Surface gas exchange determined from an aquatic eddy covariance floating platform

Long, Matthew H.; Nicholson, David P.

doi:10.1002/lom3.10233

Cited by 16 publications

(26 citation statements)

References 68 publications

(121 reference statements)

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“…Although this approach is appropriate for the reef site at the edge of the Bermuda platform that is open to interaction with the wind, it is not appropriate for the Virginia coastal bay that is enclosed by islands, marsh, and banks that limit the influence of wind. Instead, at the Virginia site, we estimated gas exchange rates from the turbulent kinetic energy dissipation rate ( ε ) based on the methods of Zappa et al (, ), as described by Long and Nicholson (). The ε was determined hourly from the fit of the vertical velocity wavenumber spectrum in the inertial subrange (Fairall and Larsen ; Zappa et al ; Long and Nicholson ):

S = α ε^{2 / 3} κ_{N}^{- 5 / 3}

where S is the wavenumber spectrum of the fluctuating components of the vertical velocity, κ N is the radian wavenumber, and α is Kolmogorov's empirical constant (= 0.52; see details in Zappa et al [, ]).…”

Section: Methodsmentioning

confidence: 99%

“…The flux across the benthic-water interface was determined with an eddy covariance system ( Fig. 1a) that consisted of an acoustic Doppler velocimeter (ADV, Nortek) coupled to a Fire-stingO 2 Mini fiber-optic O 2 meter with a temperature-compensated, fast-response (< 0.3 s), 430 μm diameter optode (Pyroscience, GE), similar to previous designs (Long et al 2015a;Long and Nicholson 2018). The mean turbulent O 2 flux was calculated over 0.25 h periods from the product of the instantaneous variations in the vertical velocity and O 2 concentration by:…”

Section: Benthic Fluxesmentioning

confidence: 99%

“…The design and motion correction is based on similar approaches used in atmospheric eddy covariance measurements to correct for platform motion (e.g., Edson et al 1998;Flügge et al 2016). This new measurement approach including microfluidics (Long et al 2015a) and IMU integration (Long and Nicholson 2018) allows the EC technique to overcome previous challenges related to platform motion, sensor bias, and sensor separation (Berg et al 2015;Donis et al 2015;Holtappels et al 2015;Reimers et al 2016). The specific configurations, data treatment, and validation can be found in Long et al (2015a) and Long and Nicholson (2018).…”

Section: Benthic Fluxesmentioning

confidence: 99%

“…Sediment core incubations, benthic chambers, pore-water profiling, and boundary layer exchange techniques (e.g., Tengberg et al 1995;Berg et al 2003;McGillis et al 2011;Long et al 2015a) can provide estimates of F bw . A variety of formulations exist for the estimation of F aw from dissolved oxygen concentrations and wind, current, and turbulence parameters (Borges et al 2004;Zappa et al 2007;Wanninkhof 2014), and direct estimates have been conducted using floating chambers and eddy covariance techniques (Marino and Howarth 1993;Edson et al 1998;Long and Nicholson 2018). Methods developed for determining R wc include bottle incubations, isotopic tracers, and automated incubators (Laws et al 2000;Luz and Barkan 2000;Collins et al 2018).…”

mentioning

confidence: 99%

“…Methods developed for determining R wc include bottle incubations, isotopic tracers, and automated incubators (Laws et al 2000;Luz and Barkan 2000;Collins et al 2018). Each of these different methods has specific biases and ideal conditions for their use, which has been discussed elsewhere (e.g., Tengberg et al 1995;Berg et al 2003;Collins et al 2018;Long and Nicholson 2018).…”

mentioning

confidence: 99%

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Closing the oxygen mass balance in shallow coastal ecosystems

Long

Rheuban

McCorkle

et al. 2019

Limnology & Oceanography

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The oxygen concentration in marine ecosystems is influenced by production and consumption in the water column and fluxes across both the atmosphere–water and benthic–water boundaries. Each of these fluxes has the potential to be significant in shallow ecosystems due to high fluxes and low water volumes. This study evaluated the contributions of these three fluxes to the oxygen budget in two contrasting ecosystems, a Zostera marina (eelgrass) meadow in Virginia, U.S.A., and a coral reef in Bermuda. Benthic oxygen fluxes were evaluated by eddy covariance. Water column oxygen production and consumption were measured using an automated water incubation system. Atmosphere–water oxygen fluxes were estimated by parameterizations based on wind speed or turbulent kinetic energy dissipation rates. We observed significant contributions of both benthic fluxes and water column processes to the oxygen mass balance, despite the often‐assumed dominance of the benthic communities. Water column rates accounted for 45% and 58% of the total oxygen rate, and benthic fluxes accounted for 23% and 39% of the total oxygen rate in the shallow (~ 1.5 m) eelgrass meadow and deeper (~ 7.5 m) reef site, respectively. Atmosphere–water fluxes were a minor component at the deeper reef site (3%) but a major component at the shallow eelgrass meadow (32%), driven by diel changes in the sign and strength of atmosphere–water gradient. When summed, the measured benthic, atmosphere–water, and water column rates predicted, with 85–90% confidence, the observed time rate of change of oxygen in the water column and provided an accurate, high temporal resolution closure of the oxygen mass balance.

