Articles | Volume 22, issue 20
https://doi.org/10.5194/bg-22-5943-2025
© Author(s) 2025. This work is distributed under
the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
https://doi.org/10.5194/bg-22-5943-2025
© Author(s) 2025. This work is distributed under
the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
Research article
| 
23 Oct 2025
Research article |
| 23 Oct 2025
| 23 Oct 2025
Nitrogen dynamics and nitrate stable isotopes indicate nitrogen loss in the Bay of Bengal
Institute for Geology, University of Hamburg ,20146 Hamburg, Germany
Institute of Carbon Cycles, Helmholtz-Zentrum Hereon, 21502 Geesthacht, Germany
Kirstin Dähnke
Institute of Carbon Cycles, Helmholtz-Zentrum Hereon, 21502 Geesthacht, Germany
Tina Sanders
Institute of Carbon Cycles, Helmholtz-Zentrum Hereon, 21502 Geesthacht, Germany
Jan Penopp
Institute for Geology, University of Hamburg ,20146 Hamburg, Germany
Hermann W. Bange
Marine Biogeochemistry Research Division, GEOMAR Helmholtz Centre for Ocean Research Kiel, 24148 Kiel, Germany
Rena Czeschel
Ocean Circulation and Climate Dynamics Research Division, GEOMAR Helmholtz Centre for Ocean Research Kiel, 24148 Kiel, Germany
Birgit Gaye
Institute for Geology, University of Hamburg ,20146 Hamburg, Germany
Related authors
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
Short summary
Short summary
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.
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
Short summary
Short summary
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.
Mona Norbisrath, Johannes Pätsch, Kirstin Dähnke, Tina Sanders, Gesa Schulz, Justus E. E. van Beusekom, and Helmuth Thomas
Biogeosciences, 19, 5151–5165, https://doi.org/10.5194/bg-19-5151-2022, https://doi.org/10.5194/bg-19-5151-2022, 2022
Short summary
Short summary
Total alkalinity (TA) regulates the oceanic storage capacity of atmospheric CO2. TA is also metabolically generated in estuaries and influences coastal carbon storage through its inflows. We used water samples and identified the Hamburg port area as the one with highest TA generation. Of the overall riverine TA load, 14 % is generated within the estuary. Using a biogeochemical model, we estimated potential effects on the coastal carbon storage under possible anthropogenic and climate changes.
Gesa Schulz, Tina Sanders, Justus E. E. van Beusekom, Yoana G. Voynova, Andreas Schöl, and Kirstin Dähnke
Biogeosciences, 19, 2007–2024, https://doi.org/10.5194/bg-19-2007-2022, https://doi.org/10.5194/bg-19-2007-2022, 2022
Short summary
Short summary
Estuaries can significantly alter nutrient loads before reaching coastal waters. Our study of the heavily managed Ems estuary (Northern Germany) reveals three zones of nitrogen turnover along the estuary with water-column denitrification in the most upstream hyper-turbid part, nitrate production in the middle reaches and mixing/nitrate uptake in the North Sea. Suspended particulate matter was the overarching control on nitrogen cycling in the hyper-turbid estuary.
Ina Stoltenberg, Lea Lange, and Hermann Bange
EGUsphere, https://doi.org/10.5194/egusphere-2025-5279, https://doi.org/10.5194/egusphere-2025-5279, 2025
This preprint is open for discussion and under review for Biogeosciences (BG).
Short summary
Short summary
In order to decipher the effect of a phytoplankton bloom on oceanic N2O, dissolved N2O was measured in the upper 1 mm of the water column (sea surface microlayer) and in the underlying water during a mesocosm study. N2O concentrations were slightly enriched in the surface microlayer compared to the underlying water and were apparently not affected by irradiation and a phytoplankton bloom. Our results indicate that the role of the surface microlayer for N2O cycling has been overlooked so far.
Eugene Odion Oboh, Niko Lahajnar, Birgit Gaye, Avanti Shrikumar, and Tim Rixen
EGUsphere, https://doi.org/10.5194/egusphere-2025-4712, https://doi.org/10.5194/egusphere-2025-4712, 2025
This preprint is open for discussion and under review for Biogeosciences (BG).
Short summary
Short summary
We studied water mass distribution and oxygen consumption changes in low oxygen regions of the Indian Ocean and found slightly more oxygen present in these regions in 2016/2018 compared to 1995, contrary to the expected decline. This change is linked to a shift in ocean circulation that brought more oxygen-rich waters from the south to the north. Our results show that the development of these low oxygen regions is connected to the relationship between climate change and ocean circulation.
Lina A. Holthusen, Hermann W. Bange, Thomas H. Badewien, Julia C. Muchowski, Tina Santl-Temkiv, Jennie Spicker Schmidt, Oliver Wurl, and Damian L. Arévalo-Martínez
EGUsphere, https://doi.org/10.5194/egusphere-2025-4056, https://doi.org/10.5194/egusphere-2025-4056, 2025
Short summary
Short summary
In spring 2023, in the Fram Strait, we investigated the near-surface distribution of the greenhouse gases methane and nitrous oxide in open leads and under sea ice to address the lack of observations in the Arctic Ocean. The study area acted as a source for both gases, and the onset of sea ice melt affected their concentrations and emissions. Surface-active substances accumulated in the sea-surface microlayer of open leads during an algal bloom, potentially attenuating greenhouse gas emissions.
