A global coordination and continuous synthesis of interoperable data related to biogeochemical Essential Ocean Variables (EOVs) is critically needed to enhance the creation of information products and services to sustainably manage the climate system and ocean health. Among the existing biogeochemical EOVs, data synthesis products—which demonstrate the immense value of data coordination—already exist for carbon-relevant data (e.g. SOCAT, Global Ocean Data Analysis Project), and for methane and nitrous oxide (MEMENTO). The roadmap for building a Global Ocean Oxygen Database and ATlas (GO _2 DAT) (Grégoire et al (2021 Front. Mar. Sci. 1638 )) provides the theoretical basis to increase the interoperability of ocean oxygen data sets, without creating yet another separate repository. The goal is now to advance from the idea of GO _2 DAT to its implementation, building a sustainable, interoperable, and inclusive digital ecosystem for all stakeholders who may use ocean oxygen data. Successful implementation will require (I) the provision of guidance on data acquisition/ocean oxygen measurements, (II) recommended practices for ocean oxygen data management, including metadata requirements, uncertainty and data quality control attribution, (III) development of the ocean oxygen data platform including data flow and application of the recommended practices introduced in I and II, as well as its deep integration with cross-domain data federations such as the Ocean Data and Information System. This document provides an outline of GO _2 DAT’s objective and progress since 2021 and contributes to addressing these three requirements, synthesizing a series of global consultations on recommended practices for marine dissolved oxygen measurements, a working definition of ocean oxygen metadata, proposed data quality control levels and flags, a described novel mechanism for uncertainty attribution to allow the determination of data suitability for different scientific applications, and it concludes with an illustration of the data flow for implementation.

Marine oxygen deficient zones (ODZs) play a major role in the Earth's biogeochemical cycles and are responsible for nitrogen and sulfur removal from the oceans. Microbial-reducing reaction processes generate nitrite (NO2-) and sulfur compounds as intermediaries that may accumulate in these zones. Current assessments on microbial transformations inside ODZs are based on shipboard measurements, and there are no well-resolved seasonal to annual observations or high-resolution vertical sampling that would characterize variability. Here, we propose an alternative statistical approach to analyze the raw output of the nitrate sensor from BGC-Argo floats with the ability to detect NO2- and thiosulfate (S2O32-) concentrations in addition to nitrate. The new approach provides data with great vertical and spatiotemporal resolution. The method can be applied to UV-spectrometer output data from SUNAs and ISUS nitrate sensors commonly deployed on various observing platforms. We validated the technique in the field by matching shipboard NO2- bottle data with float data from the Eastern Tropical North Pacific (ETNP) and Eastern Tropical South Pacific (ETSP) ODZs. We then show a complete time series of three floats as study cases. The ability to detect NO2- and S2O32- concomitantly with other key chemical variables (i.e., oxygen, pH, and bio-optics) at such fine scale allows for novel insights into the nitrogen and sulfur cycling of ODZs and processes driving these cycles. This new approach will enable fine-scale remote quantification of NO2- and S2O32- to support a better understanding of the biogeochemical transformations happening inside these already-expanding deoxygenated regions.

Marine calcifying organisms on coral reefs face significant threats from various anthropogenic stressors. To better understand how these organisms will respond to a rapidly changing ocean, it is crucial to investigate their biomineralization across different reef environments. Despite their resilience and potential as conservation hotspots, turbid reefs—projected to expand throughout the 21st century—remain understudied, including a limited knowledge of biomineralization processes within these environments. Herein, for the first time, we assess the crystallographic and geochemical signatures of aragonite giant clam shells Tridacna squamosa from high and low turbid reefs in the Coral Triangle. Shell composition is strongly influenced by turbidity and biominerals formed in a high turbid reef show a more organized crystal orientation and significantly lower element-to-calcium ratios (magnesium/calcium, strontium/calcium). We hypothesize that these variations are driven by physiological changes related to the trophic flexibility of T. squamosa, utilizing both autotrophic and heterotrophic mechanisms. Observed differences may have implications for biomechanical and defense responses of shells, important in their ability to survive future change.

