Productivity diagnosed from the diel cycle of particulate carbon in the North Pacific Subtropical Gyre

White, Angelicque E.; Barone, Benedetto; Letelier, Ricardo M.; Karl, David M.

doi:10.1002/2016gl071607

Cited by 38 publications

(58 citation statements)

References 57 publications

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“…Moreover, the derived diazotrophic growth rate of

0.5 \pm 0.25 {normald}^{- 1}

for this size fraction is consistent with estimates from laboratory cultures of 0.67 d −1 and

0.77 {normald}^{- 1}

for DDAs (Villareal ) and is expected to be lower due to the Trichodesmium in our samples (maximum growth rates 0.3 d −1 , Breitbarth et al ). Comparing C based stocks and rates, we find that (1) the concentration of total PC measured from the ships flow‐through systems (

3.4 \pm 0.6

μmol L −1 ) is consistent with PC measured from CTD‐rosette collections at 5 m (

3.8 \pm 0.8

μmol L −1 , n = 4), and (2) the average carbon in the 20–200 μ m size‐fraction (200 nmol L −1 ) accounts for 6% of total PC, a value within the range of the contribution of large diazotrophs to total suspended PC at Station ALOHA, 6–11% as per (Letelier and Karl ) and last (3) the mean diazotrophic C fixation rates estimated here, 100 ± 50 nmol C L −1 d −1 , are 7–8% of 14 C based C fixation rates from this same cruise (16.1 ± 1.5 mg C m −3 d −1 , White et al ), a contribution again consistent with inputs via large diazotrophs measured by (Letelier and Karl ) on the order of 5%. We recognize the large ranges in some of this data, but find it important that none of it falsifies our results.…”

Section: Resultssupporting

confidence: 66%

“…This source water was pre-filtered through 200 lm Nitex mesh in order to exclude grazers. This mesh also excludes large colonies of nitrogen fixers, but, at least for Trichodesmium, this effect is expected to be small ($ 6% of the total; White et al 2018). Water was then fed through a plankton net with 20 lm mesh net and cod-end.…”

Section: Field Data Collectionmentioning

confidence: 99%

“…Biogeochemical rates can also be effectively estimated from noninvasive in situ measurements if sufficient changes exist relative to the inherent spatial variability of the variable in question. This approach has been used to estimate community production from the diel change in optically derived particulate carbon (PC), which reflects net particle growth during the day and net particle loss at night (Stramska and Dickey ; Walsh et al ; Claustre et al ; White et al ). The diel cycle of nitrate has also been used to diagnose new production (Johnson et al ) and growth rates of specific planktonic groups have been estimated from diurnal changes in their cell size (Olson et al ; Sosik et al ; Lomas et al ; Hunter‐Cevera et al ; McInnes et al ; Ribalet et al ).…”

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confidence: 99%

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Nitrogen fixation rates diagnosed from diurnal changes in elemental stoichiometry

Follett

White

Wilson

et al. 2018

Limnology & Oceanography

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The carbon, nitrogen, and phosphorus (C, N, and P, respectively) composition and elemental ratios were measured in the 20–200 μm size fraction during July 2015 in the surface waters of an anticyclonic eddy encountered north of Hawaii in the oligotrophic North Pacific Subtropical Gyre. The observed particulate N : P ratio fluctuated by approximately a factor of two over the diel cycle. We present a simple mathematical argument connecting this change to a rate of biological nitrogen fixation, and calculate the nitrogen fixation rate to be ≥ 13 nmol L−1 d−1 for this size class. This value is higher than simultaneous bottle‐incubation based rates measured with isotopic tracers, yet is consistent with historic rate measurements from the region. As confirmation of our methods, diurnal changes in C : N : P of laboratory cultures of the diazotrophic genus Trichodesmium were measured. In the laboratory, we show that estimates of nitrogen fixation from stoichiometric time series are equivalent to those derived directly from mass balance. The disparity between nitrogen fixation rates derived from tracer measurements and particulate stoichiometry in the field suggests that large diazotrophs may be underestimated in small volume (∼ 4 L) bottle incubations as a result of either spatial heterogeneity or vertical migration of large cells. Otherwise, processes other than diazotrophy must cause the observed changes in stoichiometry. This approach represents a novel and scalable means of quantifying in situ nitrogen fixation rates from diurnal changes in size‐fractionated stoichiometry. We also infer carbon fixation, growth rates, and phosphorus uptake in the 20–200 μm size class.