Joachim Schönfeld, Hermann W. Bange, Helmke Hepach, and Svenja Reents
EGUsphere, https://doi.org/10.5194/egusphere-2025-2672, https://doi.org/10.5194/egusphere-2025-2672, 2025
Short summary
Short summary
The current state of intertidal waters at Bottsand lagoon on the Baltic Sea coast, and on the mudflats off Schobüll on the North Sea coast of Schleswig-Holstein, Germany was assessed with a 36-month time series of water level, temperature, and salinity measurements. Periods of strong precipitation, high Elbe river discharge, and high solar radiation caused a higher data variability as compared to the off shore monitoring stations Boknis Eck in the Baltic and Sylt Roads in the North Sea.
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
Short summary
Short summary
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.
Andreas Neumann, Justus E. E. van Beusekom, Alexander Bratek, Jana Friedrich, Jürgen Möbius, Tina Sanders, Hendrik Wolschke, and Kirstin Dähnke
EGUsphere, https://doi.org/10.5194/egusphere-2025-1803, https://doi.org/10.5194/egusphere-2025-1803, 2025
Short summary
Short summary
The North-Western shelf of the Black Sea is substantially influenced by the discharge of nutrients from River Danube. We have sampled the sediment there and measured particulate carbon and nitrogen to reconstruct the variability of nitrogen sources to the NW shelf. Our results demonstrate that the balance of riverine nitrogen input and marine nitrogen fixation is sensitive to climate changes. Nitrogen from human activities is detectable in NW shelf sediment since the 12th century.
Jan Maier, Nicole Burdanowitz, Gerhard Schmiedl, and Birgit Gaye
Clim. Past, 21, 279–297, https://doi.org/10.5194/cp-21-279-2025, https://doi.org/10.5194/cp-21-279-2025, 2025
Short summary
Short summary
We reconstruct sea surface temperatures (SSTs) of the past 43 kyr in the Gulf of Oman. We find SST variations of up to 7 °C with lower SSTs during Heinrich events (HEs), especially HE4, and higher SSTs during Dansgaard–Oeschger events. Our record shows no profound cooling during the Last Glacial Maximum but abrupt variations during the Holocene. We surmise that SST variations are influenced by the southwest (northeast) monsoon during warmer (colder) periods.
Bennet Juhls, Anne Morgenstern, Jens Hölemann, Antje Eulenburg, Birgit Heim, Frederieke Miesner, Hendrik Grotheer, Gesine Mollenhauer, Hanno Meyer, Ephraim Erkens, Felica Yara Gehde, Sofia Antonova, Sergey Chalov, Maria Tereshina, Oxana Erina, Evgeniya Fingert, Ekaterina Abramova, Tina Sanders, Liudmila Lebedeva, Nikolai Torgovkin, Georgii Maksimov, Vasily Povazhnyi, Rafael Gonçalves-Araujo, Urban Wünsch, Antonina Chetverova, Sophie Opfergelt, and Pier Paul Overduin
Earth Syst. Sci. Data, 17, 1–28, https://doi.org/10.5194/essd-17-1-2025, https://doi.org/10.5194/essd-17-1-2025, 2025
Short summary
Short summary
The Siberian Arctic is warming fast: permafrost is thawing, river chemistry is changing, and coastal ecosystems are affected. We aimed to understand changes in the Lena River, a major Arctic river flowing to the Arctic Ocean, by collecting 4.5 years of detailed water data, including temperature and carbon and nutrient contents. This dataset records current conditions and helps us to detect future changes. Explore it at https://doi.org/10.1594/PANGAEA.913197 and https://lena-monitoring.awi.de/.
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
Short summary
Short summary
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.
Medhavi Pandey, Haimanti Biswas, Daniel Birgel, Nicole Burdanowitz, and Birgit Gaye
Biogeosciences, 21, 4681–4698, https://doi.org/10.5194/bg-21-4681-2024, https://doi.org/10.5194/bg-21-4681-2024, 2024
Short summary
Short summary
We analysed sea surface temperature (SST) proxy and plankton biomarkers in sediments that accumulate sinking material signatures from surface waters in the central Arabian Sea (21°–11° N, 64° E), a tropical basin impacted by monsoons. We saw a north–south SST gradient, and the biological proxies showed more organic matter from larger algae in the north. Smaller algae and zooplankton were more numerous in the south. These trends were related to ocean–atmospheric processes and oxygen availability.
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
Short summary
Short summary
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
Short summary
Short summary
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.
Nicole Burdanowitz, Gerhard Schmiedl, Birgit Gaye, Philipp M. Munz, and Hartmut Schulz
Biogeosciences, 21, 1477–1499, https://doi.org/10.5194/bg-21-1477-2024, https://doi.org/10.5194/bg-21-1477-2024, 2024
Short summary
Short summary
We analyse benthic foraminifera, nitrogen isotopes and lipids in a sediment core from the Gulf of Oman to investigate how the oxygen minimum zone (OMZ) and bottom water (BW) oxygenation have reacted to climatic changes since 43 ka. The OMZ and BW deoxygenation was strong during the Holocene, but the OMZ was well ventilated during the LGM period. We found an unstable mode of oscillating oxygenation states, from moderately oxygenated in cold stadials to deoxygenated in warm interstadials in MIS 3.