Seasonal patterns in seasonally frozen waters have usually been derived from composites of analyses conducted in different years and largely have been confined to ice-free periods. We present the first continuous measurements of hydrographic and biogeochemical variables collected over an entire year by Biogeochemical-Argo (BGC-Argo) profiling floats on the continental shelf of the Ross Sea. Analyses were divided into two periods: autumn/winter and spring/summer. Mixed layers increased rapidly upon ice cover, and nitrate, oxygen, and dissolved inorganic carbon vertical distributions were strongly influenced by this deeper mixing. Rates of nitrification in autumn were substantial and similar to rates measured in other areas of the ocean. Organic carbon disappearance was also most rapid in March. Changes in all variables slowed considerably after May. The largest mixed layer depths occurred at the southern floats and reached 400 - 500 m. Spring/summer patterns were similar to those observed during individual cruises, with rapid nitrate removal beginning in November, continuing through early January, but ceasing during austral summer. The most rapid accumulations of chlorophyll occurred prior to complete ice retreat. Substantial spatial differences were noted that were likely related to both mixed layer depths and phytoplankton composition. Particulate matter accumulated throughout the summer below 100 m, although the rates of change suggested substantial remineralization in the water column. The temporal patterns observed show the importance of relatively short periods that markedly influence the vertical distribution of biogeochemical parameters.

The ocean plays an essential role in regulating Earth’s climate, influencing weather conditions, providing sustenance for large populations, moderating anthropogenic climate change, encompassing massive biodiversity, and sustaining the global economy. Human activities are changing the oceans, stressing ocean health, threatening the critical services the ocean provides to society, with significant consequences for human well-being and safety, and economic prosperity. Effective and sustainable monitoring of the physical, biogeochemical state and ecosystem structure of the ocean, to enable climate adaptation, carbon management and sustainable marine resource management is urgently needed. The Argo program, a cornerstone of the Global Ocean Observing System (GOOS), has revolutionized ocean observation by providing real-time, freely accessible global temperature and salinity data of the upper 2,000m of the ocean (Core Argo) using cost-effective simple robotics. For the past 25 years, Argo data have underpinned many ocean, climate and weather forecasting services, playing a fundamental role in safeguarding goods and lives. Argo data have enabled clearer assessments of ocean warming, sea level change and underlying driving processes, as well as scientific breakthroughs while supporting public awareness and education. Building on Argo’s success, OneArgo aims to greatly expand Argo’s capabilities by 2030, expanding to full-ocean depth, collecting biogeochemical parameters, and observing the rapidly changing polar regions. Providing a synergistic subsurface and global extension to several key space-based Earth Observation missions and GOOS components, OneArgo will enable biogeochemical and ecosystem forecasting and new long-term climate predictions for which the deep ocean is a key component. Driving forward a revolution in our understanding of marine ecosystems and the poorly-measured polar and deep oceans, OneArgo will be instrumental to assess sea level change, ocean carbon fluxes, acidification and deoxygenation. Emerging OneArgo applications include new views of ocean mixing, ocean bathymetry and sediment transport, and ecosystem resilience assessment. Implementing OneArgo requires about $100 million annually, a significant increase compared to present Argo funding. OneArgo is a strategic and cost-effective investment which will provide decision-makers, in both government and industry, with the critical knowledge needed to navigate the present and future environmental challenges, and safeguard both the ocean and human wellbeing for generations to come.

Marine phytoplankton biomass and chlorophyll-a concentration are often estimated from pigment fluorescence measurements, which have become routine despite known variability in the fluorescent response for a given amount of chlorophyll-a. Here, we present a near-global, monthly climatology of chlorophyll-a fluorescence measurements from profiling floats combined with ocean color satellite estimates of chlorophyll-a concentration to illuminate seasonal biases in the fluorescent response and expand upon previously observed regional patterns in this bias. Global biases span over an order of magnitude, and can vary seasonally by a factor of 10. An independent estimate of chlorophyll-a from light attenuation shows similar global patterns in the chlorophyll-fluorescence bias when compared to biases derived from satellite estimates. Without accounting for these biases, studies or models using fluorescence-estimated chlorophyll-a will inherit the seasonal and regional biases described here. Global biases in chlorophyll-a data from fluorescence measurements can vary tenfold seasonally, according to analysis of data from biogeochemical profiling floats and ocean colour satellites.

