- Griffith University
- I am an environmentalist that like to use interdisciplinary knowledge to unravel the mechanism behind environmental a... moreI am an environmentalist that like to use interdisciplinary knowledge to unravel the mechanism behind environmental and ecological problems. My study focuses on coastal wetland ecology.edit
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... more
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...
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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... more
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-1, respectively, 200 times higher than that (0.43 items kg-1) in the water column. Plastics are more abundant in mangrove forests and tidal marshes than in tidal flats and seagrass meadows. The variation in plastic abundance is related to climatic and geographic zones, seasons, and population density or plastic waste management. The abundance of plastics ingested by pelagic and demersal fish increases with fish length and dry weight. The dominant characteristics of plastics ingested by marine animals are correlated with those found in coastal wetland sediments. Microplastics exert negative effects on biota abundance and mangrove survival but positive effects on sediment nutrients, leaf drop, and carbon emission. We highlight that plastic pollution is widespread in coastal wetlands and actions are urged to include microplastics in ecosystem health and degradation assessment.
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Updated estimates of carbon accumulation rates in coastal marsh sediments
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Hg emissions from coal-fired power plants (CFPPs) in Northern China are the major source of anthropogenic atmospheric mercury (Hg) emissions. The impact of denitrification devices on Hg emission, together with difference in Hg emission... more
Hg emissions from coal-fired power plants (CFPPs) in Northern China are the major source of anthropogenic atmospheric mercury (Hg) emissions. The impact of denitrification devices on Hg emission, together with difference in Hg emission from different boilers and specific data of air pollution control devices (APCDs) are critical factors for the estimate of Hg emissions. Combined with unprecedented meta-analysis, this paper applies emission factor method to examine Hg emissions in 1995, 2003, 2011 and projection to 2015. Hg emissions from CFPPs were estimated to rise from 13.28 ton to 23.61--36.67 ton with an increase rate of 77.8% to 176.3%, while coal con-sumption increased by 325.5%. The emissions of Hg0, Hg2+ and HgP are estimated to reach 11.80--18.34 ton, 9.45--14.66 ton and 2.36--3.67 ton, respectively. Low increase of Hg emissions benefits from the wide application of APCDs, especially the sound operation of denitrification devices. However, there are uncertainties in the est...
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Abstract. 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... more
Abstract. 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 (−23.9p0.4 ‰) respired CO2 was significantly lower than that from gastropod (−17.5p1.3 ‰) 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 d...
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Aquaculture, particularly shellfish ponds, has expanded dramatically and become a major cause of mangrove deforestation and “blue carbon” loss in China. We present the first study to examine CO2 efflux from marine aquaculture/shellfish... more
Aquaculture, particularly shellfish ponds, has expanded dramatically and become a major cause of mangrove deforestation and “blue carbon” loss in China. We present the first study to examine CO2 efflux from marine aquaculture/shellfish ponds and in relation to land-use change from mangrove forests in China. Light and dark sediment CO2 efflux from shellfish ponds averaged at 0.61 ± 0.07 and 0.90 ± 0.12 kg CO2 m−2 yr−1 (= 37.67 ± 4.89 and 56.0 ± 6.13 mmol m−2 d−1), respectively. The corresponding rates (−4.21 ± 4.54 and 41.01 ± 4.15 mmol m−2 d−1) from the adjacent mangrove forests that were devoid of aquaculture wastewater were lower, while those from the adjacent mangrove forests (3.48 ± 7.83 and 73.02 ± 5.76 mmol m−2 d−1)) receiving aquaculture wastewater markedly increased. These effluxes are significantly higher than those reported for mangrove forests to date, which is attributable to the high nutrient levels and the physical disturbance of the substrate associated with the aquac...
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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... more
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.
