity worldwide. Travel to the farthest reaches of the oceans for capture is now common practice, and subsequent transport to market can require hundreds to thousands of miles of travel by sea and air. Refrigeration of seafood products is generally required at all stages of the journey from ocean to dinner plate, resulting in substantial energy expenditure. Energy input for aquaculture (including mariculture) products can also be high, namely due to the large amounts of feed required to support fish growth. As a result of these factors, the seafood industry has a substantial carbon footprint. Surprisingly, however, carbon footprints of seafood products are rarely integrated into assessments of their sustainability by eco-labels, sustainability certification, or consumer seafood sustainability guides. Suggestions are provided here for how carbon footprints could be incorporated within seafood sustainability schemes. [ABSTRACT FROM AUTHOR]

Over 7500 oil and gas structures (e.g. oil platforms) are installed in offshore waters worldwide and many will require decommissioning within the next two decades. The decision to remove such structures or turn them into reefs (i.e. ‘rigs-to-reefs’) hinges on the habitat value they provide, yet this can rarely be determined because the residency of mobile species is difficult to establish. Here, we test a novel solution to this problem for reef fishes; the use of otolith (earstone) properties to identify oil structures of residence. We compare the otolith microchemistry and otolith shape of a site-attached coral reef fish ( Pseudanthias rubrizonatus ) among four oil structures (depth 82–135 m, separated by 9.7–84.2 km) on Australia's North West Shelf to determine if populations developed distinct otolith properties during their residency. Microchemical signatures obtained from the otolith edge using laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) differed among oil structures, driven by elements Sr, Ba and Mn, and to a lesser extent Mg and Fe. A combination of microchemical data from the otolith edge and elliptical Fourier (shape) descriptors allowed allocation of individuals to their ‘home’ structure with moderate accuracy (overall allocation accuracy: 63.3%, range: 45.5–78.1%), despite lower allocation accuracies for each otolith property in isolation (microchemistry: 47.5%, otolith shape: 45%). Site-specific microchemical signatures were also stable enough through time to distinguish populations during 3 separate time periods, suggesting that residence histories could be recreated by targeting previous growth zones in the otolith. Our results indicate that reef fish can develop unique otolith properties during their residency on oil structures which may be useful for assessing the habitat value of individual structures. The approach outlined here may also be useful for determining the residency of reef fish on artificial reefs, which would assist productivity assessments of these habitats. [ABSTRACT FROM AUTHOR]

Freshwater wetlands are natural sinks of carbon; yet, wetland conversion for agricultural uses can shift these carbon sinks into large sources of greenhouse gases. We know that the anthropogenic alteration of wetland hydrology and the broad use of N-fertilizers can modify biogeochemical cycling, however, the extent of their combined effect on greenhouse gases exchange still needs further research. Moreover, there has been recent interest in wetlands rehabilitation and preservation by improving natural water flow and by seeking alternative solutions to nutrient inputs. In a microcosm setting, we experimentally exposed soils to three inundation treatments (Inundated, Moist, Drained) and a nutrient treatment by adding high nitrogen load (300 kg ha−1) to simulate physical and chemical disturbances. After, we measured the depth microprofiles of N 2 O and O 2 concentration and CO 2 and CH 4 emission rates to determine how hydrological alteration and nitrogen input affect carbon and nitrogen cycling processes in inland wetland soils. Compared to the Control soils, N-fertilizer increased CO 2 emissions by 40% in Drained conditions and increased CH 4 emissions in Inundated soils over 90%. N 2 O emissions from Moist and Inundated soils enriched with nitrogen increased by 17.4 and 18-fold, respectively. Overall, the combination of physical and chemical disturbances increased the Global Warming Potential (GWP) by 7.5-fold. The first response of hydrological rehabilitation, while typically valuable for CO 2 emission reduction, amplified CH 4 and N 2 O emissions when combined with high nitrogen inputs. Therefore, this research highlights the importance of evaluating the potential interactive effects of various disturbances on biogeochemical processes when devising rehabilitation plans to rehabilitate degraded wetlands. [Display omitted] • Short-term hydrological and N-fertilization manipulation increased the GWP by 7.5-fold. • The addition of N-fertilizer increased CO 2 , CH 4 and N 2 O by 40% up to over 90%. • Short-term hydrological restoration reduced overall GHG emissions. [ABSTRACT FROM AUTHOR]

Abstract: Broad antifungal structure–activity relationships governing epoxy-endoperoxides 2 and 3 and their parent endoperoxides 1 are reported. Their inhibitory activity against Candida albicans in conjunction with hemolytic activity and/or growth inhibition of cultured mammalian cells are reported. This information provided guidance for the further development of endoperoxide and epoxy-endoperoxides as topical antifungal agents. [Copyright &y& Elsevier]

