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Example of the procedure to estimate GOP and CR from mission C on 29 March 2016. (A) Contour plot of the O 2 concentration with the depth of the base of the surface layer (Z SL , black line) used to define the depth range of the data to be averaged. (B) Time-series of O SL (red circles) and O bio (black circles), calculated by removing the contribution of air-sea fluxes from O SL . Solid line depicts the result of the fitting algorithm that estimated GOP = 1.33 AE 0.15 mmol m −3 d −1 and CR = 1.59 AE 0.14 mmol m −3 d −1 . The gray background in (B) represents the time of day between sunset and sunrise.
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Diel variations in oxygen concentration have been extensively used to estimate rates of photosynthesis and respiration in productive freshwater and marine ecosystems. Recent improvements in optical oxygen sensors now enable us to use the same approach to estimate metabolic rates in the oligotrophic waters that cover most of the global ocean and for...
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... an example of the procedure for deriving estimates of GOP and CR from glider measurements, we report the different steps for 29 March 2016, during glider mission C (Fig. 3). As described in a previous section, we started from vertically resolved O 2 measurements (Fig. 3A) and ended with a corrected surface layer O 2 time-series and the curve that approximates it (Fig. 3B, Supporting Information Table ...
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... an example of the procedure for deriving estimates of GOP and CR from glider measurements, we report the different steps for 29 March 2016, during glider mission C (Fig. 3). As described in a previous section, we started from vertically resolved O 2 measurements (Fig. 3A) and ended with a corrected surface layer O 2 time-series and the curve that approximates it (Fig. 3B, Supporting Information Table ...
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... procedure for deriving estimates of GOP and CR from glider measurements, we report the different steps for 29 March 2016, during glider mission C (Fig. 3). As described in a previous section, we started from vertically resolved O 2 measurements (Fig. 3A) and ended with a corrected surface layer O 2 time-series and the curve that approximates it (Fig. 3B, Supporting Information Table ...
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... a last point, the detection of residual autocorrelation from several of our fits may indicate that our model assumptions do not accurately reproduce the shape of diel O 2 variations. This might be related to the observation that the average rate of O 2 change is higher in the morning than in the afternoon (Fig. 3B) rather than being symmetrical around noon. We propose that at least two processes can cause this morning-enhanced O 2 increase: (1) higher photosynthetic efficiency in the morning than in the afternoon ( Doty and Oguri 1957;Lorenzen 1963) or (2) higher respiration rates during the afternoon due to the progressive accumulation of ...
Citations
... When the average water column relative abundance of 4000 m trap SASVs at a depth of 100 m was used as the log-log intercept (S Z = S 100 (Z/100) b ), the exponent b was −0.88 and R 2 decreased to 0.68. A few studies previously suggested that net community productivity (NCP) was negligible in the mixed layer of the NPSG 55,56 . The average mixed layer during 2014-2016 was located at 59 m as estimated by a density model 57 , and at 67 m by a temperature model 58 (https://hahana.soest.hawaii.edu/hot/hotdogs/mldepth.html). ...
A considerable amount of particulate carbon produced by oceanic photosynthesis is exported to the deep-sea by the “gravitational pump” (~6.8 to 7.7 Pg C/year), sequestering it from the atmosphere for centuries. How particulate organic carbon (POC) is transformed during export to the deep sea however is not well understood. Here, we report that dominant suspended prokaryotes also found in sinking particles serve as informative tracers of particle export processes. In a three-year time series from oceanographic campaigns in the Pacific Ocean, upper water column relative abundances of suspended prokaryotes entrained in sinking particles decreased exponentially from depths of 75 to 250 m, conforming to known depth-attenuation patterns of carbon, energy, and mass fluxes in the epipelagic zone. Below ~250 m however, the relative abundance of suspended prokaryotes entrained in sinking particles increased with depth. These results indicate that microbial entrainment, colonization, and sinking particle formation are elevated at mesopelagic and bathypelagic depths. Comparison of suspended and sinking particle-associated microbes provides information about the depth-variability of POC export and biotic processes, that is not evident from biogeochemical data alone.
... For each local day from August 23 to September 7, diel gross carbon productivity (GCP) and community respiration (CR) were computed from the Wirewalker POC estimate within the mixed layer using the linear diel method from Barone et al. (2019). The method described in Barone et al. (2019) models a phytoplankton diel cycle (growth and losses), according to an idealized solar radiation curve (based on latitude, longitude and year-day), and optimizes the fit between this model and the Wirewalker data from the ML. ...
