Groundwater releases CO to diverse global coastal ecosystems.

Coastal ecosystems play a major role in marine carbon budgets, but substantial uncertainties remain in the sources and fluxes of coastal carbon dioxide (CO). Here, we assess when, where, and how submarine groundwater discharge (SGD) releases CO to shallow coastal ecosystems. Time-series observations of dissolved CO and radon (Rn, a natural groundwater tracer) across 40 coastal systems from 14 countries revealed large SGD-derived CO fluxes.

Sea-level rise and extreme Indian Ocean Dipole explain mangrove dieback in the Maldives.

Mangrove forests enhance Small Island Developing States' resilience to climate change, yet in 2020, a mangrove dieback impacted ~ 25% of mangrove-containing islands in the Maldives. Using remote sensing, dendrology and sediment geochemistry, we document a significant decrease in mangrove health post-2020 (NDVI: 0.75 ± 0.

Groundwater discharge and bank overtopping drive large carbon exports from Indian Sundarban mangroves.

The Sundarbans represent the largest mangrove system on Earth, covering >10,000 km. These mangroves can export a vast amount of aquatic carbon that can be potentially sequestered for millennia. However, the mechanisms that drive these processes remain poorly constrained.

Improving the measurement of nitrogen stable isotopes in organic materials containing high C:N ratios using a 5A molecular sieve column.

The nitrogen stable isotope composition (δN) of plant materials has numerous applications. Plant materials like bark can have a very high C:N ratio. Incomplete C combustion in such samples interferes with the δN measurement due to CO production.

Floodplain morphology influences arsenic and antimony spatial distribution in a seasonal acid sulfate soil wetland.

Arsenic (As) and antimony (Sb) often co-occur in floodplain depositional environments that are contaminated by legacy mining activities. However, the distribution of As and Sb throughout floodplains is not uniform, adding complexity and expense to management or remediation processes. Identifying floodplain morphology predictor variables that help quantify and explain As and Sb spatial distribution on floodplains is useful for management and remediation.

Extreme iron cycling in a coastal lake-lagoon system driven by interactions between climate and entrance management.

Intermittently closed and open coastal lakes and lagoons (ICOLLs) are ecologically important and hydrologically sensitive estuarine systems. We explore how extreme drought and ICOLL entrance management intersect to influence the geochemical cycling of iron. Opening the ICOLL entrance just prior to an extreme drought in 2019 led to prolonged extremely low water levels, thereby exposing intertidal/subtidal sulfidic sediments and causing oxidation of sedimentary pyrite.

Microbiome mediating methane and nitrogen transformations in a subterranean estuary.

Subterranean estuaries (STEs) are important coastal biogeochemical reactors facilitating unique niches for microbial communities. A common approach in determining STE greenhouse gas and nutrient fluxes is to use terrestrial endmembers, not accounting for microbially mediated transformations throughout the STE. As such, the microbial ecology and spatial distribution of specialists that cycle compounds in STEs remain largely underexplored.

Carbonate chemistry and carbon sequestration driven by inorganic carbon outwelling from mangroves and saltmarshes.

Mangroves and saltmarshes are biogeochemical hotspots storing carbon in sediments and in the ocean following lateral carbon export (outwelling). Coastal seawater pH is modified by both uptake of anthropogenic carbon dioxide and natural biogeochemical processes, e.g.

Practical Guide to Measuring Wetland Carbon Pools and Fluxes.

Unlabelled: Wetlands cover a small portion of the world, but have disproportionate influence on global carbon (C) sequestration, carbon dioxide and methane emissions, and aquatic C fluxes. However, the underlying biogeochemical processes that affect wetland C pools and fluxes are complex and dynamic, making measurements of wetland C challenging. Over decades of research, many observational, experimental, and analytical approaches have been developed to understand and quantify pools and fluxes of wetland C.

Rapid bark-mediated tree stem methane transport occurs independently of the transpiration stream in Melaleuca quinquenervia.

Tree stem methane emissions are important components of lowland forest methane budgets. The potential for species-specific behaviour among co-occurring lowland trees with contrasting bark characteristics has not been investigated. We compare bark-mediated methane transport in two common lowland species of contrasting bark characteristics (Melaleuca quinquenervia featuring spongy/layered bark with longitudinally continuous airspaces and Casuarina glauca featuring hard/dense common bark) through several manipulative experiments.

Submarine Groundwater Discharge Exceeds River Inputs as a Source of Nutrients to the Great Barrier Reef.

Rivers are often assumed to be the main source of nutrients triggering eutrophication in the Great Barrier Reef (GBR). However, existing nutrient budgets suggest a major missing source of nitrogen and phosphorus sustaining primary production. Here, we used radium isotopes to resolve submarine groundwater discharge (SGD)-derived, shelf-scale nutrient inputs to the GBR.