Mona Norbisrath, Andreas Neumann, Kirstin Dähnke, Tina Sanders, Andreas Schöl, Justus E. E. van Beusekom, and Helmuth Thomas
Biogeosciences, 20, 4307–4321, https://doi.org/10.5194/bg-20-4307-2023, https://doi.org/10.5194/bg-20-4307-2023, 2023
Short summary
Short summary
Total alkalinity (TA) is the oceanic capacity to store CO2. Estuaries can be a TA source. Anaerobic metabolic pathways like denitrification (reduction of NO3− to N2) generate TA and are a major nitrogen (N) sink. Another important N sink is anammox that transforms NH4+ with NO2− into N2 without TA generation. By combining TA and N2 production, we identified a TA source, denitrification, occurring in the water column and suggest anammox as the dominant N2 producer in the bottom layer of the Ems.
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
Short summary
Short summary
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
Short summary
Short summary
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.
Pierre L'Hégaret, Florian Schütte, Sabrina Speich, Gilles Reverdin, Dariusz B. Baranowski, Rena Czeschel, Tim Fischer, Gregory R. Foltz, Karen J. Heywood, Gerd Krahmann, Rémi Laxenaire, Caroline Le Bihan, Philippe Le Bot, Stéphane Leizour, Callum Rollo, Michael Schlundt, Elizabeth Siddle, Corentin Subirade, Dongxiao Zhang, and Johannes Karstensen
Earth Syst. Sci. Data, 15, 1801–1830, https://doi.org/10.5194/essd-15-1801-2023, https://doi.org/10.5194/essd-15-1801-2023, 2023
Short summary
Short summary
In early 2020, the EUREC4A-OA/ATOMIC experiment took place in the northwestern Tropical Atlantic Ocean, a dynamical region where different water masses interact. Four oceanographic vessels and a fleet of autonomous devices were deployed to study the processes at play and sample the upper ocean, each with its own observing capability. The article first describes the data calibration and validation and second their cross-validation, using a hierarchy of instruments and estimating the uncertainty.
Olga Ogneva, Gesine Mollenhauer, Bennet Juhls, Tina Sanders, Juri Palmtag, Matthias Fuchs, Hendrik Grotheer, Paul J. Mann, and Jens Strauss
Biogeosciences, 20, 1423–1441, https://doi.org/10.5194/bg-20-1423-2023, https://doi.org/10.5194/bg-20-1423-2023, 2023
Short summary
Short summary
Arctic warming accelerates permafrost thaw and release of terrestrial organic matter (OM) via rivers to the Arctic Ocean. We compared particulate organic carbon (POC), total suspended matter, and C isotopes (δ13C and Δ14C of POC) in the Lena delta and Lena River along a ~1600 km transect. We show that the Lena delta, as an interface between the Lena River and the Arctic Ocean, plays a crucial role in determining the qualitative and quantitative composition of OM discharged into the Arctic Ocean.
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
Short summary
Short summary
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
Short summary
Short summary
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.
Kirstin Dähnke, Tina Sanders, Yoana Voynova, and Scott D. Wankel
Biogeosciences, 19, 5879–5891, https://doi.org/10.5194/bg-19-5879-2022, https://doi.org/10.5194/bg-19-5879-2022, 2022
Short summary
Short summary
Nitrogen is an important macronutrient that fuels algal production in rivers and coastal regions. We investigated the production and removal of nitrogen-bearing compounds in the freshwater section of the tidal Elbe Estuary and found that particles in the water column are key for the production and removal of water column nitrate. Using a stable isotope approach, we pinpointed regions where additional removal of nitrate or input from sediments plays an important role in estuarine biogeochemistry.
Mona Norbisrath, Johannes Pätsch, Kirstin Dähnke, Tina Sanders, Gesa Schulz, Justus E. E. van Beusekom, and Helmuth Thomas
Biogeosciences, 19, 5151–5165, https://doi.org/10.5194/bg-19-5151-2022, https://doi.org/10.5194/bg-19-5151-2022, 2022
Short summary
Short summary
Total alkalinity (TA) regulates the oceanic storage capacity of atmospheric CO2. TA is also metabolically generated in estuaries and influences coastal carbon storage through its inflows. We used water samples and identified the Hamburg port area as the one with highest TA generation. Of the overall riverine TA load, 14 % is generated within the estuary. Using a biogeochemical model, we estimated potential effects on the coastal carbon storage under possible anthropogenic and climate 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
Short summary
Short summary
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.
Matthias Fuchs, Juri Palmtag, Bennet Juhls, Pier Paul Overduin, Guido Grosse, Ahmed Abdelwahab, Michael Bedington, Tina Sanders, Olga Ogneva, Irina V. Fedorova, Nikita S. Zimov, Paul J. Mann, and Jens Strauss
Earth Syst. Sci. Data, 14, 2279–2301, https://doi.org/10.5194/essd-14-2279-2022, https://doi.org/10.5194/essd-14-2279-2022, 2022
Short summary
Short summary
We created digital, high-resolution bathymetry data sets for the Lena Delta and Kolyma Gulf regions in northeastern Siberia. Based on nautical charts, we digitized depth points and isobath lines, which serve as an input for a 50 m bathymetry model. The benefit of this data set is the accurate mapping of near-shore areas as well as the offshore continuation of the main deep river channels. This will improve the estimation of river outflow and the nutrient flux output into the coastal zone.