... For each local day from August 23 to September 7, diel gross carbon productivity (GCP) and community respiration (CR) were computed from the Wirewalker POC estimate within the mixed layer using the linear diel method from Barone et al. (2019). The method described in Barone et al. (2019) models a phytoplankton diel cycle (growth and losses), according to an idealized solar radiation curve (based on latitude, longitude and year-day), and optimizes the fit between this model and the Wirewalker data from the ML. This method assumes that there is negligible input of POC from below the ML and that, over short (daily) timescales, variations due to advection of gradients in POC are small. ...
... The method therefore allows us to parse the rates of photosynthesis and respiration by modeling photosynthesis as a linear response to light intensity, E, and assuming that respiration is constant throughout the night and day. The optimized fit in the model provides an estimate of both GCP and CR, following Equation 3 in Barone et al. (2019): ...
New production (NP) and net community production (NCP) measurements are often used as estimates of carbon export potential from the mixed layer of the ocean, an important process in the regulation of global climate. Diverse methods can be used to measure NP and NCP, from research vessels, autonomous platforms, and remote sensing, each with its own set of benefits and uncertainties. The various methods are rarely applied simultaneously in a single location, limiting our ability for direct comparisons of the resulting measurements. In this study, we evaluated NP and NCP from thirteen independent datasets collected via in situ, in vitro, and satellite-based methods near Ocean Station Papa during the 2018 Northeast Pacific field campaign of the NASA project EXport Processes in the Ocean from RemoTe Sensing (EXPORTS). Altogether, the datasets indicate that carbon export potential was relatively low (median daily averages between −5.1 and 12.6 mmol C m−2 d−1), with most measurements indicating slight net autotrophy in the region. This result is consistent with NCP estimates based on satellite measurements of sea surface temperature and chlorophyll a. We explored possible causes of discrepancies among methods, including differences in assumptions about stoichiometry, vertical integration, total volume sampled, and the spatiotemporal extent considered. Results of a generalized additive mixed model indicate that the spatial variation across platforms can explain much of the difference among methods. Once spatial variation and temporal autocorrelation are considered, a variety of methods can provide consistent estimates of NP and NCP, leveraging the strengths of each approach.
... The quality of measurement that oxygen sensors can make is improving continuously (Mignot et al., 2019). Other Autonomous Underwater Vehicles (AUVs), such as Ocean gliders are now also routinely fitted with oxygen optodes (Barone et al., 2019). ...
... The rates of biological processes impacting oxygen in the Ocean can be estimated thanks to analytical advances in mass spectrometry, a technique through which dissolved gases such as oxygen (O 2 ), Nitrogen (N 2 ) and Argon (Ar) can be measured in seawater (Emerson et al., 1999). As Argon is not biologically active and is only impacted by physical mixing processes, the ratio of oxygen to Argon (O 2 :Ar) in seawater can be used to make estimates of respiration (Barone et al., 2019) and of net biological community production (the difference between gross photosynthesis, i.e. the overall photosynthesis before respiration, minus community respiration) (Teeter et al., 2018). The advent of ship-based methods for the continuous monitoring of gases dissolved in water (Membrane Inlet Mass Spectrometry) has allowed the simultaneous measurement of CO 2 and O 2 :Ar over basin scales (Guéguen & Tortell, 2008). ...
EMB Future Science Brief No. 10 highlights the most recent science on Ocean oxygen, including causes, impacts and mitigation strategies of Ocean oxygen loss, and discusses whether “every second breath we take comes from the Ocean”. It closes with key policy, management and research recommendations to address Ocean deoxygenation and communicate more accurately about the role of the Ocean in Earth’s oxygen.
... To provide constraints on the 14 CO 2 uptake-based estimates of GCP, gliders equipped with optodes were also used to estimate GCP (GCP g ) during the cruise period on waters near cruise RR1813. Mixed layer GCP g was estimated by fitting an idealized photosynthesis versus irradiance curve to observed diel cycles in dissolved oxygen measured by an Aanderaa 4831 oxygen optode from a UW APL Seaglider underwater glider (Nicholson et al., 2015;Barone et al., 2019). The diel approach is based on quantifying the daytime increase in O 2 due to photosynthesis and nighttime decrease due to respiration, which is assumed constant over each 24-h period. ...