Mangroves are known to provide many ecosystem services, however there is little information on their potential role to cap and immobilise toxic levels of total petroleum hydrocarbons (TPH). Using an Australian case study, we investigated the capacity of planted mangroves (Avicennia marina) to immobilise TPH within a small embayment (Stony Creek, Victoria, Australia) subjected to minor oil spills throughout the 1980s. Mangroves were planted on the oil rich strata in 1984 to rehabilitate the site. Currently the area is covered with a dense mangrove forest. One-meter-long sediment cores revealed that mangroves have formed a thick (up to 30 cm) organic layer above the TPH-contaminated sediments, accumulating on average 6.6 mm of sediment per year. Mean TPH levels below this organic layer (30–50 cm) are extremely toxic (30,441.6 mg kg−1), exceeding safety thresholds up to 220-fold which is eight times higher when compared to top layer (0–10 cm). • Mangroves represent ability to immobilise sediments contaminated by total petroleum hydrocarbons (TPH) • Planted mangroves immobilised TPH-contaminated sediments that exceeded toxicity thresholds by up to 220-fold • Capping the TPH-contaminated sediments is linked to ability of mangroves to grow and accumulate sediments above contaminated sediments • Mangroves in this study accumulated relatively high organic matter content within rhizosphere (~16.6% in top 30 cm). [ABSTRACT FROM AUTHOR]

Eutrophication (excessive plant/algal growth caused by nutrient pollution) of coastal waters has increased globally and is associated with many ecological and environmental problems. In China, eutrophication is recognized as a key threat to sustainable economic development and human wellbeing. To address the eutrophication problem, the first step is to identify the sources and drivers of nutrient input. This, however, is challenging in densely populated areas of rapid land use and land cover change (LUCC) because there are so many potential sources of nutrient pollution. In this study, we sought to estimate nutrient pollution, determine drivers, and develop reduction strategies for Daya Bay, southeastern China's most densely populated and industrialized coastal region with a small watershed. We identified six key sources of total nitrogen (TN) and total phosphorus (TP) loading into Daya Bay. We developed spatially-explicit heat maps to guide resource managers to priority areas and demonstrate how different pollution generation and discharge characteristics are linked to land use and landscape pattern (LULP). We found that the generation, emission and input of terrigenous TN loads were 5863.7, 1975.3 and 1540.4 t yr−1, respectively, while those of TP were 762.2, 197.1 and 134.1 t yr−1, respectively. Urban domestic pollution loads (UDPL) were the main source of TN, while agrochemical pollution loads (APL) were the main source of TP. The Dan'ao River basin was the critical source region of TN loads, while the Baiyun-Zhuyuan River basin was the critical source region of TP loads. The area of urban construction lands (UCL) and rural residential lands (RRL) were the dominant factors controlling TN loads, while cultivated land (CL) and RRL controlled TP loads. Increasing green in shores (GS), inland water bodies (IWB) and coastal wetlands (CW) could effectively reduce the amount of TN flowing into the bay, while increasing forest land (FL), IWB, CW and GS were able to effectively reduce the amount of TP. These findings suggest that we could reduce the TN load entering Daya Bay by controlling the area of UCL, increasing GS and CW, protecting IWB in the critical source region of TN; and we could reduce the TP load through planting forest, protecting IWB, and restoring CW in the critical source region of TP. This study provides important new practical guidance on priority areas to combine control nutrients with ecological restoration in watershed-bay ecosystem management. [Display omitted] • Six terrigenous input loads of TN and TP to a near-eutrophic bay were estimated. • LULP can effectively explain the nutrients loads and reduction flux entering the bay. • UCL and RRL were the dominant factors controlling TN, while CL and RRL controlling TP. • GS, IWB and CW could reduce TN loads, while FL and IWB for TP loads. • Ecological restoration could be applied in watershed-bay nutrients management. [ABSTRACT FROM AUTHOR]

Coastal ecosystems are under increasing pressure from land-derived eutrophication in most developed coastlines worldwide. Here, we tested for 277 days the effects of a nutrient pulse on blue carbon retention and cycling within an Australian temperate coastal system. After 56 days of exposure, saltmarsh and mangrove plots subject to a high-nutrient treatment (~20 g N m−2 yr−1 and ~2 g P m−2 yr−1) had ~23% lower superficial soil carbon stocks. Mangrove plots also experienced a ~33% reduction in the microbe Amplicon Sequence Variant richness and a shift in community structure linked to elevated ammonium concentrations. Live plant cover, tea litter decomposition, and soil carbon fluxes (CO 2 and CH 4) were not significantly affected by the pulse. Before the end of the experiment, soil carbon- and nitrogen-cycling had returned to control levels, highlighting the significant but short-lived impact that a nutrient pulse can have on the carbon sink capacity of coastal wetlands. • We tested the impact of a fertiliser pulse on Australian mangroves and saltmarshes. • The nutrient pulse led to 23% lower soil carbon stocks in both ecosystems. • The microbial ASV richness decreased by 33% in mangrove plots. • Plant cover, litter decomposition, and soil carbon fluxes remained unaffected. • The nutrient pulse had a significant, but short-lived impact on both ecosystems. [ABSTRACT FROM AUTHOR]

