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Abstract Mangroves can retain both autochthonous and allochthonous marine and/or terrestrial organic carbon (OC) in sediments. Accurate quantification of these OC sources is essential for the proper allocation of blue C credits. Here, we conduct a global-scale analysis of sediments autochthonous and allochthonous OC contributions in estuarine and marine mangroves using stable isotopes. Globally, mangrove-derived autochthonous OC was the main contributor to estuarine and marine mangrove top-meter soil organic carbon (SOC) (49% and 62%, respectively). Less marine allochthonous OC (21%) was deposited than terrestrial allochthonous OC (30%) in estuarine mangrove sediments. Estuarine mangroves accumulated more SOC in sediments than marine mangroves (282 ± 8.1 Mg C ha−1 and 250 ± 5.0 Mg C ha−1, respectively), primarily due to the additional terrestrial OC inputs. Globally, marine mangroves held 67% of the total mangrove SOC, reaching 3025 ± 345 Tg C, while 1502 ± 154 Tg C was stored in estuarine mangrove sediments. The findings emphasize the substantial influence of coastal environmental settings on OC contributions, underlining the necessity of accurate OC source quantification for the effective allocation of blue carbon credits.

Blue carbon benefit has not been compared among mangrove reforestation and afforestation pathways at the global scale. This study shows that mangrove reforestation could perform a greater carbon storage potential per hectare than afforestation as its higher nitrogen availability and lower salinity.

The dynamics of lateral nutrient fluxes through hydrological movements are crucial for understanding ecological functions related to the flow of energy, materials, and organisms across various spatiotemporal scales. To investigate the connectivity of multiple spatial flow processes, we conducted a one-year field study to measure lateral hydrologic carbon (C) and nitrogen (N) fluxes across the continental shelf in the Yangtze estuary. We observed a significant correlation between the differences in remote sensing-based estimates of gross primary production (GPP) (ΔGPP _MODIS ) and the differences in eddy covariance (EC) tower-based GPP (ΔGPP _EC ) at both high-elevation and low-elevation sites. Our findings indicate that the saltmarsh acts as a net source of dissolved total C while serving as a net sink for dissolved total N. Furthermore, there was a significant correlation in the total dissolved stoichiometry of the C/N ratio between imports from and exports to adjacent aquatic systems. These findings highlight the importance of integrating ecological stoichiometric principles to improve our understanding of the complex relationships among physical, chemical, and ecological processes, particularly within the context of the meta-ecosystem framework. Additionally, when reciprocal hydrological lateral C and N flows are considered, a single ecosystem can function as both a source and sink within the meta-ecosystem framework.

Blue carbon is identified as a natural climate solution as it provides multiple ecosystem services, including climate mitigation, adaptation, and other co-benefits. There remain ongoing challenges for blue carbon as a natural climate solution, particularly as blue carbon ecosystems are at risk from climate change. Concepts of uniformitarianism were applied to consider how the present and past behaviour of blue carbon ecosystems can inform decision-makers of blue carbon risks. Climate change may increase the capture and storage of blue carbon in the short to medium term; this is largely due to negative feedbacks between elevated atmospheric carbon dioxide and temperature, and supplemented by natural processes of sediment supply and accumulation. Opportunities for retreat and increasing carbon storage as sea levels rise are likely to be greater where sea level has a longer history of relative stability, largely in the Southern Hemisphere. Landward retreat will be crucial where millennia of sea-level rise have limited the capacity for in situ blue carbon additionality; this may be thwarted by highly developed coastal zones and coastal squeeze effects. Negative feedbacks may fail under higher emissions, greater warming and rates of sea-level rise exceeding ~5–7 mm yr.−1; this tipping point may be surpassed within the next century under a high emissions scenario. Retreat of blue carbon ecosystems to higher elevations where they are afforded protection from the effects of sea-level rise will be critical for blue carbon additionality. Carbon markets are prepared to incentivise restoration of blue carbon ecosystems as they adapt to climate change; however, knowledge gaps remain, particularly regarding the behaviour of blue carbon ecosystems in the global south. Given the momentum in blue carbon research, scientists and practitioners are well placed to continue addressing blue carbon risks.

