Articles | Volume 10, issue 8
https://doi.org/10.5194/bg-10-5325-2013
© Author(s) 2013. This work is distributed under
the Creative Commons Attribution 3.0 License.
the Creative Commons Attribution 3.0 License.
Special issue:
https://doi.org/10.5194/bg-10-5325-2013
© Author(s) 2013. This work is distributed under
the Creative Commons Attribution 3.0 License.
the Creative Commons Attribution 3.0 License.
Research article
| 
06 Aug 2013
Research article |
| 06 Aug 2013
Seasonal signatures in SFG vibrational spectra of the sea surface nanolayer at Boknis Eck Time Series Station (SW Baltic Sea)
Institute of Physical Chemistry, Kiel University, Max-Eyth-Str. 1, 24118 Kiel, Germany
H. W. Bange
GEOMAR Helmholtz Centre for Ocean Research Kiel, Düsternbrooker Weg 20, 24105 Kiel, Germany
G. Friedrichs
Institute of Physical Chemistry, Kiel University, Max-Eyth-Str. 1, 24118 Kiel, Germany
KMS Kiel Marine Science – Centre for Interdisciplinary Marine Science Kiel University, Olshausenstr. 40, 24098 Kiel, Germany
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Pratirupa Bardhan, Claudia Frey, Gregor Rehder, and Hermann W. Bange
EGUsphere, https://doi.org/10.5194/egusphere-2025-2518, https://doi.org/10.5194/egusphere-2025-2518, 2025
This preprint is open for discussion and under review for Biogeosciences (BG).
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Nitrous oxide (N2O), a potent greenhouse gas, is released from coastal seas & estuaries, yet we don't fully understand how it is formed and consumed. In this study we collected water from several sites in the central Baltic Sea. N2O came from ammonia in oxic waters. Deep waters with low to no oxygen noted more active N2O cycling. The seafloor was a source in some areas. Typically N2O is produced by bacteria, but our results indicate possibility of other players like fungi or chemical reactions.
Riaz Bibi, Mariana Ribas-Ribas, Leonie Jaeger, Carola Lehners, Lisa Gassen, Edgar Cortés, Jochen Wollschläger, Claudia Thölen, Hannelore Waska, Jasper Zöbelein, Thorsten Brinkhoff, Isha Athale, Rüdiger Röttgers, Michael Novak, Anja Engel, Theresa Barthelmeß, Josefine Karnatz, Thomas Reinthaler, Dmytro Spriahailo, Gernot Friedrichs, Falko Schäfer, and Oliver Wurl
EGUsphere, https://doi.org/10.5194/egusphere-2025-1773, https://doi.org/10.5194/egusphere-2025-1773, 2025
This preprint is open for discussion and under review for Biogeosciences (BG).
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A multidisciplinary mesocosm study was conducted to investigate biogeochemical processes and their relationships in the sea-surface microlayer and underlying water during an induced phytoplankton bloom. Phytoplankton-derived organic matter, fuelled microbial activity and biofilm formation, supporting high bacterial abundance. Distinct temporal patterns in biogeochemical parameters and greater variability in the sea-surface microlayer highlight its influence on air–sea interactions.
Gesa Schulz, Kirstin Dähnke, Tina Sanders, Jan Penopp, Hermann W. Bange, Rena Czeschel, and Birgit Gaye
EGUsphere, https://doi.org/10.5194/egusphere-2025-1660, https://doi.org/10.5194/egusphere-2025-1660, 2025
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Oxygen minimum zones (OMZs) are low-oxygen ocean areas that deplete nitrogen, a key marine nutrient. Understanding nitrogen cycling in OMZs is crucial for the global nitrogen cycle. This study examined nitrogen cycling in the OMZ of the Bay of Bengal and East Equatorial Indian Ocean, revealing limited mixing between both regions. Surface phytoplankton consumes nitrate, while deeper nitrification recycles nitrogen. In the BoB’s OMZ (100–300 m), nitrogen loss likely occurs via anammox.
Johnathan Daniel Maxey, Neil D. Hartstein, Hermann W. Bange, and Moritz Müller
Biogeosciences, 21, 5613–5637, https://doi.org/10.5194/bg-21-5613-2024, https://doi.org/10.5194/bg-21-5613-2024, 2024
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The distribution of N2O in fjord-like estuaries is poorly described in the Southern Hemisphere. Our study describes N2O distribution and its drivers in one such system in Macquarie Harbour, Tasmania. Water samples were collected seasonally in 2022 and 2023. Results show the system removes atmospheric N2O when river flow is high, whereas the system emits N2O when the river flow is low. N2O generated in basins is intercepted by the surface water and exported to the ocean during high river flow.
Riel Carlo O. Ingeniero, Gesa Schulz, and Hermann W. Bange
Biogeosciences, 21, 3425–3440, https://doi.org/10.5194/bg-21-3425-2024, https://doi.org/10.5194/bg-21-3425-2024, 2024
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Our research is the first to measure dissolved NO concentrations in temperate estuarine waters, providing insights into its distribution under varying conditions and enhancing our understanding of its production processes. Dissolved NO was supersaturated in the Elbe Estuary, indicating that it is a source of atmospheric NO. The observed distribution of dissolved NO most likely resulted from nitrification.
Hanqin Tian, Naiqing Pan, Rona L. Thompson, Josep G. Canadell, Parvadha Suntharalingam, Pierre Regnier, Eric A. Davidson, Michael Prather, Philippe Ciais, Marilena Muntean, Shufen Pan, Wilfried Winiwarter, Sönke Zaehle, Feng Zhou, Robert B. Jackson, Hermann W. Bange, Sarah Berthet, Zihao Bian, Daniele Bianchi, Alexander F. Bouwman, Erik T. Buitenhuis, Geoffrey Dutton, Minpeng Hu, Akihiko Ito, Atul K. Jain, Aurich Jeltsch-Thömmes, Fortunat Joos, Sian Kou-Giesbrecht, Paul B. Krummel, Xin Lan, Angela Landolfi, Ronny Lauerwald, Ya Li, Chaoqun Lu, Taylor Maavara, Manfredi Manizza, Dylan B. Millet, Jens Mühle, Prabir K. Patra, Glen P. Peters, Xiaoyu Qin, Peter Raymond, Laure Resplandy, Judith A. Rosentreter, Hao Shi, Qing Sun, Daniele Tonina, Francesco N. Tubiello, Guido R. van der Werf, Nicolas Vuichard, Junjie Wang, Kelley C. Wells, Luke M. Western, Chris Wilson, Jia Yang, Yuanzhi Yao, Yongfa You, and Qing Zhu
Earth Syst. Sci. Data, 16, 2543–2604, https://doi.org/10.5194/essd-16-2543-2024, https://doi.org/10.5194/essd-16-2543-2024, 2024
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Atmospheric concentrations of nitrous oxide (N2O), a greenhouse gas 273 times more potent than carbon dioxide, have increased by 25 % since the preindustrial period, with the highest observed growth rate in 2020 and 2021. This rapid growth rate has primarily been due to a 40 % increase in anthropogenic emissions since 1980. Observed atmospheric N2O concentrations in recent years have exceeded the worst-case climate scenario, underscoring the importance of reducing anthropogenic N2O emissions.
Gesa Schulz, Tina Sanders, Yoana G. Voynova, Hermann W. Bange, and Kirstin Dähnke
Biogeosciences, 20, 3229–3247, https://doi.org/10.5194/bg-20-3229-2023, https://doi.org/10.5194/bg-20-3229-2023, 2023
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Nitrous oxide (N2O) is an important greenhouse gas. However, N2O emissions from estuaries underlie significant uncertainties due to limited data availability and high spatiotemporal variability. We found the Elbe Estuary (Germany) to be a year-round source of N2O, with the highest emissions in winter along with high nitrogen loads. However, in spring and summer, N2O emissions did not decrease alongside lower nitrogen loads because organic matter fueled in situ N2O production along the estuary.
Guanlin Li, Damian L. Arévalo-Martínez, Riel Carlo O. Ingeniero, and Hermann W. Bange
EGUsphere, https://doi.org/10.5194/egusphere-2023-771, https://doi.org/10.5194/egusphere-2023-771, 2023
Preprint archived
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Dissolved carbon monoxide (CO) surface concentrations were first measured at 14 stations in the Ria Formosa Lagoon system in May 2021. Ria Formosa was a source of atmospheric CO. Microbial consumption accounted for 83 % of the CO production. The results of a 48-hour irradiation experiment with aquaculture effluent water indicated that aquaculture facilities in the Ria Formosa Lagoon seem to be a negligible source of atmospheric CO.
Hanna I. Campen, Damian L. Arévalo-Martínez, and Hermann W. Bange
Biogeosciences, 20, 1371–1379, https://doi.org/10.5194/bg-20-1371-2023, https://doi.org/10.5194/bg-20-1371-2023, 2023
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Carbon monoxide (CO) is a climate-relevant trace gas emitted from the ocean. However, oceanic CO cycling is understudied. Results from incubation experiments conducted in the Fram Strait (Arctic Ocean) indicated that (i) pH did not affect CO cycling and (ii) enhanced CO production and consumption were positively correlated with coloured dissolved organic matter and nitrate concentrations. This suggests microbial CO uptake to be the driving factor for CO cycling in the Arctic Ocean.
