Inorganic carbon and oxygen dynamics in a marsh‐dominated estuary

Wang, Shiyu Rachel; Iorio, Daniela Di; Cai, Wei‐Jun; Hopkinson, Charles S.

doi:10.1002/lno.10614

Cited by 30 publications

(28 citation statements)

References 74 publications

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“…From September 2017 to January 2018, DIC concentrations increased from a low of 25 mg L −1 to a maximum of >55 mg L −1 , before declining to lows of~25 mg L −1 again by summer 2018 (Figure 2a). On shorter, daily/tidal timescales, DIC concentrations ranged considerably, often by >15 mg L −1 with high DIC waters peaking at ebbing tide and low values peaking during flooding tides, consistent with previous studies (Cai & Wang, 1998;Neubauer & Anderson, 2003;Santos et al, 2019;Wang et al, 2018).…”

Section: Measuring and Modeling Aquatic C Concentrationssupporting

confidence: 90%

Hydrologic Export Is a Major Component of Coastal Wetland Carbon Budgets

Bogard

Bergamaschi

Butman

et al. 2020

Global Biogeochemical Cycles

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Coastal wetlands are among the most productive habitats on Earth and sequester globally significant amounts of atmospheric carbon (C). Extreme rates of soil C accumulation are widely assumed to reflect efficient C storage. Yet the fraction of wetland C lost via hydrologic export has not been directly quantified, since comprehensive budgets including direct estimates of lateral C loss are lacking. We present a complete net ecosystem C budget (NECB), demonstrating that lateral losses of C are a major component of the NECB for the largest stable brackish tidal marsh on the U.S. Pacific coast. Mean annual net ecosystem exchange of CO2 with the atmosphere (NEE = −185 g C m2 year−1, negative NEE denoting ecosystem uptake) was compared to long‐term soil C burial (87–110 g C m2 year−1), suggesting only 47–59% of fixed atmospheric C accumulates in soils. Consistently, direct monitoring in 2017–2018 showed NEE of −255 g C m−2 year−1, and hydrologic export of 105 g C m−2 year−1 (59% of NEE remaining on site). Despite their high C sequestration capacity, lateral losses from coastal wetlands are typically a larger fraction of the NECB when compared to other terrestrial ecosystems. Loss of inorganic C (the least measured NECB term) was 91% of hydrologic export and may be the most important term limiting C sequestration. The high productivity of coastal wetlands thus serves a dual function of C burial and estuarine export, and the multiple fates of fixed C must be considered when evaluating wetland capacity for C sequestration.

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Section: Measuring and Modeling Aquatic C Concentrationssupporting

confidence: 90%

Hydrologic Export Is a Major Component of Coastal Wetland Carbon Budgets

Bogard

Bergamaschi

Butman

et al. 2020

Global Biogeochemical Cycles

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“…Average salt marsh NEE on the Atlantic coast has recently been reported to take up 19 ± 7 mol C m −2 year −1 (Windham-Myers et al, 2018); sites that were net heterotrophic were considered outliers and not included in this average. However, a growing number of studies have shown marshes to be net sources of CO 2 (Krauss et al, 2016;Wang et al, 2017;Wilson et al, 2015), raising questions regarding the origin of the OC respired. In salt marshes, OC is produced by autochthonous primary production but may also be delivered via sediment deposition during tidal flooding.…”

Section: Vertical Carbon Fluxes 431 Metabolic Ratesmentioning

confidence: 99%

The Effect of Fertilization on Biomass and Metabolism in North Carolina Salt Marshes: Modulated by Location‐Specific Factors