Seafood elemental profiling (SEP) is the quantification of a range of elements in seafood products and may serve in addressing questions of seafood provenance and quality. Traditional methods for analyzing soft tissue present several limitations for the industry-level use of SEP. Portable handheld X-ray fluorescence (pXRF) analysis is a promising alternative to conventional methods; however, its application for biological analysis has not been fully established. Intact giant tiger prawn (Penaeus monodon) abdomens were analyzed with a Vanta M series XRF portable analyzer following a novel soft tissue protocol. Exploratory statistics (principal component analysis, nonmetric multidimensional scaling, and canonical discriminant analysis), as well as random forest models, have been implemented with pXRF profiles, yielding 81% accuracy when assigning the geographical origin of P. monodon. The results of this study highlight that SEP via pXRF is a viable industry-level analysis, and its application will depend on improved instrument calibration to account for fluctuating wetness factors that are influenced by cooking, storage, and other pre- and post-harvest treatments.

As the demand for seafood increases, so does the incidence of seafood fraud. Confirming provenance of seafood is important to combat fraudulent labelling but requires a database that contains the isotopic and elemental “fingerprints” of authentic seafood samples. Local isotopic and elemental databases can be scaled up or combined with other databases to increase the spatial and species coverage to create a larger database. This study showcases the use of isotopic and elemental fingerprints of the black tiger prawn (Penaeus monodon) to develop a database that can be used to securely store the data necessary for determining provenance. The utility of this database was tested through querying and building seven different datasets that were used to develop models to determine the provenance of P. monodon. The models built using the data retrieved from the database demonstrated that the provenance of P. monodon could be determined with >80% accuracy. As the database was developed using MySQL, it can be scaled up to include additional regions, species, or methodologies depending on the needs of the users. Combining the database with methods of determining provenance will provide regulatory bodies and the seafood industry with another provenance tool to combat fraudulent seafood labelling.

The Australian ‘New South Wales Estuary health assessment and biodiversity monitoring program’ has set state-wide targets for estuary health. A selection of water bodies is being monitored by in situ chlorophyll a concentration and turbidity measurements, indicators for water quality. We investigate whether the current monitoring program can benefit from the use of remote sensing derived data, analyzing chlorophyll a and water clarity estimates by the C2RCC and ACOLITE products based on Sentinel-2 MSI imagery for three lakes along the New South Wales coast. The C2RCC and ACOLITE products were partly successful in predicting chlorophyll a concentration and water clarity. Estimates based on Sentinel-2 MSI imagery were in the range of in situ measurements. However, results varied across years and lakes, and a significant correlation could not be found in every case. It is likely that the physical differences between the systems, such as nutrient input, tannins, and suspended algae/sediment matrix, influence the output of the algorithm. This may preclude the application of a ‘one size fits all’ monitoring approach, given the importance of local ecological phenomena in both influencing remote sensing observations and the nature of appropriate targets. However, the design of a monitoring program that incorporates remote sensing provides a way forward.

The fate of mangroves and saltmarshes under conditions of accelerating sea-level rise is dependent upon sedimentation and surface elevation gain that is sufficient to maintain substrate positions within a shifting tidal frame. This study focuses on coastal wetlands fringing Westernport Bay, a large tidal embayment of southeastern Australia where mangroves occupy lower tidal positions than saltmarshes. Estimates of vertical accretion, surface elevation change, and autocompaction derived from a 20-year record of observations were integrated with estimates of sedimentation at the decadal to century time-scale derived from 210Pb chronology to model the relationship between surface elevation gain and accommodation space at timescales relevant to management and decision-making. This model was validated against records of shoreline changes extracted from time-series aerial photography. Sedimentation and surface elevation gain vary spatially on the basis of available accommodation space and sediment supply, which are influenced by hydrodynamic conditions within the bay. Since sea-level rise increases available accommodation space, these relationships provided the means to project the outcome of accelerating sea-level rise on equilibrium accommodation space of mangroves and saltmarshes. Sea-level rise will generally deepen substrate positions within the tidal frame, creating conditions favorable for mangrove forests. Where sediment supply is high, maintenance (and some progradation) of mangrove shorelines may occur under projected low rates of sea-level rise; these conditions are limited to shorelines near sedimentary basins and where there is considerable lateral accommodation space. The same fate is not likely under a high sea-level rise scenario where shoreline retreat is projected in all settings. Given the limited accommodation space within saltmarshes at Westernport Bay, sedimentation will not be sufficient to maintain tidal positions and landward retreat will be critical for maintenance of saltmarsh biodiversity. This will require planning decisions to facilitate tidal incursions and conserve retreat pathways.

