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Global Theories of Change (ToCs), such as the post-2020 Global Biodiversity Framework (GBF), provide broad, overarching guidance for achieving conservation goals. However, broad guidance cannot inform how conservation actions will lead to desired outcomes. We provide a framework for translating a global-scale ToC into focussed, ecosystem-specific ToCs that consider feasibility of actions, as determined by national socioeconomic and political context (i.e., enabling conditions). We demonstrate the framework using coastal wetland ecosystems as a case study. We identified six distinct multinational profiles of enabling conditions (‘enabling profiles’) for coastal wetland conservation. For countries belonging to enabling profiles with high internal capacity to enable conservation, we described plausible ToCs that involved strengthening policy and regulation. Alternatively, for enabling profiles with low internal enabling capacity, plausible ToCs typically required formalising community-led conservation. Our ‘enabling profile’ framework could be applied to other ecosystems to help operationalise the post-2020 GBF.

The ubiquitous occurrence of microplastics in coastal habitats is widely reported. As an anthropogenic material with high carbon content, the contribution of microplastics to the coastal sediment carbon stock is still unassessed. Here, we report the occurrence pattern of microplastics (20-2000 μm) and estimate their contribution to the carbon stock in different coastal sediments in Hong Kong, a metropolis in the Pearl River estuary and part of the Greater Bay Area with a population of 70 million. Our data reveal that microplastics are more concentrated in the surface sediment and in vegetated coastal sediments. We also estimate that at present carbon from microplastics contributes between 0.001% and 1.197% to the sediment carbon pool at different depths. Despite the low contribution, microplastics have already made a hidden contribution to the coastal sediment carbon stock. Our data help to establish a baseline for future contributions of microplastics to total carbon storage in peri-urban coastal sediments.

Introduction of species by humans breaks down biogeographic boundaries and results in the homogenization of species composition, yet empirical tests of this impact in marine forest ecosystems are still scarce. Large-scale planting aimed at reversing losses of mangroves has been the dominant strategy for mangrove restoration adopted by many organizations in the past decades, but there is a lack of quantitative understanding of the impacts of such large-scale plantings on mangrove biogeography. Here we used data collected before and after large-scale planting to compare the species richness and compositional similarities among 72 mangrove sites over a biogeographic scale (18–28°N) in China. After the large-scale planting, 15 of the mangrove species spread toward the higher latitudes, reflecting the geographical barriers of the mangrove plants have been broken. Local species richness of mangrove increased by 44.82% and biogeographic compositional similarity of mangroves increased by 13.33%, reflecting large-scale introduction and planting increase local diversity of mangrove but enhance biological homogenization. The dispersal limitation of mangrove communities reduced by 11.1%, which indicates that the community assemblage process of mangrove changed obviously. Worryingly, two alien species, Sonneratia apetala and Laguncularia racemosa, have dispersal across the biogeographic scale studied, reflecting an increase in the risk of biogeographic invasion. It is expected that biological homogeneity and species invasion will further influence the functional biogeography of mangroves. Our results highlight that mangrove biogeography is defined by human activities in the Anthropocene.

Previous studies on mangrove carbon utilisation and mineralisation were focused on mangrove sesarmid crabs (Grapsoidea: Sesarmidae) because they are initial processors of mangrove organic carbon. Grapsoid crabs from other families and habitats were generally ignored although they also perform various levels of herbivory. It remains unclear how the herbivorous crabs utilise the production from mangrove or vascular plants because of the high C/N ratio and high structural carbon content of these materials. In this study, production of cellulase and expression of hepatopancreatic glycosyl hydrolase of grapsoid crabs were investigated in a more extensive way in terms of their taxa (15 species) and habitats (i.e., land margin, mangrove, mudflat, and subtidal area). Generally, low gastric endoglucanase (1.46-2.98 μmol min−1 ml−1) and β-glucosidase (0.06-0.61 μmol min−1 ml−1) activity was detected in 15 grapsoid crabs distributed along the land-sea transition. The activity of both enzymes was significantly affected by the taxonomic affiliation and habitat of the crabs: endoglucanase in sesarmids > varunids > grapsids; and land margin, mangrove and limnic habitats > mudflat and subtidal area. For β-glucosidase: sesarmids > varunids and grapsids; and land and limnic > mangrove and subtidal > mudflat. Our detection of gastric cellulases in mudflat and subtidal grapsoid crabs has rarely been reported. These results show that there is a need to re-evaluate the role of crabs from these habitats in mangrove/vascular plant carbon mineralisation. Further, low cellulase activity could be a common trait among crabs along the land-sea transition and the importance of cellulase in vascular plant carbon utilisation could have been previously over-rated. Glycosyl hydrolase family 9 (GH9) genes were identified in the hepatopancreatic transcriptome of all 15 species, indicating endogenous production of cellulase. In addition, the presence of other digestive carbohydrate-active enzymes (CAZymes), including GH5_10, GH13, GH13_24, and GH16, suggests that a capacity for the utilisation of carbon sources other than cellulose by the grapsoid crabs, which may enable sufficient assimilation of vascular plant carbon despite the low cellulase activity.