• We assess the potential inclusion of blue carbon within Australia's Emissions Reduction Fund, emphasizing issues and approaches that have global relevance. • We identify twelve potential management actions then quantify and discuss the five most promising activities, encompassing the protection, restoration and creation of mangroves, tidal marshes and seagrasses. • On a per area basis, mean abatement intensity of organic carbon was highest for the management activity ' (re)introduction of tidal flow' which may result in mean annual abatement of 13 – 15 Mg C org ha−1 yr−1 for mangrove and 6 – 8 Mg C org ha−1 yr−1 for tidal marsh. • Our approach offers a template that uses best available information to identify options for carbon abatement through management of coastal landscapes. There is increasing interest in protecting, restoring and creating 'blue carbon' ecosystems (BCE; mangroves, tidal marshes and seagrasses) to sequester atmospheric CO 2 -C and thereby contribute to climate change mitigation. While a growing number of countries aspire to report greenhouse gas emission and carbon sequestration changes from these ecosystems under voluntary international reporting requirements, few countries have domestic policy frameworks that specifically support the quantification and financing of carbon emission abatement through BCE management. Australia, as home to approximately 5–11% of global blue carbon stocks, has a substantial interest in the development of blue carbon policy. Here we assess the potential inclusion of blue carbon within Australia's Emissions Reduction Fund, emphasizing issues and approaches that have global relevance. We used a participatory workshop of scientific experts and carbon industry stakeholders to identify blue carbon management actions that would meet the requirements of the Fund. In total, twelve actions were assessed for their greenhouse gas emission abatement potential and the ability to measure abatement reliably, using a combination of available data and qualitative and quantitative methods, including expert knowledge. We identify and discuss the five most relevant and promising activities, encompassing the protection, restoration and creation of mangroves, tidal marshes and seagrasses. On a per area basis, mean abatement intensity of organic carbon (C org) was highest for the (re)introduction of tidal flow resulting in establishment of mangrove (13–15 Mg C org ha−1 yr−1) and tidal marsh (6–8 Mg C org ha−1 yr−1), followed by land use planning for sea-level rise for the creation of new mangrove habitat (8 Mg C org ha−1 yr−1). The avoided disturbance of existing mangroves, tidal marshes and seagrasses has the twofold benefit of avoiding remineralisation of existing stocks, plus the future annual abatement associated with the net sequestration of atmospheric CO 2 -C as C org with the continued functioning of these BCE. Our approach offers a template that uses best available information to identify options for carbon abatement through management of coastal landscapes, and details current knowledge gaps and important technical aspects that need to be considered for implementation in carbon crediting schemes. [ABSTRACT FROM AUTHOR]

Abstract Thousands of offshore oil and gas structures are approaching the end of their operating life globally, yet our understanding of the environmental effects of different decommissioning strategies is incomplete. Past focus on a narrow set of criteria has limited evaluation of decommissioning effects, restricting decommissioning options in most regions. We broadly review the environmental effects of decommissioning, analyse case studies, and outline analytical approaches that can advance our understanding of ecological dynamics on oil and gas structures. We find that ecosystem functions and services increase with the age of the structure and vary with geographical setting, such that decommissioning decisions need to take an ecosystem approach that considers their broader habitat and biodiversity values. Alignment of decommissioning assessment priorities among regulators and how they are evaluated, will reduce the likelihood of variable and sub-optimal decommissioning decisions. Ultimately, the range of allowable decommissioning options must be expanded to optimise the environmental outcomes of decommissioning across the broad range of ecosystems in which platforms are located. Graphical abstract Unlabelled Image Highlights • After decades at sea, oil and gas structures support diverse marine life. • Decommissioning decisions need to reflect this changed ecological context. • Approaches to weigh risks, benefits and trade-offs of decommissioning options vary. • Assessing a wide range of decommissioning options and environmental aspects is key. • This will help better understand the environmental effects of decommissioning. [ABSTRACT FROM AUTHOR]

Habitat loss is a key factor in the ongoing freshwater biodiversity crisis. A promising way to help tackle the rapid decline in freshwater biodiversity is to improve the potential for artificial wetlands to provide habitat for aquatic wildlife. Farm dams (also known as agricultural ponds) are among the most abundant waterbodies in agricultural landscapes and can act as "oases" against droughts for many species. Despite their prominent role in agriculture, predictive models to evaluate their ecological potential are yet to emerge. Here we use a continental-scale data set of 104,013 audio recordings from citizen scientists to identify and locate 107 species of frogs near 8800 Australian farm dams. Frog species are among the most threatened taxa on earth and we asked: What characteristics promote higher frog species richness at farm dams ? We found that the highest values of frog species richness were at old (>20 years) farm dams of intermediate size (0.1 ha in surface area), with small or medium rainfall catchments (<10 ha), and situated near other freshwater systems or conservation sites. The relationships shown here are highly generalisable and applicable on a continental scale. By identifying quantifiable features improving the ecological value of farm dams, we help identify "win-win" outcomes for agricultural productivity and conservation. In the future, "biodiversity credit" policies could incentivise large-scale ecological restoration by rewarding individuals who invest in enhancing their farm dams to support and promote local biodiversity. [ABSTRACT FROM AUTHOR]