Bacterioplankton play a central role in carbon cycling, yet their relative contributions to carbon production and removal can be difficult to constrain. As part of the Export Processes in the Ocean from RemoTe Sensing (EXPORTS) program, this study identifies potential influences of bacterioplankton community and dissolved organic matter (DOM) composition on carbon cycling at Ocean Station Papa in August 2018. Surface (5–35 m) bacterioplankton production rates and stocks spanned a 2- to 3-fold range over the 3-week cruise and correlated positively with the DOM degradation state, estimated using the mole proportion of total dissolved amino acids. When the DOM was more degraded, 16S rRNA gene amplicon data revealed a less diverse bacterioplankton community with a significant contribution from members of the Flavobacteriaceae family. Over the course of 7–10 d, as the DOM quality improved (became less degraded) and bacterioplankton productivity increased, the responding bacterioplankton community became more diverse, with increased relative contributions from members of the SAR86, SAR11 and AEGEAN-169 clades. The cruise mean for mixed layer, depth-integrated bacterioplankton carbon demand (gross bacterioplankton production) was 5.2 mmol C m−2 d−1, representing 60% of net primary production, where the difference between net primary production and bacterioplankton carbon demand was less than sinking flux at 50 m. The concentrations of dissolved organic carbon (cruise average of 58.5 µM C) did not exhibit a systematic change over the cruise period. Therefore, we hypothesize that carbon supplied from gross carbon production, values that were 2- to 3-fold greater than net primary production, provided the carbon necessary to account for the sinking flux and bacterioplankton carbon demand that were in excess of net primary production. These findings highlight the central contributions of bacterioplankton to carbon cycling at Ocean Station Papa, a site of high carbon recycling.
... For GPP calculations, multiple measurements per day are necessary to adequately resolve the diurnal cycle. Initially, GPP studies used a single profiling instrument, such as a glider (Nicholson et al., 2015;Barone et al., 2019), Lagrangian surface float , or biogeochemical profiling float whose mission cycle was adjusted for frequent upper ocean profiling (Barbieux et al., 2022;Gordon et al., 2020;Henderikx Freitas et al., 2020) (Fig. 3a,b). Gordon et al. (2020) and Barbieux et al. (2022), for example, used floats with profiling intervals of 3 and 6 140 hrs, respectively, to obtain diurnal cycle observations. ...
... A third approach for estimating GPP has been applied successfully using O2 observations from gliders (Nicholson et al., 2015;Barone et al., 2019), a rapidly profiling BGC-Argo float (Henderikx Freitas et al., 2020), and a composite of O2 and bbp-POC cycles from BGC-Argo floats (Johnson and Bif, 2021;Stoer and Fennel, 2022). In this method, introduced by Nicholson et al. 215 (2015), Eq. 2 is re-written to describe discrete, time-dependent changes in POC or O2 as a function of time-variable irradiance, Barone et al., 2019), and GPP and CR are approximated as the least squares coefficients required to fit ...
... A third approach for estimating GPP has been applied successfully using O2 observations from gliders (Nicholson et al., 2015;Barone et al., 2019), a rapidly profiling BGC-Argo float (Henderikx Freitas et al., 2020), and a composite of O2 and bbp-POC cycles from BGC-Argo floats (Johnson and Bif, 2021;Stoer and Fennel, 2022). In this method, introduced by Nicholson et al. 215 (2015), Eq. 2 is re-written to describe discrete, time-dependent changes in POC or O2 as a function of time-variable irradiance, Barone et al., 2019), and GPP and CR are approximated as the least squares coefficients required to fit ...
This paper provides an overview and demonstration of emerging float-based methods for quantifying gross primary production (GPP) and net community production (NCP) using Biogeochemical-Argo (BGC-Argo) float data. Recent publications have described GPP methods that are based on the detection of diurnal oscillations in upper ocean oxygen or particulate organic carbon concentrations using single profilers or a composite of BGC-Argo floats. NCP methods rely on budget calculations to partition observed tracer variations into physical or biological processes occurring over timescales greater than one day. Presently, multi-year NCP time-series are feasible at near-weekly resolution, using consecutive or simultaneous float deployments at local scales. Results, however, are sensitive to the choice of tracer used in the budget calculations and uncertainties in the budget parametrizations employed across different NCP approaches. Decadal, basin-wide GPP calculations are currently achievable using data compiled from the entire BGC-Argo array, but finer spatial and temporal resolution requires more float deployments to construct diurnal tracer curves. A projected, global BGC-Argo array of 1000 floats should be sufficient to attain annual GPP estimates at 10-degree latitudinal resolution, if floats profile at off-integer intervals (e.g., 5.2 or 10.2 days). Addressing the current limitations of float-based methods should enable enhanced spatial and temporal coverage of marine GPP and NCP measurements, facilitating global-scale determinations of the carbon export potential, training of satellite primary production algorithms, and evaluations of biogeochemical numerical models.