Globally dominant marine bacterioplankton lineages are often limited in metabolic versatility, owing to their extensive genome reductions, and thus cannot take advantage of transient nutrient patches. It is therefore perplexing how the nutrient-poor bulk seawater sustains the pelagic streamlined lineages, each containing numerous populations. Here, we sequenced the genomes of 33 isolates of the recently discovered CHUG lineage (~2.6 Mbp), which have some of the smallest genomes in the globally abundant Roseobacter group (commonly over 4 Mbp). These genome-reduced bacteria were isolated from a transient habitat: seawater surrounding the brown alga, Sargassum hemiphyllum. Population genomic analyses showed that: (i) these isolates, despite sharing identical 16S rRNA genes, were differentiated into several genetically isolated populations through successive speciation events; (ii) only the first speciation event led to the genetic separation of both core and accessory genomes; and (iii) populations resulting from this event are differentiated at many loci involved in carbon utilization and oxygen respiration, corroborated by BiOLOG phenotype microarray assays and oxygen uptake kinetics experiments, respectively. These differentiated traits match well with the dynamic nature of the macroalgal seawater, in which the quantity and quality of carbon sources and the concentration of oxygen likely vary spatially and temporally, though other habitats, like fresh organic aggregates, cannot be ruled out. Our study implies that transient habitats in the overall nutrient-poor ocean can shape the microdiversity and population structure of genome-reduced bacterioplankton lineages.

Protecting existing mangrove forests is a priority for global conservation because of the wide range of services that these coastal forests provide to humankind. Despite the recent reduction in global rates of mangrove loss, high historical loss rates mean that there are at least 800,000 ha globally that are potentially suitable for mangrove re-establishment. Recently deposited mud banks or intertidal, previously terrestrial, land might provide additional habitat for expanding mangrove areas locally. There is a long history of mangrove rehabilitation. However, despite numerous good examples of, and growing expertise in, natural or assisted (re-)establishment activities, most mangrove planting efforts, for instance, either fail entirely or meet with only limited success. Exposed to waves and currents and subject to tidal inundation, mangroves differ from terrestrial forests, and approaches to, or tools for, terrestrial forest restoration cannot easily be transferred to mangrove forests. Successful mangrove (re-)establishment usually requires a robust understanding of the abiotic and biotic conditions of the chosen site, the ecological requirements of the mangrove species used or facilitated, the reasons for previous mangrove loss or degradation, as well as the barriers–both societal and ecological–that have prevented natural recovery to date. Because most mangrove forests are socio-ecological systems, with which local human populations are intimately engaged, (re-)establishment will normally require the support of, and engagement with, local communities and other local stakeholders. Here, we summarize where, when and why (re-)establishment of mangroves is needed and how to assess this need. We discuss a range of potential aims and goals of mangrove (re-)establishment along with potential pitfalls along the way from conceiving the initial idea to its realization. We compare different technical and conceptual approaches to mangrove (re-)establishment, their challenges and opportunities, and their design and financial requirements, as well as potential solutions. We ground our final outlook and recommendations on examples of successful efforts and the factors that rendered (re-)establishment successful in the past.

Tidal flats are widely distributed and provide a variety of ecosystem services. Nevertheless, the consequences of tidal flat loss and implications for services such as carbon (C) sequestration have not been assessed. In unvegetated tidal flat ecosystems, sediment is the most important carbon reservoir, similar to that of vegetated coastal wetlands (i.e., mangroves, salt marshes, and seagrass). We examined the C stocks and C accumulation rate (CAR) reported from 123 locations of tidal flat around the world and compared these results with data from mangroves, salt marshes, and seagrass meadows. The global average CAR of tidal flats is 129.8 g C m-2 yr-1, with the top-meter sediments containing on average 86.3 Mg C ha-1. Globally, tidal flat can bury 6.8 Tg C (24.9 Tg CO2) per year and can store 0.9 Pg C (3.3 Pg CO2) in the top meter sediment. Assuming the same rate of loss tidal flats as in the past three decades and that all disturbed sediment C is remineralized, 4.8 Tg C will be lost from tidal flat sediments every year, equivalent to an emission of 17.6 Tg CO2 to the water column and atmosphere.

Despite worldwide efforts to restore degraded mangrove forests in the past decades, defining and tracking restoration success remains a major challenge. In this study, we used a multi-isotope approach to trace ecosystem responses to forest clearing and replanting in a tropical mangrove forest reserve at Matang, Malaysia. We measured δ2H or δD deuterium, δ13C and δ15N (HCN isotopes) in common macroinvertebrate consumers (barnacles, prawns, gastropods, and crabs) across a 70-year chronosequence of mangroves. Functional food web recovery was indicated by a decrease in δ13C and δ15N and increase in δD for gastropod and crab consumers in older forests. Timing of this shift in food web isotopic signals took place between 5 and 15 years post-clearing of mangroves. These changes in food web function paralleled changes in crab community composition, but also reflected changes in physicochemical conditions within the forest, such as increased tree cover and shading, which resulted in a shift of the food web base from microalgal-derived to mangrove-derived organic matter. Prawns and barnacles from tidal waters adjacent to the mangrove forests were estimated to derive 17 to 25% of their nutrition from mangroves, primarily from a microbial loop that was processing localised dissolved and particulate organic matter exported from mangrove marshes. The top-down mixing model approach using combined HCN isotope measurements clearly separated inputs from mangroves versus microalgae for the first time in estuarine food web studies, and tracked ecological mangrove ecosystem recovery. This combination of tracers is recommended for future studies of mangrove conservation and restoration.

Tidal marshes are not only lost to human disturbance but also face the threat of sea level rise (SLR). However, current earth system models used to estimate future changes in wetland extent omit wetland’s real responses to SLR without field observations. We synthesised global data on sediment accretion rate (SAR) and surface elevation change (SEC) for tidal marshes and developed a mathematical model to assess their resilience to future SLR. Sediment loadings and precipitation largely explain the variance of marsh SAR and SEC. Human disturbance resulted in less sediment accretion and existing conservation activities were inefficient in promoting sediment accretion. Under the representative concentration pathways and nature-based human adaptation scenarios, tidal marshes will gain up to 63% of the current area by 2100 if sufficient sediment loadings and accommodation space allow landward migration. If current accommodation space maintains, net areal losses of > 30% are possible and hotspots of future marsh loss are largely in North America, Australia and China. Projections for most SLR scenarios see marsh area peaking in the mid rather than late 21st century. This implicates that tidal marshes may contribute to achieve a climate neutral world by 2050. We highlight the importance of nature- based adaptation in enhancing the resilience of tidal marshes to future SLR.