Damian L. Arévalo-Martínez, Amir Haroon, Hermann W. Bange, Ercan Erkul, Marion Jegen, Nils Moosdorf, Jens Schneider von Deimling, Christian Berndt, Michael Ernst Böttcher, Jasper Hoffmann, Volker Liebetrau, Ulf Mallast, Gudrun Massmann, Aaron Micallef, Holly A. Michael, Hendrik Paasche, Wolfgang Rabbel, Isaac Santos, Jan Scholten, Katrin Schwalenberg, Beata Szymczycha, Ariel T. Thomas, Joonas J. Virtasalo, Hannelore Waska, and Bradley A. Weymer
Biogeosciences, 20, 647–662, https://doi.org/10.5194/bg-20-647-2023, https://doi.org/10.5194/bg-20-647-2023, 2023
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Groundwater flows at the land–ocean transition and the extent of freshened groundwater below the seafloor are increasingly relevant in marine sciences, both because they are a highly uncertain term of biogeochemical budgets and due to the emerging interest in the latter as a resource. Here, we discuss our perspectives on future research directions to better understand land–ocean connectivity through groundwater and its potential responses to natural and human-induced environmental changes.
Sonja Gindorf, Hermann W. Bange, Dennis Booge, and Annette Kock
Biogeosciences, 19, 4993–5006, https://doi.org/10.5194/bg-19-4993-2022, https://doi.org/10.5194/bg-19-4993-2022, 2022
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Methane is a climate-relevant greenhouse gas which is emitted to the atmosphere from coastal areas such as the Baltic Sea. We measured the methane concentration in the water column of the western Kiel Bight. Methane concentrations were higher in September than in June. We found no relationship between the 2018 European heatwave and methane concentrations. Our results show that the methane distribution in the water column is strongly affected by temporal and spatial variabilities.
Yanan Zhao, Dennis Booge, Christa A. Marandino, Cathleen Schlundt, Astrid Bracher, Elliot L. Atlas, Jonathan Williams, and Hermann W. Bange
Biogeosciences, 19, 701–714, https://doi.org/10.5194/bg-19-701-2022, https://doi.org/10.5194/bg-19-701-2022, 2022
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We present here, for the first time, simultaneously measured dimethylsulfide (DMS) seawater concentrations and DMS atmospheric mole fractions from the Peruvian upwelling region during two cruises in December 2012 and October 2015. Our results indicate low oceanic DMS concentrations and atmospheric DMS molar fractions in surface waters and the atmosphere, respectively. In addition, the Peruvian upwelling region was identified as an insignificant source of DMS emissions during both periods.
Wangwang Ye, Hermann W. Bange, Damian L. Arévalo-Martínez, Hailun He, Yuhong Li, Jianwen Wen, Jiexia Zhang, Jian Liu, Man Wu, and Liyang Zhan
Biogeosciences Discuss., https://doi.org/10.5194/bg-2021-334, https://doi.org/10.5194/bg-2021-334, 2022
Manuscript not accepted for further review
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CH4 is the second important greenhouse gas after CO2. We show that CH4 consumption and sea-ice melting influence the CH4 distribution in the Ross Sea (Southern Ocean), causing undersaturation and net uptake of CH4 during summertime. This study confirms the capability of surface water in the high-latitude Southern Ocean regions to take up atmospheric CH4 which, in turn, will help to improve predictions of how CH4 release/uptake from the ocean will develop when sea-ice retreats in the future.
Yanan Zhao, Cathleen Schlundt, Dennis Booge, and Hermann W. Bange
Biogeosciences, 18, 2161–2179, https://doi.org/10.5194/bg-18-2161-2021, https://doi.org/10.5194/bg-18-2161-2021, 2021
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We present a unique and comprehensive time-series study of biogenic sulfur compounds in the southwestern Baltic Sea, from 2009 to 2018. Dimethyl sulfide is one of the key players regulating global climate change, as well as dimethylsulfoniopropionate and dimethyl sulfoxide. Their decadal trends did not follow increasing temperature but followed some algae group abundances at the Boknis Eck Time Series Station.
Samuel T. Wilson, Alia N. Al-Haj, Annie Bourbonnais, Claudia Frey, Robinson W. Fulweiler, John D. Kessler, Hannah K. Marchant, Jana Milucka, Nicholas E. Ray, Parvadha Suntharalingam, Brett F. Thornton, Robert C. Upstill-Goddard, Thomas S. Weber, Damian L. Arévalo-Martínez, Hermann W. Bange, Heather M. Benway, Daniele Bianchi, Alberto V. Borges, Bonnie X. Chang, Patrick M. Crill, Daniela A. del Valle, Laura Farías, Samantha B. Joye, Annette Kock, Jabrane Labidi, Cara C. Manning, John W. Pohlman, Gregor Rehder, Katy J. Sparrow, Philippe D. Tortell, Tina Treude, David L. Valentine, Bess B. Ward, Simon Yang, and Leonid N. Yurganov
Biogeosciences, 17, 5809–5828, https://doi.org/10.5194/bg-17-5809-2020, https://doi.org/10.5194/bg-17-5809-2020, 2020
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The oceans are a net source of the major greenhouse gases; however there has been little coordination of oceanic methane and nitrous oxide measurements. The scientific community has recently embarked on a series of capacity-building exercises to improve the interoperability of dissolved methane and nitrous oxide measurements. This paper derives from a workshop which discussed the challenges and opportunities for oceanic methane and nitrous oxide research in the near future.
Xiao Ma, Mingshuang Sun, Sinikka T. Lennartz, and Hermann W. Bange
Biogeosciences, 17, 3427–3438, https://doi.org/10.5194/bg-17-3427-2020, https://doi.org/10.5194/bg-17-3427-2020, 2020
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Monthly measurements of dissolved methane (CH4), a potent greenhouse gas, were conducted at Boknis Eck (BE), a time-series station in the southwestern Baltic Sea, from June 2006. In general CH4 concentrations increased with depth. High concentrations in the upper layer were linked to saline water inflow. Eckernförde Bay emitted CH4 to the atmosphere throughout the monitoring period. No significant trend was detected in CH4 concentrations or emissions during 2006–2017.
Claudia Frey, Hermann W. Bange, Eric P. Achterberg, Amal Jayakumar, Carolin R. Löscher, Damian L. Arévalo-Martínez, Elizabeth León-Palmero, Mingshuang Sun, Xin Sun, Ruifang C. Xie, Sergey Oleynik, and Bess B. Ward
Biogeosciences, 17, 2263–2287, https://doi.org/10.5194/bg-17-2263-2020, https://doi.org/10.5194/bg-17-2263-2020, 2020
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The production of N2O via nitrification and denitrification associated with low-O2 waters is a major source of oceanic N2O. We investigated the regulation and dynamics of these processes with respect to O2 and organic matter inputs. The transcription of the key nitrification gene amoA rapidly responded to changes in O2 and strongly correlated with N2O production rates. N2O production by denitrification was clearly stimulated by organic carbon, implying that its supply controls N2O production.
Carolin R. Löscher, Wiebke Mohr, Hermann W. Bange, and Donald E. Canfield
Biogeosciences, 17, 851–864, https://doi.org/10.5194/bg-17-851-2020, https://doi.org/10.5194/bg-17-851-2020, 2020
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Oxygen minimum zones (OMZs) are ocean areas severely depleted in oxygen as a result of physical, chemical, and biological processes. Biologically, organic material is produced in the sea surface and exported to deeper waters, where it respires. In the Bay of Bengal (BoB), an OMZ is present, but there are traces of oxygen left. Our study now suggests that this is because one key process, nitrogen fixation, is absent in the BoB, thus preventing primary production and consecutive respiration.
Ye Tian, Gui-Peng Yang, Chun-Ying Liu, Pei-Feng Li, Hong-Tao Chen, and Hermann W. Bange
Ocean Sci., 16, 135–148, https://doi.org/10.5194/os-16-135-2020, https://doi.org/10.5194/os-16-135-2020, 2020
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Nitric oxide (NO) could be produced by nitrite photolysis; the rates from dissolved nitrite in artificial seawater showed increasing trends with decreasing pH, increasing temperatures, and increasing salinity. However, NO photoproduction from the natural seawater samples did not show correlations with pH, water temperature, salinity, or dissolved nitrite concentrations in the western tropical North Pacific Ocean (WNTP). And there were other NO loss processes in the surface layer of WNTP.
Thomas Holding, Ian G. Ashton, Jamie D. Shutler, Peter E. Land, Philip D. Nightingale, Andrew P. Rees, Ian Brown, Jean-Francois Piolle, Annette Kock, Hermann W. Bange, David K. Woolf, Lonneke Goddijn-Murphy, Ryan Pereira, Frederic Paul, Fanny Girard-Ardhuin, Bertrand Chapron, Gregor Rehder, Fabrice Ardhuin, and Craig J. Donlon
Ocean Sci., 15, 1707–1728, https://doi.org/10.5194/os-15-1707-2019, https://doi.org/10.5194/os-15-1707-2019, 2019
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FluxEngine is an open-source software toolbox designed to allow for the easy and accurate calculation of air–sea gas fluxes. This article describes new functionality and capabilities, which include the ability to calculate fluxes for nitrous oxide and methane, optimisation for running FluxEngine on a stand-alone desktop computer, and extensive new features to support the in situ measurement community. Four research case studies are used to demonstrate these new features.
Ye Tian, Chao Xue, Chun-Ying Liu, Gui-Peng Yang, Pei-Feng Li, Wei-Hua Feng, and Hermann W. Bange
Biogeosciences, 16, 4485–4496, https://doi.org/10.5194/bg-16-4485-2019, https://doi.org/10.5194/bg-16-4485-2019, 2019
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Nitric oxide (NO) seems to be widespread, with different functions in the marine ecosystem, but we know little about it. Concentrations of NO were in a range from below the limit of detection to 616 pmol L−1 at the surface and 482 pmol L−1 at the bottom of the Bohai and Yellow seas. The study region was a source of atmospheric NO. Net NO sea-to-air fluxes were much lower than NO photoproduction rates, implying that the NO produced in the mixed layer was rapidly consumed before entering the air.