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Tidal wetlands are global hotspots of carbon storage but errors exist with current estimates on their carbon density due to the use of factors estimated from other habitats for converting loss-on-ignition (LOI) to organic carbon (OC); and... more
Tidal wetlands are global hotspots of carbon storage but errors exist with current estimates on their carbon density due to the use of factors estimated from other habitats for converting loss-on-ignition (LOI) to organic carbon (OC); and the omission of certain significant carbon pools. Here we show that the widely used conversion factor (LOI/OC = 1.724) is significantly lower than our measurements for saltmarsh sediments (1.92 ± 0.01) and oversimplifies the polynomial relationship between sediment OC and LOI for mangrove forests. Global mangrove OC stock in the top-meter sediment reaches 1.93 Pg when corrected for this bias, and is 20% lower than the previous estimates. Ecosystem carbon stock (living and dead biomass, sediment OC and inorganic carbon) is estimated at 3.7–6.2 Pg. Mangrove deforestation leads to carbon emission rates at 23.5–38.7 Tg yr−1 after 2000. Mangrove sediment OC stock has previously been over-estimated while ecosystem carbon stock underestimated.
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Abstract The use of adsorption methods to recover vitamin B12 (VB12) from wastewater has been increasingly studied. However, there is a lack of knowledge on optimization of the methods. This study established a feedback network to... more
Abstract The use of adsorption methods to recover vitamin B12 (VB12) from wastewater has been increasingly studied. However, there is a lack of knowledge on optimization of the methods. This study established a feedback network to evaluate alternatives regarding VB12 adsorption from wastewater. The network comprises environmental, economic and technological criteria and their feedbacks. Based on the network, the fuzzy matter-element theory was integrated with an analytical network process to rank the alternatives. Among five alternatives, activated carbon with KOH as activation media was suggested to be the optimal alternative for VB12 recycling from wastewater, while mesoporous activated carbon fibre was the least preferred alternative. Particularly, the adsorption technology reusing biomass ranked second to the optimal alternative, and has great application potential due to low costs and biological waste reuse. Sensitivity analysis does show that the ranking of alternatives was robust and was not subject to the change in weight.
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Mangroves have been increasingly recognized for treating wastewater from aquaculture, sewage and other sources with the overwhelming urbanization trend. This study clarified the three paradigms of mangroves in disposing wastewater... more
Mangroves have been increasingly recognized for treating wastewater from aquaculture, sewage and other sources with the overwhelming urbanization trend. This study clarified the three paradigms of mangroves in disposing wastewater contaminants: natural mangroves, constructed wetlands (including free water surface and subsurface flow) and mangrove-aquaculture coupling systems. Plant uptake is the common major mechanism for nutrient removal in all the paradigms as mangroves are generally nitrogen and phosphorus limited. Besides, sediments accrete and provide substrates for microbial activities, thereby removing organic matter and nutrients from wastewater in natural mangroves and constructed wetlands. Among the paradigms, the mangrove-aquaculture coupling system was determined to be the optimal alternative for aquaculture wastewater treatment by multi-criterion decision making. Sensitivity analysis shows variability of alternative ranking but underpins the coupling system as the most ...
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Vertical accretion rate reflects how coastal sedimentary environment responds to sea level and climate change, and is widely employed to estimate relative sea level rise. This study reviews the methods used to measure and model vertical... more
Vertical accretion rate reflects how coastal sedimentary environment responds to sea level and climate change, and is widely employed to estimate relative sea level rise. This study reviews the methods used to measure and model vertical accretion rate of salt marshes. Measuring methods fall into nine categories on the basis of time scales. The main features of each method are presented, including resolution, accuracy, spatial coverage, dating ages and key instruments. Coupled with the calculation equations, advantages and disadvantages of each method are identified and compared. The pecking order of both measuring and modelling methods is sequenced according to their applicable spatial and temporal scales. This study provides a perspective for readers on the selection of appropriate estimate methods for vertical accretion rate of salt marshes.