Mangrove forests provide numerous valuable ecosystem services and can sequester a large volume of carbon that can help mitigate climate change impacts. Modeling mangrove carbon with robust and valid approaches is crucial to better understanding existing conditions. The study aims to estimate mangrove Above-Ground Carbon (AGC) at Loh Buaya located in the Komodo National Park (Indonesia) using novel Extreme Gradient Boosting (XGB) and Genetic Algorithm (GA) analyses integrating multiple sources of remote sensing (optical, Synthetic Aperture Radar (SAR), and Digital Elevation Model (DEM)) data. Several steps were conducted to assess the model’s accuracy, starting with a field survey of 50 sampling plots, processing the images, selecting the variables, and examining the appropriate machine learning (ML) models. The effectiveness of the proposed XGB-GA was assessed via comparison with other well-known ML techniques, i.e., the Random Forest (RF) and the Support Vector Machine (SVM) models. Our results show that the hybrid XGB-GA model yielded the best results (R2 = 0.857 in the training and R2 = 0.758 in the testing phase). The proposed hybrid model optimized by the GA consisted of six spectral bands and five vegetation indices generated from Sentinel 2B together with a national DEM that had an RMSE = 15.40 Mg C ha−1 and outperformed other ML models for quantifying mangrove AGC. The XGB-GA model estimated mangrove AGC ranging from 2.52 to 123.89 Mg C ha−1 (with an average of 57.16 Mg C ha−1). Our findings contribute an innovative method, which is fast and reliable using open-source data and software. Multisource remotely sensed data combined with advanced machine learning techniques can potentially be used to estimate AGC in tropical mangrove ecosystems worldwide.

A pixel-based algorithm for multi-temporal Landsat (TM/ETM+/OLI/OLI-2) imagery between 1990 and 2022 monitored mangrove dynamics and detected their changes in the three provinces (i.e., Thai Binh, Nam Dinh and Hai Phong), which are located on the Northern coast of Vietnam, through the Google Earth Engine (GEE) cloud computing platform. Results showed that the mangrove area in the study area decreased from 2960 ha in 1990 to 2408 ha in 1995 and then significantly increased to 4435 ha in 2000 but later declined to 3502 ha in 2005. The mangrove areas experienced an increase from 4706 ha in 2010 to 10,125 ha in 2020 and reached a highest peak of 10,630 ha in 2022. In 2022, Hai Phong province had the largest area of mangrove (3934 ha), followed by Nam Dinh (3501 ha) and Thai Binh (3195 ha) provinces. The overall accuracies for 2020 and 2022 were 94.94% and 91.98%, while the Kappa coefficients were 0.90 and 0.84, respectively. The mangrove restoration programs and policies by the Vietnamese government and local governments are the key drivers of this increase in mangroves in the three provinces from 1990 to 2022. The results also demonstrated that the combination of Landsat time series images, a pixel-based algorithm, and the GEE platform has a high potential for monitoring long-term change of mangrove forests during 32 years in the tropics. Moreover, the obtained mangrove forest maps at a 30-m spatial resolution can serve as a useful and up-to-date dataset for sustainable management and conservation of these mangrove forests in the Red River Delta, Vietnam.

