A Global Ocean Oxygen Database and Atlas for Assessing and Predicting Deoxygenation and Ocean Health in the Open and Coastal Ocean

Grégoire, Marilaure; Garçon, Véronique; Garcia, Hernan E.; Breitburg, Denise L.; Isensee, Kirsten; Oschlies, Andreas; Telszewski, Maciej; Barth, Alexander; Bittig, Henry C.; Carstensen, Jacob; Carval, Thierry; Chai, Fei; Chávez, Francisco P.; Conley, Daniel J.; Coppola, Laurent; Crowe, Sean A.; Currie, Kim; Dai, Minhan; Deflandre, Bruno; Dewitte, Boris; Díaz, Robert J.; García‐Robledo, Emilio; Gilbert, Denis; Giorgetti, Alessandra; Glud, Ronnie N.; Gutiérrez, Dimitri; Hosoda, Shigeki; Ishii, Masao; Jacinto, Gil S.; Langdon, Chris; Lauvset, Siv K.; Levin, Lisa A.; Limburg, Karin E.; Mehrtens, Hela; Montès, Ivonne; Naqvi, Wajih; Paulmier, Aurélien; Pfeil, Benjamin; Pitcher, Grant C.; Pouliquen, Sylvie; Rabalais, Nancy N.; Rabouille, Christophe; Recape, Virginie; Roman, Michael R.; Rose, Kenneth A.; Rudnick, Daniel L.; Rummer, Jodie L.; Schmechtig, Catherine; Schmidtko, Sunke; Seibel, Brad A.; Slomp, Caroline P.; Sumalia, U. Rashid; Tanhua, Toste; Thierry, Virginie; Uchida, Hiroshi; Wanninkhof, Rik; Yasuhara, Moriaki

doi:10.3389/fmars.2021.724913

Cited by 44 publications

(37 citation statements)

References 202 publications

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“…Most oxygen sensors, including the SBE43, suffer from a background signal in the absence of oxygen. Since Winkler titrations also suffer from artefacts at low oxygen concentrations, these cannot be used for calibration (Greǵoire et al, 2021). Here, we assume that oxygen was absent from the water when oxygen concentrations were low and the profile became a vertical line.…”

Section: Study Areamentioning

confidence: 99%

Pathways of methane removal in the sediment and water column of a seasonally anoxic eutrophic marine basin

et al. 2023

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Methane (CH4) is a key greenhouse gas. Coastal areas account for a major proportion of marine CH4 emissions. Eutrophication and associated bottom water hypoxia enhance CH4 production in coastal sediments. Here, we assess the fate of CH4 produced in sediments at a site in a seasonally anoxic eutrophic coastal marine basin (Scharendijke, Lake Grevelingen, the Netherlands) in spring (March) and late summer (September) in 2020. Removal of CH4 in the sediment through anaerobic oxidation with sulfate (SO42-) is known to be incomplete in this system, as confirmed here by only slightly higher values of δ13C-CH4 and δD-CH4 in the porewater in the shallow sulfate-methane-transition zone (~5-15 cm sediment depth) when compared to deeper sediment layers. In March 2020, when the water column was fully oxygenated, CH4 that escaped from the sediment was at least partially removed in the bottom water through aerobic oxidation. In September 2020, when the water column was anoxic below ~35 m water depth, CH4 accumulated to high concentrations (up to 73 µmol L-1) in the waters below the oxycline. The sharp counter gradient in oxygen and CH4 concentrations at ~35 m depth and increase in δ13C-CH4 and δD-CH4 above the oxycline indicate mostly aerobic water column removal of CH4. Water column profiles of particulate and dissolved Fe and Mn suggest redox cycling of both metals at the oxycline, pointing towards a potential role of metal oxides in CH4 removal. Water column profiles of NH4+ and NO3- indicate removal of both solutes near the oxycline. Analyses of 16S rRNA gene sequences retrieved from the water column reveal the presence of aerobic CH4 oxidizing bacteria (Methylomonadaceae) and anaerobic methanotrophic archaea (Methanoperedenaceae), with the latter potentially capable of NO3- and/or metal-oxide dependent CH4 oxidation, near the oxycline. Overall, our results indicate sediment and water column removal of CH4 through a combination of aerobic and anaerobic pathways, which vary seasonally. Some of the CH4 appears to escape from the surface waters to the atmosphere, however. We conclude that eutrophication may make coastal waters a more important source of CH4 to the atmosphere than commonly assumed.