Hermann W. Bange, Chun Hock Sim, Daniel Bastian, Jennifer Kallert, Annette Kock, Aazani Mujahid, and Moritz Müller
Biogeosciences, 16, 4321–4335, https://doi.org/10.5194/bg-16-4321-2019, https://doi.org/10.5194/bg-16-4321-2019, 2019
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Nitrous oxide (N2O) and methane (CH4) are atmospheric trace gases which play important roles in the climate and atmospheric chemistry of the Earth. However, little is known about their emissions from rivers and estuaries. To this end, concentrations of N2O and CH4 were measured during a seasonal study in six rivers and estuaries in northwestern Borneo. The concentrations of both gases were mainly driven by rainfall. The rivers and estuaries were an overall net source of atmospheric N2O and CH4.
Xiao Ma, Sinikka T. Lennartz, and Hermann W. Bange
Biogeosciences, 16, 4097–4111, https://doi.org/10.5194/bg-16-4097-2019, https://doi.org/10.5194/bg-16-4097-2019, 2019
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Monthly measurements of nitrous oxide (N2O), a potent greenhouse gas and ozone depletion agent, were conducted at Boknis Eck (BE), a time series station in the southwestern Baltic Sea, since July 2005. Low N2O concentrations were observed in autumn and high in winter and early spring. Dissolved nutrients and oxygen played important roles in N2O distribution. Although we did not observe a significant N2O trend during 2005–2017, a decrease in N2O concentration and emission seems likely in future.
Eric J. Morgan, Jost V. Lavric, Damian L. Arévalo-Martínez, Hermann W. Bange, Tobias Steinhoff, Thomas Seifert, and Martin Heimann
Biogeosciences, 16, 4065–4084, https://doi.org/10.5194/bg-16-4065-2019, https://doi.org/10.5194/bg-16-4065-2019, 2019
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Taking a 2-year atmospheric record of atmospheric oxygen and the greenhouse gases N2O, CO2, and CH4, made at a coastal site in the Namib Desert, we estimated the fluxes of these gases from upwelling events in the northern Benguela Current region. We compared these results with flux measurements made on a research vessel in the study area at the same time and found that the two approaches agreed well. The study region was a source of N2O, CO2, and CH4 to the atmosphere during upwelling events.
Tim Fischer, Annette Kock, Damian L. Arévalo-Martínez, Marcus Dengler, Peter Brandt, and Hermann W. Bange
Biogeosciences, 16, 2307–2328, https://doi.org/10.5194/bg-16-2307-2019, https://doi.org/10.5194/bg-16-2307-2019, 2019
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We investigated air–sea gas exchange in oceanic upwelling regions for the case of nitrous oxide off Peru. In this region, routine concentration measurements from ships at 5 m or 10 m depth prove to overestimate surface (bulk) concentration. Thus, standard estimates of gas exchange will show systematic error. This is due to very shallow stratified layers that inhibit exchange between surface water and waters below and can exist for several days. Maximum bias occurs in moderate wind conditions.
Qixing Ji, Mark A. Altabet, Hermann W. Bange, Michelle I. Graco, Xiao Ma, Damian L. Arévalo-Martínez, and Damian S. Grundle
Biogeosciences, 16, 2079–2093, https://doi.org/10.5194/bg-16-2079-2019, https://doi.org/10.5194/bg-16-2079-2019, 2019
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A strong El Niño event occurred in the Peruvian coastal region in 2015–2016, during which higher sea surface temperatures co-occurred with significantly lower sea-to-air fluxes of nitrous oxide, an important greenhouse gas and ozone depletion agent. Stratified water column during El Niño retained a larger amount of nitrous oxide that was produced via multiple microbial pathways; and intense nitrous oxide effluxes could occur when normal upwelling is resumed after El Niño.
Samuel T. Wilson, Hermann W. Bange, Damian L. Arévalo-Martínez, Jonathan Barnes, Alberto V. Borges, Ian Brown, John L. Bullister, Macarena Burgos, David W. Capelle, Michael Casso, Mercedes de la Paz, Laura Farías, Lindsay Fenwick, Sara Ferrón, Gerardo Garcia, Michael Glockzin, David M. Karl, Annette Kock, Sarah Laperriere, Cliff S. Law, Cara C. Manning, Andrew Marriner, Jukka-Pekka Myllykangas, John W. Pohlman, Andrew P. Rees, Alyson E. Santoro, Philippe D. Tortell, Robert C. Upstill-Goddard, David P. Wisegarver, Gui-Ling Zhang, and Gregor Rehder
Biogeosciences, 15, 5891–5907, https://doi.org/10.5194/bg-15-5891-2018, https://doi.org/10.5194/bg-15-5891-2018, 2018
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To determine the variability between independent measurements of dissolved methane and nitrous oxide, seawater samples were analyzed by multiple laboratories. The results revealed the influences of the different parts of the analytical process, from the initial sample collection to the calculation of the final concentrations. Recommendations are made to improve dissolved methane and nitrous oxide measurements to help preclude future analytical discrepancies between laboratories.
Johanna Maltby, Lea Steinle, Carolin R. Löscher, Hermann W. Bange, Martin A. Fischer, Mark Schmidt, and Tina Treude
Biogeosciences, 15, 137–157, https://doi.org/10.5194/bg-15-137-2018, https://doi.org/10.5194/bg-15-137-2018, 2018
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The activity and environmental controls of methanogenesis (MG) within the sulfate-reducing zone (0–30 cm below the seafloor) were investigated in organic-rich sediments of the seasonally hypoxic Eckernförde Bay, SW Baltic Sea. MG activity was mostly linked to non-competitive substrates. The major controls identified were organic matter availability, C / N, temperature, and O2 in the water column, revealing higher rates in warm, stratified, hypoxic seasons compared to colder, oxygenated seasons.
Chun-Ying Liu, Wei-Hua Feng, Ye Tian, Gui-Peng Yang, Pei-Feng Li, and Hermann W. Bange
Ocean Sci., 13, 623–632, https://doi.org/10.5194/os-13-623-2017, https://doi.org/10.5194/os-13-623-2017, 2017
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We developed a new method for the determination of dissolved nitric oxide (NO) in discrete seawater samples based on the combination of a purge-and-trap setup and a fluorometric detection of NO. With this method we have a reliable and comparably easy to use method to measure oceanic NO surface concentrations, which can be used to decipher both its temporal and spatial distributions as well as its biogeochemical pathways in the oceans.
Lea Steinle, Johanna Maltby, Tina Treude, Annette Kock, Hermann W. Bange, Nadine Engbersen, Jakob Zopfi, Moritz F. Lehmann, and Helge Niemann
Biogeosciences, 14, 1631–1645, https://doi.org/10.5194/bg-14-1631-2017, https://doi.org/10.5194/bg-14-1631-2017, 2017
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Large amounts of methane are produced in anoxic, coastal sediments, from which it can seep into the overlying water column. Aerobic oxidation of methane (MOx) mediated by methanotrophic bacteria is an important sink for methane before its evasion to the atmosphere. In a 2-year seasonal study, we investigated the spatio-temporal variability of MOx in a seasonally hypoxic coastal inlet using radiotracer-based methods. In experiments, we assessed the effect of variable oxygen concentrations on MOx.
Lothar Stramma, Tim Fischer, Damian S. Grundle, Gerd Krahmann, Hermann W. Bange, and Christa A. Marandino
Ocean Sci., 12, 861–873, https://doi.org/10.5194/os-12-861-2016, https://doi.org/10.5194/os-12-861-2016, 2016
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Results from a research cruise on R/V Sonne to the eastern tropical Pacific in October 2015 during the 2015–2016 El Niño show the transition of current, hydrographic, and nutrient conditions to El Niño conditions in the eastern tropical Pacific in October 2015. Although in early 2015 the El Niño was strong and in October 2015 showed a clear El Niño influence on the EUC, in the eastern tropical Pacific the measurements only showed developing El Niño water mass distributions.
Carolin R. Löscher, Hermann W. Bange, Ruth A. Schmitz, Cameron M. Callbeck, Anja Engel, Helena Hauss, Torsten Kanzow, Rainer Kiko, Gaute Lavik, Alexandra Loginova, Frank Melzner, Judith Meyer, Sven C. Neulinger, Markus Pahlow, Ulf Riebesell, Harald Schunck, Sören Thomsen, and Hannes Wagner
Biogeosciences, 13, 3585–3606, https://doi.org/10.5194/bg-13-3585-2016, https://doi.org/10.5194/bg-13-3585-2016, 2016
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The ocean loses oxygen due to climate change. Addressing this issue in tropical ocean regions (off Peru and Mauritania), we aimed to understand the effects of oxygen depletion on various aspects of marine biogeochemistry, including primary production and export production, the nitrogen cycle, greenhouse gas production, organic matter fluxes and remineralization, and the role of zooplankton and viruses.
Carolin R. Löscher, Annie Bourbonnais, Julien Dekaezemacker, Chawalit N. Charoenpong, Mark A. Altabet, Hermann W. Bange, Rena Czeschel, Chris Hoffmann, and Ruth Schmitz
Biogeosciences, 13, 2889–2899, https://doi.org/10.5194/bg-13-2889-2016, https://doi.org/10.5194/bg-13-2889-2016, 2016
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The ocean is full of eddies and they play a key role for ocean biogeochemistry. In order to understand dinitrogen (N2) fixation, one major control of oceanic primary production, we investigated three eddies in the eastern tropical South Pacific off Peru. We conducted the first detailed survey and found increased N2 fixation in the oxygen-depleted cores of anticyclonic mode water eddies. Taken together, we could – for the first time – show that eddies play an important role in N2 fixation off Peru.
Denise Müller, Hermann W. Bange, Thorsten Warneke, Tim Rixen, Moritz Müller, Aazani Mujahid, and Justus Notholt
Biogeosciences, 13, 2415–2428, https://doi.org/10.5194/bg-13-2415-2016, https://doi.org/10.5194/bg-13-2415-2016, 2016
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Estuaries act as sources of the greenhouse gases nitrous oxide (N2O) and methane (CH4) to the atmosphere. We provide first measurements of N2O and CH4 in two estuaries in north-western Borneo, a region which is dominated by peatlands. We show that N2O and CH4 concentrations in these estuaries are moderate despite high organic carbon loads, that nutrient enhancement does not lead to enhanced N2O emissions, and that the wet season dominates the variability of the emissions in these systems.