Low-Cost Nitric Oxide Sensors: Assessment of Temperature and Humidity Effects.

High equipment cost is a significant entry barrier to research for small organizations in developing solutions to air pollution problems. Low-cost electrochemical sensors show sensitivity at parts-per-billion by volume mixing ratios but are subject to variation due to changing environmental conditions, in particular temperature. In this study, we demonstrate a low-cost Internet of Things (IoT)-based sensor system for nitric oxide analysis.

The Role of Hydraulic Failure in a Massive Mangrove Die-Off Event.

Between late 2015 and early 2016, more than 7,000 ha of mangrove forest died along the coastline of the Gulf of Carpentaria, in northern Australia. This massive die-off was preceded by a strong 2015/2016 El Niño event, resulting in lower precipitation, a drop in sea level and higher than average temperatures in northern Australia. In this study, we investigated the role of hydraulic failure in the mortality and recovery of the dominant species, , 2 years after the mortality event.

Climate change mitigation and improvement of water quality from the restoration of a subtropical coastal wetland.

Coastal wetland restoration is an important activity to achieve greenhouse gas (GHG) reduction targets, improve water quality, and reach the Sustainable Development Goals. However, many uncertainties remain in connection with achieving, measuring, and reporting success from coastal wetland restoration. We measured levels of carbon (C) abatement and nitrogen (N) removal potential of restored coastal wetlands in subtropical Queensland, Australia.

Hot spot of CH production and diffusive flux in rivers with high urbanization.

Rivers and streams play a central role in global carbon budget, but our knowledge is limited on the magnitude and extent of urbanization influence on riverine methane (CH) dynamics. In this study, we investigated dissolved CH (dCH) concentration and CH diffusive fluxes in 27 river segments of two 4-order and three 3-order tributary rivers to the Yangtze River in China, which drained land areas with varied urbanization intensities. We found that urban development was the key factor responsible for high fluvial dCH concentration and diffusive flux, exceeding the influence of agricultural farming, and these headwater rivers were over-saturated in CH with respect to atmospheric equilibrium.

Bark-dwelling methanotrophic bacteria decrease methane emissions from trees.

Tree stems are an important and unconstrained source of methane, yet it is uncertain whether internal microbial controls (i.e. methanotrophy) within tree bark may reduce methane emissions.

Isotopic evidence for axial tree stem methane oxidation within subtropical lowland forests.

Knowledge regarding mechanisms moderating methane (CH ) sink/source behaviour along the soil-tree stem-atmosphere continuum remains incomplete. Here, we applied stable isotope analysis (δ C-CH ) to gain insights into axial CH transport and oxidation in two globally distributed subtropical lowland species (Melaleuca quinquenervia and Casuarina glauca). We found consistent trends in CH flux (decreasing with height) and δ C-CH enrichment (increasing with height) in relation to stem height from ground.

Carbon dioxide hydrodynamics along a wetland-lake-stream-waterfall continuum (Blue Mountains, Australia).

The small-scale spatial variability in dissolved carbon dioxide (CO) and water-air CO flux dynamics were investigated within first-order catchments of the upper Blue Mountains Plateau (New South Wales, Australia). Water samples were collected at 81 locations during winter and summer over two consecutive years across seven aquatic ecosystem types: wetland, impoundment, lake, tributary stream, mainstem, escarpment complex, and urban-aquatic interface. Dissolved [CO] ranged from 15 to 880 μM (94 to 4760%Sat), and dissolved [O] from 0 to 350 μM (0 to 101%Sat).

Shifts in methanogenic archaea communities and methane dynamics along a subtropical estuarine land use gradient.

In coastal aquatic ecosystems, prokaryotic communities play an important role in regulating the cycling of nutrients and greenhouse gases. In the coastal zone, estuaries are complex and delicately balanced systems containing a multitude of specific ecological niches for resident microbes. Anthropogenic influences (i.

The legacy and drivers of groundwater nutrients and pesticides in an agriculturally impacted Quaternary aquifer system.

Nutrient and pesticide pollution are among the major threats to groundwater quality in agriculturally impacted aquifers. Understanding their legacy effects and drivers are important to protect aquifers from exposures to contamination. However, the complexities of groundwater flowpaths make it difficult to predict the time-scales of groundwater flow and contaminant transport.

Net landscape carbon balance of a tropical savanna: Relative importance of fire and aquatic export in offsetting terrestrial production.

The magnitude of the terrestrial carbon (C) sink may be overestimated globally due to the difficulty of accounting for all C losses across heterogeneous landscapes. More complete assessments of net landscape C balances (NLCB) are needed that integrate both emissions by fire and transfer to aquatic systems, two key loss pathways of terrestrial C. These pathways can be particularly significant in the wet-dry tropics, where fire plays a fundamental part in ecosystems and where intense rainfall and seasonal flooding can result in considerable aquatic C export (ΣF ).