Evaluation of laser‐based spectrometers for greenhouse gas flux measurements in coastal marshes

Brannon, E.; Moseman‐Valtierra, Serena; Rella, Chris W.; Martin, Rose M.; Chen, Xuechu; Tang, Jianwu

doi:10.1002/lom3.10105

Cited by 40 publications

(36 citation statements)

References 25 publications

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“…Our results suggest a relative elevation threshold (−25 cm MHW) above which N 2 O emissions increase substantially with nutrient enrichment (Figure ). Fluxes at lower elevations may have varied between treatments or among elevation zones but been below the detection limit of the analyzer (0.44 μmol m −2 hr −1 ) (Brannon et al., ). Detecting small emissions is important as, given the large global warming potential of this potent GHG, small increases in emission per unit area could have an outsized impact on salt marsh radiative forcing.…”

Section: Discussionmentioning

confidence: 99%

“…Detecting small emissions is important as, given the large global warming potential of this potent GHG, small increases in emission per unit area could have an outsized impact on salt marsh radiative forcing. To refine the apparent elevation threshold for N 2 O, future investigations should employ techniques, such as use of available analyzers with lower detection limits (Brannon et al., ), to test for finer‐scale differences in N 2 O emissions from low marsh elevations. Future investigations could make use of the long‐term nutrient loading gradient at Great Sippewissett Marsh, and associated changes in vegetation communities and elevation, to discern finer‐scale responses of N 2 O emissions to nutrient loading.…”

Section: Discussionmentioning

confidence: 99%

“…We covered chambers with white, light‐blocking fabric to exclude photosynthetic CO 2 uptake and measured community respiration and GHG gas fluxes. We conducted all GHG flux measurements for 4–6 min per plot (with approximately one‐second sampling intervals), based on observed periods for linear rates of change and to avoid excessive chamber warming (Brannon et al., ; Martin & Moseman‐Valtierra, ). To record air temperature at 30‐s interval, we suspended Hobo ® data loggers (Onset, Bourne, MA, USA) within the chamber during all flux measurements.…”

Section: Methodsmentioning

confidence: 99%

“…We used the Ideal Gas Law to calculate changes in gas concentrations using within‐chamber air temperatures, ambient atmospheric pressure, and chamber volume and footprint area. Using published, empirically determined minimum detectable slopes of concentration over time for each gas for the Picarro analyzer (Brannon et al., ), we computed minimum detectable fluxes for this experiment accounting for chamber size and measurement durations: 0.07 μmol m −2 hr −1 (CH 4 ); 0.44 μmol m −2 hr −1 (N 2 O) and 0.0001 mmol m −2 hr −1 (CO 2 ). When the p ‐value of the comparison of the slope with a horizontal line was >0.01 (indicating no concentration change), we assigned fluxes a value of zero.…”

Section: Methodsmentioning

confidence: 99%

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Long‐term nutrient addition increases respiration and nitrous oxide emissions in a New England salt marsh

Martin

Wigand

Elmstrom

et al. 2018

Ecology and Evolution

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Salt marshes may act either as greenhouse gas (GHG) sources or sinks depending on hydrological conditions, vegetation communities, and nutrient availability. In recent decades, eutrophication has emerged as a major driver of change in salt marsh ecosystems. An ongoing fertilization experiment at the Great Sippewissett Marsh (Cape Cod, USA) allows for observation of the results of over four decades of nutrient addition. Here, nutrient enrichment stimulated changes to vegetation communities that, over time, have resulted in increased elevation of the marsh platform. In this study, we measured fluxes of carbon dioxide (CO 2), methane (CH 4) and nitrous oxide (N2O) in dominant vegetation zones along elevation gradients of chronically fertilized (1,572 kg N ha−1 year−1) and unfertilized (12 kg N ha−1 year−1) experimental plots at Great Sippewissett Marsh. Flux measurements were performed using darkened chambers to focus on community respiration and excluded photosynthetic CO 2 uptake. We hypothesized that N‐replete conditions in fertilized plots would result in larger N2O emissions relative to control plots and that higher elevations caused by nutrient enrichment would support increased CO 2 and N2O and decreased CH 4 emissions due to the potential for more oxygen diffusion into sediment. Patterns of GHG emission supported our hypotheses. Fertilized plots were substantially larger sources of N2O and had higher community respiration rates relative to control plots, due to large emissions of these GHGs at higher elevations. While CH 4 emissions displayed a negative relationship with elevation, they were generally small across elevation gradients and nutrient enrichment treatments. Our results demonstrate that at decadal scales, vegetation community shifts and associated elevation changes driven by chronic eutrophication affect GHG emission from salt marshes. Results demonstrate the necessity of long‐term fertilization experiments to understand impacts of eutrophication on ecosystem function and have implications for how chronic eutrophication may impact the role that salt marshes play in sequestering C and N.