We investigated the sediment carbon (C) stocks, sequestration and sources in tidal flats and their adjacent mangroves in two coastal wetlands in Hong Kong (the Mai Po Nature Reserve (MPNR) and Ting Kok (TK)), part of a megacity of ∼20 million. At both locations, the C stock of tidal flats was lower than that of mangroves. In MPNR, tidal flats indicated a higher C burial rate (75.2 g C m

Coastal wetlands trap plastics from terrestrial and marine sources, but the stocks of plastics and their impacts on coastal wetlands are poorly known. We evaluated the stocks, fate, and biological and biogeochemical effects of plastics in coastal wetlands with plastic abundance data from 112 studies. The representative abundance of plastics that occurs in coastal wetland sediments and is ingested by marine animals reaches 156.7 and 98.3 items kg

Fine root dynamics have the potential to contribute to ecosystem biogeochemical cycling, especially for carbon. This is particularly true in mangroves which are the most productive and carbon-rich ecosystems of the world. However, few studies comprehensively evaluated the contribution of mangrove fine root dynamics to soil organic carbon accumulation. In southern China, while the introduced fast-growing Sonneratia apetala and native shrubby Kandelia obovata have been widely used in mangrove reforestation/afforestation programs since the mid-1980s, their implications and ecosystem services are still unclear. Here we show distinct differences in fine root dynamic among 12-year-old S. apetala, K. obovata monocultures, and their mixed stand using root coring, ingrowth core, and intact-core methods. Soil organic carbon storage was examined by soil coring method. One-year observation showed significant differences among the three mangrove plantations in fine root biomass, necromass, turnover rate, and decomposition decay rate constant. Soil organic carbon stock was 15.8 ± 0.8, 7.8 ± 0.5, and 11.9 ± 1.6 Mg C ha–1 for K. obovata, S. apetala monocultures and their mixed stand, respectively. Live fine root biomass, fine root necromass, annual fine root production and fine root mass decay rate constant are significantly correlated to soil organic carbon content across plantations. We suggest that mangrove fine root dynamics were mainly affected by soil nutrient conditions and species composition. Mixed stands may not have higher soil organic carbon storage than monocultures. The functional trait of different mangrove species is responsible to determine the carbon storage function of mixed stands. Fine roots play an important role in carbon storage, and fine root dynamics have a significant effect on carbon sequestration in mangrove ecosystems. The shrubby native K. obovata had a higher potential for belowground carbon sequestration and storage than the tall introduced S. apetala.

Extreme climatic events can trigger sudden but often long‐lasting impacts in ecosystems by causing near to complete mortality of foundation (habitat‐forming) species. The magnitude and frequency of such events are expected to rise due to anthropogenic climate change, but the impacts that such events have on many foundation species and the ecosystems that they support remains poorly understood. In many cases, manipulative experimentation is extremely challenging and rarely feasible at a large scale. In late 2015 to early 2016, an extensive area of mangrove forest along ∼ 1000 km of coastline in the Gulf of Carpentaria, Australia, experienced severe dieback, an event associated with climatic extremes. To assess the effect this dieback event had on the mangrove ecosystem, we assessed benthic faunal assemblages and food web structure using stable carbon and nitrogen isotopes in a comparative experiment of impacted forest and adjacent unimpacted forest. Eighteen months after the dieback, the forest that suffered dieback contained significantly fewer crabs that rely on mangrove litter food source but more crabs that rely on microphytobenthos food source than the unimpacted forest. However, the infaunal biomass was largely unaffected by the mortality effect. This is most likely because microphytobenthos was largely unaffected and consequently, this buffered the food web responses. However, overall, the habitat value for mangrove ecosystem services most likely decreased due to lower physical habitat complexity following tree mortality. Longer‐term monitoring could lead to better understanding of biological effects of this extreme event and underlying biological mechanisms that drive changes and recovery.

Intertidal mangrove forests are a dynamic ecosystem experiencing rapid changes in extent and habitat quality over geological history, today and into the future. Climate and sea level have drastically altered mangrove distribution since their appearance in the geological record ∼75 million years ago (Mya), through to the Holocene. In contrast, contemporary mangrove dynamics are driven primarily by anthropogenic threats, including pollution, overextraction, and conversion to aquaculture and agriculture. Deforestation rates have declined in the past decade, but the future of mangroves is uncertain; new deforestation frontiers are opening, particularly in Southeast Asia and West Africa, despite international conservation policies and ambitious global targets for rehabilitation. In addition, geological and climatic processes such as sea-level rise that were important over geological history will continue to influence global mangrove distribution in the future. Recommendations are given to reframe mangrove conservation, with a view to improving the state of mangroves in the future.