... For a recent review on the topic see Schuback et al. (2021). Dissolved oxygen measurements, derived from oxygen optode sensors on autonomous platforms, can be used to estimate and quantify photosynthesis and respiration rates (Addey, 2022), as well as to quantify gross oxygen production that can be used to constrain net PP estimates (Odum, 1956;Barone et al., 2019;Johnson and Bif, 2021). Johnson and Bif (2021) used diurnal oxygen cycles from BGC-Argo floats to estimate global net PP at 53 Gt C yr − 1 , by assuming a fixed ratio of net to gross PP (as many net PP methods do). ...
The ocean plays a central role in modulating the Earth’s carbon cycle. Monitoring how the ocean carbon cycle is changing is fundamental to managing climate change. Satellite remote sensing is currently our best tool for viewing the ocean surface globally and systematically, at high spatial and temporal resolutions, and the past few decades have seen an exponential growth in studies utilising satellite data for ocean carbon research. Satellite-based observations must be combined with in-situ observations and models, to obtain a comprehensive view of ocean carbon pools and fluxes. To help prioritise future research in this area, a workshop was organised that assembled leading experts working on the topic, from around the world, including remote-sensing scientists, field scientists and modellers, with the goal to articulate a collective view of the current status of ocean carbon research, identify gaps in knowledge, and formulate a scientific roadmap for the next decade, with an emphasis on evaluating where satellite remote sensing may contribute. A total of 449 scientists and stakeholders participated (with balanced gender representation), from North and South America, Europe, Asia, Africa, and Oceania. Sessions targeted both inorganic and organic pools of carbon in the ocean, in both dissolved and particulate form, as well as major fluxes of carbon between reservoirs (e.g., primary production) and at interfaces (e.g., air-sea and land–ocean). Extreme events, blue carbon and carbon budgeting were also key topics discussed. Emerging priorities identified include: expanding the networks and quality of in-situ observations; improved satellite retrievals; improved uncertainty quantification; improved understanding of vertical distributions; integration with models; improved techniques to bridge spatial and temporal scales of the different data sources; and improved fundamental understanding of the ocean carbon cycle, and of the interactions among pools of carbon and light. We also report on priorities for the specific pools and fluxes studied, and highlight issues and concerns that arose during discussions, such as the need to consider the environmental impact of satellites or space activities; the role satellites can play in monitoring ocean carbon dioxide removal approaches; economic valuation of the satellite based information; to consider how satellites can contribute to monitoring cycles of other important climatically-relevant compounds and elements; to promote diversity and inclusivity in ocean carbon research; to bring together communities working on different aspects of planetary carbon; maximising use of international bodies; to follow an open science approach; to explore new and innovative ways to remotely monitor ocean carbon; and to harness quantum computing. Overall, this paper provides a comprehensive scientific roadmap for the next decade on how satellite remote sensing could help monitor the ocean carbon cycle, and its links to the other domains, such as terrestrial and atmosphere.
... Seasonally, elevated temperature in late summer leads to outgassing and low surface oxygen (Figure 3a). At the daily scale, oxygen variability is dominated by photosynthesis and respiration, with rates that can be estimated from the shape of the diel oxygen variation (Barone et al., 2019). Using this method, we found that three-day average gross oxygen production (GOP) and community respiration (CR) were higher in late August/early September (Figure 3b). ...
Biogenic particles originating in the ocean’s well-lit, shallow layer help regulate Earth's climate by absorbing carbon dioxide from the atmosphere and subsequently sinking to the ocean’s depths. Subtropical gyres are the largest ocean habitats on Earth and are characterized by year-round high light, warm temperatures, and low supply of nutrients. However, even in persistently these low-nutrient regions, conditions vary on multiple temporal and spatial scales, making low-frequency observations—even monthly—difficult to interpret.
... The resulting daily pattern in these products is sinusoidal in shape and phase locked to the solar light cycle. One can infer GPP and CR by integrating the changes in these metabolites over a 24-h cycle (Siegel et al. 1989;Barone et al. 2019), assuming biological processes dominate, and respiration is constant throughout the day (see discussion in Barone et al. 2019). ...