Shichao Tian, Birgit Gaye, Jianhui Tang, Yongming Luo, Wenguo Li, Niko Lahajnar, Kirstin Dähnke, Tina Sanders, Tianqi Xiong, Weidong Zhai, and Kay-Christian Emeis
Biogeosciences, 19, 2397–2415, https://doi.org/10.5194/bg-19-2397-2022, https://doi.org/10.5194/bg-19-2397-2022, 2022
Short summary
Short summary
We constrain the nitrogen budget and in particular the internal sources and sinks of nitrate in the Bohai Sea by using a mass-based and dual stable isotope approach based on δ15N and δ18O of nitrate. Based on available mass fluxes and isotope data an updated nitrogen budget is proposed. Compared to previous estimates, it is more complete and includes the impact of the interior cycle (nitrification) on the nitrate pool. The main external nitrogen sources are rivers contributing 19.2 %–25.6 %.
Charlotte Haugk, Loeka L. Jongejans, Kai Mangelsdorf, Matthias Fuchs, Olga Ogneva, Juri Palmtag, Gesine Mollenhauer, Paul J. Mann, P. Paul Overduin, Guido Grosse, Tina Sanders, Robyn E. Tuerena, Lutz Schirrmeister, Sebastian Wetterich, Alexander Kizyakov, Cornelia Karger, and Jens Strauss
Biogeosciences, 19, 2079–2094, https://doi.org/10.5194/bg-19-2079-2022, https://doi.org/10.5194/bg-19-2079-2022, 2022
Short summary
Short summary
Buried animal and plant remains (carbon) from the last ice age were freeze-locked in permafrost. At an extremely fast eroding permafrost cliff in the Lena Delta (Siberia), we found this formerly frozen carbon well preserved. Our results show that ongoing degradation releases substantial amounts of this carbon, making it available for future carbon emissions. This mobilisation at the studied cliff and also similarly eroding sites bear the potential to affect rivers and oceans negatively.
Gesa Schulz, Tina Sanders, Justus E. E. van Beusekom, Yoana G. Voynova, Andreas Schöl, and Kirstin Dähnke
Biogeosciences, 19, 2007–2024, https://doi.org/10.5194/bg-19-2007-2022, https://doi.org/10.5194/bg-19-2007-2022, 2022
Short summary
Short summary
Estuaries can significantly alter nutrient loads before reaching coastal waters. Our study of the heavily managed Ems estuary (Northern Germany) reveals three zones of nitrogen turnover along the estuary with water-column denitrification in the most upstream hyper-turbid part, nitrate production in the middle reaches and mixing/nitrate uptake in the North Sea. Suspended particulate matter was the overarching control on nitrogen cycling in the hyper-turbid estuary.
Birgit Gaye, Niko Lahajnar, Natalie Harms, Sophie Anna Luise Paul, Tim Rixen, and Kay-Christian Emeis
Biogeosciences, 19, 807–830, https://doi.org/10.5194/bg-19-807-2022, https://doi.org/10.5194/bg-19-807-2022, 2022
Short summary
Short summary
Amino acids were analyzed in a large number of samples of particulate and dissolved organic matter from coastal regions and the open ocean. A statistical analysis produced two new biogeochemical indicators. An indicator of sinking particle and sediment degradation (SDI) traces the degradation of organic matter from the surface waters into the sediments. A second indicator shows the residence time of suspended matter in the ocean (RTI).
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
Short summary
Short summary
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
Short summary
Short summary
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.
Nicole Burdanowitz, Tim Rixen, Birgit Gaye, and Kay-Christian Emeis
Clim. Past, 17, 1735–1749, https://doi.org/10.5194/cp-17-1735-2021, https://doi.org/10.5194/cp-17-1735-2021, 2021
Short summary
Short summary
To study the interaction of the westerlies and Indian summer monsoon (ISM) during the Holocene, we used paleoenvironmental reconstructions using a sediment core from the northeast Arabian Sea. We found a climatic transition period between 4.6 and 3 ka BP during which the ISM shifted southwards and the influence of Westerlies became prominent. Our data indicate a stronger influence of agriculture activities and enhanced soil erosion, adding to Bond event impact after this transition period.
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
Short summary
Short summary
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.
Tim Rixen, Greg Cowie, Birgit Gaye, Joaquim Goes, Helga do Rosário Gomes, Raleigh R. Hood, Zouhair Lachkar, Henrike Schmidt, Joachim Segschneider, and Arvind Singh
Biogeosciences, 17, 6051–6080, https://doi.org/10.5194/bg-17-6051-2020, https://doi.org/10.5194/bg-17-6051-2020, 2020
Short summary
Short summary
The northern Indian Ocean hosts an extensive oxygen minimum zone (OMZ), which intensified due to human-induced global changes. This includes the occurrence of anoxic events on the Indian shelf and affects benthic ecosystems and the pelagic ecosystem structure in the Arabian Sea. Consequences for biogeochemical cycles are unknown, which, in addition to the poor representation of mesoscale features, reduces the reliability of predictions of the future OMZ development in the northern Indian Ocean.
Henrike Schmidt, Rena Czeschel, and Martin Visbeck
Ocean Sci., 16, 1459–1474, https://doi.org/10.5194/os-16-1459-2020, https://doi.org/10.5194/os-16-1459-2020, 2020
Short summary
Short summary
Our investigations give detailed insight on the seasonally changing current system at intermediate depth in the Arabian Sea that is influenced by the monsoon. The changing currents influence the oxygen transport in the interior ocean and thus allow us to draw conclusions on the maintenance and seasonal variability of the upper part of the oxygen minimum zone in the Arabian Sea.
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
Short summary
Short summary
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.