Abstract Decommissioning of offshore infrastructure has become a major issue facing the global offshore energy industry. In the North Sea alone, the decommissioning liability is estimated at £40 billion by 2040. Current international policy requires removal of offshore infrastructure when their production life ends; however, this policy is being questioned as emerging data reveal the importance of these structures to fish and invertebrate populations. Indeed, some governments are developing 'rigs-to-reef' (RTR) policies in situations where offshore infrastructure is demonstrated to have important environmental benefits. Using Remotely Operated Vehicles (ROVs), this study quantified and analysed fish and invertebrate assemblage dynamics associated with an oil and gas (O&G) complex in the Dogger Bank Special Area of Conservation (SAC), in the North Sea, Germany. We found clear depth zonation of organisms: infralittoral communities (0–15 m), circalittoral assemblages (15–45 m) and epi-benthic communities (45–50 m), which implies that 'topping' or 'toppling' decommissioning strategies could eliminate communities that are unique to the upper zones. Sessile invertebrate assemblages were significantly different between structures, which appeared to be driven by both biotic and abiotic mechanisms. The O&G complex accommodated diverse and abundant motile invertebrate and fish assemblages within which the whelk Buccinium undatum , cod fish Gadus morhua and lumpsucker fish Cyclopterus lumpus used the infrastructure for different stages of reproduction. This observation of breeding implies that the structures may be producing more fish and invertebrates, as opposed to simply acting as sites of attraction (sensu the 'attraction vs production' debate). At present, there are no records of C. lumpus spawning at such depth and distance from the coast, and this is the first published evidence of this species using an offshore structure as a spawning site. Overall, this study provides important new insight into the role of offshore O&G structures as habitat for fish and invertebrates in the North Sea, thereby helping to inform decommissioning decisions. Highlights • Decommissioning of North Sea oil and gas infrastructure is a £40 billion liability. • We assessed fish and invertebrate habitat value of a North Sea oil and gas complex. • A diverse range of reef-dependent and transient pelagic species were observed. • Clear depth zonation occurred, helping inform in situ decommissioning strategies. • Evidence of reproduction suggests the complex was producing fish-invertebrates. [ABSTRACT FROM AUTHOR]

In marine environments characterised by habitat-forming plants, the relative allocation of resources into vegetative growth and flowering is an important indicator of plant condition and hence ecosystem health. In addition, the production and abundance of seeds can give clues to local resilience. Flowering density, seed bank, biomass and epiphyte levels were recorded for the temperate seagrass Zostera nigricaulis in Port Phillip Bay, south east Australia at 14 sites chosen to represent several regions with different physicochemical conditions. Strong regional differences were found within the large bay. Spathe and seed density were very low in the north of the bay (3 sites), low in the centre of the bay (2 sites) intermediate in the Outer Geelong Arm (2 sites), high in Swan Bay (2 sites) and very high in the Inner Geelong Arm (3 sites). In the south (2 sites) seed density was low and spathe density was high. These regional patterns were largely consistent for the 5 sites sampled over the three year period. Timing of flowering was consistent across sites, occurring from August until December with peak production in October, except during the third year of monitoring when overall densities were lower and peaked in November. Seagrass biomass, epiphyte load, canopy height and stem density showed few consistent spatial and temporal patterns. Variation in spathe and seed density and morphology across Port Phillip Bay reflects varying environmental conditions and suggests that northern sites may be restricted in their ability to recover from disturbance through sexual reproduction. In contrast, sites in the west and south of the bay have greater potential to recover from disturbances due to a larger seed bank and these sites could act as source populations for sites where seed production is low. [ABSTRACT FROM AUTHOR]

[Display omitted] • Machine learning reveals spatiotemporal dynamics of SOC stocks in tidal marshes. • Sediment salinity and tidal range are key factors influencing SOC stocks prediction. • Invasive S. alterniflora contributes over half of SOC stocks in Yangtze Estuary. • S. alterniflora increased SOC stocks within the first 15 years of its invasion. • S. alternifloras high SOC storage capacity is not sustained in the long term. Spatial quantification of blue carbon ecosystem stocks is crucial for developing policies to mitigate climate change, especially in regions experiencing ongoing wetland disturbance from biological invasions. We integrated multiple machine learning models with the space-for-time substitution method to quantify the spatiotemporal impact of Spartina alterniflora invasion on tidal marsh sediment blue carbon (soil organic carbon – 'SOC') stocks at 100 cm depth in the Yangtze Estuary. Our results show that the invasive S. alterniflora contributed more than half of the total SOC stocks (2,056 ± 379 Gg C, 1 Gg = 106 kg) in the 27,600 ha tidal marshes of the Yangtze Estuary, which were estimated to be 1,107 ± 176 Gg C. S. alterniflora increased the SOC stocks in the Yangtze Estuary within the first 15 years, but this gain was not sustained in the long term, with a gradual decline (by 13.14 Mg C/ha) observed after 15 years of S. alterniflora growth. We found that sediment salinity, tidal range, and human accessibility were strong indicators for modeling and predicting SOC stocks, with Random Forest providing the best simulation of tidal marsh SOC stocks (R2 = 0.894, RMSE=7.646 Mg C/ha, and MAPE=9.469 %). Our study provides much needed information on blue carbon stocks in the Yangtze Estuary under biological invasion stress, and offers guidance for targeted S. alterniflora management actions in the future. [ABSTRACT FROM AUTHOR]