The fate of coastal wetlands and their ecosystem services is dependent upon maintaining substrate elevations within a tidal frame that is influenced by sea-level rise. Development and application of morphodynamic models has been limited as few empirical studies have measured the contribution of key processes to surface elevation change, including mineral and organic matter addition, autocompaction of accumulating sediments and deep subsidence. Accordingly, many models presume that substrates are in equilibrium with relative sea-level rise (RSLR) and the composition of substrates are relatively homogenous. A 20-year record of surface elevation change and vertical accretion from a large tidal embayment in Australia coupled with analyses of inundation frequency and the character of sediments that have accumulated above mean sea level was analyzed to investigate processes influencing surface elevation adjustment. This study confirms the varying contribution of addition, decomposition and compression of organic material, and mineral sediment consolidation. Autocompaction of substrates was proportional to the overburden of accumulating sediments. These processes operate concurrently and are influenced by sediment supply and deposition. Vertical accretion was linearly related to accommodation space. Surface elevation change was related to vertical accretion and substrate organic matter, indicated by carbon storage above mean sea level. Surface elevation change also conformed to models that initially increase and then decrease as accommodation space diminishes. Rates of surface elevation change were largely found to be in equilibrium with sea-level rise measured at the nearest tide gauge, which was estimated at 3.5 mm y–1 over the period of measurements. As creation of new accommodation space with sea-level rise is contrary to the longer-term history of relative sea-level stability in Australia since the mid-Holocene, striking stratigraphic variation arises with deeper sediments dominated by mineral sands and surficial sediments increasingly fine grained and having higher carbon storage. As the sediment character of substrates was found to influence rates of surface elevation gain, we caution against the unqualified use of models derived from the northern hemisphere where substrates have continuously adjusted to sea-level rise and sediment character is likely to be more homogenous.

Abstract For sustaining ecosystem functions and services, environmental conservation strategies increasingly target to maintain the multiple facets of biodiversity, such as functional diversity (FD) and phylogenetic diversity (PD), not just taxonomic diversity (TD). However, spatial mismatches among these components of biodiversity can impose challenges for conservation decisions. Hence, understanding the drivers of biodiversity is critical. Here, we investigated the global distribution patterns of TD, FD, and PD of breeding Anatidae. Using null models, we clarified the relative importance of mechanisms that influence Anatidae community. We also developed random forest models to evaluate the effects of environmental variables on the Anatidae TD, FD, and PD. Our results showed that geographical variation in Anatidae diversity is hemispheric rather than latitudinal. In the species‐rich Northern Hemisphere (NH), the three diversity indices decreased with latitude within the tropical zone of the NH, but increased in the temperate zone reaching a peak at 44.5–70.0°N, where functional and phylogenetic clustering was a predominant feature. In the Southern Hemisphere (SH), Anatidae diversity increased poleward and a tendency to overdispersion was common. In NH, productivity seasonality and temperature in the coldest quarter were the most important variables. Productivity seasonality was also the most influential predictor of SH Anatidae diversity, along with peak productivity. These findings suggested that seasonality and productivity, both consistent with the energy‐diversity hypothesis, interact with the varying histories to shape the contrasting hemispheric patterns of Anatidae diversity. Phylogenetic diversity (PD) and FD underdispersion, widespread across the species‐rich, seasonally productive mid‐to‐high latitudes of the NH, reflects a rapid evolutionary radiation and resorting associated with Pleistocene cycles of glaciation. The SH continents (and southern Asia) are characterized by a widespread tendency toward PD and FD overdispersion, with their generally species‐poor communities comprising proportionately more older lineages in thermally more stable but less predictably productive environments.

