Revising Estimates of Aquatic Gross Oxygen Production by the Triple Oxygen Isotope Method to Incorporate the Local Isotopic Composition of Water

Manning, Cara C.; Howard, Evan M.; Nicholson, David P.; Ji, Brenda Y.; Sandwith, Zoe O.; Stanley, Rachel H. R.

doi:10.1002/2017gl074375

Cited by 14 publications

(17 citation statements)

References 68 publications

(144 reference statements)

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“…On the few samples that δ 18 O-H 2 O was not available, δ 18 O-H 2 O was estimated from a relationship with salinity from all the measured samples from that year. Including the measured δ 18 O-H 2 O is important in the Arctic-neglecting it can lead to errors of up to 50% (Manning et al, 2017). Varying the 17 Δ excess of seawater by 8 per meg (2 standard deviations of the global average (Luz & Barkan, 2010)) changes the GOP estimate by 5-6% on average (Manning et al, 2017).…”

Section: Gop and Ncp Calculationsmentioning

confidence: 99%

“…Including the measured δ 18 O-H 2 O is important in the Arctic-neglecting it can lead to errors of up to 50% (Manning et al, 2017). Varying the 17 Δ excess of seawater by 8 per meg (2 standard deviations of the global average (Luz & Barkan, 2010)) changes the GOP estimate by 5-6% on average (Manning et al, 2017). The combined error in the calculations excluding the contribution from gas transfer velocity is 12% for GOP.…”

Section: Gop and Ncp Calculationsmentioning

confidence: 99%

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Variations in Rates of Biological Production in the Beaufort Gyre as the Arctic Changes: Rates From 2011 to 2016

Sandwith

Williams

et al. 2019

JGR Oceans

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The Arctic Ocean is experiencing profound environmental changes as the climate warms. Understanding how these changes will affect Arctic biological productivity is key for predicting future Arctic ecosystems and the global CO2 balance. Here we use in situ gas measurements to quantify rates of gross oxygen production (GOP, total photosynthesis) and net community production (NCP, net CO2 drawdown by the biological pump) in the mixed layer in summer or fall from 2011 to 2016 in the Beaufort Gyre. NCP and GOP show spatial and temporal variations with higher values linked with lower concentrations of sea ice and increased upper ocean stratification. Mean rates of GOP range from 8 ± 1 to 54 ± 9 mmol O2·m−2·d−1 with the highest mean rates occurring in summer of 2012. Mean rates of NCP ranged from 1.3 ± 0.2 to 2.9 ± 0.5 mmol O2·m−2·d−1. The mean ratio of NCP/GOP, a measure of how efficiently the ecosystem is recycling its nutrients, ranged from 0.04 to 0.17, similar to ratios observed at lower latitudes. Additionally, a large increase in total photosynthesis that occurred in 2012, a year of historically low sea ice coverage, persisted for many years. Taken together, these data provide one of the most complete characterizations of interannual variations of biological productivity in this climatically important region, can serve as a baseline for future changes in rates of production, and give an intriguing glimpse of how this region of the Arctic may respond to future lack of sea ice.

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Section: Gop and Ncp Calculationsmentioning

confidence: 99%

Section: Gop and Ncp Calculationsmentioning

confidence: 99%

Variations in Rates of Biological Production in the Beaufort Gyre as the Arctic Changes: Rates From 2011 to 2016

Sandwith

Williams

et al. 2019

JGR Oceans

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“…This value for λ is selected so that 17 is nearly unaffected by respiratory O 2 consumption and reflects the proportion of O 2 that is derived from photosynthesis relative to air-water gas exchange (Hendricks et al, 2005;Juranek and Quay, 2013;Nicholson et al, 2014). We report 17 in per meg (1 per meg = 0.001 ‰) due to the small range of values in natural waters, typically 8-242 per meg (Juranek and Quay, 2013;Manning et al, 2017a). Two key constraints in the calculation of GOP from measurements of the triple isotopic composition of O 2 are the isotopic composition of O 2 derived from air-water exchange and the isotopic composition of photosynthetic O 2 .…”