Information on the contribution of offshore oil and gas (O&G) platforms to fish productivity is required to contribute to the decision-making process to remove, partially remove, or retain these structures during decommissioning after petroleum production ceases. The present study assesses the biomass and fish production of one common and abundant fish species (Caesioperca lepidoptera – butterfly perch) and two commercially fished species (Helicolenus percoides – reef ocean perch; Nemadactylus macropterus – jackass morwong) on eight O&G platforms and in surrounding natural habitats in the Bass Strait, south-east Australia, where options for decommissioning are being assessed. High-definition stereo-video imagery was collected by remotely operated vehicle (ROV) from eight platform facilities, their immediate benthic surrounds, reference areas reflective of the likely pre-installation seabed state (sand-dominated) and a nearby natural 'reef' area referred to as south-east reef (some limestone foundation). The biomass of all three species was low in the benthic surrounds of platforms, at reference locations and at south-east reef where minimal cover by benthic organisms was recorded and, as such, there was little to no fish production for the three study species in these areas. We observed a total fish biomass of 2.85 tonnes across the eight platforms for the three fish species surveyed, with high variability across platforms. Total production (P) across all platforms was estimated at 1244 kg/year for the three species, with a mean fish production density of 82 g/m2/year. Approximately 79% of total production is considered 'new' production (984 kg/year i.e., the production attributed to the presence of the platforms; with a mean production density of 64 g/m2/year). The remaining 21% could be retained or redistributed into the surrounding area if platforms were removed. C. lepidoptera accounted for the majority (90%) of biomass and of total production for all three species across all locations surveyed. Despite only accounting for a small proportion of platform surface area, the bottom 5 m sections of platforms had 41% of the total biomass observed and accounted for 46% of total production of these three study species. Production measures for platforms surveyed here are relatively high compared to other artificial reefs and habitats around the world. Total removal of these platforms will likely result in a reduction of fish biomass and fish productivity (incl. several fishery species) in the immediate vicinity. • Platforms promote fish diversity and abundance in areas where it would be otherwise be minimal. • Platform production measures were relatively high compared to other artificial reefs and habitats around the world. • The bottom 5 m sections of platforms contained 41% of the total biomass observed and accounted for 46% of total production. • Complete removal of infrastructure would likely eliminate most fish production at that location. [ABSTRACT FROM AUTHOR]

Seagrass biomass represents an important source of organic carbon that can contribute to long-term sediment carbon stocks in coastal ecosystems. There is little empirical data on the long-term microbial decomposition of seagrass detritus, despite this process being one of the key drivers of carbon-cycling in coastal ecosystems, that is, it influences the amount and quality of carbon available for sequestration. Here, our goal was to investigate how litter quality (leaf vs. rhizome/root) and the microbial communities involved in organic matter remineralisation shift over a 2-year field decomposition study north of Sydney, Australia using the temperate seagrass Zostera muelleri. The sites varied in bulk sediment characteristics and the sediment-associated microbial communities, but these variables overall had little influence on long-term seagrass decomposition rates or seagrass-associated microbiomes. The results showed a clear succession of bacterial and archaeal communities for both tissues types from r -strategists such as α- and γ-proteobacteria to K -strategies, including δ-proteobacteria, Bacteroidia and Spirochaetes. We used a new mathematical model to capture how decay rates varied over time and found that two decomposition events occurred for some seagrass leaf samples, possibly due to exudate input from living seagrass roots growing into the litter bag. The new model also indicated that conventional single exponential models overestimate long-term decay rates, and we detected for the first time the refractory, or stable, phase of decomposition for rhizome/root biomass. The stable phase began at approximately 20% mass remaining and after 600 days, and the persistence of rhizome/root biomass was attributed to the anoxic conditions and the preservation of refractory organic matter. While we predict that rhizome/root biomass will contribute more to the long-term sediment carbon stocks, the preservation of leaf carbon may be enhanced at locations were sedimentation is high and burial in anoxic conditions is rapid and constant. Unlabelled Image • Long-term seagrass decay rates may be previously overestimated. • Decomposition of seagrass above- and belowground litter was measured over two years. • The stable phase of decay was captured for belowground rhizome/root litter. • Microbial community succession matches shifts in organic matter recalcitrance. • Root exudates could enhance litter remineralisation. [ABSTRACT FROM AUTHOR]

[Display omitted] • Nutrient load elevated seagrass leaf quality but decreased refractory carbon. • High quality detritus decomposed 13% more of lignin and 80% more CO 2 emission. • Nutrient addition enhanced 48% higher CO 2 emissions of detritus. • CO 2 emissions of high quality detritus to a greater extent under nutrient addition. Coastal nutrient loading has been linked to a decline in the capacity of seagrass ecosystems to sequester carbon ('blue carbon'); however, the mechanisms are unclear. Here we investigated how nutrient loading can affect the contribution that seagrass plant material makes to blue carbon stocks by investigating plant quality-decomposition dynamics. Specifically, we used a combination of laboratory and field experiments to account for various changes in biogeochemical cycling from seagrass meadows, ranging from changes in leaf quality to CO 2 fluxes. It was found that nutrient loading increased the 'labile' content of seagrass (i.e. increased levels of leaf nitrogen, phosphorus and soluble organic carbon (amino acid and soluble sugar content), and at the same time decreased levels of 'recalcitrant' carbon (i.e. materials that are harder for microbes to break down, such hemicellulose, cellulose and lignin contents). Nutrient-enriched leaves decomposed ∼ 18 % faster than non-enriched leaves (i.e. greater biomass loss from nutrient-affected seagrass), resulting in ∼ 80 % more CO 2 emissions from nutrient-enriched seagrass. We also found that seagrass that naturally contained high levels of labile carbon at the start of the experiment were affected to a greater degree (i.e. higher CO 2 emissions) by nutrients addition than seagrass that had high proportions of recalcitrant carbon to begin with. Overall, these findings suggest that nutrient loading can weaken the capacity of seagrass ecosystems to act as blue carbon sinks through its effect on seagrass leaf decomposability. [ABSTRACT FROM AUTHOR]