Holistic ecosystem health indices are urgently needed for conserving and managing rapidly dwindling mangrove ecosystems. The appropriate indices should provide consistent outcomes that enable both the assessment of current conditions and assist future planning. The previous approaches mostly focus on the structural condition of trees, with mangrove ecosystems often treated as terrestrial forests. Structural features are too insensitive as representatives of negative internal creeping changes. Some unique mangrove ecosystem attributes can react to anthropogenic pressures much faster than tree or forest structures do, making them more useful as early warning indicators. The development of holistic indicators requires a multidimensional approach engaging specific functions and services underpinning the characteristics of mangrove ecosystems. We present an approach to identify potential variables ranging from assemblage structure to physiological and biochemical variables for reliably indicating mangrove condition. These indicators could then be tested against a range of ecosystem conditions (e.g. disturbance levels) to reveal their response to different degrees of pressures. These variables were first nominated based on the driver-response model relating changes in environmental conditions and ecosystem responses. The nominated variables were then prioritised through an expert questionnaire survey, in which the experts scored every nominated variable on the efficiency, the number of pertinent ecosystem services and the time required them to reflect the impact of the pressure. Sediment properties and elements of forest structure featured strongly in the survey, followed by variables pertaining to biomass, vegetation status and carbon cycling. With respect to community composition, components of the higher trophic levels (e.g. crabs, other macrofauna) were ranked higher by the experts. The mangrove-tree-related variables (e.g. Importance Value Index, IVI), associated biotic components of insects, annelids and moss were ranked lowest. These results provide the basis for establishing a specific framework for mangrove ecosystem assessment.

During daily fishing operations, spanner crab Ranina ranina catch rates can fluctuate substantially, but the environmental drivers responsible for these fluctuations largely remain unresolved. Earlier research suggests that spanner crab catchability increases with strengthening currents, but uncertainties surround the magnitude of the measured current speeds and, consequently, their relationship with catch rates. Here, we explore the effects of bottom currents on spanner crab catch rates in South East Queensland, Australia. Using generalized additive mixed modeling, our results indicated that strengthening current speeds increased catch rates until reaching approximately 0.15 m/s, at which point the catch rates began to gradually decline. Results from a general linear regression model also showed that between fishing periods carried out on the same day, catch rates increased or decreased concurrently with current speeds. We conclude that bottom current speed should be considered in future stock assessment models. Better understanding the processes responsible for changes in bottom current speed will enable more accurate estimates of spanner crab population densities in the Australian fishery and will benefit the economic efficiency of commercial crabbing operations. Furthermore, future studies that investigate the effects of current speed on catch rates for other crab species should consider differences in locomotory characteristics and how they may impact the foraging efficiency of crabs under different flow conditions.

“The value of life lies not in the length of days, but in the use we make of them.” (Michel de Montaigne) The 28th March 2021 was, and remains, a day of great sadness for many marine biologists worldwide who mourn the passing of Professor Brian Morton (Fig. 1), a distinguished marine biologist, an exemplary teacher and a dear friend, after a brave battle with his chronic lung disease over three years. As the pioneer of marine biology in Hong Kong, Brian dedicated his lifetime to ploughing the fields, sowing the seeds, and cultivating marine biological research and marine conservation, achieving an enormous impact in Hong Kong, China, and beyond, which we see and enjoy today. Brian not only enlightened his students intellectually, his positive, energizing attitude changed the outlook on life for many of us. While we deeply grieve the loss of Brian, we also celebrate his life, so full of memories and achievements.

Intertidal benthos link tertiary predators and primary producers in marine food webs as well as directly contribute to sediment CO

Background：The fast-growing introduced mangrove Sonneratia apetala is widely used for mangrove afforestation and reforestation in China. Some studies suggested that this exotic species outperforms native species in terms of carbon sequestration potential. This study tested the hypothesis that multi-species mangrove plantations might have higher carbon sequestration potential than S. apetala monocultures.Results: Our field measurements at Hanjiang River Estuary (Guangdong province, China) showed that the carbon stock (46.0±3.0 Mg/ha) in S. apetala plantations where the native Kandelia obovata formed an understory shrub layer was slightly higher than that in S. apetala monocultures (36.6±1.3 Mg/ha). Moreover, the carbon stock in monospecific K. obovata stands (106.6±1.4 Mg/ha ) was much larger than that of S. apetala monocultures.Conclusions: Our results show that K. obovata monocultures may have a higher carbon accumulation rate than S. apetala monocultures. Planting K. obovata seedlings in existing S. apetala plantations may enhance the carbon sink associated with these plantations.

Intertidal benthos link tertiary predators and primary producers in marine food webs as well as directly contribute to sediment CO2 emission. However, current methods for studying food sources of marine benthos are time-consuming and does not allow direct estimates on feeding regime-related CO2 production. We examined the foods of mangrove crabs and gastropods as well as their corresponding CO2 production by using cavity-ring down spectroscopy to measure the δ13C of consumer-respired CO2, considering the effects of feeding regime, benthos taxa, and dominant feeding habit. Benthos taxa and feeding habit have significant impact on δ13C of respired CO2. Particularly, the δ13C of crab (−23.9±0.4 ‰) respired CO2 was significantly lower than that from gastropod (−17.5±1.3 ‰) respiration. The δ13C of deposit-feeder respired CO2 was significantly higher than that from detritivores. There are significant differences in the amount of CO2 emitted and δ13C of crab respired CO2 under different feeding regimes. The differences reflect diet-switching and fuel-switching in the crabs, i.e. you breathe what you eat. Significant differences in CO2 production of crabs also exist between those feeding on microphytobenthos (0.13±0.02 mmol g−1 day−1) and on field collection (0.31±0.03 mmol g−1 day−1). CO2 production of crabs is strongly related to carapace width and length. The δ13C of respired CO2 from mangrove crabs reflects their diet while crab-respired CO2 flux is related to crab size. These relationships enable partitioning the feeding habit and food sources of key benthos, and help incorporate their contribution into the overall sediment-atmosphere CO2 fluxes in mangroves.