Cited articles
Altieri, K. E., Fawcett, S. E., and Hastings, M. G.: Reactive Nitrogen Cycling in the Atmosphere and Ocean, Annu. Rev. Earth Pl. Sc., 49, 523–550, https://doi.org/10.1146/annurev-earth-083120-052147, 2021.
Bange, H. W., Stoltenberg, I., Andersch, T., Arévalo-Martínez, D. L., Atlas, E. L., Babu Suja, A., Barbot, A., Barthelmeß, T., Becker, K. W., Booge, D., Bristow, L. A., Conventz, A., Czeschel, R., Dähnke, K., Deshmukh, S., Duerkop, F., Eisnecker, P., Engel, A., Engelen, B., Feil, H., Fernández-Juárez, V., Firus, A., Frank, M., Gaye, B., Gledhill, M., Golde, S., Großelindemann, H., Hathorne, E., Henning, S., Hentschel, I., Herrmann, H., Ingeniero, R. C. O., Jacobsen, M., Kiko, R., Lahajnar, N., Lange, K., Löscher, C. R., Marandino, C. A., McKellar, C., Mickenbecker, J., Müller, M., Müller, T., Nazzari, L., Nielsen, L., Ploschke, J., Pohlker, M., Pontiller, B., Poulain, L., Quack, B., Rabe, R., Roa, J., Rolfes, S., Sanders, T., Schlangen, I., Schmidt, L., Schulz, G., Sommer, M., Thamdrup, B., Usinger, J., van Bonn, L., van Pinxteren, M., and Zhong, Q.: Biogeochemistry/atmosphere processes in the Bay of Bengal: A contribution to the 2nd International Indian Ocean Expedition, Cruise No. SO305 10 April–22 May 2024, Colombo (Sri Lanka) – Singapore (Singapore), Begutachtungspanel Forschungsschiffe, SONNE-Berichte, 86 pp., https://doi.org/10.48433/cr_so305, 2024.
Bristow, L. A., Dalsgaard, T., Tiano, L., Mills, D. B., Bertagnolli, A. D., Wright, J. J., Hallam, S. J., Ulloa, O., Canfield, D. E., Revsbech, N. P., and Thamdrup, B.: Ammonium and nitrite oxidation at nanomolar oxygen concentrations in oxygen minimum zone waters, P. Natl. Acad. Sci. USA, 113, 10601–10606, https://doi.org/10.1073/pnas.1600359113, 2016.
Bristow, L. A., Callbeck, C. M., Larsen, M., Altabet, M. A., Dekaezemacker, J., Forth, M., Gauns, M., Glud, R. N., Kuypers, M. M. M., Lavik, G., Milucka, J., Naqvi, S. W. A., Pratihary, A., Revsbech, N. P., Thamdrup, B., Treusch, A. H., and Canfield, D. E.: N2 production rates limited by nitrite availability in the Bay of Bengal oxygen minimum zone, Nat. Geosci., 10, 24–29, https://doi.org/10.1038/ngeo2847, 2017.
Brunner, B., Contreras, S., Lehmann, M. F., Matantseva, O., Rollog, M., Kalvelage, T., Klockgether, G., Lavik, G., Jetten, M. S. M., Kartal, B., and Kuypers, M. M. M.: Nitrogen isotope effects induced by anammox bacteria, P. Natl. Acad. Sci. USA, 110, 18994–18999, https://doi.org/10.1073/pnas.1310488110, 2013.
Buchwald, C. and Casciotti, K. L.: Oxygen isotopic fractionation and exchange during bacterial nitrite oxidation, Limnol. Oceanogr., 55, 1064–1074, https://doi.org/10.4319/lo.2010.55.3.1064, 2010.
Buchwald, C., Santoro, A. E., McIlvin, M. R., and Casciotti, K. L.: Oxygen isotopic composition of nitrate and nitrite produced by nitrifying cocultures and natural marine assemblages, Limnol. Oceanogr., 57, 1361–1375, https://doi.org/10.4319/lo.2012.57.5.1361, 2012.
Carvalho Junior, O. de O.: Water Masses at the Surface of the Indian Ocean, Eur. J. Environ. Earth Sci., 4, 11–21, https://doi.org/10.24018/ejgeo.2023.4.2.389, 2023.
Casciotti, K. L.: Inverse kinetic isotope fractionation during bacterial nitrite oxidation, Geochim. Cosmochim. Ac., 73, 2061–2076, https://doi.org/10.1016/j.gca.2008.12.022, 2009.
Casciotti, K. L.: Nitrogen and Oxygen Isotopic Studies of the Marine Nitrogen Cycle, Annu. Rev. Mar. Sci., 8, 379–407, https://doi.org/10.1146/annurev-marine-010213-135052, 2016.
Casciotti, K. L. and McIlvin, M. R.: Isotopic analyses of nitrate and nitrite from reference mixtures and application to Eastern Tropical North Pacific waters, Mar. Chem., 107, 184–201, https://doi.org/10.1016/j.marchem.2007.06.021, 2007.
Casciotti, K. L., Sigman, D. M., Hastings, M. G., Böhlke, J. K., and Hilkert, A.: Measurement of the Oxygen Isotopic Composition of Nitrate in Seawater and Freshwater Using the Denitrifier Method, Anal. Chem., 74, 4905–4912, https://doi.org/10.1021/ac020113w, 2002.
Casciotti, K. L., Sigman, D. M., and Ward, B. B.: Linking Diversity and Stable Isotope Fractionation in Ammonia-Oxidizing Bacteria, Geomicrobiol. J., 20, 335–353, https://doi.org/10.1080/01490450303895, 2003.