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S = α ε^{2 / 3} κ_{N}^{- 5 / 3}

Section: Methodsmentioning

confidence: 99%

Section: Benthic Fluxesmentioning

confidence: 99%

Section: Benthic Fluxesmentioning

confidence: 99%

mentioning

confidence: 99%

mentioning

confidence: 99%

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Closing the oxygen mass balance in shallow coastal ecosystems

Long

Rheuban

McCorkle

et al. 2019

Limnology & Oceanography

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Taxon‐specific primary production rates on coral reefs in the Florida Keys

Owen

Long

Fitt

et al. 2020

Limnology & Oceanography

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Coral reefs are known to have extremely high rates of primary production. However, common geochemical methods for determining bulk rates of reef metabolism cannot distinguish which organisms are responsible for primary production. Here we used a "bottom-up" approach to estimate the contribution of diverse primary producers including hard corals, octocorals, and algae to gross primary production on coral reefs by scaling up taxon-specific rates by the abundance of those taxa in the environment. Chamber-based production rates of the dominant primary producers were obtained as a function of irradiance, the primary short-term driver of photosynthesis. These rates were then combined with annotated three-dimensional (3D) reconstructions of reef sections and a simple light field model to estimate reef-scale gross and net primary production rates over time. At a degraded reef in the Florida Keys octocorals and algae were the main producers, but at a more intact site a scleractinian coral (Acropora palmata) was the most important producer. As a validation of the approach, rates of primary production estimated using the "bottom-up" approach were compared with in situ eddy covariance fluxes. The daily integrated rates agreed within 16%, though maximal production was 35% lower in the "bottom-up" approach likely due to under-representation of octocorals and macroalgae in the 3D reconstructions. The "bottom up" approach yielded results that were largely consistent with the in situ measurements of primary production and irradiance with the significant benefit of providing taxon-specific and spatially-explicit primary production rates.

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Headwater gas exchange quantified from O₂ mass balances at the reach scale

Rovelli

Attard

Heppell

et al. 2018

Limnology & Ocean Methods

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Headwater streams are important in the carbon cycle and there is a need to better parametrize and quantify exchange of carbon‐relevant gases. Thus, we characterized variability in the gas exchange coefficient (k 2) and dissolved oxygen (O2) gas transfer velocity (k) in two lowland headwaters of the River Avon (UK). The traditional one‐station open‐water method was complemented by in situ quantification of riverine sources and sinks of O2 (i.e., groundwater inflow, photosynthesis, and respiration in both the water column and benthic compartment) enabling direct hourly estimates of k 2 at the reach–scale (~ 150 m) without relying on the nighttime regression method. Obtained k 2 values ranged from 0.001 h−1 to 0.600 h−1. Average daytime k 2 were a factor two higher than values at night, likely due to diel changes in water temperature and wind. Temperature contributed up to 46% of the variability in k on an hourly scale, but clustering temperature incrementally strengthened the statistical relationship. Our analysis suggested that k variability is aligned with dominant temperature trends rather than with short‐term changes. Similarly, wind correlation with k increased when clustering wind speeds in increments correspondent with dominant variations (1 m s−1). Time scale is thus an important consideration when resolving physical drivers of gas exchange. Mean estimates of k 600 from recent parametrizations proposed for upscaling, when applied to the settings of this study, were found to be in agreement with our independent O2 budget assessment (within < 10%), adding further support to the validity of upscaling efforts aiming at quantifying large‐scale riverine gas emissions.

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Surface gas exchange determined from an aquatic eddy covariance floating platform

Cited by 16 publications

References 68 publications

Closing the oxygen mass balance in shallow coastal ecosystems

Closing the oxygen mass balance in shallow coastal ecosystems

Taxon‐specific primary production rates on coral reefs in the Florida Keys

Headwater gas exchange quantified from O₂ mass balances at the reach scale

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Surface gas exchange determined from an aquatic eddy covariance floating platform

Cited by 16 publications

References 68 publications

Closing the oxygen mass balance in shallow coastal ecosystems

Closing the oxygen mass balance in shallow coastal ecosystems

Taxon‐specific primary production rates on coral reefs in the Florida Keys

Headwater gas exchange quantified from O2 mass balances at the reach scale

Contact Info

Product

Resources

About

Headwater gas exchange quantified from O₂ mass balances at the reach scale