Happy Hu, Annie Bourbonnais, Jennifer Larkum, Hermann W. Bange, and Mark A. Altabet
Biogeosciences, 13, 1453–1468, https://doi.org/10.5194/bg-13-1453-2016, https://doi.org/10.5194/bg-13-1453-2016, 2016
Damian L. Arévalo-Martínez, Annette Kock, Carolin R. Löscher, Ruth A. Schmitz, Lothar Stramma, and Hermann W. Bange
Biogeosciences, 13, 1105–1118, https://doi.org/10.5194/bg-13-1105-2016, https://doi.org/10.5194/bg-13-1105-2016, 2016
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We present the first measurements of N2O across three mesoscale eddies in the eastern tropical South Pacific. Eddie's vertical structure, offshore transport, properties during its formation and near-surface primary production determined the N2O distribution. Substantial depletion of N2O within the core of anticyclonic eddies suggests that although these are transient features, N-loss processes within their centres can lead to an enhanced N2O sink which is not accounted for in marine N2O budgets.
A. Kock, D. L. Arévalo-Martínez, C. R. Löscher, and H. W. Bange
Biogeosciences, 13, 827–840, https://doi.org/10.5194/bg-13-827-2016, https://doi.org/10.5194/bg-13-827-2016, 2016
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We measured the nitrous oxide (N2O) distribution in the water column in the oxygen minimum zone off Peru, an area with extremely high N2O emissions. Our data show very variable and often very high N2O concentrations in the water column at the coast, which lead to high N2O emissions when these waters are brought to the surface. The very high N2O production off Peru may be caused by high nutrient turnover rates together with rapid changes in the oxygen concentrations.
A. R. Baker, M. Thomas, H. W. Bange, and E. Plasencia Sánchez
Biogeosciences, 13, 817–825, https://doi.org/10.5194/bg-13-817-2016, https://doi.org/10.5194/bg-13-817-2016, 2016
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Concentrations of major ions and trace metals were measured in aerosols off the coast of Peru in December 2012. A few trace metals (iron, copper, nickel, and cobalt) had anomalously high concentrations, which may be associated with industrial metal smelting activities in the region. The atmosphere appears to supply an excess of iron (relative to atmospheric nitrogen supply) to the phytoplankton community of the Peruvian upwelling system.
D. Müller, T. Warneke, T. Rixen, M. Müller, A. Mujahid, H. W. Bange, and J. Notholt
Biogeosciences, 13, 691–705, https://doi.org/10.5194/bg-13-691-2016, https://doi.org/10.5194/bg-13-691-2016, 2016
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We studied organic carbon and the dissolved greenhouse gases carbon dioxide (CO2) and carbon monoxide (CO) in two estuaries in Sarawak, Malaysia, whose coast is covered by carbon-rich peatlands. The estuaries received terrestrial organic carbon from peat-draining tributaries. A large fraction was converted to CO2 and a minor fraction to CO. Both gases were released to the atmosphere. This shows how these estuaries function as efficient filters between land and ocean in this important region.
H. E. Lutterbeck and H. W. Bange
Ocean Sci., 11, 937–946, https://doi.org/10.5194/os-11-937-2015, https://doi.org/10.5194/os-11-937-2015, 2015
P. Brandt, H. W. Bange, D. Banyte, M. Dengler, S.-H. Didwischus, T. Fischer, R. J. Greatbatch, J. Hahn, T. Kanzow, J. Karstensen, A. Körtzinger, G. Krahmann, S. Schmidtko, L. Stramma, T. Tanhua, and M. Visbeck
Biogeosciences, 12, 489–512, https://doi.org/10.5194/bg-12-489-2015, https://doi.org/10.5194/bg-12-489-2015, 2015
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Our observational study looks at the structure of the eastern tropical North Atlantic (ETNA) oxygen minimum zone (OMZ) in comparison with the less-ventilated, eastern tropical South Pacific OMZ. We quantify the OMZ’s oxygen budget composed of consumption, advection, lateral and vertical mixing. Substantial oxygen variability is observed on interannual to multidecadal timescales. The deoxygenation of the ETNA OMZ during the last decades represents a substantial imbalance of the oxygen budget.
S. T. Lennartz, A. Lehmann, J. Herrford, F. Malien, H.-P. Hansen, H. Biester, and H. W. Bange
Biogeosciences, 11, 6323–6339, https://doi.org/10.5194/bg-11-6323-2014, https://doi.org/10.5194/bg-11-6323-2014, 2014
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A time series of nine oceanic parameters from the coastal time series station Boknis Eck (BE, southwestern Baltic Sea) in the period of 1957-2013 is analysed with respect to seasonal cycles and long-term trends. Most striking was a paradoxical decreasing trend in oxygen with a simultaneous decline in eutrophication. Possible reasons for this paradox, e.g. processes related to warming temperatures such as increased decomposition of organic matter or altered ventilation, are discussed.
J. Friedrich, F. Janssen, D. Aleynik, H. W. Bange, N. Boltacheva, M. N. Çagatay, A. W. Dale, G. Etiope, Z. Erdem, M. Geraga, A. Gilli, M. T. Gomoiu, P. O. J. Hall, D. Hansson, Y. He, M. Holtappels, M. K. Kirf, M. Kononets, S. Konovalov, A. Lichtschlag, D. M. Livingstone, G. Marinaro, S. Mazlumyan, S. Naeher, R. P. North, G. Papatheodorou, O. Pfannkuche, R. Prien, G. Rehder, C. J. Schubert, T. Soltwedel, S. Sommer, H. Stahl, E. V. Stanev, A. Teaca, A. Tengberg, C. Waldmann, B. Wehrli, and F. Wenzhöfer
Biogeosciences, 11, 1215–1259, https://doi.org/10.5194/bg-11-1215-2014, https://doi.org/10.5194/bg-11-1215-2014, 2014
D. L. Arévalo-Martínez, M. Beyer, M. Krumbholz, I. Piller, A. Kock, T. Steinhoff, A. Körtzinger, and H. W. Bange
Ocean Sci., 9, 1071–1087, https://doi.org/10.5194/os-9-1071-2013, https://doi.org/10.5194/os-9-1071-2013, 2013
L. Stramma, H. W. Bange, R. Czeschel, A. Lorenzo, and M. Frank
Biogeosciences, 10, 7293–7306, https://doi.org/10.5194/bg-10-7293-2013, https://doi.org/10.5194/bg-10-7293-2013, 2013
I.-N. Kim, K. Lee, H. W. Bange, and A. M. Macdonald
Biogeosciences, 10, 6783–6792, https://doi.org/10.5194/bg-10-6783-2013, https://doi.org/10.5194/bg-10-6783-2013, 2013
C. A. Marandino, S. Tegtmeier, K. Krüger, C. Zindler, E. L. Atlas, F. Moore, and H. W. Bange
Atmos. Chem. Phys., 13, 8427–8437, https://doi.org/10.5194/acp-13-8427-2013, https://doi.org/10.5194/acp-13-8427-2013, 2013
C. Zindler, A. Bracher, C. A. Marandino, B. Taylor, E. Torrecilla, A. Kock, and H. W. Bange
Biogeosciences, 10, 3297–3311, https://doi.org/10.5194/bg-10-3297-2013, https://doi.org/10.5194/bg-10-3297-2013, 2013
L. M. Zamora, A. Oschlies, H. W. Bange, K. B. Huebert, J. D. Craig, A. Kock, and C. R. Löscher
Biogeosciences, 9, 5007–5022, https://doi.org/10.5194/bg-9-5007-2012, https://doi.org/10.5194/bg-9-5007-2012, 2012
Related subject area
Biogeochemistry: Coastal Ocean
Spring–neap tidal cycles modulate the strength of the carbon source at the estuary–coast interface
Spatiotemporal variations in surface marine carbonate system properties across the western Mediterranean Sea using volunteer observing ship data
Amplified bottom water acidification rates on the Bering Sea shelf from 1970–2022
Depositional controls and budget of organic carbon burial in fine-grained sediments of the North Sea – the Helgoland Mud Area as a natural laboratory
Effects of submarine groundwater on nutrient concentration and primary production in a deep bay of the Japan Sea
The bacteria–protist link as a main route of dissolved organic matter across contrasting productivity areas on the Patagonian Shelf
Ocean alkalinity enhancement (OAE) does not cause cellular stress in a phytoplankton community of the subtropical Atlantic Ocean
Reviews and syntheses: On increasing hypoxia in eastern boundary upwelling systems – zooplankton under metabolic stress
Technical note: Testing a new approach for the determination of N2 fixation rates by coupling a membrane equilibrator to a mass spectrometer for long-term observations
A niche for diverse cable bacteria in continental margin sediments overlain by oxygen-deficient waters
Phytoplankton community succession and biogeochemistry in a bloom simulation experiment at an estuary-ocean interface
Long-term variations in pH in coastal waters along the Korean Peninsula
The effect of carbonate mineral additions on biogeochemical conditions in surface sediments and benthic–pelagic exchange fluxes
Evaluating ocean alkalinity enhancement as a carbon dioxide removal strategy in the North Sea
Assessing the impacts of simulated ocean alkalinity enhancement on viability and growth of nearshore species of phytoplankton
Responses of microbial metabolic rates to non-equilibrated silicate- versus calcium-based ocean alkalinity enhancement
High metabolic zinc demand within native Amundsen and Ross sea phytoplankton communities determined by stable isotope uptake rate measurements
The influence of zooplankton and oxygen on the particulate organic carbon flux in the Benguela Upwelling System
Reviews and syntheses: Biological indicators of low-oxygen stress in marine water-breathing animals
Temperature-enhanced effects of iron on Southern Ocean phytoplankton
Riverine nutrient impact on global ocean nitrogen cycle feedbacks and marine primary production in an Earth system model
The Northeast Greenland Shelf as a potential late-summer CO2 source to the atmosphere
Technical note: Ocean Alkalinity Enhancement Pelagic Impact Intercomparison Project (OAEPIIP)
Estimates of carbon sequestration potential in an expanding Arctic fjord (Hornsund, Svalbard) affected by dark plumes of glacial meltwater
An assessment of ocean alkalinity enhancement using aqueous hydroxides: kinetics, efficiency, and precipitation thresholds
Dissolved nitric oxide in the lower Elbe Estuary and the Port of Hamburg area