Casciotti, K. L., McIlvin, M., and Buchwald, C.: Oxygen isotopic exchange and fractionation during bacterial ammonia oxidation, Limnol. Oceanogr., 55, 753–762, https://doi.org/10.4319/lo.2010.55.2.0753, 2010.
Dalsgaard, T., Canfield, D. E., Petersen, J., Thamdrup, B., and Acuña-González, J.: N2 production by the anammox reaction in the anoxic water column of Golfo Dulce, Costa Rica, Nature, 422, 606–608, https://doi.org/10.1038/nature01526, 2003.
Dalsgaard, T., Stewart, F. J., Thamdrup, B., De Brabandere, L., Revsbech, N. P., Ulloa, O., Canfield, D. E., and DeLong, E. F.: Oxygen at Nanomolar Levels Reversibly Suppresses Process Rates and Gene Expression in Anammox and Denitrification in the Oxygen Minimum Zone off Northern Chile, mBio, 5, https://doi.org/10.1128/mbio.01966-14, 2014.
Deuser, W.: Reducing environments, in: Chemical Oceanography, vol. 3, edited by: Riley, J. P. and Skirrow, G., New York, 1–37, ISBN 0-12-588606-3, 1975.
DeVries, T., Deutsch, C., Primeau, F., Chang, B., and Devol, A.: Global rates of water-column denitrification derived from nitrogen gas measurements, Nat. Geosci., 5, 547–550, https://doi.org/10.1038/ngeo1515, 2012.
Ditkovsky, S., Resplandy, L., and Busecke, J.: Unique ocean circulation pathways reshape the Indian Ocean oxygen minimum zone with warming, Biogeosciences, 20, 4711–4736, https://doi.org/10.5194/bg-20-4711-2023, 2023.
Emery, W. J.: Water Types and Water Masses, in: Encyclopedia of Ocean Sciences, 2nd edn., edited by: Steele, J. H., Academic Press, Oxford, 291–299, https://doi.org/10.1016/B978-012374473-9.00108-9, 2001.
Fawcett, S. E., Ward, B. B., Lomas, M. W., and Sigman, D. M.: Vertical decoupling of nitrate assimilation and nitrification in the Sargasso Sea, Deep-Sea Res. Pt. I, 103, 64–72, https://doi.org/10.1016/j.dsr.2015.05.004, 2015.
Felden, J., Möller, L., Schindler, U., Huber, R., Schumacher, S., Koppe, R., Diepenbroek, M., and Glöckner, F. O.: PANGAEA – Data Publisher for Earth and Environmental Science, Sci. Data, 10, 347, https://doi.org/10.1038/s41597-023-02269-x, 2023.
Gaye, B., Nagel, B., Dähnke, K., Rixen, T., and Emeis, K.-C.: Evidence of parallel denitrification and nitrite oxidation in the ODZ of the Arabian Sea from paired stable isotopes of nitrate and nitrite, Global Biogeochem. Cy., 27, 1059–1071, https://doi.org/10.1002/2011GB004115, 2013.
Gordon, A. L.: Oceanography of the Indonesian Seas and Their Throughflow, Oceanography, 18, 14–27, https://doi.org/10.5670/oceanog.2005.01, 2005.
Granger, J. and Sigman, D. M.: Removal of nitrite with sulfamic acid for nitrate N and O isotope analysis with the denitrifier method, Rapid Commun. Mass Sp., 23, 3753–3762, https://doi.org/10.1002/rcm.4307, 2009.
Granger, J. and Wankel, S.: Isotopic overprinting of nitrification on denitrification as a ubiquitous and unifying feature of environmental nitrogen cycling, P. Natl. Acad. Sci. USA, 113, E6391–E6400, https://doi.org/10.1073/pnas.1601383113, 2016.
Granger, J., Sigman, D. M., Needoba, J. A., and Harrison, P. J.: Coupled nitrogen and oxygen isotope fractionation of nitrate during assimilation by cultures of marine phytoplankton, Limnol. Oceanogr., 49, 1763–1773, https://doi.org/10.4319/lo.2004.49.5.1763, 2004.
Granger, J., Sigman, D. M., Lehmann, M. F., and Tortell, P. D.: Nitrogen and oxygen isotope fractionation during dissimilatory nitrate reduction by denitrifying bacteria, Limnol. Oceanogr., 53, 2533–2545, https://doi.org/10.4319/lo.2008.53.6.2533, 2008.
Granger, J., Sigman, D. M., Rohde, M. M., Maldonado, M. T., and Tortell, P. D.: N and O isotope effects during nitrate assimilation by unicellular prokaryotic and eukaryotic plankton cultures, Geochim. Cosmochim. Ac., 74, 1030–1040, https://doi.org/10.1016/j.gca.2009.10.044, 2010.
Gruber, N.: Chapter 1 – The Marine Nitrogen Cycle: Overview and Challenges, in: Nitrogen in the Marine Environment, 2nd edn., edited by: Capone, D. G., Bronk, D. A., Mulholland, M. R., and Carpenter, E. J., Academic Press, San Diego, 1–50, https://doi.org/10.1016/B978-0-12-372522-6.00001-3, 2008.
Hansen, H. P.: Determination of oxygen, in: Methods of Seawater Analysis, edited by: Grasshoff, K. K. and Ehrhardt, M., John Wiley & Sons, Ltd, 75–89, https://doi.org/10.1002/9783527613984.ch4, 1999.