Semi-arid floodplain vegetation is an essential component of floodplain and terrestrial ecosystems due to the wide range of services provided for waterbirds, woodland birds, amphibians and mammals, together with their contribution to natural carbon sequestration. Since overbank flooding has been considered the driving factor of vegetation distribution on floodplains, sustainable water resource management requires a better understanding of the influence of inundation on vegetation distribution. We examined the relationship between the distribution of four flood-dependant vegetation communities and associated long term inundation metrics on the upper Darling River floodplain using electivity analysis and a generalised additive model (GAM) by generating a total of 10,478 individual inundation maps with a high spatial resolution over a period of 29 years. Our results show that the four dominant vegetation communities are situated differently in relation to inundation attributes. The inundation metrics better explained the variation in the distribution of River Red Gum than those of Black box, Coolabah and Lignum communities. We found that the floodplain forests and woodlands in the upper Darling can survive longer periods of drought and shorter inundation duration than previously reported. The results provide practical information for ecosystem management by offering a means of predicting changes in vegetation distribution in relation to alteration in flow regime resulting from water planning arrangements or climate change.

It remains difficult to compare the state of conservation of forests of different nations. Essential Biodiversity Variables (EBVs) are a set of variables designed as a framework for harmonizing biodiversity monitoring. Methods to monitor forest biodiversity are traditional monitoring (according to conservation policy requirements), remote sensing, environmental DNA, and the information products that are derived from them (RS/eDNA biodiversity products). However, it is not clear to what extent indicators from conservation policies align with EBVs and RS/eDNA biodiversity products. This research evaluated current gaps in harmonization between EBVs, RS/eDNA biodiversity products and forest conservation indicators. We compared two sets of biodiversity variables: (1) forest conservation indicators and (2) RS/eDNA biodiversity products, within the context of the Essential Biodiversity Variables framework. Indicators derived from policy documents can mostly be categorized within the EBV ‘ecosystem vertical profile’, while ‘ecosystem function’ remains underrepresented. RS/eDNA biodiversity products, however, can provide information about ‘ecosystem function’. Integrating RS/eDNA biodiversity products that monitor ecosystem functioning into monitoring programs will lead to a more comprehensive and balanced reporting on forest biodiversity. In addition, using the same variables and similar RS/eDNA products for forest biodiversity and conservation policies is a requirement for harmonization and international policy reporting.

Determination of the elemental composition of soft biological tissue is a time-consuming and tedious process when using traditional analytical techniques. In this method, micro X-ray fluorescence (μXRF) via Itrax, a scanning instrument, was used to determine elemental abundance at a resolution of 200 μm. Itrax μXRF was initially designed for elemental profiling of geological cores, and the capability of this technique was extended to soft biological tissue samples. The samples were dried and ground into a fine powder before analysis. The scanner generates elemental values as counts per 1 mm and these values are standardised to obtain the relative elemental abundance of the elements present in the samples. The acquired data can be used for environmental and biological research. • No literature could be found whereby the capability of Itrax μXRF has been extended to soft biological tissue samples. • The major advantages Itrax has over conventional methods is that it is a simultaneous technique which allows data to be acquired for over 30 elements at once with minimal sample preparation. • It is a non-destructive process where the samples can be re-used for additional analyses if necessary; this is especially useful when there is only a limited amount of sample available for other analyses. Method name: Determining the elemental profile of soft biological tissue samples through Itrax, Keywords: Itrax, Biological samples, Elemental profile, Micro X-ray fluorescence

Predictions of coastal wetland response to sea-level rise often neglect attenuation effects due to vegetation and infrastructure. Here, the authors show that including attenuation effects improves prediction of wetland evolution and suggests increases in wetland vulnerability to sea-level rise.

Juveniles of commercially important fish species congregate in shallow vegetated estuarine habitats during high tides. Considerable debate has centred on whether the significance of these habitats lies in their provision of greater feeding opportunities, or shelter from predation afforded by greater structural complexity. We tested the hypothesis that an inundated mangrove and saltmarsh wetland provided feeding opportunities for itinerant species, and that the contribution of wetland primary producers and grazing herbivores could be identified in their diet, using stable isotopes of carbon and nitrogen. Potential sources of dietary carbon included mangrove, saltmarsh, seagrass, seagrass epiphytic material and benthic organic material. Saltmarsh plants (mostly Sporobolus virginicusand Juncus kraussii) and fine benthic organic material appeared to be the primary sources of dietary carbon for the resident grazing herbivores in the wetlands, based on IsoSource mixing models. During high tide, species of itinerant fish enter the mangrove and, when inundated, the saltmarsh, and feed primarily on crab larvae and copepods. Fine benthic organic matter, seagrass epiphyte, and C3and C4plant materials also supplement the diet of some fish. The crab larvae therefore provide a significant source of nutrition and an important link between the intertidal wetlands and the adjacent estuarine ecosystem. The carnivorous fish Acanthopagrus australis, at the highest trophic level, hunted within or adjacent to the mangrove–saltmarsh wetland and fed on several lower-order consumers within the wetland. The present study highlights the significance of mangrove and saltmarsh wetlands as a feeding habitat for resident grazers and itinerant nekton. [ABSTRACT FROM AUTHOR]