Variable contribution of wastewater treatment plant effluents to downstream nitrous oxide concentrations and emissions
Improved understanding of eutrophication trends, indicators and problem areas using machine learning
Distribution of nutrients and dissolved organic matter in a eutrophic equatorial estuary: the Johor River and the East Johor Strait
Investigating the effect of silicate- and calcium-based ocean alkalinity enhancement on diatom silicification
Ocean alkalinity enhancement using sodium carbonate salts does not lead to measurable changes in Fe dynamics in a mesocosm experiment
Quantification and mitigation of bottom-trawling impacts on sedimentary organic carbon stocks in the North Sea
Influence of ocean alkalinity enhancement with olivine or steel slag on a coastal plankton community in Tasmania
Multi-model comparison of trends and controls of near-bed oxygen concentration on the northwest European continental shelf under climate change
Picoplanktonic methane production in eutrophic surface waters
Vertical mixing alleviates autumnal oxygen deficiency in the central North Sea
Hypoxia also occurs in small highly turbid estuaries: the example of the Charente (Bay of Biscay)
Seasonality and response of ocean acidification and hypoxia to major environmental anomalies in the southern Salish Sea, North America (2014–2018)
Oceanographic processes driving low-oxygen conditions inside Patagonian fjords
Above- and belowground plant mercury dynamics in a salt marsh estuary in Massachusetts, USA
Variability and drivers of carbonate chemistry at shellfish aquaculture sites in the Salish Sea, British Columbia
Unusual Hemiaulus bloom influences ocean productivity in Northeastern US Shelf waters
Insights into carbonate environmental conditions in the Chukchi Sea
UAV approaches for improved mapping of vegetation cover and estimation of carbon storage of small saltmarshes: examples from Loch Fleet, northeast Scotland
Iron “ore” nothing: benthic iron fluxes from the oxygen-deficient Santa Barbara Basin enhance phytoplankton productivity in surface waters
Marine anoxia initiates giant sulfur-oxidizing bacterial mat proliferation and associated changes in benthic nitrogen, sulfur, and iron cycling in the Santa Barbara Basin, California Borderland
Uncertainty in the evolution of northwestern North Atlantic circulation leads to diverging biogeochemical projections
The additionality problem of ocean alkalinity enhancement
Short-term variation in pH in seawaters around coastal areas of Japan: characteristics and forcings
Revisiting the applicability and constraints of molybdenum- and uranium-based paleo redox proxies: comparing two contrasting sill fjords
Vlad A. Macovei, Louise C. V. Rewrie, Rüdiger Röttgers, and Yoana G. Voynova
Biogeosciences, 22, 3375–3396, https://doi.org/10.5194/bg-22-3375-2025, https://doi.org/10.5194/bg-22-3375-2025, 2025
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We found that biogeochemical variability at the land–sea interface (LSI) in two major temperate estuaries is modulated by the 14 d spring–neap tidal cycle, with large effects on dissolved inorganic and organic carbon concentrations and distribution. As this effect increases the strength of the carbon source to the atmosphere by up to 74 % during spring tide, it should be accounted for in regional models, which aim to resolve biogeochemical processing at the LSI.
David Curbelo-Hernández, David González-Santana, Aridane G. González, J. Magdalena Santana-Casiano, and Melchor González-Dávila
Biogeosciences, 22, 3329–3356, https://doi.org/10.5194/bg-22-3329-2025, https://doi.org/10.5194/bg-22-3329-2025, 2025
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This study offers a unique high-resolution dataset (2019–2024) on surface physicochemical properties in the western Mediterranean Sea. It reveals accelerated surface warming, significantly altering CO2 levels and pH. Currently a net CO2 sink, the region may become a CO2 source by 2030 due to weakening in-gassing. The research highlights the value of VOS (volunteer observing ship) lines for monitoring climate impacts and emphasizes the need for ongoing observations to enhance long-term trend accuracy and future projections.
Darren J. Pilcher, Jessica N. Cross, Natalie Monacci, Linquan Mu, Kelly A. Kearney, Albert J. Hermann, and Wei Cheng
Biogeosciences, 22, 3103–3125, https://doi.org/10.5194/bg-22-3103-2025, https://doi.org/10.5194/bg-22-3103-2025, 2025
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The Bering Sea shelf is a highly productive marine ecosystem that is vulnerable to ocean acidification. We use a computational model to simulate the carbon cycle and acidification rates from 1970–2022. The results suggest that bottom water acidification rates are more than twice as great as surface rates. Bottom waters are also naturally more acidic. Thus these waters will pass key thresholds known to negatively impact marine organisms, such as red king crab, much sooner than surface waters.
Daniel Müller, Bo Liu, Walter Geibert, Moritz Holtappels, Lasse Sander, Elda Miramontes, Heidi Taubner, Susann Henkel, Kai-Uwe Hinrichs, Denise Bethke, Ingrid Dohrmann, and Sabine Kasten
Biogeosciences, 22, 2541–2567, https://doi.org/10.5194/bg-22-2541-2025, https://doi.org/10.5194/bg-22-2541-2025, 2025
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Coastal and shelf sediments are the most important sinks for organic carbon (OC) on Earth. We produced a new high-resolution sediment and porewater data set from the Helgoland Mud Area (HMA), North Sea, to determine which depositional factors control the preservation of OC. The burial efficiency is highest in an area of high sedimentation and terrigenous OC. The HMA covers 0.09 % of the North Sea but accounts for 0.76 % of its OC accumulation, highlighting the importance of the depocentre.
Menghong Dong, Xinyu Guo, Takuya Matsuura, Taichi Tebakari, and Jing Zhang
Biogeosciences, 22, 2383–2402, https://doi.org/10.5194/bg-22-2383-2025, https://doi.org/10.5194/bg-22-2383-2025, 2025
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Submarine groundwater discharge (SGD), a common coastal hydrological process that involves submarine inflow of groundwater into the sea, is associated with a large nutrient load. To clarify the distribution of SGD-derived nutrients after release at the bottom of the sea and their contribution to phytoplankton growth in the marine ecosystem, we modeled the SGD process in Toyama Bay using a specialized computer code that can distinguish SGD-derived nutrients from nutrients from other sources.
M. Celeste López-Abbate, John E. Garzón-Cardona, Ricardo Silva, Juan-Carlos Molinero, Laura A. Ruiz-Etcheverry, Ana M. Martínez, Azul S. Gilabert, and Rubén J. Lara
Biogeosciences, 22, 2309–2325, https://doi.org/10.5194/bg-22-2309-2025, https://doi.org/10.5194/bg-22-2309-2025, 2025
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This study explores how microbial dynamics influence the dissolved organic matter (DOM) pool in the Patagonian Shelf. Despite high phytoplankton biomass, selective grazing on fast-growing bacteria led to DOM accumulation, likely due to reduced DOM-consuming bacteria and added egestion compounds. Experiments showed that bacteria not only acted as a carbon sink through mineralization but also transferred assimilated carbon dioxide (CO2) to higher trophic levels.
Librada Ramírez, Leonardo J. Pozzo-Pirotta, Aja Trebec, Víctor Manzanares-Vázquez, José L. Díez, Javier Arístegui, Ulf Riebesell, Stephen D. Archer, and María Segovia
Biogeosciences, 22, 1865–1886, https://doi.org/10.5194/bg-22-1865-2025, https://doi.org/10.5194/bg-22-1865-2025, 2025
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We studied the potential effects of increasing ocean alkalinity on a natural plankton community in subtropical waters of the Atlantic near Gran Canaria, Spain. Alkalinity is the capacity of water to resist acidification, and plankton are usually microscopic plants (phytoplankton) and animals (zooplankton), often less than 2.5 cm in length. This study suggests that increasing ocean alkalinity did not have a significant negative impact on the plankton community studied.
Leissing Frederick, Mauricio A. Urbina, and Ruben Escribano
Biogeosciences, 22, 1839–1852, https://doi.org/10.5194/bg-22-1839-2025, https://doi.org/10.5194/bg-22-1839-2025, 2025
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Evidence shows that due to global warming, zooplankton inhabiting the coastal upwelling zone are exposed to increasing hypoxia affecting their physiology, metabolism, and population dynamics. The adaptive responses of zooplankton to cope with mild/severe hypoxia may depend on trade-offs with other metabolic/energy demands, implying less energy for growth, feeding, and reproduction, with ecological consequences for the zooplankton population and the marine food web.
Sören Iwe, Oliver Schmale, and Bernd Schneider
Biogeosciences, 22, 1767–1779, https://doi.org/10.5194/bg-22-1767-2025, https://doi.org/10.5194/bg-22-1767-2025, 2025
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We present a novel method for quantifying N2 fixation by cyanobacteria, which is crucial in Baltic Sea eutrophication. Our Gas Equilibrium – Membrane-Inlet Mass Spectrometer (GE-MIMS), designed for operation on voluntary observing ships (VOSs), enables large-scale monitoring of surface water N2 depletion caused by N2 fixation. Laboratory tests confirm the device’s accuracy and precision, ensuring that it can complement current methods and contribute valuable data for better understanding N2 fixation in the Baltic Sea.