... The resulting daily pattern in these products is sinusoidal in shape and phase locked to the solar light cycle. One can infer GPP and CR by integrating the changes in these metabolites over a 24-h cycle (Siegel et al. 1989;Barone et al. 2019), assuming biological processes dominate, and respiration is constant throughout the day (see discussion in Barone et al. 2019). ...
... We calculated GOP and GCP from the median daily cycles of ΔO 2 and C biomass, respectively, using the algorithm from Johnson and Bif (2021), which is a modified version of a previously published algorithm (Barone et al. 2019). The model assumes that CR is equal to GPP: ...
The dependence of net primary productivity (NPP), a central metric in ecology and biogeochemistry, on sunlight drives daily cycles in carbon biomass in the ocean's euphotic zone. In this study, we infer NPP from the daily cycle of biomass. These estimates were extracted from bio‐optical measurements collected by an array of robotic profilers distributed across temperate and polar regions of the southern hemisphere. We estimate NPP in the region south of 30°S as ~11.4 Pg C yr−1, and south of 50°S (the Southern Ocean) as ~4.6 Pg C yr−1. We obtain comparable estimates when complementary daily cycles of oxygen are used instead (11.7 and 3.5 Pg C yr−1). This approach will be valuable for providing the basin‐scale, ground‐truthed information necessary to assess changes in subsurface primary productivity related to climate.
... In recent years, autonomous platforms have been used to obtain productivity estimates based on diel signals using oxygen (Barone et al., 2019;Briggs et al., 2018;Johnson and Bif, 2021) and bio-optical estimates of particulate organic carbon , Loisel et al., 2011, White et al., 2017. These approaches are based on measuring changes over the diel period in the surface mixed layer and estimate the volumetric primary productivity (GPPV) averaged over the surface mixed layer. ...
... where C is a constant of integration. If the functional form of GPP is assumed (for example, to be linearly related to PAR), then the theoretical shape of a diel O2 curve can be statistically fit to observations to estimate the magnitude of GPP and CR as well as the uncertainty of each daily estimate (Barone et al., 2019). A statistical significance test to each daily estimate can help to filter out estimates contaminated by physical O2 fluxes. ...
In 2018, a working group sponsored by the NASA Plankton, Aerosol, Cloud, and ocean Ecosystem (PACE) project, in conjunction with the International Ocean Colour Coordinating Group (IOCCG), European Organization for the Exploitation of Meteorological Satellites (EUMETSAT), and Japan Aerospace Exploration Agency (JAXA), was assembled with the aim to develop community consensus on multiple methods for measuring aquatic primary productivity used for satellite validation and model synthesis. A workshop to commence the working group efforts was held December 5–7, 2018, at the University Space Research Association headquarters in Columbia, MD, USA, bringing together 26 active researchers from 16 institutions. In this document, we discuss and develop the workshop findings as they pertain to primary productivity measurements, including the essential issues, nuances, definitions, scales, uncertainties, and ultimately best practices for data collection across multiple methodologies.
... In recent years, autonomous platforms have been used to obtain productivity estimates based on diel signals using oxygen (Barone et al., 2019;Briggs et al., 2018;Johnson and Bif, 2021) and bio-optical estimates of particulate organic carbon , Loisel et al., 2011, White et al., 2017. These approaches are based on measuring changes over the diel period in the surface mixed layer and estimate the volumetric primary productivity (GPPV) averaged over the surface mixed layer. ...
... where C is a constant of integration. If the functional form of GPP is assumed (for example, to be linearly related to PAR), then the theoretical shape of a diel O2 curve can be statistically fit to observations to estimate the magnitude of GPP and CR as well as the uncertainty of each daily estimate (Barone et al., 2019). A statistical significance test to each daily estimate can help to filter out estimates contaminated by physical O2 fluxes. ...
The measurement of aquatic primary productivity (PP) is central to the quantitative understanding of the global biosphere, yielding critical insights into the role and magnitude of carbon, oxygen, and other bioactive element fluxes between the ocean, the geosphere, and the atmosphere. The accumulation of theoretical, methodological, and technological advances from this endeavor has led to the development of numerous approaches to measure oceanic PP, all with the common objective of quantifying the fluxes of reduced carbon into aquatic ecosystems. While these advances have furthered the understanding of carbon dynamics, from intracellular to global scales, it is notable that perhaps no single measurement in the suite of significant oceanographic observations exhibits as much methodological diversity and interpretive ambiguity