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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... more
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 13C 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 13C of respired CO2. Particularly, the 13C of crab (-23.90.4‰) respired CO2 was significantly lower than that from gastropod (-17.51.3‰) respiration. The 13C of deposit-feeder respired CO2 was significantly higher than that from detritivores. There are significant differences in the amount of CO2 emitted and 13C 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 (0.130.02 mmol g-1 day-1) and on field collection (0.310.03 mmol g-1 day-1). CO2 production of crabs is strongly related to carapace width and length. The 13C 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.
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Tidal wetlands are global hotspots of carbon storage but errors exist with current estimates on their carbon density due to the use of factors estimated from other habitats for converting loss-on-ignition (LOI) to organic carbon (OC); and... more
Tidal wetlands are global hotspots of carbon storage but errors exist with current estimates on their carbon density due to the use of factors estimated from other habitats for converting loss-on-ignition (LOI) to organic carbon (OC); and the omission of certain significant carbon pools. Here we show that the widely used conversion factor (LOI/OC = 1.724) is significantly lower than our measurements for saltmarsh sediments (1.92 ± 0.01) and oversimplifies the polynomial relationship between sediment OC and LOI for mangrove forests. Global man- grove OC stock in the top-meter sediment reaches 1.93 Pg when corrected for this bias, and is 20% lower than the previous estimates. Ecosystem carbon stock (living and dead biomass, sediment OC and inorganic carbon) is estimated at 3.7 – 6.2 Pg. Mangrove deforestation leads to carbon emission rates at 23.5 – 38.7 Tg yr−1 after 2000. Mangrove sediment OC stock has previously been over-estimated while ecosystem carbon stock underestimated.
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Carbon dioxide (CO 2) flux is a critical component of the global C budget. While CO 2 flux has been increasingly studied in mangroves, better partitioning of components contributing to the overall flux will be useful in constraining C... more
Carbon dioxide (CO 2) flux is a critical component of the global C budget. While CO 2 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 CO 2 flux may vary with forest age and conditions. We used a combination of 13 C stable isotope labeling and closed chambers to partition CO 2 efflux from the seedlings of the widespread mangrove Avicennia marina in laboratory microcosms, with a focus on sediment CO 2 efflux in establishing forests. We showed that (1) above-ground part of plants were the chief component of overall CO 2 efflux; and (2) the degradation of sediment organic matter was the major component of sediment CO 2 efflux, followed by root respiration and litter decomposition, as determined using isotope mixing models. There was a significant relationship between C isotope values of CO 2 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 CO 2 efflux can be used in partitioning of the sources of overall respiration and sediment C mineralization in establishing mangroves.
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This study aims to determine the drivers of root decomposition and its role in carbon (C) budgets in mangroves and salt-marsh. We review the patterns of root decomposition, and its contribution to C budgets, in mangroves and saltmarsh:... more
This study aims to determine the drivers of root decomposition and its role in carbon (C) budgets in mangroves and salt-marsh. 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.
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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... more
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 sepa- rately, 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 (10 cm) 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 (b 63 μm), surface sediment chlorophyll and light condition collectively drive sediment CO2 flux, explaining 41% of their variation. Sediment water content, the percentage of fine sediment, season, land- form setting, mangrove species, sediment salinity and chlorophyll collectively drive surface SOC, explaining 93% of its variance. Sediment water content and the percentage of fine sediment have a negative impact on sediment CO2 flux but a positive effect on surface SOC content, while sediment chlorophyll is a positive driver of both. Surface SOC was significantly higher in Avicennia marina (2994 ± 186 g m− 2, mean ± SD) than in Rhizophora stylosa (2383 ± 209 g m−2). SOC was significantly higher in winter (2771 ± 192 g m−2) than in summer (2599 ± 211 g m−2). SOC significantly increased from creek-side (865 ± 89 g m−2) through mid (3298 ± 137 g m−2) to landward (3933 ± 138 g m−2) locations. Sediment salinity was a positive driver of SOC. Sediment CO2 flux without the influence of biogenic structures (crab burrows, aerial roots) averaged 15.4 mmol m−2 d−1 in A. marina stands under dark conditions, lower than the global average dark flux (61 mmol m−2 d−1) for mangroves.