BackgroundThe exotic Sonneratia apetala and native Kandelia obovata have been widely planted in mangrove afforestation and reforestation programmes in China. However, their capacity for carbon sequestration is still controversial. ResultsThe total vegetation biomass was highest in K. obovata monoculture, followed by the mixed forest and lowest in S. apetala monoculture. Such difference is attributed to the inconsistency by means of stem density of forests. This trend also applies to total vegetation and soil organic carbon storages. ConclusionsContrary to the original expectation, shrubby native K. obovata may be preferred to exotic S. apetala for mangrove carbon-based reforestation/afforestation prgrammes. It is recommended the carbon storage capacity of the existing S. apetala plantation may be enhanced by introducing native mangrove species. As an optional strategy of mangrove rehabilitation, the establishment of mixed plantations with different stem densities could improve the capacity of carbon storage for mono-specific plantations dominated by exotic species in Southern China.

Cyclone disturbance results in mangrove foliage loss, tree mortality and other changes in ecosystem processes. However, the impact of cyclones on mangrove sediment nutrient density, sediment-air CO2 and CH4 fluxes and their isotopes remains largely unknown. Super-typhoon Mangkhut (maximum gust 256 km h−1) hit Hong Kong in September 2018. We investigated the influence of the cyclone by comparing pre- and post-cyclone sediment carbon cycling processes as well as nitrogen density during an 8-month period in a mangrove forest at Ting Kok, Hong Kong. Time and/or nitrogen density are the dominant drivers of the variation of dark sediment-air CO2 fluxes (Rd) and sediment nutrient density. Significant changes in Rd and their δ13CO2 values, sediment organic carbon density (SOC) and nitrogen density (SON) occurred after the cyclone. Rd were highest one month after the cyclone (0.05 ± 0.01 mmol m−2 min−1) and lowest before the cyclone (8.32 ± 2.84 μmol m−2 min−1). δ13CO2 of pre-cyclone Rd (−18.2 ± 1.7‰) was significantly higher than that of all post-cyclone fluxes (−22.9 ± 1.5‰ to −23.6 ± 1.8‰). Both SOC and SON were highest one month after the cyclone (23.05 ± 1.92 kg C m−3, 2.42 ± 0.11 kg N m−3, 20–40 cm). A significant positive relationship exists between Rd and SON. Sediment-air CH4 fluxes did not show significant changes over time but along the sea-land gradient (0.28 ± 0.21 to 0.61 ± 0.22 μmol m−2 min−1). Cyclone disturbance results in the pulse input of litter, which may explain the significant increase in post-cyclone Rd and lower δ13CO2 of Rd. With anticipated climate change-driven effects on cyclone occurrence and intensity, our data underscores the significance of incorporating the influence of cyclone disturbance in constraining the global nutrient budgets in mangroves.

There is an urgent need to halt and reverse loss of mangroves and seagrass to protect and increase the ecosystem services they provide to coastal communities, such as enhancing coastal resilience and contributing to climate stability.

Species catchability is an important parameter used to help optimise stock assessment modelling and the economic efficiency of commercial fishing operations. Previous studies have shown several physical oceanographic parameters, including ambient temperature, waves and currents, affect the catchability of spanner crabs (Ranina ranina) throughout the Indo-Pacific. Most notably in the Australian fishery, where oceanographic processes vary over space and time, a positive relationship between bottom boundary layer temperature (BBLT) and catch rates was observed. Here, we aimed to better understand how localised oceanographic processes affected this relationship in the southernmost South-East Queensland (SEQ) sector of the Australian fishery at seasonal and short temporal scales. Our results show cooler BBLT, upwelling-favourable alongshore wind stress and increased catch rates occurred during mating season in austral spring. At the end of austral summer, BBLT began warming, downwelling-favourable winds were dominant, and catch rates declined around the post-moult period. Outputs from the generalised linear models (GLMs) that separated these effects in each season show that, at shorter temporal scales, daily catch rates also increased with episodic BBLT cooling and upwelling-favourable alongshore wind stress, but only during austral autumn and winter. These new findings suggest that region-specific, short-term and seasonal variability of oceanographic processes responsible for changes in BBLT play an important role in influencing the catchability of spanner crabs. We suggest that the effects of region-specific physical oceanographic processes must be considered in future work when investigating the catchability of commercially important fisheries species fished over large spatial domains.

Increased recognition of mangrove high carbon storage potential has prompted carbon sequestration as one of the main goals in mangrove afforestation. In southern China, the introduced fast-growing Sonneratia apetala and native Kandelia obovata have been widely afforested since the mid-1980s. While S. apetala has spread extensively, the implications and ecosystem services are yet to be ascertained. Soil/root coring was conducted in two 12-year-old S. apetala and K. obovata plantations, respectively. Fine-root mass and soil physicochemical properties were obtained and compared. Fine-root mass and soil organic carbon stock ranged between 129 and 394 g m−2 and 7.9 and 15.8 Mg C ha−1, respectively. Soil organic carbon stock and fine-root mass were both significantly different between the forests. Organic carbon in soil is significantly correlated to fine-root mass and organic carbon in fine roots. The contribution to soil organic carbon by fine-root mass may be different between the two species. Growth and physiological traits not only may influence stand characteristics but also soil properties that drive overall carbon accumulation. Contrary to the original expectation driving the introduction, the shrubby native K. obovata may have higher potential as a carbon sink than the introduced S. apetala.