Tidal marsh ecosystems are among earth's most efficient natural organic carbon (C) sinks and provide myriad ecosystem services. However, approximately half have been 'reclaimed' – i.e. converted to other land uses – potentially turning them into sources of greenhouse gas emissions. In this study, we applied C stock measurements and paleoanalytical techniques to sediments from reclaimed and intact tidal marshes in southeast Australia. We aimed to assess the impacts of reclamation on: 1) the magnitude of existing sediment C stocks; 2) ongoing C sequestration and storage; and 3) C quality. Differences in sediment horizon depths (indicated by Itrax-XRF scanning) and ages (indicated by lead-210 and radiocarbon dating) suggest a physical loss of sediments following reclamation, as well as slowing of sediment accumulation rates. Sediments at one meter depth were between ~2000 and ~5300 years older in reclaimed cores compared to intact marsh cores. We estimate a 70% loss of sediment C in reclaimed sites (equal to 73 Mg C ha−1), relative to stocks in intact tidal marshes during a comparable time period. Following reclamation, sediment C was characterized by coarse particulate organic matter with lower alkyl-o-alkyl ratios and higher amounts of aromatic C, suggesting a lower extent of decomposition and therefore lower likelihood of being incorporated into long-term C stocks compared to that of intact tidal marshes. We conclude that reclamation of tidal marshes can diminish C stocks that have accumulated over millennial time scales, and these losses may go undetected if additional analyses are not employed in conjunction with C stock estimates. Unlabelled Image • Reclamation of tidal marshes resulted in a 70% loss of sediment carbon stocks. • Carbon stock losses caused by reclamation may go undetected without in-depth analysis. • "New" carbon in reclaimed sites was more degradable than in pristine tidal marshes. [ABSTRACT FROM AUTHOR]

Microbes are the ‘gatekeepers’ of the marine carbon cycle, yet the mechanisms for how microbial metabolism drives carbon sequestration in coastal ecosystems are still being defined. The proximity of coastal habitats to runoff and disturbance creates ideal conditions for microbial priming, i.e., the enhanced remineralisation of stored carbon in response to fresh substrate availability and oxygen introduction. Microbial priming, therefore, poses a risk for enhanced CO 2 release in these carbon sequestration hotspots. Here we quantified the existence of priming in seagrass sediments and showed that the addition of fresh carbon stimulated a 1.7- to 2.7-fold increase in CO 2 release from recent and accumulated carbon deposits. We propose that priming taking place at the sediment surface is a natural occurrence and can be minimised by the recalcitrant components of the fresh inputs (i.e., lignocellulose) and by reduced metabolism in low oxygen and high burial rate conditions. Conversely, priming of deep sediments after the reintroduction to the water column through physical disturbances (e.g., dredging, boat scars) would cause rapid remineralisation of previously preserved carbon. Microbial priming is identified as a process that weakens sediment carbon storage capacity and is a pathway to CO 2 release in disturbed or degraded seagrass ecosystems; however, increased management and restoration practices can reduce these anthropogenic disturbances and enhance carbon sequestration capacity. [ABSTRACT FROM AUTHOR]

Marine disease ecology is a growing field of research, particularly for host organisms negatively impacted by a changing climate and anthropogenic activities. A decrease in health and increase in susceptibility to disease has been hypothesised as the mechanism behind wide-spread seagrass die-offs related to wasting disease in the past. However, seagrass wasting disease and the causative pathogen, Labyrinthula , have been vastly understudied in the southern hemisphere. Our aim was to build on the current knowledge of Australian Labyrinthula descriptions and phylogeny, while also providing a first look at wasting disease ecology in Australia. Five seagrass species along a 750 km stretch of coastline in southeastern Australia were sampled. The resulting 38 Labyrinthula isolates represented a diversity of morphotypes and five haplotypes of varying phylogenetic clade positions and virulence. The haplotypes clustered with previously-described phylogenetic clades containing isolates from Asia, USA and Europe. Pathogenicity tests confirmed, for the first time, the presence of at least two pathogenic haplotypes in Australia. While historically there have been no reports of wasting disease-related seagrass habitat loss, the presence of pathogenic Labyrinthula highlights the need for disease monitoring and research to understand seagrass wasting disease ecology in Australia. [ABSTRACT FROM AUTHOR]

Recent studies have reported significant variability in sediment organic carbon (SOC) storage capacity among seagrass species, but the factors driving this variability are poorly understood, limiting our ability to make informed decisions about which seagrass types are optimal for carbon offsetting and why. Here we show that differences in SOC storage capacity among species within the same geomorphic environment can be explained (in part) by below-ground processes in response to nutrient load; specifically, differences in the activity of microbes harboured by morphologically-different seagrass species. We found that increasing nutrient load enhanced the relative contribution of seagrass and algal sources to SOC pools, boosting sediment microbial biomass and extracellular enzyme activity within mixed seagrass meadows composed of Thalassia hemprichii and Enhalus acoroides , and thus possibly weaken the seagrass blue carbon sequestration capacity. The relative contribution of seagrass plant material to sediment bacterial organic carbon (BOC) and the influencing SOC-decomposing enzymes in E. acoroides meadows were half that of T. hemprichii meadows living side-by-side, even though the mixed seagrass meadows received SOC from the same sources. Overall this research suggests that microbial activity can vary significantly among seagrass species, thereby causing fine-scale (within-meadow) variability in SOC sequestration capacity in response to nutrient load. [ABSTRACT FROM AUTHOR]