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The use of adsorption methods to recover vitamin B12 (VB12) from wastewater has been increasingly studied. However, there is a lack of knowledge on optimization of the methods. This study established a feedback network to evaluate... more
The use of adsorption methods to recover vitamin B12 (VB12) from wastewater has been increasingly studied. However, there is a lack of knowledge on optimization of the methods. This study established a feedback network to evaluate alternatives regarding VB12 adsorption from wastewater. The network comprises environmental, economic and technological criteria and their feedbacks. Based on the network, the fuzzy matter-element theory was integrated with an analytical network process to rank the alternatives. Among five alternatives, activated carbon with KOH as activation media was suggested to be the optimal alternative for VB12 recycling from wastewater, while mesoporous activated carbon fibre was the least preferred alternative. Particularly, the adsorption technology reusing biomass ranked second to the optimal alternative, and has great application potential due to low costs and biological waste reuse. Sensitivity analysis does show that the ranking of alternatives was robust and was not subject to the change in weight.
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ABSTRACT Studies on carbon stock in salt marsh sediments are increasing. However, uncertainties exist in estimating global carbon storage in these vulnerable coastal habitats, thus hindering the assessment of their importance. Combining... more
ABSTRACT Studies on carbon stock in salt marsh sediments are increasing. However, uncertainties exist in estimating global carbon storage in these vulnerable coastal habitats, thus hindering the assessment of their importance. Combining direct data and indirect estimation, this study compiled studies involving 158 sites across the southern and Northern Hemispheres, and estimated the global average carbon accumulation rate (CAR) at 242.2 g C m-2 yr-1 in saltmarsh sediments. Based on region-specific CAR and estimates of salt marsh area in various geographic regions between 40° S to 78.3° N, total CAR in global salt marsh sediments is ~ 10.1 Tg C yr-1. The data indicate that while the capacity for carbon sequestration by salt marsh sediments ranked the first amongst coastal wetland and forested terrestrial ecosystems, their carbon budget was the smallest due to their limited and declining global areal extent. However, there may be uncertainties for our global estimate owing to limited and patchy data availability. CAR of salt marsh sediments changes with latitude, tidal range, halophyte genera and elevation, with considerable variation among different biogeographic regions.
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Studies on carbon stock in salt marsh sediments have increased since the review by Chmura et al. (2003). However, uncertainties exist in estimating global carbon storage in these vulnerable coastal habitats, thus hindering the assessment... more
Studies on carbon stock in salt marsh sediments
have increased since the review by Chmura et al. (2003).
However, uncertainties exist in estimating global carbon storage
in these vulnerable coastal habitats, thus hindering the assessment
of their importance. Combining direct data and indirect
estimation, this study compiled studies involving 143
sites across the Southern and Northern hemispheres, and provides
an updated estimate of the global average carbon accumulation
rate (CAR) at 244.7 g Cm−2 yr−1 in salt marsh
sediments. Based on region-specific CAR and estimates of
salt marsh area in various geographic regions between 40 S
to 69.7 N, total CAR in global salt marsh sediments is estimated
at 10.2 TgC yr−1. Latitude, tidal range and elevation
appear to be important drivers for CAR of salt marsh sediments,
with considerable variation among different biogeographic
regions. The data indicate that while the capacity for
carbon sequestration by salt marsh sediments ranked the first
amongst coastal wetland and forested terrestrial ecosystems,
their carbon budget was the smallest due to their limited and
declining global areal extent. However, some uncertainties
remain for our global estimate owing to limited data availability.
have increased since the review by Chmura et al. (2003).