Offsetting carbon (C) emissions and reducing nitrogen (N) pollution have been goals of mangrove restoration programs around the world. There is a common, yet dubious expectation that mangrove restoration will result in immediate and perpetual delivery of ecosystem services. There are expected time lags between mangrove clearing and C and N losses, and between restoration and C and N gains. Obtaining accurate rates of losses and gains requires frequent and long-term sampling, which is expensive and time consuming. To address this knowledge gap, we used a chronosequence of mangrove forests in mangroves in Matang Mangrove Forest Reserve (MMFR) in Malaysia, a region with one of the most C dense forests in the world. In this site, we assessed the ecosystem C and N stocks, including soil, downed wood, downed litter, and trees. The objective was to measure C and N changes through time. After mangrove clearing, C and N losses in soil and downed wood were rapid, with stocks halved after just one year. In the first 10 years after replantation, the forest recovered quickly, with rates of C accumulation of 9.5 Mg C ha−1 yr−1. After ten years, the rate of accumulation decreased to 2.8 Mg C ha−1 yr−1. However, 40 years after replantation, mangroves were still about 26% lower in C and 15% lower in N compared to our reference forest. The trajectory of recovery of C and N stocks in these forests was different among mangrove components: forest litter recovered rapidly, but downed wood and soil recovered much slower. Programs aimed at reducing C emissions and N pollution should consider that there are temporal lags and ecosystem trade-offs when assessing the effectiveness of mangrove protection and restoration as climate change mitigation strategies.

Environmental cues in mangroves such as chemicals released from senescent leaf litter could help guide juvenile nekton to their nursery habitats. A laboratory olfactory choice experiment was conducted using a three-channel choice flume to assess the ability of juveniles of the caridean shrimp Palaemon debilis Dana (1852) to distinguish between water containing leachates from the leaf litter of the mangroves Avicennia marina (Forsk.) Vierh., Rhizophora stylosa Griff. and a mixture of the two species. Senescent leaves of these species of mangroves were soaked for 14 days in artificial seawater before being exposed to juvenile P. debilis in the flume. P. debilis spent significantly more time in R. stylosa water, followed by mixed R. stylosa and A. marina water, and least time in A. marina water. The consistent preference for R. stylosa water suggests that the chemical cues from senescent leaves of this mangrove species might influence choice selection by the shrimp. The olfactory choice experiment was further investigated to assess if the preference for senescent R. stylosa leachate (water) was due to the water-borne chemicals (either from the senescent R. stylosa leaf litter water or aged R. stylosa detritus) serving as an attractant to the shrimps, by comparing it to aged R. stylosa detritus and artificial seawater. Juvenile shrimp preferred senescent R. stylosa water, therefore suggesting a role of chemical attractants in the shrimp's choice of habitat.

The purpose of this study was to examine the involvement of fatty acid–binding protein 5 (FABP5), a lipid-binding protein expressed at the blood-brain barrier (BBB), in fatty acid and drug uptake into human brain endothelial cells. Following transfection with siRNA against hFABP5, human brain endothelial cell (hCMEC/D3) uptake of lipophilic ligands with varying affinity to FABP5 was assessed with intracellular concentrations quantified by liquid scintillation counting, HPLC, or LCMS/MS. The in situ BBB transport of [ 3 H]-diazepam was also assessed in wild type and FABP5-deficient mice. hFABP5 siRNA reduced FABP5 expression in hCMEC/D3 cells by 39.9 ± 3.8% (mRNA) and 38.8 ± 6.6% (protein; mean ± SEM), leading to a reduction in uptake of [ 14 C]-lauric acid, [ 3 H]-oleic acid, and [ 14 C]-stearic acid by 37.5 ± 8.8%, 41.7 ± 11.6%, and 50.7 ± 13.6%, respectively, over 1 min. No significant changes in [ 14 C]-diazepam, pioglitazone, and troglitazone uptake were detected following FABP5 knockdown in hCMEC/D3 cells. Similarly, no difference in BBB transport of [ 3 H]-diazepam was observed between wild type and FABP5-deficient mice. Therefore, although FABP5 facilitates brain endothelial cell uptake of fatty acids, it has limited effects on brain endothelial cell uptake and BBB transport of drugs with lower affinity for FABP5.

Current mangrove planting schemes aimed at reversing global losses are prioritising short-term increases in area over long-term establishment. Without sound, evidence-based restoration policies, this approach could accelerate the demise of mangrove forests and the ecosystem services they provide.

Meiofauna are ubiquitous but poorly-studied components of soft-bottom marine habitats around the world, including mangroves. The dynamic environmental conditions and heterogeneous sediments of mangroves present challenges to understanding the structure of mangrove meiofaunal assemblages at various spatial and temporal scales. In this study, we investigated the meiofaunal assemblage structure of sediments colonised by three mangrove species, namely, Avicennia marina, Rhizophora stylosa and Aegiceras corniculatum , at three locations in subtropical eastern Australia. Spatial and temporal variations were tested by sampling at the three mangrove locations (i.e. Tallebudgera, Currumbin and Terranora) in autumn, with samplings repeated at Tallebudgera at two other times broadly representing during dry/cool winter and wet/hot summer seasons. We examined the variability of the sediment environments within each of the different mangrove species, and investigated how meiofaunal assemblages would respond to the particular changes in their habitats to result in differences in assemblage structure between and within sites. Total meiofaunal density was highest in Tallebudgera and Currumbin and lowest in Terranora (mean density of 424, 393 and 239 ind.10 cm −2 , respectively). In Tallebudgera, the density was higher in winter and summer (mean density of 546 and 530 ind.10 cm −2 , respectively). The meiofaunal assemblage in this study shows a trend and association with the environmental variables. High availability of food proxies such phaeopigments, Chl a or TOC, with moderate tannin content and appropriate habitat structure (sediment particle size, belowground root biomass and/or moisture content provide the best condition for the meiofauna to achieve the highest density. However, given the complex dynamic habitats and the spatial heterogeneity of the mangrove environments across different locations and seasons, no clear generalization could be made regarding the key environmental variables that predominantly shape the meiofaunal assemblages’ structure.