Hansen, H. P. and Koroleff, F.: Determination of nutrients, in: Methods of Seawater Analysis, edited by: Grasshoff, K. K. and Ehrhardt, M., John Wiley & Sons, Ltd, 159–228, https://doi.org/10.1002/9783527613984.ch10, 1999.
Harms, N. C., Lahajnar, N., Gaye, B., Rixen, T., Dähnke, K., Ankele, M., Schwarz-Schampera, U., and Emeis, K.-C.: Nutrient distribution and nitrogen and oxygen isotopic composition of nitrate in water masses of the subtropical southern Indian Ocean, Biogeosciences, 16, 2715–2732, https://doi.org/10.5194/bg-16-2715-2019, 2019.
Holmes, R. M., Aminot, A., Kérouel, R., Hooker, B. A., and Peterson, B. J.: A simple and precise method for measuring ammonium in marine and freshwater ecosystems, Can. J. Fish. Aquat. Sci., 56, 1801–1808, https://doi.org/10.1139/f99-128, 1999.
Howell, E. A., Doney, S. C., Fine, R. A., and Olson, D. B.: Geochemical estimates of denitrification in the Arabian Sea and the Bay of Bengal during WOCE, Geophys. Res. Lett., 24, 2549–2552, https://doi.org/10.1029/97GL01538, 1997.
Jain, V., Shankar, D., Vinayachandran, P. N., Kankonkar, A., Chatterjee, A., Amol, P., Almeida, A. M., Michael, G. S., Mukherjee, A., Chatterjee, M., Fernandes, R., Luis, R., Kamble, A., Hegde, A. K., Chatterjee, S., Das, U., and Neema, C. P.: Evidence for the existence of Persian Gulf Water and Red Sea Water in the Bay of Bengal, Clim. Dynam., 48, 3207–3226, https://doi.org/10.1007/s00382-016-3259-4, 2017.
Johnson, K. S., Riser, S. C., and Ravichandran, M.: Oxygen Variability Controls Denitrification in the Bay of Bengal Oxygen Minimum Zone, Geophys. Res. Lett., 46, 804–811, https://doi.org/10.1029/2018GL079881, 2019.
Kalvelage, T., Jensen, M. M., Contreras, S., Revsbech, N. P., Lam, P., Günter, M., LaRoche, J., Lavik, G., and Kuypers, M. M. M.: Oxygen sensitivity of anammox and coupled N-cycle processes in oxygen minimum zones, PloS One, 6, e29299, https://doi.org/10.1371/journal.pone.0029299, 2011.
Karsh, K. L., Granger, J., Kritee, K., and Sigman, D. M.: Eukaryotic Assimilatory Nitrate Reductase Fractionates N and O Isotopes with a Ratio near Unity, Environ. Sci. Technol., 46, 5727–5735, https://doi.org/10.1021/es204593q, 2012.
Kassambara, A.: ggpubr: “ggplot2” Based Publication Ready Plots, CRAN [code], https://doi.org/10.32614/CRAN.package.ggpubr, 2023.
Kawano, T.: Method for Salinity (Conductivity Ratio) Measurement, GO-SHIP Repeat Hydrogr. Man. Collect. Expert Rep. Guidel. Eds Al, IOCCP Report, https://search.oceanbestpractices.org/search?q=kawano&fields=all&activeField=all, 2010.
Kendall, C., Elliott, E. M., and Wankel, S. D.: Tracing Anthropogenic Inputs of Nitrogen to Ecosystems, in: Stable Isotopes in Ecology and Environmental Science, edited by: Michener, R. and Lajtha, K., John Wiley & Sons, Ltd, 375–449, https://doi.org/10.1002/9780470691854.ch12, 2007.
Kim, Y., Rho, T., and Kang, D.-J.: Oxygen isotope composition of seawater and salinity in the western Indian Ocean: Implications for water mass mixing, Mar. Chem., 237, 104035, https://doi.org/10.1016/j.marchem.2021.104035, 2021.
Knapp, A. N., DiFiore, P. J., Deutsch, C., Sigman, D. M., and Lipschultz, F.: Nitrate isotopic composition between Bermuda and Puerto Rico: Implications for N2 fixation in the Atlantic Ocean, Global Biogeochem. Cy., 22, GB3014, https://doi.org/10.1029/2007GB003107, 2008.
Knowles, R.: Denitrification, Microbiol. Rev., 46, 43–70, https://doi.org/10.1128/mr.46.1.43-70.1982, 1982.
Kobayashi, K., Makabe, A., Yano, M., Oshiki, M., Kindaichi, T., Casciotti, K. L., and Okabe, S.: Dual nitrogen and oxygen isotope fractionation during anaerobic ammonium oxidation by anammox bacteria, ISME J., 13, 2426–2436, https://doi.org/10.1038/s41396-019-0440-x, 2019.
Kool, D. M., Wrage, N., Oenema, O., Dolfing, J., and Van Groenigen, J. W.: Oxygen exchange between (de)nitrification intermediates and H2O and its implications for source determination of
Kumar, S., Ramesh, R., Sardesai, S., and Sheshshayee, M. S.: High new production in the Bay of Bengal: Possible causes and implications, Geophys. Res. Lett., 31, L18304, https://doi.org/10.1029/2004GL021005, 2004.