However, uncertainties exist in estimating global carbon storage
in these vulnerable coastal habitats, thus hindering the assessment
of their importance. Combining direct data and indirect
estimation, this study compiled studies involving 143
sites across the Southern and Northern hemispheres, and provides
an updated estimate of the global average carbon accumulation
rate (CAR) at 244.7 g Cm−2 yr−1 in salt marsh
sediments. Based on region-specific CAR and estimates of
salt marsh area in various geographic regions between 40 S
to 69.7 N, total CAR in global salt marsh sediments is estimated
at 10.2 TgC yr−1. Latitude, tidal range and elevation
appear to be important drivers for CAR of salt marsh sediments,
with considerable variation among different biogeographic
regions. The data indicate that while the capacity for
carbon sequestration by salt marsh sediments ranked the first
amongst coastal wetland and forested terrestrial ecosystems,
their carbon budget was the smallest due to their limited and
declining global areal extent. However, some uncertainties
remain for our global estimate owing to limited data availability.
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Loss-on-ignition (LOI) is widely used to estimate organic carbon (OC) content, and thus carbon stocks, due to easy operation and low costs. The wide use of a conversion factor of 1.724 (LOI:OC) oversimplifies the relationship between LOI... more
Loss-on-ignition (LOI) is widely used to estimate organic carbon (OC) content, and thus carbon stocks, due to easy operation and low costs. The wide use of a conversion factor of 1.724 (LOI:OC) oversimplifies the relationship between LOI and OC, and may lead to significant biases in estimating global sediment carbon stocks in 'blue carbon' ecosystems. We estimated sediment OC using LOI at different mangrove and saltmarsh sites in Hong Kong. OC of matched samples from the same sites was independently measured using an elemental analyzer. The sites are mostly typical mineral sediments with LOI less than 8%. The conversion factors of LOI:OC are 5.376 and 4.673 for mangroves and saltmarshes, respectively. This means the use of the common conversion factor will overestimate mangrove and saltmarsh sediment carbon stocks by 212% and 171%, respectively, in our studied sites. We also found that LOI can be used to estimate leaf and root OC (organic nitrogen) by conversion factors of 2.978 (12.837) and 1.737 (27.027), respectively. Our results highlight the urgency to correct the bias in estimating OC and carbon stocks from LOI in 'blue carbon' ecosystems, and the potential of using LOI for estimating leaf and root OC and organic nitrogen. The difference in the conversion factors between mangroves and saltmarshes, and between mineral and organic sediments should be taken into account when estimating OC from LOI for these wetlands.
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Global, mangrove forests (mangals) harbor about 80 plant species including hybrids and provide habitats and food for a diversified fauna. Mangrove productivity is high and changes with latitudes. However, there is a lack of systematic... more
Global, mangrove forests (mangals) harbor about 80 plant species including hybrids and provide habitats and food for a diversified fauna. Mangrove productivity is high and changes with latitudes. However, there is a lack of systematic knowledge on how mangroves cope with the harsh saline conditions to gain high productivity and provide support for marine fauna. Mangrove halophytes cope with the saline environment mainly by excluding, excreting, or storing salts via salt glands on the leaves or by other mechanisms. Mangrove litterfall and net primary productivity (NPP) are related to plant traits. Mangrove litter production increases with tree ages, basal area, and stem density. Forest structural parameters (including diameter at breast height (DBH), canopy height, basal area, and stem density) are positive, while salinity is negative controls on mangrove above- ground NPP. Stem density also has positive impact on mangrove belowground NPP. In contrast, canopy height has negative impacts, but salinity has positive impacts on mangrove belowground NPP. Leaves contribute 87.5% to mangrove live aboveground NPP. Mangroves provide a nursery for juvenile fish and refuges from predators owing to the structural complexity of the habitats. Mangrove litter and macro-/microalgae also fuel marine food webs consisting of bacteria and fungi associated with litter, epiphytic algae, benthos, sponges, and other sessile forms, phytoplankton, zooplankton, and nekton.