The positioning of habitats interacts with variability in abiotic factors (e.g. seasonal changes in temperature and extreme weather events) to change how animals use a land or seascape. Marine reserves can regulate how human activities alter fish communities and increase the abundance of targeted species, but the combined influence of reserves and seascape context on species habitat use remains uncertain in many ecosystems. Further, marine reserve effectiveness might be low for mobile species if the size of the reserve is less than a species usual range, reducing the overall time a individual may be protected. In this study, we tracked 19 giant shovelnose rays (Glaucostegus typus), an IUCN listed vulnerable species within the Moreton Bay Marine Park in eastern Australia. We used an array of 28 acoustic receivers within a complex mosaic of seagrass patches, bare sand, mangrove forests and deep-water channels and used regression tree analyses to determine which spatial, temporal and protection factors contributed most to G. typus habitat use. Overall, 50% of the total detections in the study occurred inside marine reserves containing large seagrass beds (>7.09 m2) and in close proximity to mangroves ( 20.2 °C), the habitat use of individuals is contained in smaller centres of activity compared with winter, however, protection effects varied. Our results show that seascape context and marine reserves combine to provide the optimal areas for G. typus habitat selection. Limited food resources likely caused larger centres of activity during winter. Identifying priority habitats for vulnerable species is critical for ongoing protection and maintaining effective conservation initiatives. We have shown here that incorporating spatial features into the design of marine reserves can improve conservation outcomes for mobile benthic predators such as G. typus and other species that use such seascapes.

Carbon dioxide (CO2) flux is a critical component of the global C budget. While CO2 flux has been increasingly studied in mangroves, better partitioning of components contributing to the overall flux will be useful in constraining C budgets. Little information is available on how CO2 flux may vary with forest age and conditions. We used a combination of 13C stable isotope labeling and closed chambers to partition CO2 efflux from the seedlings of the widespread mangrove Avicennia marina in laboratory microcosms, with a focus on sediment CO2 efflux in establishing forests. We showed that (1) above-ground part of plants were the chief component of overall CO2 efflux; and (2) the degradation of sediment organic matter was the major component of sediment CO2 efflux, followed by root respiration and litter decomposition, as determined using isotope mixing models. There was a significant relationship between C isotope values of CO2 released at the sediment–air interface and both root respiration and sediment organic matter decomposition. These relative contributions of different components to overall and sediment CO2 efflux can be used in partitioning of the sources of overall respiration and sediment C mineralization in establishing mangroves.

The pulmonate gastropods, Phallomedusa solida (Martens, 1878) and Ophicardelus ornatus (Ferussac, 1821), exhibit characteristic distributional patterns at the upper intertidal zones in estuarine mangrove and saltmarsh habitats on the eastern Australian coast. Past studies suggested inundation condition, soil salinity, and percent of vegetation cover were responsible for these patterns. In this study, the role of environmental parameters, food availability, physical stress, and predation pressure in determining the distributional patterns of these gastropods was evaluated along transects spanning saltmarsh, mangrove, and the ecotone habitats. For both species, the maximum population abundance occurred in the upper saltmarsh and the ecotone between mangrove and saltmarsh at 361.0 and 358.0 ind.m −2 , respectively, which was four times that of the lower saltmarsh. Mangroves were evaluated as the optimal habitat for the pulmonates in terms of the environmental parameters moisture content and food availability. However, due to its longer inundation duration within each tidal cycle, use of the mangrove habitat by the pulmonates was impeded because of difficulties in oxygen acquisition under submerged conditions. Laboratory experiments revealed the oxygen intake of the pulmonates dropped abruptly to 4.3–9.0% of aerial rates when submerged. This result indicated that mangroves were not the optimal habitat for the pulmonates. Furthermore, the visiting frequency of predators (yellowfin bream Acanthopagrus australis and toadfishes, Tetraodontidae) was 1.3 times higher in the mangrove compared to those in the ecotone and upper saltmarsh habitats. Underwater video recording also suggested high mortality of these gastropods at 31.7–88.9% in mangrove and 0.80–0.98 times higher than that in saltmarsh, resulting from the predators preying in the mangrove habitat during high tides. Despite the abiotic factors facilitating the distribution of the pulmonates in the mangrove, the higher predation risk restricted the occurrence of P. solida and O. ornatus in the mangrove areas. More than verifying that the distributional pattern of macrobenthos is a complex outcome from environmental factors and interaction with predators, our study also indicated that the influencing strength of the biotic and abiotic factors on the pulmonates distribution might be spatially changeable within a geographically small-scale continuum.

One of the main services offered by mangroves is their capacity for trapping sediment. We investigated how spatial complexity of pneumatophores of Avicennia marina may influence fine-scale sediment particle size distribution. Using realistic three-dimensional models captured from pneumatophore patches, indices of complexity (the area/volume ratio, the Getis-Ord Gi* statistic) were calculated to quantify mangrove root structural complexity in five 1 × 1 m2 plots. The complexity of pneumatophores in 16 0.25 × 0.25 m2 subplots in each of the 5 plots was measured and its relationship with the relative abundance of fine sediment particles (clay and silt