Abstract Marine calcifying organisms on coral reefs are under threat from a range of anthropogenic stressors. Understanding their biomineralization pathways in different reef environments is key to unravelling their response to a rapidly changing ocean. Turbid reefs are forecast to increase throughout the 21st century and are resilient conservation hotspots, yet understudied due to a lack of information resolving biomineralization processes. Herein, for the first time, we assess the crystallographic and geochemical signatures of aragonite giant clam shells Tridacna squamosa from high and low turbid reefs in the Coral Triangle. Shell composition is strongly influenced by turbidity and biominerals formed in a high turbid reef show a more organized crystal orientation and significantly lower element-to-calcium ratios (Magnesium/Calcium, Strontium/Calcium). We hypothesize that these variations are driven by physiological changes related to the trophic flexibility of T. squamosa. Observed differences have implications for biomechanical and defence responses of shells, important in their ability to survive future change.

As global ocean monitoring programs and marine carbon dioxide removal methods expand, so does the need for scalable biogeochemical sensors. Currently, pH sensors are widely used to measure the ocean carbonate system on a variety of autonomous platforms. This paper assesses a commercially available optical pH sensor (optode) distributed by PyroScience GmbH for oceanographic applications. Results from this study show that the small, solid-state pH optode demonstrates a precision of 0.001 pH and relative accuracy of 0.01 pH using an improved calibration routine outlined in the manuscript. A consistent pressure coefficient of 0.029 pH/1000 dbar is observed across multiple pH optodes tested in this study. The response time is investigated for standard and fast-response versions over a range of temperatures and flow rates. Field deployments include direct comparison to ISFET-based pH sensor packages for both moored and profiling platforms where the pH optodes experience sensor-specific drift rates up to 0.006 pH d-1. In its current state, the pH optode potentially offers a viable and scalable option for short-term field deployments and laboratory mesocosm studies, but not for long term deployments with no possibility for recalibration like on profiling floats.

The strength and variability of the Southern Ocean carbon sink is a significant source of uncertainty in the global carbon budget. One barrier to reconciling observations and models is understanding how synoptic weather patterns modulate air-sea carbon exchange. Here, we identify and track storms using atmospheric sea level pressure fields from reanalysis data to assess the role that storms play in driving air-sea CO2 exchange. We examine the main drivers of CO2 fluxes under storm forcing and quantify their contribution to Southern Ocean annual air-sea CO2 fluxes. Our analysis relies on a forced ocean-ice simulation from the Community Earth System Model, as well as CO2 fluxes estimated from Biogeochemical Argo floats. We find that extratropical storms in the Southern Hemisphere induce CO2 outgassing, driven by CO2 disequilibrium. However, this effect is an order of magnitude larger in observations compared to the model and caused by different reasons. Despite large uncertainties in CO2 fluxes and storm statistics, observations suggest a pivotal role of storms in driving Southern Ocean air-sea CO2 outgassing that remains to be well represented in climate models, and needs to be further investigated in observations.

Here we used data from six BGC-floats deployed in the southeast Pacific and southwest Atlantic Oceans, within the Southern Ocean's Subtropical Zone, to assess the seasonality of particulate organic carbon production from phytoplankton (POCphyto) and estimate POC transfer efficiencies at 100 m below the euphotic zone (T_100). While small particles <100 μM dominated the mixed layer, large particles >100 μM comprised a significant fraction of POCphyto below the mixed layer in both areas, possibly due to a "shade flora" composed by large diatoms. POCphyto was highly seasonal with highest biomass accumulation in the Atlantic side for both small and large particles. In the Pacific, the seasonal change in small particle production ΔPOCphyto was ∼66 mg m−2 versus ∼54 mg m−2 from large particles. In the Atlantic, ΔPOCphyto was ∼852 mg m−2 for small particles versus ΔPOCphyto ∼ 262 mg m−2 for large particles. Monthly T_100s in the Pacific ranged from 76% to 92% with maximum efficiencies during the deepening of the mixed layer depth. In the Atlantic, T_100s ranged from 43% to 76% with two periods of high T_100s: the first coinciding with the decline of large particles from the "shade flora", and the second coinciding with the deepening of the mixed layer during elevated small particle production.