2020

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The resilience of salt marshes to sea level rise depends on vertical accretion through belowground biomass production and sediment deposition to maintain elevation above sea level. Increased nitrogen (N) availability from anthropogenic sources may stimulate aboveground biomass production and sediment deposition and, thus, accretion; however, increased N may also negatively impact marsh accretion by decreasing belowground biomass and increasing net CO 2 emissions. A study was conducted in Spartina alterniflora-dominated salt marshes in North Carolina, USA, to determine how responses to fertilization vary across locations with different physical and chemical characteristics. Pore water residence time, inundation time, and proximity to tidal creeks drove spatial differences in pore water sulfide, ammonium, and dissolved carbon concentrations. Although annual respiration and gross primary production were greater at the creek edge than interior marsh sites, net ecosystem CO 2 exchange (NEE) was nearly balanced at all the sites. Fertilization decreased belowground biomass in the interior sites but not on the creek edge. Aboveground biomass, respiration, gross primary production, and net CO 2 emissions increased in response to fertilization, but responses were diminished in interior marsh locations with high pore water sulfide. Hourly NEE measured by chambers were similar to hourly NEE observed by a nearby eddy covariance tower, but correcting for inundation depth relative to plant height was critical for accurate extrapolation to annual fluxes. The impact of fertilization on biomass and NEE, and thus marsh resilience, varied across marsh locations depending upon location-specific pore water sulfide concentrations. Plain Language Summary Salt marshes provide valuable services, such as protecting the coast from storms, removing excess nutrient pollution from water, and long-term burial of carbon. Because sea level is currently rising, salt marshes need to build up elevation at the same rate as sea level rise to survive. Human-produced nitrogen pollution is rising in salt marshes, often increasing the growth of grass, which may cause the marsh to trap sediment more efficiently and build elevation faster. However, increased nitrogen may also decrease root growth and increase sediment microbial activity (which decomposes sediment organic carbon to carbon dioxide), causing elevation-building to slow down. It is unclear whether the addition of nitrogen affects the marsh's elevation-building rate in a positive or negative way. We found that the effect of nitrogen on elevation-building depends on location. Factors such as tidal inundation and residence time influence sediment water chemistry and, thereby, the response to excess nitrogen. Sulfide inhibits the uptake of nitrogen by plant roots and also microbial activity; thus, marsh locations with more sulfide have diminished responses to nitrogen pollution. This knowledge may be used for management of marshes at risk due to nitrogen pollution.

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“…Tidal inundation can result in the lateral export of DIC into the water column (Wang et al, ), thereby suppressing the full estimate of R E when using EC measurement methods alone (Knox et al, ). This situation creates uncertainty in a GPP estimate.…”

Section: Discussionmentioning

confidence: 99%

Tidal Wetland Gross Primary Production Across the Continental United States, 2000–2019

Feagin

Forbrich

Huff

et al. 2020

Global Biogeochemical Cycles

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We mapped tidal wetland gross primary production (GPP) with unprecedented detail for multiple wetland types across the continental United States (CONUS) at 16‐day intervals for the years 2000–2019. To accomplish this task, we developed the spatially explicit Blue Carbon (BC) model, which combined tidal wetland cover and field‐based eddy covariance tower data into a single Bayesian framework, and used a super computer network and remote sensing imagery (Moderate Resolution Imaging Spectroradiometer Enhanced Vegetation Index). We found a strong fit between the BC model and eddy covariance data from 10 different towers (r2 = 0.83, p < 0.001, root‐mean‐square error = 1.22 g C/m2/day, average error was 7% with a mean bias of nearly zero). When compared with NASA's MOD17 GPP product, which uses a generalized terrestrial algorithm, the BC model reduced error by approximately half (MOD17 had r2 = 0.45, p < 0.001, root‐mean‐square error of 3.38 g C/m2/day, average error of 15%). The BC model also included mixed pixels in areas not covered by MOD17, which comprised approximately 16.8% of CONUS tidal wetland GPP. Results showed that across CONUS between 2000 and 2019, the average daily GPP per m2 was 4.32 ± 2.45 g C/m2/day. The total annual GPP for the CONUS was 39.65 ± 0.89 Tg C/year. GPP for the Gulf Coast was nearly double that of the Atlantic and Pacific Coasts combined. Louisiana alone accounted for 15.78 ± 0.75 Tg C/year, with its Atchafalaya/Vermillion Bay basin at 4.72 ± 0.14 Tg C/year. The BC model provides a robust platform for integrating data from disparate sources and exploring regional trends in GPP across tidal wetlands.

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Inorganic carbon and oxygen dynamics in a marsh‐dominated estuary

Cited by 30 publications

References 74 publications

Hydrologic Export Is a Major Component of Coastal Wetland Carbon Budgets

Hydrologic Export Is a Major Component of Coastal Wetland Carbon Budgets

The Effect of Fertilization on Biomass and Metabolism in North Carolina Salt Marshes: Modulated by Location‐Specific Factors

Tidal Wetland Gross Primary Production Across the Continental United States, 2000–2019

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