Section: Calculationmentioning

confidence: 99%

“…The composition of photosynthetic O 2 is dependent on the triple oxygen isotopic composition of H 2 O, the substrate for photosynthetic O 2 , and the isotopic fractionation associated with photosynthetic O 2 production. In oceanic studies, a common assumption is that the H 2 O isotopic composition is equivalent to VSMOW (standard mean ocean water), but in brackish systems it is necessary to estimate the isotopic composition of water and incorporate this into the GOP calculation (Manning et al, 2017a).…”

Section: Calculationmentioning

confidence: 99%

Changes in gross oxygen production, net oxygen production, and air-water gas exchange during seasonal ice melt in Whycocomagh Bay, a Canadian estuary in the Bras d'Or Lake system

et al. 2019

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Abstract. Sea ice is an important control on gas exchange and primary production in polar regions. We measured net oxygen production (NOP) and gross oxygen production (GOP) using near-continuous measurements of the O2∕Ar gas ratio and discrete measurements of the triple isotopic composition of O2, during the transition from ice-covered to ice-free conditions, in Whycocomagh Bay, an estuary in the Bras d'Or Lake system in Nova Scotia, Canada. The volumetric gross oxygen production was 5.4+2.8-1.6 mmol O2 m−3 d−1, similar at the beginning and end of the time series, and likely peaked at the end of the ice melt period. Net oxygen production displayed more temporal variability and the system was on average net autotrophic during ice melt and net heterotrophic following the ice melt. We performed the first field-based dual tracer release experiment in ice-covered water to quantify air–water gas exchange. The gas transfer velocity at >90 % ice cover was 6 % of the rate for nearly ice-free conditions. Published studies have shown a wide range of results for gas transfer velocity in the presence of ice, and this study indicates that gas transfer through ice is much slower than the rate of gas transfer through open water. The results also indicate that both primary producers and heterotrophs are active in Whycocomagh Bay during spring while it is covered in ice.

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“…All uncertainties are expressed as the standard deviation. (Manning et al, 2017a). If the 17 O-excess of H 2 O is increased or decreased by 20 per meg, GOP changes by an average of 10 %.…”

Section: Gross Oxygen Production 331 Calculationmentioning

confidence: 99%

Changes in gross oxygen production, net oxygen production, and air-water gas exchange during seasonal ice melt in the Bras d'Or Lake, a Canadian estuary

Manning

Stanley

Nicholson

et al. 2017

Preprint

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Abstract. Sea ice is an important control on gas exchange and primary production in polar regions. We measured net oxygen production and gross oxygen production using near-continuous measurements of the O 2 /Ar gas ratio and discrete measurements of the triple isotopic composition of O 2 in the Bras d'Or Lake, an estuary in Nova Scotia, Canada, as the bay transitioned from ice-covered to ice-free conditions. The volumetric gross oxygen production was 5.4( +2.8 −1.6 ) mmol O 2 m −3 d −1 , similar at the beginning and end of the time-series, and likely peaked at the end of the ice melt period. Net oxygen production displayed more 5 temporal variability and the system was on average net autotrophic during ice melt and net heterotrophic following the ice melt.We performed the first field-based dual tracer release experiment in ice-covered water to quantify air-water gas exchange. The gas transfer velocity at >90 % ice cover was 6 % of the rate for nearly ice-free conditions. Published studies have shown a wide range of results for gas transfer velocity in the presence of ice, and this study indicates that gas transfer through ice is much slower than the rate of gas transfer through open water. The results also indicate that both primary producers and heterotrophs 10 are active in Whycocomagh Bay during spring while it is covered in ice.

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Revising Estimates of Aquatic Gross Oxygen Production by the Triple Oxygen Isotope Method to Incorporate the Local Isotopic Composition of Water

Cited by 14 publications

References 68 publications

Variations in Rates of Biological Production in the Beaufort Gyre as the Arctic Changes: Rates From 2011 to 2016

Variations in Rates of Biological Production in the Beaufort Gyre as the Arctic Changes: Rates From 2011 to 2016

Changes in gross oxygen production, net oxygen production, and air-water gas exchange during seasonal ice melt in Whycocomagh Bay, a Canadian estuary in the Bras d'Or Lake system

Changes in gross oxygen production, net oxygen production, and air-water gas exchange during seasonal ice melt in the Bras d'Or Lake, a Canadian estuary

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