Limnology and Oceanography BulletinEarly View Member News Kenneth Hamilton Coale (1955–2022): The Life and Times of a Left Coast Marine Scientist David L. Garrison, Corresponding Author David L. Garrison david_garrison@verizon.net orcid.org/0000-0002-1167-3249 National Science Foundation, Retired, Alexandria, VASearch for more papers by this authorKenneth S. Johnson, Kenneth S. Johnson johnson@mbari.org orcid.org/0000-0001-5513-5584 Monterey Bay Aquarium Research Institute, Moss Landing, CASearch for more papers by this author David L. Garrison, Corresponding Author David L. Garrison david_garrison@verizon.net orcid.org/0000-0002-1167-3249 National Science Foundation, Retired, Alexandria, VASearch for more papers by this authorKenneth S. Johnson, Kenneth S. Johnson johnson@mbari.org orcid.org/0000-0001-5513-5584 Monterey Bay Aquarium Research Institute, Moss Landing, CASearch for more papers by this author First published: 07 December 2022 https://doi.org/10.1002/lob.10533Read the full textAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat Early ViewOnline Version of Record before inclusion in an issue RelatedInformation

Ocean acidification has potentially large impacts on calcifying organisms and ecosystems. Argo floats equipped with biogeochemical (BGC) sensors have been continuously measuring Southern Ocean pH since 2014. These BGC-Argo floats were deployed as part of the Southern Ocean Carbon and Climate Observations and Modeling project. Here we present a SOCCOM-era Objectively Mapped pH (SOM-pH) 2014-2019 climatology and explain the method for constructing this product. We show example SOM-pH fields demonstrating the spatial and temporal structure of Southern Ocean pH. Comparison with previous ship-based measurements reveals decreases in pH of up to 0.02 per decade, with a structure decaying with depth. An assessment of the trend structure reveals a pattern indicative of the meridional overturning circulation. Upwelling waters that have not been in recent contact with the atmosphere show negligible or small trends, while surface and downwelling waters that have had more exposure to the atmosphere show the strongest trends. Thus comparison of this new BGC-Argo mapped pH estimate to historic observations allows quantifying the structure of Southern Ocean acidification.

The Southern Ocean serves as the primary gateway through which the intermediate, deep, and bottom waters of the ocean interact with the surface ocean (and thus the atmosphere), and it has a profound influence on the oceanic uptake of anthropogenic carbon and heat as well as nutrient resupply from the abyss to the surface. Yet it has been the least observed and understood region of the world ocean. The Southern Ocean Carbon and Climate Observations and Modeling (SOCCOM) project was implemented in 2014 with a goal to help remedy this deficit in observations and understanding. The SOCCOM project is based on two major advances that have the potential to transform understanding of the Southern Ocean. The first is the development of new biogeochemical sensors mounted on autonomous profiling floats that allow sampling of ocean biogeochemistry in 3-dimensional space. Floats may detect processes with a temporal resolution that ranges from hours to years. The second is that the climate modeling community finally has the computational resources and physical understanding to develop fully coupled climate models that can represent crucial, mesoscale processes in the Southern Ocean, as well as corresponding models that assimilate observations to produce a state estimate. The observational component, based on deployment of profiling floats with oxygen, nitrate, pH and bio-optical sensors, is generating vast amounts of new biogeochemical data that provide a year-round view of the Southern Ocean from the surface to 2000 m. The modeling effort is applying these observations and enhancing our understanding of the current ocean, and reducing uncertainty in projections of future carbon and nutrient cycles and climate. After nine years of operation, including a project renewal in the sixth year, the SOCCOM project has deployed more than 260 profiling floats. These floats have collected over 27,000 vertical profiles throughout the Southern Ocean. A data assimilating biogeochemical state estimate model has been implemented. Here, the design of the SOCCOM project is reviewed and the scientific results that have been obtained are described. The project's capability to help meet the observing system priorities outlined for a notional UN Decade for Ocean Sciences Southern Ocean observing system is assessed.