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“…Moreover, the derived diazotrophic growth rate of

0.5 \pm 0.25 {normald}^{- 1}

for this size fraction is consistent with estimates from laboratory cultures of 0.67 d −1 and

0.77 {normald}^{- 1}

3.4 \pm 0.6

μmol L −1 ) is consistent with PC measured from CTD‐rosette collections at 5 m (

3.8 \pm 0.8

Section: Resultssupporting

confidence: 66%

Section: Field Data Collectionmentioning

confidence: 99%

mentioning

confidence: 99%

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Nitrogen fixation rates diagnosed from diurnal changes in elemental stoichiometry

Follett

White

Wilson

et al. 2018

Limnology & Oceanography

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“…High temporal resolution surface water sampling of dissolved Zn (circles, top panel) and dissolved Fe (circles, bottom panel) compared against changes to the mixed layer depth (solid line, top panel; Wilson et al, 2017) and against particulate organic carbon concentration (solid line, bottom panel; White et al, 2017) in the bottom panel.…”

Section: Discussionmentioning

confidence: 99%

A Lagrangian View of Trace Elements and Isotopes in the North Pacific

et al. 2020

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Ocean time‐series sites are influenced by both temporal variability, as in situ conditions change, as well as spatial variability, as water masses move across the fixed observation point. To remove the effect of spatial variability, this study made sub‐daily Lagrangian observations of trace elements and isotopes (Al, Sc, Mn, Fe, Co, Ni, Cu, Zn, Cd, Pb, 232Th, and 230Th) in surface water over a 12‐day period (July–August 2015) in the North Pacific near the Hawaii Ocean Time‐series Station ALOHA. Additionally, a vertical profile in the upper 250 m was analyzed. This dataset is intercalibrated with GEOTRACES standards and provides a consistent baseline for trace element studies in the oligotrophic North Pacific. No diel changes in trace elements could be resolved, although day‐to‐day variations were resolved for some elements (Fe, Cu, and Zn), which may be related to organic matter cycling or ligand availability. Pb concentrations remained relatively constant during 1997–2015, presenting a change from previous decreases. Nutrient to trace element stoichiometric ratios were compared to those observed in phytoplankton as an indication of the extent of biological trace element utilization in this ecosystem, providing a basis for future ecological trace element studies.

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“…3a). Relative to the drifter 1 site, diel cycles in ∆O2/Ar and POC were more closely coupled, while phytoplankton biomass (Cph) In the absence of significant POC sinking and net loss to the dissolved organic carbon (DOC) pool, NCPPOC should approximate NCPO2/Ar (Claustre et al, 2007;White et al, 2017).…”

Section: Discussionmentioning

confidence: 99%

Decoupling of net community production and particulate organic carbon dynamics in near shore surface ocean waters

Rosengard

Izett

Burt

et al. 2019

Preprint

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Abstract. We report results from two Lagrangian surveys off the coast of Oregon, using continuous ship-board sensors to estimate mixed layer net community production (NCP) from diel cycles in biological oxygen saturation (∆O2 / Ar) and optically-derived estimates of particulate organic carbon (POC) and phytoplankton carbon (Cph). The first drifter survey, conducted in a nearshore upwelling zone during the development of a microplankton bloom, exhibited significant differences in NCP derived from ∆O2 / Ar and POC diel cycles, suggesting the presence of large POC losses from the mixed layer. At this site, we utilized the discrepancy between NCPO2 / Ar and NCPPOC, along with additional constraints derived from mixed layer nutrient inventories and surface water excess nitrous oxide (N2O), to estimate particle export, vertical mixing fluxes and DOC production. We estimate that export, vertical mixing and DOC production account for 13–45 %, 24–38 % and 25–49 % of the daily NCP discrepancy, respectively. In contrast, the second drifter survey occurred in more oligotrophic offshore waters, where NCP derived from ∆O2 / Ar and POC measurements were more closely coupled, suggesting a tighter relationship between production and community respiration. These results support the use of diel POC measurements to accurately estimate NCP in lower productivity waters with limited vertical carbon export. Although diel POC measurements may underestimate NCP in higher productivity waters, our results highlight the potential utility of coupled O2 and optical measurements to estimate the fate of POC in such regions.

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Productivity diagnosed from the diel cycle of particulate carbon in the North Pacific Subtropical Gyre

Cited by 38 publications

References 57 publications

Nitrogen fixation rates diagnosed from diurnal changes in elemental stoichiometry

Nitrogen fixation rates diagnosed from diurnal changes in elemental stoichiometry

A Lagrangian View of Trace Elements and Isotopes in the North Pacific

Decoupling of net community production and particulate organic carbon dynamics in near shore surface ocean waters

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