Sediment, vegetation carbon stocks, and sediment–water CO₂ and CH₄ effluxes across tropical salt flat, saltmarsh, mangrove and tidally restricted wetlands in northern Australia

Dataset descriptionThis repository contains field- and laboratory-derived datasets supporting the paper entitled "Contrasting sediment and aquatic CO₂ and CH₄ effluxes across Australian tropical salt flat, saltmarsh, mangrove and tidally restricted wetlands" published in <i>Estuarine, Coastal and Shelf Science</i>.The datasets contain sediment physical properties, sediment and vegetation carbon stocks, and greenhouse gas (GHG) fluxes (CO₂ and CH₄) across multiple tropical coastal wetland ecosystem types in north-eastern Queensland, Australia. Measurements were designed to explicitly compare:vegetated (mangrove and saltmarsh) versus unvegetated (salt flat) habitats, andtidally connected versus tidally restricted wetlands,under comparable environmental conditions.All measurements were collected during the cool dry season (August–September 2025) at low tide, and therefore represent dry season baseline fluxes rather than annual budgets.Study areaField measurements were conducted at two coastal wetland complexes near Townsville, Queensland, Australia (approximately 19.3° S, 146.8° E):Oonoonba Wetlands – comprising mangroves, <i>Sarcocornia quinqueflora</i> saltmarsh, <i>Sporobolus virginicus</i> saltmarsh, and unvegetated salt flats distributed along distinct elevation and tidal inundation gradient.Town Common Conservation Park – comprising tidally connected wetlands and tidally restricted (impounded) freshwater wetlands.These systems occur in a tropical monsoonal climate with strong seasonal contrasts in rainfall, salinity, and hydrological connectivity.Contents of the repositoryDataset 1: Soil propertiesFile: <code>01Sasmito – Soil properties_v2.csv</code>Sediment physical and biogeochemical properties derived from field coring and laboratory analysis, including bulk density, water-filled pore space, loss-on-ignition (LOI), carbon concentration, carbon density, and depth aggregared sediment carbon stocks to 50 cm depth.Dataset 2: Vegetation carbonFile: <code>02Sasmito – Vegetation carbon.csv</code>Vegetation structure and biomass carbon estimates for mangrove and saltmarsh ecosystems. For mangrove, above- and below-ground biomass and associated carbon stocks derived from field surveys and established allometric relationships, while direct harvests for parts of the quadrat were done for saltmarsh.Dataset 3: Greenhouse gas fluxesFile: <code>03Sasmito – GHG fluxes data_v2.csv</code>In situ measurements of sediment and aquatic CO₂ and CH₄ effluxes were obtained using static dark chambers and floating chambers, respectively. Gas concentration linear regression statistics used for flux quality control are also included in the dataset.Dataset 3: Data dictionaryFile: <code>04Sasmito – Data dictionary.csv</code>This file provides a comprehensive variable-level description of all datasets contained in this repository. The data dictionary defines column names, units, data types, and detailed descriptions for each variable across the soil properties, vegetation carbon, and greenhouse gas flux datasets.Methods summarySediment and vegetation samplingSediment cores were mostly collected to 50 cm depth and sectioned into depth intervals following standard blue carbon protocols. Bulk density was determined from oven-dried samples, organic matter content by loss-on-ignition (550 °C), and sediment carbon content estimated using published SOM–OC conversion relationships for mangroves and saltmarshes. Carbon stocks were normalised to 50 cm depth.Vegetation biomass was quantified using plot-based surveys. Mangrove biomass was estimated using general allometric equations, while saltmarsh biomass was derived from direct harvest within quadrats. Biomass was converted to carbon concentration using published conversion factors.Greenhouse gas flux measurementsSediment CO₂ and CH₄ effluxes were measured using static dark PVC chambers. Aquatic fluxes were measured using floating chambers connected to a portable gas analyser. Gas concentrations were recorded at high temporal resolution (every second), and fluxes calculated from linear concentration–time relationships, corrected for temperature and pressure. Only fluxes meeting quality criteria (minimum deployment duration and regression fit thresholds) were retained.Data usage notes and limitationsFlux measurements represent instantaneous low tide conditions during the cool dry season and should not be interpreted as annual emission budgets.Seasonal variability (e.g. wet season inundation, temperature, and salinity effects) is not captured in this dataset.Sediment organic carbon concentrations are estimated using LOI-based conversion relationships, which introduce uncertainty relative to direct elemental analysis.Low or negative CH₄ flux values may reflect near-zero emissions or methodological detection limits and should be interpreted cautiously.Users are strongly encouraged to consult the associated paper for full methodological detail and interpretation context.Intended useThese datasets are suitable for:comparative analyses of GHG fluxes across coastal wetland habitat types,refining emission factors for blue carbon accounting frameworks,synthesis and meta-analysis of tropical coastal wetland carbon dynamics,informing restoration and tidal reconnection planning.Related publicationSasmito, S.D., Mishra, A.K., Duvert, C., Montagna, L., Barkley, A.S., Widanto, D.S., Mulloy, R., Cartwright, P., Waltham, N.J. 2026. Contrasting sediment and aquatic CO₂ and CH₄ effluxes across Australian tropical salt flat, saltmarsh, mangrove and tidally restricted wetlands. <i>Estuarine, Coastal and Shelf Science</i>, doi: https://doi.org/10.1016/j.ecss.2025.109693.