The impacts of climate change are becoming more evident in recent years. Future projections suggest that heat stress events will likely be more frequent and severe over the next century, threatening the high diversity of the Coral Triangle. Shallow turbid reefs may help dampen some of these effects as several studies have shown their inherent resilience to heat stress events. Therefore, our main goal was to test this hypothesis by assessing the response of corals to the heat stress event of 2020. We conducted bleaching surveys in two contrasting habitats in Darvel Bay, Sabah: the turbid reef of Sakar, and the clear-water reef of Blue Lagoon. Relatively high coral cover (40-43%) was observed on both reefs in 2019. Underwater data loggers were used to monitor temperature and light. Coral colonies were scored from video transects of 100 m at 5 m and 10 m depth in both localities, with an additional transect at 15 m depth in Blue Lagoon. A total of 1326 coral colonies were evaluated for bleaching presence and bleaching severity based on the six-point scoring method. Bleaching severity varied significantly between both reefs. Low bleaching impacts were observed in the high turbid reef, with an average of 9.6% of colonies having bleached. Meanwhile, the clear-water reef of Blue Lagoon had an average of 37.1% of coral colonies affected by bleaching. Bleaching severity also varied significantly among depth, where corals in deeper depths bleached less in Blue Lagoon. Foliose coral forms were most affected in Blue Lagoon, while massive coral forms suffered the most in Sakar reef. Bleaching responses were also significantly different among coral genera. While Ctenactis and Herpolitha were consistently resistant in both reefs, Leptoseris, Fungia and Goniopora were most affected in the 5 m of Blue Lagoon. Meanwhile, Pachyseris was notably more affected in Sakar reef at 10 m than in Blue Lagoon. Overall, bleaching indices within these two reefs are lower than most that were assessed around the globe during heat stress events in 2020. These outcomes support the hypothesis of turbid reefs hosting resilient coral communities in the face of climate change.

Biogeochemical- (BGC-) Argo aims to deploy and maintain a global array of autonomous profiling floats to monitor ocean biogeochemistry. With over 250,000 profiles collected so far, the BGC-Argo network is rapidly expanding toward the target of a sustained fleet of 1,000 floats. These floats prioritize the measurement of six key properties: oxygen, nitrate, pH, chlorophyll-a, suspended particles, and downwelling light. To assess the current biogeochemical state of the ocean, its variability, and trends with confidence, it is crucial to quality control these measurements. Accordingly, BGC-Argo maintains a quality control system using manual inspection and parameter-specific algorithms for flagging and adjusting data. In this study, we provide a census of the quantity and quality of measurements from BGC-Argo based on their quality flagging system. The purpose of this census is to assess the current status of the array in terms of data quality, how data quality has changed over time, and to provide a better understanding of the quality-controlled data to current and future users. Alongside increasing profile numbers and spatial coverage, we report that for most parameters between 80 and 95% of the profiles collected so far contain high-quality BGC data, with an exception for pH. The quality of pH profiles has seen a large improvement in the last five years and is on track to match the data quality of other BGC parameters. We highlight how BGC-Argo is improving and discuss strategies to increase the quality and quantity of BGC profiles available to users. This census shows that tracking percentages of high-quality data through time is useful for monitoring float sensor technology and helpful for ensuring the long-term success of BGC-Argo.