Seagrasses are important marine foundation species, which are presently threatened by coastal development and global change worldwide. The molecular mechanisms that drive seagrass responses to anthropogenic stresses, including elevated levels of nutrients such as ammonium, remains poorly understood. Despite the evidence that seagrasses can assimilate ammonium by using glutamine synthetase (GS)/glutamate synthase (glutamine-oxoglutarate amidotransferase or GOGAT) cycle, the regulation of this fundamental metabolic pathway has never been studied at the gene expression level in seagrasses so far. Here, we combine (i) reverse transcription quantitative real-time PCR (RT-qPCR) to measure expression of key genes involved in the GS/GOGAT cycle, and (ii) stable isotope labelling and mass spectrometry to investigate 15 N-ammonium assimilation in the widespread Australian species Zostera muelleri subsp. capricorni (Z. muelleri ). We demonstrate that exposure to a pulse of ammonium in seawater can induce changes in GS gene expression of Z. muelleri, and further correlate these changes in gene expression with 15 N-ammonium uptake rate in above- and below-ground tissue. [ABSTRACT FROM AUTHOR]

It is global practice to construct wetlands in urban environments to treat pollutants from stormwater and overland runoff. However, constructed wetlands can also trigger climatic consequences by releasing a considerable amount of greenhouse gas emissions via diffusion and ebullition. While diffusive emissions are broadly measured, assessing the extent of ebullitive emissions is less common. This is due to the stochastic nature of ebullitive emissions and the complexity in their measurement. In addition, the soil microbiome community involved in greenhouse gas transport pathway has been generally understudied in Constructed wetlands although widely recognized in natural wetlands. Here we investigated diffusive and ebullitive CO 2 and CH 4 and ebullitive N 2 O emissions and the prokaryotic community from four municipal Surface Flow Constructed wetlands in southeast Australia over a 4-week period. We found that the total Global Warming Potential over a 100-year horizon of diffusive and ebullitive emissions was 0.44 kg CO 2 -equivalents m-2 day-1, which is 3-fold higher than the European estimates that accounted for diffusive emissions alone. Among the microbial functional groups that drove the main differences in β-diversity, putative methanotrophs represented the 3.6%, nitrogen-cycling microbes the 44.5% and sulfate/iron cycling microbes the 13.5%, indicating that several taxa, other than methanogens, can be key in microbial dynamics, nutrient turnover and in the shift in the production of greenhouse gas thus amplifying the role of constructed wetlands as sources of CH 4. We present evidence that Constructed wetlands can be major sources of greenhouse gases, particularly ebullitive CH 4 that accounted for more than two-thirds of the total emissions. As such, ebullitive flux rate measurements are critical to assemble national greenhouse gas budgets, particularly from Constructed wetlands. • Ebullitive N 2 O emissions were negligible. • Ebullitive emissions accounted for nearly 70% of the total emissions. • By including ebullition, the Global Warming Potential increased by 3-fold. • Microbes involved in nitrogen, sulfate and iron cycles drove β-diversity variation. • Archaeal relative abundance was low and dominated by Phylum Parvarchaeota. [ABSTRACT FROM AUTHOR]

[Display omitted] • Current speed and wave orbital velocity are important indicators of fish abundance. • A hectare of seagrass produces 110 – 1,080 kg−1 of fish per year. • A hectare of seagrass supports 69 – 865 fishing trips per year. • Studied 6662 ha of seagrass are valued at AUD 36,782 million annually. The value of critical habitats, such as seagrass, to act as a nursery varies spatially and temporally; however, such information is essential for the public and stakeholders to appropriately value and manage these habitats. We use an existing systematic long-term fisheries dataset in Port Phillip Bay to examine variability in nursery habitat value for an important commercial and recreational species, King George Whiting (Sillaginodes punctatus). Port Phillip Bay represents one of the most important marine assets in the southern hemisphere and is surrounded by the second-largest city in Australia, Melbourne, home to 4.5 million people. We modelled the abundance of King George whiting as a function of environmental variables, using Boosted Regression Trees (BRT). Fish densities ranged from 1,000 to 30,000 individuals ha−1y−1, equalling an adult biomass of 110–3,300 kg ha−1y−1. This production supports between 69 and 2,062 recreational fishing trips a year, with an estimated value of seagrass of AUD 687–20,625 ha−1y−1. Based on biomass production of King George Whiting and recreational fisheries data, the 6662 ha of seagrass in Port Phillip Bay are valued at around AUD 36 million annually. [ABSTRACT FROM AUTHOR]