Caroline P. Slomp, Martijn Hermans, Niels A. G. M. van Helmond, Silke Severmann, James McManus, Marit R. van Erk, and Sairah Malkin
EGUsphere, https://doi.org/10.5194/egusphere-2025-817, https://doi.org/10.5194/egusphere-2025-817, 2025
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Cable bacteria couple oxidation of sulfide at depth in sediments with reduction of oxygen, nitrate or nitrite near the sediment surface, thereby preventing release of toxic hydrogen sulfide to the overlying water. We show evidence for a diversity of cable bacteria in sediments from hypoxic and anoxic basins along the continental margin of California and Mexico. Cable bacteria activity in this setting is likely periodic and dependent on the supply of organic matter and/or oxygen.
Jenna Alyson Lee, Joseph H. Vineis, Mathieu A. Poupon, Laure Resplandy, and Bess B. Ward
EGUsphere, https://doi.org/10.5194/egusphere-2025-871, https://doi.org/10.5194/egusphere-2025-871, 2025
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Concurrent sampling of environmental parameters, productivity rates, photopigments, and DNA were used to analyze a 24–L estuarine diatom bloom microcosm. Biogeochemical data and an ecological model indicated that the bloom was terminated by grazing. Comparisons to previous studies revealed (1) additional community and diversity complexity using 18S amplicon vs. traditional pigment–based analyses, and (2) a potential global productivity–diversity relationship using 18S and carbon transport rates.
Yong-Woo Lee, Mi-Ok Park, Seong-Gil Kim, Tae-Hoon Kim, Yong Hwa Oh, Sang Heon Lee, and DongJoo Joung
Biogeosciences, 22, 675–690, https://doi.org/10.5194/bg-22-675-2025, https://doi.org/10.5194/bg-22-675-2025, 2025
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Long-term pH variation in coastal waters along the Korean Peninsula was assessed for the first time, and it exhibited no significant pH change over an 11-year period. This contrasts with the ongoing pH decline in open oceans and other coastal areas. Analysis of environmental data showed that pH is mainly controlled by dissolved oxygen in bottom waters. This suggests that ocean warming could cause a pH decline in Korean coastal waters, affecting many fish and seaweed aquaculture operations.
Kadir Biçe, Tristen Myers Stewart, George G. Waldbusser, and Christof Meile
Biogeosciences, 22, 641–657, https://doi.org/10.5194/bg-22-641-2025, https://doi.org/10.5194/bg-22-641-2025, 2025
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We studied the effect of addition of carbonate minerals on coastal sediments. We carried out laboratory experiments to quantify the dissolution kinetics and integrated these observations into a numerical model that describes biogeochemical cycling in surficial sediments. Using the model, we demonstrate the buffering effect of the mineral additions and their duration. We quantify the effect under different environmental conditions and assess the potential for increased atmospheric CO2 uptake.
Feifei Liu, Ute Daewel, Jan Kossack, Kubilay Timur Demir, Helmuth Thomas, and Corinna Schrum
EGUsphere, https://doi.org/10.5194/egusphere-2025-81, https://doi.org/10.5194/egusphere-2025-81, 2025
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Ocean Alkalinity Enhancement boosts oceanic CO₂ absorption, offering a climate solution. Using a regional model, we examined OAE in the North Sea, revealing that shallow coastal areas achieve higher CO₂ uptake than offshore, where alkalinity is more susceptible to deep-ocean loss. Long-term carbon storage is limited, and pH shifts vary by location. Our findings guide OAE deployment to optimize carbon removal while minimizing ecological effects, supporting global climate mitigation efforts.
Jessica L. Oberlander, Mackenzie E. Burke, Cat A. London, and Hugh L. MacIntyre
Biogeosciences, 22, 499–512, https://doi.org/10.5194/bg-22-499-2025, https://doi.org/10.5194/bg-22-499-2025, 2025
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Ocean alkalinity enhancement (OAE) is a promising negative emission technology that results in the net sequestration of atmospheric carbon. In this paper, we assess the potential impact of OAE on phytoplankton through an analysis of prior studies and the effects of simulated OAE on photosynthetic competence. Our findings suggest that there may be little if any significant impact on most phytoplankton studied to date if OAE is conducted in well-flushed, nearshore environments.
Laura Marín-Samper, Javier Arístegui, Nauzet Hernández-Hernández, and Ulf Riebesell
Biogeosciences, 21, 5707–5724, https://doi.org/10.5194/bg-21-5707-2024, https://doi.org/10.5194/bg-21-5707-2024, 2024
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This study exposed a natural community to two non-CO2-equilibrated ocean alkalinity enhancement (OAE) deployments using different minerals. Adding alkalinity in this manner decreases dissolved CO2, essential for photosynthesis. While photosynthesis was not suppressed, bloom formation was mildly delayed, potentially impacting marine food webs. The study emphasizes the need for further research on OAE without prior equilibration and on its ecological implications.
Riss M. Kell, Rebecca J. Chmiel, Deepa Rao, Dawn M. Moran, Matthew R. McIlvin, Tristan J. Horner, Nicole L. Schanke, Ichiko Sugiyama, Robert B. Dunbar, Giacomo R. DiTullio, and Mak A. Saito
Biogeosciences, 21, 5685–5706, https://doi.org/10.5194/bg-21-5685-2024, https://doi.org/10.5194/bg-21-5685-2024, 2024
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Despite interest in modeling the biogeochemical uptake and cycling of the trace metal zinc (Zn), measurements of Zn uptake in natural marine phytoplankton communities have not been conducted previously. To fill this gap, we employed a stable isotope uptake rate measurement method to quantify Zn uptake into natural phytoplankton assemblages within the Southern Ocean. Zn demand was high and rapid enough to depress the inventory of Zn available to phytoplankton on seasonal timescales.
Luisa Chiara Meiritz, Tim Rixen, Anja Karin van der Plas, Tarron Lamont, and Niko Lahajnar
Biogeosciences, 21, 5261–5276, https://doi.org/10.5194/bg-21-5261-2024, https://doi.org/10.5194/bg-21-5261-2024, 2024
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Moored and drifting sediment trap experiments in the northern (nBUS) and southern (sBUS) Benguela Upwelling System showed that active carbon fluxes by vertically migrating zooplankton were about 3 times higher in the sBUS than in the nBUS. Despite these large variabilities, the mean passive particulate organic carbon (POC) fluxes were almost equal in the two subsystems. The more intense near-bottom oxygen minimum layer seems to lead to higher POC fluxes and accumulation rates in the nBUS.
Michael R. Roman, Andrew H. Altieri, Denise Breitburg, Erica M. Ferrer, Natalya D. Gallo, Shin-ichi Ito, Karin Limburg, Kenneth Rose, Moriaki Yasuhara, and Lisa A. Levin
Biogeosciences, 21, 4975–5004, https://doi.org/10.5194/bg-21-4975-2024, https://doi.org/10.5194/bg-21-4975-2024, 2024
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Oxygen-depleted ocean waters have increased worldwide. In order to improve our understanding of the impacts of this oxygen loss on marine life it is essential that we develop reliable indicators that track the negative impacts of low oxygen. We review various indicators of low-oxygen stress for marine animals including their use, research needs, and application to confront the challenges of ocean oxygen loss.
Charlotte Eich, Mathijs van Manen, J. Scott P. McCain, Loay J. Jabre, Willem H. van de Poll, Jinyoung Jung, Sven B. E. H. Pont, Hung-An Tian, Indah Ardiningsih, Gert-Jan Reichart, Erin M. Bertrand, Corina P. D. Brussaard, and Rob Middag
Biogeosciences, 21, 4637–4663, https://doi.org/10.5194/bg-21-4637-2024, https://doi.org/10.5194/bg-21-4637-2024, 2024
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Phytoplankton growth in the Southern Ocean (SO) is often limited by low iron (Fe) concentrations. Sea surface warming impacts Fe availability and can affect phytoplankton growth. We used shipboard Fe clean incubations to test how changes in Fe and temperature affect SO phytoplankton. Their abundances usually increased with Fe addition and temperature increase, with Fe being the major factor. These findings imply potential shifts in ecosystem structure, impacting food webs and elemental cycling.
Miriam Tivig, David P. Keller, and Andreas Oschlies
Biogeosciences, 21, 4469–4493, https://doi.org/10.5194/bg-21-4469-2024, https://doi.org/10.5194/bg-21-4469-2024, 2024
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Marine biological production is highly dependent on the availability of nitrogen and phosphorus. Rivers are the main source of phosphorus to the oceans but poorly represented in global model oceans. We include dissolved nitrogen and phosphorus from river export in a global model ocean and find that the addition of riverine phosphorus affects marine biology on millennial timescales more than riverine nitrogen alone. Globally, riverine phosphorus input increases primary production rates.
Esdoorn Willcox, Marcos Lemes, Thomas Juul-Pedersen, Mikael Kristian Sejr, Johnna Marchiano Holding, and Søren Rysgaard
Biogeosciences, 21, 4037–4050, https://doi.org/10.5194/bg-21-4037-2024, https://doi.org/10.5194/bg-21-4037-2024, 2024
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In this work, we measured the chemistry of seawater from samples obtained from different depths and locations off the east coast of the Northeast Greenland National Park to determine what is influencing concentrations of dissolved CO2. Historically, the region has always been thought to take up CO2 from the atmosphere, but we show that it is possible for the region to become a source in late summer. We discuss the variables that may be related to such changes.
Lennart Thomas Bach, Aaron James Ferderer, Julie LaRoche, and Kai Georg Schulz
Biogeosciences, 21, 3665–3676, https://doi.org/10.5194/bg-21-3665-2024, https://doi.org/10.5194/bg-21-3665-2024, 2024
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Ocean alkalinity enhancement (OAE) is an emerging marine CO2 removal method, but its environmental effects are insufficiently understood. The OAE Pelagic Impact Intercomparison Project (OAEPIIP) provides funding for a standardized and globally replicated microcosm experiment to study the effects of OAE on plankton communities. Here, we provide a detailed manual for the OAEPIIP experiment. We expect OAEPIIP to help build scientific consensus on the effects of OAE on plankton.