Sensors that use ultraviolet (UV) light absorption to measure nitrate in seawater at in situ temperatures require a correction to the calibration coefficients if the calibration and sample temperatures are not identical. This is mostly due to the bromide molecule, which absorbs more UV light as temperature increases. The current correction applied to in situ ultraviolet spectrophotometer (ISUS) and submersible ultraviolet nitrate analyzer (SUNA) nitrate sensors generally follows Sakamoto et al. (2009, Limnol. Oceanogr. Methods 7, 132-143). For waters warmer than the calibration temperature, this correction model can lead to a 1-2 & mu;mol kg(-1) positive bias in nitrate concentration. Here we present an updated correction model, which reduces this small but noticeable bias by at least 50%. This improved model is based on additional laboratory data and describes the temperature correction as an exponential function of wavelength and temperature difference from the calibration temperature. It is a better fit to the experimental data than the current model and the improvement is validated using two populations of nitrate profiles from Biogeochemical Argo floats navigating through tropical waters. One population is from floats equipped with ISUS sensors while the other arises from floats with SUNA sensors on board. Although this model can be applied to both ISUS and SUNA nitrate sensors, it should not be used for OPUS UV nitrate sensors at this time. This new approach is similar to that used for OPUS sensors (Nehir et al., 2021, Front. Mar. Sci. 8, 663800) with differing model coefficients. This difference suggests that there is an instrumental component to the temperature correction or that there are slight differences in experimental methodologies.

The deep ocean releases large amounts of old, pre-industrial carbon dioxide (CO2) to the atmosphere through upwelling in the Southern Ocean, which counters the marine carbon uptake occurring elsewhere. This Southern Ocean CO2 release is relevant to the global climate because its changes could alter atmospheric CO2 levels on long time scales, and also affects the present-day potential of the Southern Ocean to take up anthropogenic CO2. Here, year-round profiling float measurements show that this CO2 release arises from a zonal band of upwelling waters between the Subantarctic Front and wintertime sea-ice edge. This band of high CO2 subsurface water coincides with the outcropping of the 27.8 kg m(-3) isoneutral density surface that characterizes Indo-Pacific Deep Water (IPDW). It has a potential partial pressure of CO2 exceeding current atmospheric CO2 levels ( increment PCO2) by 175 +/- 32 mu atm. Ship-based measurements reveal that IPDW exhibits a distinct increment PCO2 maximum in the ocean, which is set by remineralization of organic carbon and originates from the northern Pacific and Indian Ocean basins. Below this IPDW layer, the carbon content increases downwards, whereas increment PCO2 decreases. Most of this vertical increment PCO2 decline results from decreasing temperatures and increasing alkalinity due to an increased fraction of calcium carbonate dissolution. These two factors limit the CO2 outgassing from the high-carbon content deep waters on more southerly surface outcrops. Our results imply that the response of Southern Ocean CO2 fluxes to possible future changes in upwelling are sensitive to the subsurface carbon chemistry set by the vertical remineralization and dissolution profiles.

Measurements of pH and nitrate from the Southern Ocean Carbon and Climate Observations and Modeling array of profiling floats were used to assess the ratios of dissolved inorganic carbon (DIC) and nitrate (NO3) uptake during the spring to summer bloom period throughout the Southern Ocean. Two hundred and forty-three bloom periods were observed by 115 floats from 30 degrees S to 70 degrees S. Similar calculations were made using the Takahashi surface DIC and nitrate climatology. To separate the effects of atmospheric CO2 exchange and mixing from phytoplankton uptake, the ratios of changes in DIC to nitrate of surface waters (Delta DIC/Delta NO3) were computed in the Biogeochemical Southern Ocean State Estimate (B-SOSE) model. Phytoplankton uptake of DIC and nitrate are fixed in B-SOSE at the Redfield Ratio (RR; 6.6 mol C/mol N). Deviations in the B-SOSE Delta DIC/Delta NO3 must be due to non-biological effects of CO2 gas exchange and mixing. Delta DIC/Delta NO3 values observed by floats and in the Takahashi climatology were corrected for the non-biological effects using B-SOSE. The corrected, in situ biological uptake ratio (C:N) occurs at values similar to the RR, with two major exceptions. North of 40 degrees S biological DIC uptake is observed with little or no change in nitrate giving high C:N. In the latitude band at 55 degrees S, the Takahashi data give a low C:N value, while floats are high. This may be due to a change in CO2 air-sea exchange in this region from uptake during the Takahashi reference year of 2005 to outgassing of CO2 during the years sampled by floats.