The importance of estuarine wetlands to ecosystem services such as primary productivity and flood attenuation, as well as their function as habitat for threatened species has prompted efforts to restore tidal flows to degraded wetlands. We tracked the response of estuarine vegetation to tidal-flow reinstatement over 12 years (1995–2007) in a wetland of the Hunter estuary, Australia. This site provides important habitat for migratory shorebird species, which favour shallow tidal pools and saltmarsh over mangrove forest. Increased tidal flows following culvert removal reduced shorebird roost habitat by 17% because of mangrove encroachment on saltmarsh and shallow tidal pools. Saltmarsh occurred in areas with a spring tidal range <0.3 m, hydroperiod <1.0 and elevation >0.4 above the Australian height datum (mAHD), whereas mangrove occupied areas with spring tidal range >0.3 m, hydroperiod <0.45 and elevation <0.4 mAHD. By using these parameters, it is possible to exclude mangrove from saltmarsh areas and to establish saltmarsh at lower elevations in the tidal frame than would occur under natural conditions, effectively expanding saltmarsh area. These measures can be useful where landward migration of estuarine communities is restricted by infrastructure; however, they should not be considered a substitute for conservation of remnant saltmarsh or establishment of landward buffer zones. [ABSTRACT FROM AUTHOR]

On Australian semiarid floodplains, large herbivores such as kangaroos have a role in the cycling of energy (carbon) through the mechanism of feeding and defaecation of vegetative material. The degree to which kangaroos are vectors of energy within this system is not fully understood. This study describes the stable carbon isotope signature of floodplain plants and kangaroo scats at two close study sites. Kangaroos were found to deposit scats that mirrored the forage composition at each particular feeding site. Scats were 3.94‰ higher in δ13C values at the site where C4grasses were available, indicating that this grass contributed ~25–30% of the diet of these kangaroos. The difference in diet due to the relative availability of C3and C4forage, detectable in the carbon stable isotope signature of scats, is used to demonstrate that kangaroos are recycling and redistributing energy locally, rather than transporting it more broadly across the floodplain. [ABSTRACT FROM AUTHOR]

Saltmarsh floristic diversity declines with increasing latitude on the Australian east coast, with the dominant tropical C4grass Sporobolus virginicusbeing replaced progressively by a suite of mostly succulent C3species. The temperate Towra Point saltmarsh consists of a mosaic of vegetation communities, including stands of the C4saltmarsh grass Sporobolus virginicus, and the C3succulents Suaeda australisand Sarcocornia quinqueflora. The contrasting stable isotope signatures of these plants provide an opportunity to determine the extent to which plant material is contributing to the diet of grazing invertebrates inhabiting these communities. The grazing crabs Parasesarma erythrodactylaand Helograpsus haswellianus, and the snail Littoraria luteola, were sampled for their carbon and nitrogen isotope signatures. In the Sarcocorniacommunities, crab and snail δ13C signatures could not be matched to the signature of dominant plants, but were close to the fine benthic material on the marsh surface. In the Sporoboluscommunity, the δ13C signatures of the same species were enriched and closer to that of the dominant plant. Results suggest that grazing herbivores feed over very small spatial ranges within mosaics of vegetation on locally sourced benthic material, with S. virginicusplant material making a contribution to dietary carbon where present. [ABSTRACT FROM AUTHOR]