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Section: Study Areamentioning

confidence: 99%

Pathways of methane removal in the sediment and water column of a seasonally anoxic eutrophic marine basin

et al. 2023

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“…In fact, several historical massive fish and crustacea mortality events were recorded in the study area (Hernandez-Miranda et al, 2010;Hernandez-Miranda et al, 2012). Recently, an analysis from reports and monitoring by the National Fisheries and Aquaculture Service (SERNAPESCA) over the last 15 years (2006)(2007)(2008)(2009)(2010)(2011)(2012)(2013)(2014)(2015)(2016)(2017)(2018)(2019)(2020)(2021) has suggested that most massive fish mortally events occur during events of dominant south or southwest winds (i.e. with a significant equatorward component), These mass mortality events have intensified on the central Chilean coast, especially in small pelagic fish (anchoveta and sardine) and crustaceans (Sepúlveda, 2022).…”

Section: Impact and Risks Of Hypoxiamentioning

confidence: 99%

The intensification of coastal hypoxia off central Chile: Long term and high frequency variability

Maza

2023

Front. Earth Sci.

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Hypoxia is a phenomenon where dissolved oxygen (DO) is reduced to levels that are low enough to strongly affect ecological and biogeochemical processes. This occurs within the continental shelf off central Chile (36°S), influenced by seasonal coastal upwelling (Spring-Summer). Monthly measurements of DO and other oceanographic variables in the water column (1997−2021) over the 92 m isobath along with high-resolution and near-surface observations (POSAR buoy), are analyzed to examine incidences of hypoxia and understand the physical and biogeochemical processes modulating DO vertical distribution and its temporal variability. On average, the percentage of the water column with DO levels below 89 (hypoxia) and 22 (severe hypoxia) μmol L−1 reaches 68% (i.e., hypoxic waters are found below 30 m) and 44% (below 50 m depth), respectively, but during the upwelling season, as much as 87% (below 12 m depth) and 81% (below 17 m depth) of the water column exhibits these levels. On the sub-seasonal scale during upwelling season six hypoxic events lasting at least 2 days occur at 10 m depth. There is a strong seasonal correlation between the volume of the seawater presenting hypoxia and upwelling favorable winds. Furthermore, there is a high DO interannual variability partially related to the El Niño Southern Oscillation (ENSO). Over 2 decades, it is estimated that DO concentration in surface and subsurface layers decreases (up to 21 μmol L−1 decade−1) as waters get colder (up to 0.29°C decade−1). Remarkably, the volume of hypoxic and severe hypoxic waters over the shelf has increased more than 2 times since 1997 and shows a significant positive correlation with the upwelling index. These preliminary findings indicate that the increase in local DO consumption is partially associated with upwelling intensification. Given the clear evidence of wind intensification in coastal upwelling ecosystems and thus the increase in hypoxic events, the coastal zone may be highly vulnerable to hypoxia, impacting biological resources and biogeochemical cycles.

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“…Any data loss can be felt in a lack of representativeness of the pandemic years within the overall time period mean, as well as a delay in the accumulation of sufficient data to document global time variations. For ocean dissolved oxygen, global inventory time series are in the research stage (Ito et al, 2017;Grégoire et al, 2021). Operationalizing in situ global dissolved oxygen monitoring will be dependent on the proliferation of BGC Argo and other independent platforms with oxygen sensors and the quality assessment of this sensor data through high quality research cruise data, all of which were affected by the pandemic.…”

Section: Effects Of the Pandemic On Other Ocean Ecvsmentioning

confidence: 99%

Effects of the Pandemic on Observing the Global Ocean

Boyer

Zhang

O’Brien

et al. 2023

Bulletin of the American Meteorological Society

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The years since 2000 have been a golden age in in situ ocean observing with the proliferation and organization of autonomous platforms such as surface drogued buoys and subsurface Argo profiling floats augmenting ship-based observations. Global time series of mean sea surface temperature and ocean heat content are routinely calculated based on data from these platforms, enhancing our understanding of the ocean’s role in the Earth’s climate system. Individual measurements of meteorological, sea surface and subsurface variables directly improve our understanding of the Earth System, weather forecasting, and climate projections. They also provide the data necessary for validating and calibrating satellite observations. Maintaining this ocean observing system has been a technological, logistical, and funding challenge. The global COVID-19 pandemic, which took hold in 2020, added strain to the maintenance of the observing system. A survey of the contributing components of the observing system illustrates the impacts of the pandemic from January 2020 through December 2021. The pandemic did not reduce the short-term geographic coverage (days to months) capabilities mainly due to the continuation of autonomous platform observations. In contrast, the pandemic caused critical loss to longer-term (years to decades) observations, greatly impairing the monitoring of such crucial variables as ocean carbon and the state of the deep ocean. So, while the observing system has held under the stress of the pandemic, work must be done to restore the interrupted replenishment of the autonomous components and plan for more resilient methods to support components of the system that rely on cruise-based measurements.

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A Global Ocean Oxygen Database and Atlas for Assessing and Predicting Deoxygenation and Ocean Health in the Open and Coastal Ocean

Cited by 44 publications

References 202 publications

Pathways of methane removal in the sediment and water column of a seasonally anoxic eutrophic marine basin

Pathways of methane removal in the sediment and water column of a seasonally anoxic eutrophic marine basin

The intensification of coastal hypoxia off central Chile: Long term and high frequency variability

Effects of the Pandemic on Observing the Global Ocean

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