Diet composition of leaf-eating mangrove crabs is a puzzle among mangrove ecologists. Nutrient-poor leaf litter can in most cases not support animal growth. Food partitioning (mangrove leaves, animal tissue, and microphytobenthos [MPB]) of sesarmid and ucidid mangrove crabs from eight locations in four countries was assessed using the concentration-dependent stable isotope mixing model, IsoConc. While stable C and N isotopes have the potential to track the origin and proportion of food sources for these crabs, only few values of trophic discrimination are available. This problem was addressed here for crabs foraging on leaf litter to identify discrimination values that provide a balanced diet with sufficient nutrients (i.e., N) when combined with other food sources. The data from all mangrove locations suggest that sesarmid and ucidid crabs ingest and assimilate mixtures of available food items. Leaf litter in the form of brown leaves was always the most important C source, while animal tissue in the form live and dead “prey” or MPB in the form of diatoms at the sediment surface were the dominant N sources. Model scenarios were generated to obtain the upper thresholds of trophic 13C discrimination between the examined crab species and leaf litter, while complying with the molar C/N

This study aims to determine the drivers of root decomposition and its role in carbon (C) budgets in mangroves and saltmarsh. We review the patterns of root decomposition, and its contribution to C budgets, in mangroves and saltmarsh: the impact of climatic (temperature and precipitation), geographic (latitude), temporal (decay period) and biotic (ecosystem type) drivers using multiple regression models. Best-fit models explain 50% and 48% of the variance in mangrove and saltmarsh root decay rates, respectively. A combination of biotic, climatic, geographic and temporal drivers influences root decay rates. Rainfall and latitude have the strongest influence on root decomposition rates in saltmarsh. For mangroves, forest type is the most important; decomposition is faster in riverine mangroves than other types. Mangrove species Avicennia marina and saltmarsh species Spartina maritima and Phragmites australis have the highest root decomposition rates. Root decomposition rates of mangroves were slightly higher in the Indo-west Pacific region (average 0.16% day− 1) than in the Atlantic-east Pacific region (0.13% day− 1). Mangrove root decomposition rates also show a negative exponential relationship with porewater salinity. In mangroves, global root decomposition rates are 0.15% day− 1 based on the median value of rates in individual studies (and 0.14% day− 1 after adjusting for area of mangroves at different latitudes). In saltmarsh, global root decomposition rates average 0.12% day− 1 (no adjustment for area with latitude necessary). Our global estimate of the amount of root decomposing is 10 Tg C yr− 1 in mangroves (8 Tg C yr− 1 adjusted for area by latitude) and 31 Tg C yr− 1 in saltmarsh. Local root C burial rates reported herein are 51–54 g C m− 2 yr− 1 for mangroves (58–61 Tg C yr− 1 adjusted for area by latitude) and 191 g C m− 2 yr− 1 for saltmarsh. These values account for 24.1–29.1% (mangroves) and 77.9% (saltmarsh) of the reported sediment C accumulation rates in these habitats. Globally, dead root C production is the significant source of stored sediment C in mangroves and saltmarsh.

This review examines the influence of physical oceanographic processes on catchability of spanner crab (Ranina ranina) in northeast Australia. Physical oceanographic processes may affect crab catchability by influencing their activity levels and ability to detect bait. Bottom temperature, current velocity, and swell intensity appear to influence catches of spanner crab. At this stage, it appears warmer temperatures enhance catchability of spanner crab. Spanner crabs were more catchable in stronger currents, and crabs were observed to arrive from down-current of baited traps. However, a decline in catch was observed following periods of intense swell. Data derived from Waverider buoys suggest that occasionally these periods create strong wave-induced seabed current velocities, lead to at depths of 70 m. The oscillatory motion of wave-induced seabed velocities may cause higher suspended sediment concentrations. These observations corroborate the views of local fishermen that spanner crabs avoid ‘murky’ water. The effect of turbidity on catchability requires further research. Overall, we advocate that studies employ robust methodologies to measure physical oceanographic processes to accurately predict catchability. Moreover, large-scale physical oceanographic processes may also play an important role in catchability of spanner crab; including upwelling, eddies, and the East Australian Current. Integrating physical oceanography and fisheries interactions will considerably benefit commercial fishermen as well as provide valuable information for evidence-based management of these valuable resources.

Mangroves are blue carbon ecosystems that sequester significant carbon but release CO2, and to a lesser extent CH4, from the sediment through oxidation of organic carbon or from overlying water when flooded. Previous studies, e.g. Leopold et al. (2015), have investigated sediment organic carbon (SOC) content and CO2 flux separately, but could not provide a holistic perspective for both components of blue carbon. Based on field data from a mangrove in southeast Queensland, Australia, we used a structural equation model to elucidate (1) the biotic and abiotic drivers of surface SOC (10cm) and sediment CO2 flux; (2) the effect of SOC on sediment CO2 flux; and (3) the covariation among the environmental drivers assessed. Sediment water content, the percentage of fine-grained sediment (

Friess et al. discuss the results of conservation efforts for mangrove forests in recent years., SCOPUS: le.j, info:eu-repo/semantics/published

Background The fast-growing introduced mangrove Sonneratia apetala is widely used for mangrove afforestation and reforestation in China. Some studies suggested that this exotic species outperforms native species in terms of carbon sequestration potential. This study tested the hypothesis that multi-species mangrove plantations might have higher carbon sequestration potential than S. apetala monocultures. Results Our field measurements at Hanjiang River Estuary (Guangdong province, China) showed that the carbon stock (46.0 ± 3.0 Mg/ha) in S. apetala plantations where the native Kandelia obovata formed an understory shrub layer was slightly higher than that in S. apetala monocultures (36.6 ± 1.3 Mg/ha). Moreover, the carbon stock in monospecific K. obovata stands (106.6 ± 1.4 Mg/ha) was much larger than that of S. apetala monocultures. Conclusions Our results show that K. obovata monocultures may have a higher carbon accumulation rate than S. apetala monocultures. Planting K. obovata seedlings in existing S. apetala plantations may enhance the carbon sink associated with these plantations.