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

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Long‐term nutrient addition increases respiration and nitrous oxide emissions in a New England salt marsh

Martin

Wigand

Elmstrom

et al. 2018

Ecology and Evolution

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“…However, some progress has been made for continuous ongoing measurements in the field, using an equilibrator connected to CRDS for N 2 O and CH 4 (ArevaloMartinez et al, 2013;Grefe and Kaiser, 2014;O'Reilly et al, 2015;Roberts and Shiller, 2015;Brannon et al, 2016;Kock et al, 2016). Recently, polydimethylsiloxane membranes (PDMS) (Helixmark, Carpinteria, CA, USA), coupled with MIMS and CDRS, have shown promising advances for GHGs measurements in freshwater (Bell et al, 2007;Gonzalez-Valencia et al, 2014).…”

Section: Introductionmentioning

confidence: 99%

Toward High-Resolution Vertical Measurements of Dissolved Greenhouse Gases (Nitrous Oxide and Methane) and Nutrients in the Eastern South Pacific

2018

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In this study, in situ, real-time and high-resolution vertical measurements of dissolved greenhouse gases (GHGs) such as nitrous oxide (N 2 O) and methane (CH 4 ) and nutrients are reported for the eastern South Pacific (ESP); a region with marked zonal gradients, ranging from highly productive and suboxic conditions in coastal upwelling systems to oligotrophic and oxygenated conditions in the subtropical gyre. Four high-resolution vertical profiles for gases (N 2 O and CH 4 ) and nutrients (NO − 3 and PO 3− 4 ) were measured using a Pumped Profiling System (PPS), connected with a liquid degassing membrane coupled with Cavity Ring-Down Spectroscopy (CRDS) and a nutrient auto-analyzer, respectively. The membrane-CRDS system maintains a linear response over a wide range of gas concentrations, detecting N 2 O and CH 4 levels as low as 0.0774 ± 0.0004 and 0.1011 ± 0.001 ppm, respectively. Continuous profiles for gases and nutrients were similar to those reported throughout the ESP, with pronounced N 2 O and CH 4 peaks at the upper oxycline and at the base of the euphotic zone and pycnocline, respectively, in the coastal zone; but almost constant depth profiles in the subtropical gyre. Additionally, other vertical gas and nutrient structures were observed using continuous sampling, which would not have been detected by discrete sampling. Our results demonstrate that continuous measurements can be a potentially useful methodology for future GHGs cycle studies.

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

Iram

Maher

Lovelock

et al. 2022

Ecological Applications

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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. The site was originally a supratidal forest composed of Melaleuca spp. that was cleared and drained in the 1990s for sugarcane production. In 2010, tidal inundation was reinstated, and a mosaic of coastal vegetation (saltmarshes, mangroves, and supratidal forests) emerged. We measured soil GHG fluxes (CH 4 , N 2 O, CO 2 ) and sequestration of organic C in the trees and soil to estimate the net C abatement associated with the reference, converted, and restored sites. To assess the influence of restoration on water quality improvement, we measured denitrification and soil N accumulation. We calculated C abatement of 18.5 Mg CO 2Àeq ha À1 year À1 when sugarcane land transitioned to supratidal forests, 11.0 Mg CO 2Àeq ha À1 year À1 when the land transitioned to mangroves, and 6.2 Mg CO 2Àeq ha À1 year À1 when the land transitioned to saltmarshes. The C abatement was due to tree growth, soil accumulation, and reduced N 2 O emissions due to the cessation of fertilization. Carbon abatement was still positive, even accounting for CH 4 emissions, which increased in the wetlands due to flooding and N 2 O production due to enhanced levels of denitrification.Coastal wetland restoration in this subtropical setting effectively reduces CO 2 emissions while providing additional cobenefits, notably water quality improvement.

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Evaluation of laser‐based spectrometers for greenhouse gas flux measurements in coastal marshes

Abstract: Precise and rapid analyses of greenhouse gases (GHGs) will advance understanding of the net climatic forcing of coastal marsh ecosystems. We examined the ability of a cavity ring down spectroscopy (CRDS) analyzer (Model G2508, Picarro) to measure carbon dioxide (CO 2 ), methane (CH 4

Cited by 40 publications

References 25 publications

Long‐term nutrient addition increases respiration and nitrous oxide emissions in a New England salt marsh

Long‐term nutrient addition increases respiration and nitrous oxide emissions in a New England salt marsh

Toward High-Resolution Vertical Measurements of Dissolved Greenhouse Gases (Nitrous Oxide and Methane) and Nutrients in the Eastern South Pacific

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

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