Marlena Szeligowska, Déborah Benkort, Anna Przyborska, Mateusz Moskalik, Bernabé Moreno, Emilia Trudnowska, and Katarzyna Błachowiak-Samołyk
Biogeosciences, 21, 3617–3639, https://doi.org/10.5194/bg-21-3617-2024, https://doi.org/10.5194/bg-21-3617-2024, 2024
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The European Arctic is experiencing rapid regional warming, causing glaciers that terminate in the sea to retreat onto land. Due to this process, the area of a well-studied fjord, Hornsund, has increased by around 100 km2 (40%) since 1976. Combining satellite and in situ data with a mathematical model, we estimated that, despite some negative consequences of glacial meltwater release, such emerging coastal waters could mitigate climate change by increasing carbon uptake and storage by sediments.
Mallory C. Ringham, Nathan Hirtle, Cody Shaw, Xi Lu, Julian Herndon, Brendan R. Carter, and Matthew D. Eisaman
Biogeosciences, 21, 3551–3570, https://doi.org/10.5194/bg-21-3551-2024, https://doi.org/10.5194/bg-21-3551-2024, 2024
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Ocean alkalinity enhancement leverages the large surface area and carbon storage capacity of the oceans to store atmospheric CO2 as dissolved bicarbonate. We monitored CO2 uptake in seawater treated with NaOH to establish operational boundaries for carbon removal experiments. Results show that CO2 equilibration occurred on the order of weeks to months, was consistent with values expected from equilibration calculations, and was limited by mineral precipitation at high pH and CaCO3 saturation.
Riel Carlo O. Ingeniero, Gesa Schulz, and Hermann W. Bange
Biogeosciences, 21, 3425–3440, https://doi.org/10.5194/bg-21-3425-2024, https://doi.org/10.5194/bg-21-3425-2024, 2024
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Our research is the first to measure dissolved NO concentrations in temperate estuarine waters, providing insights into its distribution under varying conditions and enhancing our understanding of its production processes. Dissolved NO was supersaturated in the Elbe Estuary, indicating that it is a source of atmospheric NO. The observed distribution of dissolved NO most likely resulted from nitrification.
Weiyi Tang, Jeff Talbott, Timothy Jones, and Bess B. Ward
Biogeosciences, 21, 3239–3250, https://doi.org/10.5194/bg-21-3239-2024, https://doi.org/10.5194/bg-21-3239-2024, 2024
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Wastewater treatment plants (WWTPs) are known to be hotspots of greenhouse gas emissions. However, the impact of WWTPs on the emission of the greenhouse gas N2O in downstream aquatic environments is less constrained. We found spatially and temporally variable but overall higher N2O concentrations and fluxes in waters downstream of WWTPs, pointing to the need for efficient N2O removal in addition to the treatment of nitrogen in WWTPs.
Deep S. Banerjee and Jozef Skakala
EGUsphere, https://doi.org/10.22541/essoar.171405637.76928549/v1, https://doi.org/10.22541/essoar.171405637.76928549/v1, 2024
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Nitrate is a crucial nutrient in oceans. Excess nutrients can trigger uncontrolled algae growth (eutrophication), damaging marine ecosystems. We used a machine learning tool to generate a skilled, gap-free, bi-decadal surface nitrate dataset from sparse observations. This dataset reveals areas on the North West European Shelf at risk of eutrophication, bi-decadal trends in coastal nitrate, and an impact of winter nitrate on spring phytoplankton blooms.
Amanda Y. L. Cheong, Kogila Vani Annammala, Ee Ling Yong, Yongli Zhou, Robert S. Nichols, and Patrick Martin
Biogeosciences, 21, 2955–2971, https://doi.org/10.5194/bg-21-2955-2024, https://doi.org/10.5194/bg-21-2955-2024, 2024
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We measured nutrients and dissolved organic matter for 1 year in a eutrophic tropical estuary to understand their sources and cycling. Our data show that the dissolved organic matter originates partly from land and partly from microbial processes in the water. Internal recycling is likely important for maintaining high nutrient concentrations, and we found that there is often excess nitrogen compared to silicon and phosphorus. Our data help to explain how eutrophication persists in this system.
Aaron Ferderer, Kai G. Schulz, Ulf Riebesell, Kirralee G. Baker, Zanna Chase, and Lennart T. Bach
Biogeosciences, 21, 2777–2794, https://doi.org/10.5194/bg-21-2777-2024, https://doi.org/10.5194/bg-21-2777-2024, 2024
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Ocean alkalinity enhancement (OAE) is a promising method of atmospheric carbon removal; however, its ecological impacts remain largely unknown. We assessed the effects of simulated silicate- and calcium-based mineral OAE on diatom silicification. We found that increased silicate concentrations from silicate-based OAE increased diatom silicification. In contrast, the enhancement of alkalinity had no effect on community silicification and minimal effects on the silicification of different genera.
David González-Santana, María Segovia, Melchor González-Dávila, Librada Ramírez, Aridane G. González, Leonardo J. Pozzo-Pirotta, Veronica Arnone, Victor Vázquez, Ulf Riebesell, and J. Magdalena Santana-Casiano
Biogeosciences, 21, 2705–2715, https://doi.org/10.5194/bg-21-2705-2024, https://doi.org/10.5194/bg-21-2705-2024, 2024
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In a recent experiment off the coast of Gran Canaria (Spain), scientists explored a method called ocean alkalinization enhancement (OAE), where carbonate minerals were added to seawater. This process changed the levels of certain ions in the water, affecting its pH and buffering capacity. The researchers were particularly interested in how this could impact the levels of essential trace metals in the water.
Lucas Porz, Wenyan Zhang, Nils Christiansen, Jan Kossack, Ute Daewel, and Corinna Schrum
Biogeosciences, 21, 2547–2570, https://doi.org/10.5194/bg-21-2547-2024, https://doi.org/10.5194/bg-21-2547-2024, 2024
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Seafloor sediments store a large amount of carbon, helping to naturally regulate Earth's climate. If disturbed, some sediment particles can turn into CO2, but this effect is not well understood. Using computer simulations, we found that bottom-contacting fishing gears release about 1 million tons of CO2 per year in the North Sea, one of the most heavily fished regions globally. We show how protecting certain areas could reduce these emissions while also benefitting seafloor-living animals.
Jiaying A. Guo, Robert F. Strzepek, Kerrie M. Swadling, Ashley T. Townsend, and Lennart T. Bach
Biogeosciences, 21, 2335–2354, https://doi.org/10.5194/bg-21-2335-2024, https://doi.org/10.5194/bg-21-2335-2024, 2024
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Ocean alkalinity enhancement aims to increase atmospheric CO2 sequestration by adding alkaline materials to the ocean. We assessed the environmental effects of olivine and steel slag powder on coastal plankton. Overall, slag is more efficient than olivine in releasing total alkalinity and, thus, in its ability to sequester CO2. Slag also had less environmental effect on the enclosed plankton communities when considering its higher CO2 removal potential based on this 3-week experiment.
Giovanni Galli, Sarah Wakelin, James Harle, Jason Holt, and Yuri Artioli
Biogeosciences, 21, 2143–2158, https://doi.org/10.5194/bg-21-2143-2024, https://doi.org/10.5194/bg-21-2143-2024, 2024
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This work shows that, under a high-emission scenario, oxygen concentration in deep water of parts of the North Sea and Celtic Sea can become critically low (hypoxia) towards the end of this century. The extent and frequency of hypoxia depends on the intensity of climate change projected by different climate models. This is the result of a complex combination of factors like warming, increase in stratification, changes in the currents and changes in biological processes.
Sandy E. Tenorio and Laura Farías
Biogeosciences, 21, 2029–2050, https://doi.org/10.5194/bg-21-2029-2024, https://doi.org/10.5194/bg-21-2029-2024, 2024
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Time series studies show that CH4 is highly dynamic on the coastal ocean surface and planktonic communities are linked to CH4 accumulation, as found in coastal upwelling off Chile. We have identified the crucial role of picoplankton (> 3 µm) in CH4 recycling, especially with the addition of methylated substrates (trimethylamine and methylphosphonic acid) during upwelling and non-upwelling periods. These insights improve understanding of surface ocean CH4 recycling, aiding CH4 emission estimates.
Charlotte A. J. Williams, Tom Hull, Jan Kaiser, Claire Mahaffey, Naomi Greenwood, Matthew Toberman, and Matthew R. Palmer
Biogeosciences, 21, 1961–1971, https://doi.org/10.5194/bg-21-1961-2024, https://doi.org/10.5194/bg-21-1961-2024, 2024
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Oxygen (O2) is a key indicator of ocean health. The risk of O2 loss in the productive coastal/continental slope regions is increasing. Autonomous underwater vehicles equipped with O2 optodes provide lots of data but have problems resolving strong vertical O2 changes. Here we show how to overcome this and calculate how much O2 is supplied to the low-O2 bottom waters via mixing. Bursts in mixing supply nearly all of the O2 to bottom waters in autumn, stopping them reaching ecologically low levels.
Sabine Schmidt and Ibrahima Iris Diallo
Biogeosciences, 21, 1785–1800, https://doi.org/10.5194/bg-21-1785-2024, https://doi.org/10.5194/bg-21-1785-2024, 2024
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Along the French coast facing the Bay of Biscay, the large Gironde and Loire estuaries suffer from hypoxia. This prompted a study of the small Charente estuary located between them. This work reveals a minimum oxygen zone in the Charente estuary, which extends for about 25 km. Temperature is the main factor controlling the hypoxia. This calls for the monitoring of small turbid macrotidal estuaries that are vulnerable to hypoxia, a risk expected to increase with global warming.