Wetlands have a major influence on the global carbon cycle, with capacity to act as carbon 'sinks' or 'sources'. The source-sink capacity of wetlands is governed by microbially-mediated biogeochemical processes, which are furthermore regulated by environmental conditions. With growing interest in nature-based climate solutions, policymakers and resource managers seek information on ways how wetlands can be managed to maximize carbon drawdown. Here, we explored how rehabilitation (i.e., fencing and grazing removal) influences greenhouse gas (GHG) emissions and soil biogeochemistry (microbial communities and soil quality) from semi-arid, rain-filled freshwater wetlands in south-eastern Australia. Specifically, we investigated the carbon and microbes response under major local environmental factors, such as vegetation type (graminoids vs eucalyptus tree) and seasonal hydroperiod (spring vs autumn), across wetlands that are currently used for grazing or cropping and those that have been under fencing rehabilitation for up to 20 years. We found that rehabilitation did not reduce CO 2 and CH 4 emissions, rather CH 4 flux rates were elevated when the wetlands were flooded (spring). Anaerobic conditions from spring waterlogged soils also increased microbial diversity by 2.6-fold, and influenced the relative abundance of putative methane oxidizers (Nitrososphaerales and Mixococcales) and methanogenic archaea (Methanomicrobia, Methanobacteria). Organic matter quality (measured as C:N ratio) was reduced by the removal of grazing pressure in eucalyptus-dominated sites only. Soil quality, influenced by vegetation type, also had a significant impact on relative abundance of putative nitrogen and carbon cyclers. Overall, our results suggest that fencing rehabilitation in semi-arid rain-filled wetlands had a minor impact on microbial dynamics and carbon processes, overshadowed by the influence of the water table and vegetation type. Focusing future research on spatial and temporal patterns of carbon and microbe rehabilitation responses will help managers devise the most effective rehabilitation practice within a particular geographical area. • Passive rehabilitation did not reduce CO 2 and CH 4 emissions. • Hydroperiod influenced taxa involved in nitrogen, sulfate, and methane cycle. • CH 4 emissions were highest in sites that were flooded. • Vegetation type influenced microbes involved in nitrogen and carbon cycling. • CO 2 emissions were highest in sites dominated by Eucalyptus trees. [ABSTRACT FROM AUTHOR]

• Investigation on virus-host interactions during a wetland hydrological restoration • Viral life strategy switched after the introduction of water • Correlation between the carbon released by the viral lysis and total carbon emissions • Viral life strategies potentially contribute to the regulation of greenhouse gas emissions Image, graphical abstract Wetlands are among the earth's most efficient ecosystems for carbon sequestration, but can also emit potent greenhouse gases (GHGs) depending on how they are managed. Global management strategies have sought to maximize carbon drawdown by wetlands by manipulating wetland hydrology to inhibit bacterially-mediated emissions. However, it has recently been hypothesized within wetlands that viruses have the potential to dictate the magnitude and direction of GHG emissions by attacking prokaryotes involved in the carbon cycle. Here we tested this hypothesis in a whole-ecosystem manipulation by hydrologically-restoring a degraded wetland ('rewetting') and investigated the changes in GHG emissions, prokaryotes, viruses, and virus-host interactions. We found that hydrological restoration significantly increased prokaryotic diversity, methanogenic Methanomicrobia, as well as putative iron/sulfate-cyclers (Geobacteraceae), nitrogen-cyclers (Nitrosomonadaceae), and fermentative bacteria (Koribacteraceae). These results provide insights into successional microbial community shifts during rehabilitation. Additionally, in response to watering, viral-induced prokaryotic mortality declined by 77%, resulting in limited carbon released by viral shunt that was significantly correlated with the 2.8-fold reduction in wetland carbon emissions. Our findings highlight, for the first time, the potential implications of viral infections in soil prokaryotes on wetland greenhouse gas dynamics and confirm the importance of wetland rehabilitation as a tool to offset carbon emissions. [ABSTRACT FROM AUTHOR]

Seawater dissolved organic carbon (DOC) in seagrass meadows is gaining attention for its role in carbon sequestration. Abundant refractory compounds in DOC are exported by seagrass meadows to the deep sea, thereby contributing to long-term carbon drawdown. DOC lability and bacterioplankton communities are key determining factors in this carbon sequestration process, and it has been hypothesized that these may be affected by nutrient loading – however, scientific evidence is so far weak. Here, we studied the response of DOC composition and bacterioplankton communities to nutrient loading in seagrass meadows of the South China Sea. We found that increasing nutrient loads enhanced nitrogen and phosphorus concentrations in DOC, which promoted algae blooms (i.e. epiphyte, phytoplankton and macroalgae) in seagrass meadows, and presumably increased the lability of DOC and its bioavailability to microbes. Also, the relative abundance of K -strategist bacterioplankton communities with the potential to degrade refractory compounds (Acidimicrobiia, Verrucomicrobiales and Micrococcales) increased in the seagrass meadows exposed to high nutrient loads. These results suggest that high nutrient loading can enhance labile DOC composition, and thus increase refractory DOC remineralization rate, thereby weakening the DOC contribution potential of seagrass meadows to long-term carbon sequestration. Note: Diagram produced using the Integration and Application Network (IAN), University of Maryland Center for Environmental Science, Cambridge, Maryland. Unlabelled Image • We studied effects of nutrient loading on seagrass ecosystem carbon storage potential. • Nutrients increased the lability (decomposability) of dissolved organic carbon (DOC). • Refractory DOC degrading K -strategy bacterioplankton were boosted by nutrient loading. • Overall, nutrients decreased the carbon storage capacity of DOC in seagrass meadows. [ABSTRACT FROM AUTHOR]