Simone R. Alin, Jan A. Newton, Richard A. Feely, Samantha Siedlecki, and Dana Greeley
Biogeosciences, 21, 1639–1673, https://doi.org/10.5194/bg-21-1639-2024, https://doi.org/10.5194/bg-21-1639-2024, 2024
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We provide a new multi-stressor data product that allows us to characterize the seasonality of temperature, O2, and CO2 in the southern Salish Sea and delivers insights into the impacts of major marine heatwave and precipitation anomalies on regional ocean acidification and hypoxia. We also describe the present-day frequencies of temperature, O2, and ocean acidification conditions that cross thresholds of sensitive regional species that are economically or ecologically important.
Pamela Linford, Iván Pérez-Santos, Paulina Montero, Patricio A. Díaz, Claudia Aracena, Elías Pinilla, Facundo Barrera, Manuel Castillo, Aida Alvera-Azcárate, Mónica Alvarado, Gabriel Soto, Cécile Pujol, Camila Schwerter, Sara Arenas-Uribe, Pilar Navarro, Guido Mancilla-Gutiérrez, Robinson Altamirano, Javiera San Martín, and Camila Soto-Riquelme
Biogeosciences, 21, 1433–1459, https://doi.org/10.5194/bg-21-1433-2024, https://doi.org/10.5194/bg-21-1433-2024, 2024
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The Patagonian fjords comprise a world region where low-oxygen water and hypoxia conditions are observed. An in situ dataset was used to quantify the mechanism involved in the presence of these conditions in northern Patagonian fjords. Water mass analysis confirmed the contribution of Equatorial Subsurface Water in the advection of the low-oxygen water, and hypoxic conditions occurred when the community respiration rate exceeded the gross primary production.
Ting Wang, Buyun Du, Inke Forbrich, Jun Zhou, Joshua Polen, Elsie M. Sunderland, Prentiss H. Balcom, Celia Chen, and Daniel Obrist
Biogeosciences, 21, 1461–1476, https://doi.org/10.5194/bg-21-1461-2024, https://doi.org/10.5194/bg-21-1461-2024, 2024
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The strong seasonal increases of Hg in aboveground biomass during the growing season and the lack of changes observed after senescence in this salt marsh ecosystem suggest physiologically controlled Hg uptake pathways. The Hg sources found in marsh aboveground tissues originate from a mix of sources, unlike terrestrial ecosystems, where atmospheric GEM is the main source. Belowground plant tissues mostly take up Hg from soils. Overall, the salt marsh currently serves as a small net Hg sink.
Eleanor Simpson, Debby Ianson, Karen E. Kohfeld, Ana C. Franco, Paul A. Covert, Marty Davelaar, and Yves Perreault
Biogeosciences, 21, 1323–1353, https://doi.org/10.5194/bg-21-1323-2024, https://doi.org/10.5194/bg-21-1323-2024, 2024
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Shellfish aquaculture operates in nearshore areas where data on ocean acidification parameters are limited. We show daily and seasonal variability in pH and saturation states of calcium carbonate at nearshore aquaculture sites in British Columbia, Canada, and determine the contributing drivers of this variability. We find that nearshore locations have greater variability than open waters and that the uptake of carbon by phytoplankton is the major driver of pH and saturation state variability.
S. Alejandra Castillo Cieza, Rachel H. R. Stanley, Pierre Marrec, Diana N. Fontaine, E. Taylor Crockford, Dennis J. McGillicuddy Jr., Arshia Mehta, Susanne Menden-Deuer, Emily E. Peacock, Tatiana A. Rynearson, Zoe O. Sandwith, Weifeng Zhang, and Heidi M. Sosik
Biogeosciences, 21, 1235–1257, https://doi.org/10.5194/bg-21-1235-2024, https://doi.org/10.5194/bg-21-1235-2024, 2024
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The coastal ocean in the northeastern USA provides many services, including fisheries and habitats for threatened species. In summer 2019, a bloom occurred of a large unusual phytoplankton, the diatom Hemiaulus, with nitrogen-fixing symbionts. This led to vast changes in productivity and grazing rates in the ecosystem. This work shows that the emergence of one species can have profound effects on ecosystem function. Such changes may become more prevalent as the ocean warms due to climate change.
Claudine Hauri, Brita Irving, Sam Dupont, Rémi Pagés, Donna D. W. Hauser, and Seth L. Danielson
Biogeosciences, 21, 1135–1159, https://doi.org/10.5194/bg-21-1135-2024, https://doi.org/10.5194/bg-21-1135-2024, 2024
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Arctic marine ecosystems are highly susceptible to impacts of climate change and ocean acidification. We present pH and pCO2 time series (2016–2020) from the Chukchi Ecosystem Observatory and analyze the drivers of the current conditions to get a better understanding of how climate change and ocean acidification could affect the ecological niches of organisms.
William Hiles, Lucy C. Miller, Craig Smeaton, and William E. N. Austin
Biogeosciences, 21, 929–948, https://doi.org/10.5194/bg-21-929-2024, https://doi.org/10.5194/bg-21-929-2024, 2024
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Saltmarsh soils may help to limit the rate of climate change by storing carbon. To understand their impacts, they must be accurately mapped. We use drone data to estimate the size of three saltmarshes in NE Scotland. We find that drone imagery, combined with tidal data, can reliably inform our understanding of saltmarsh size. When compared with previous work using vegetation communities, we find that our most reliable new estimates of stored carbon are 15–20 % smaller than previously estimated.
De'Marcus Robinson, Anh L. D. Pham, David J. Yousavich, Felix Janssen, Frank Wenzhöfer, Eleanor C. Arrington, Kelsey M. Gosselin, Marco Sandoval-Belmar, Matthew Mar, David L. Valentine, Daniele Bianchi, and Tina Treude
Biogeosciences, 21, 773–788, https://doi.org/10.5194/bg-21-773-2024, https://doi.org/10.5194/bg-21-773-2024, 2024
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The present study suggests that high release of ferrous iron from the seafloor of the oxygen-deficient Santa Barabara Basin (California) supports surface primary productivity, creating positive feedback on seafloor iron release by enhancing low-oxygen conditions in the basin.
David J. Yousavich, De'Marcus Robinson, Xuefeng Peng, Sebastian J. E. Krause, Frank Wenzhöfer, Felix Janssen, Na Liu, Jonathan Tarn, Franklin Kinnaman, David L. Valentine, and Tina Treude
Biogeosciences, 21, 789–809, https://doi.org/10.5194/bg-21-789-2024, https://doi.org/10.5194/bg-21-789-2024, 2024
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Declining oxygen (O2) concentrations in coastal oceans can threaten people’s ways of life and food supplies. Here, we investigate how mats of bacteria that proliferate on the seafloor of the Santa Barbara Basin sustain and potentially worsen these O2 depletion events through their unique chemoautotrophic metabolism. Our study shows how changes in seafloor microbiology and geochemistry brought on by declining O2 concentrations can help these mats grow as well as how that growth affects the basin.
Krysten Rutherford, Katja Fennel, Lina Garcia Suarez, and Jasmin G. John
Biogeosciences, 21, 301–314, https://doi.org/10.5194/bg-21-301-2024, https://doi.org/10.5194/bg-21-301-2024, 2024
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We downscaled two mid-century (~2075) ocean model projections to a high-resolution regional ocean model of the northwest North Atlantic (NA) shelf. In one projection, the NA shelf break current practically disappears; in the other it remains almost unchanged. This leads to a wide range of possible future shelf properties. More accurate projections of coastal circulation features would narrow the range of possible outcomes of biogeochemical projections for shelf regions.
Lennart Thomas Bach
Biogeosciences, 21, 261–277, https://doi.org/10.5194/bg-21-261-2024, https://doi.org/10.5194/bg-21-261-2024, 2024
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Ocean alkalinity enhancement (OAE) is a widely considered marine carbon dioxide removal method. OAE aims to accelerate chemical rock weathering, which is a natural process that slowly sequesters atmospheric carbon dioxide. This study shows that the addition of anthropogenic alkalinity via OAE can reduce the natural release of alkalinity and, therefore, reduce the efficiency of OAE for climate mitigation. However, the additionality problem could be mitigated via a variety of activities.
Tsuneo Ono, Daisuke Muraoka, Masahiro Hayashi, Makiko Yorifuji, Akihiro Dazai, Shigeyuki Omoto, Takehiro Tanaka, Tomohiro Okamura, Goh Onitsuka, Kenji Sudo, Masahiko Fujii, Ryuji Hamanoue, and Masahide Wakita
Biogeosciences, 21, 177–199, https://doi.org/10.5194/bg-21-177-2024, https://doi.org/10.5194/bg-21-177-2024, 2024
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We carried out parallel year-round observations of pH and related parameters in five stations around the Japan coast. It was found that short-term acidified situations with Omega_ar less than 1.5 occurred at four of five stations. Most of such short-term acidified events were related to the short-term low salinity event, and the extent of short-term pH drawdown at high freshwater input was positively correlated with the nutrient concentration of the main rivers that flow into the coastal area.
K. Mareike Paul, Martijn Hermans, Sami A. Jokinen, Inda Brinkmann, Helena L. Filipsson, and Tom Jilbert
Biogeosciences, 20, 5003–5028, https://doi.org/10.5194/bg-20-5003-2023, https://doi.org/10.5194/bg-20-5003-2023, 2023
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Seawater naturally contains trace metals such as Mo and U, which accumulate under low oxygen conditions on the seafloor. Previous studies have used sediment Mo and U contents as an archive of changing oxygen concentrations in coastal waters. Here we show that in fjords the use of Mo and U for this purpose may be impaired by additional processes. Our findings have implications for the reliable use of Mo and U to reconstruct oxygen changes in fjords.
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