LeGrande, A. N. and Schmidt, G. A.: Global gridded data set of the oxygen isotopic composition in seawater, Geophys. Res. Lett., 33, https://doi.org/10.1029/2006GL026011, 2006.
Löscher, C. R., Mohr, W., Bange, H. W., and Canfield, D. E.: No nitrogen fixation in the Bay of Bengal?, Biogeosciences, 17, 851–864, https://doi.org/10.5194/bg-17-851-2020, 2020.
Marshall, T. A., Sigman, D. M., Beal, L. M., Foreman, A., Martínez-García, A., Blain, S., Campbell, E., Fripiat, F., Granger, R., Harris, E., Haug, G. H., Marconi, D., Oleynik, S., Rafter, P. A., Roman, R., Sinyanya, K., Smart, S. M., and Fawcett, S. E.: The Agulhas Current Transports Signals of Local and Remote Indian Ocean Nitrogen Cycling, J. Geophys. Res.-Oceans, 128, e2022JC019413, https://doi.org/10.1029/2022JC019413, 2023.
Martin, T. S. and Casciotti, K. L.: Paired N and O isotopic analysis of nitrate and nitrite in the Arabian Sea oxygen deficient zone, Deep-Sea Res. Pt. I, 121, 121–131, https://doi.org/10.1016/j.dsr.2017.01.002, 2017.
Massicotte, P. and South, A.: rnaturalearth: World Map Data from Natural Earth, CRAN [code], https://doi.org/10.32614/CRAN.package.rnaturalearth, 2025.
Naqvi, S. W. A., DeSousa, S. N., and Reddy, C. V. G.: Relationship between nutrients and dissolved oxygen with special reference to water masses in westrn Bay of Bengal, Indian J. Geo-Mar. Sci., 7, 15–17, 1978.
Naqvi, S. W. A., Yoshinari, T., Brandes, J. A., Devol, A. H., Jayakumar, D. A., Narvekar, P. V., Altabet, M. A., and Codispoti, L. A.: Nitrogen isotopic studies in the suboxic Arabian Sea, P. Indian AS.-Earth, 107, 367–378, https://doi.org/10.1007/BF02841603, 1998.
Okabe, S., Ye, S., Lan, X., Nukada, K., Zhang, H., Kobayashi, K., and Oshiki, M.: Oxygen tolerance and detoxification mechanisms of highly enriched planktonic anaerobic ammonium-oxidizing (anammox) bacteria, ISME Commun., 3, 45, https://doi.org/10.1038/s43705-023-00251-7, 2023.
Pebesma, E. and Bivand, R.: Spatial Data Science: With Applications in R, Chapman and Hall/CRC, New York, 314 pp., https://doi.org/10.1201/9780429459016, 2023.
Peng, X., Fawcett, S. E., van Oostende, N., Wolf, M. J., Marconi, D., Sigman, D. M., and Ward, B. B.: Nitrogen uptake and nitrification in the subarctic North Atlantic Ocean, Limnol. Oceanogr., 63, 1462–1487, https://doi.org/10.1002/lno.10784, 2018.
Phillips, H. E., Menezes, V. V., Nagura, M., McPhaden, M. J., Vinayachandran, P. N., and Beal, L. M.: Indian Ocean circulation?, in: The Indian Ocean and its Role in the Global Climate System, edited by: Ummenhofer, C. C. and Hood, R. R., Elsevier, 169–203, https://doi.org/10.1016/B978-0-12-822698-8.00012-3, 2024.
R Core Team: R: A Language and Environment for Statistical Computing, R Foundation for Statistical Computing, Vienna, Austria, https://www.R-project (last access: 9 September 2025), 2022.
Rahman, A., Khan, M. A., Singh, A., and Kumar, S.: Hydrological characteristics of the Bay of Bengal water column using δ18O during the Indian summer monsoon, Cont. Shelf Res., 226, 104491, https://doi.org/10.1016/j.csr.2021.104491, 2021.
Rao, C. K., Naqvi, S. W. A., Kumar, M. D., Varaprasad, S. J. D., Jayakumar, D. A., George, M. D., and Singbal, S. Y. S.: Hydrochemistry of the Bay of Bengal: possible reasons for a different water-column cycling of carbon and nitrogen from the Arabian Sea, Mar. Chem., 47, 279–290, https://doi.org/10.1016/0304-4203(94)90026-4, 1994.
Rixen, T., Cowie, G., Gaye, B., Goes, J., do Rosário Gomes, H., Hood, R. R., Lachkar, Z., Schmidt, H., Segschneider, J., and Singh, A.: Reviews and syntheses: Present, past, and future of the oxygen minimum zone in the northern Indian Ocean, Biogeosciences, 17, 6051–6080, https://doi.org/10.5194/bg-17-6051-2020, 2020.
Sardessai, S., Ramaiah, N., Kumar, S., and Sousa, S. de: Influence of environmental forcings on the seasonality of dissolved oxygen and nutrients in the Bay of Bengal, J. Mar. Res., 65, 301–316, 2007.
Sarma, V. V. S. S.: An evaluation of physical and biogeochemical processes regulating the oxygen minimum zone in the water column of the Bay of Bengal, Global Biogeochem. Cy., 16, 46-1–46-10, https://doi.org/10.1029/2002GB001920, 2002.
Sarma, V. V. S. S.: Biogeochemistry of carbon, nitrogen and oxygen in the Bay of Bengal: New insights through re-analysis of data, J. Earth Syst. Sci., 131, 159, https://doi.org/10.1007/s12040-022-01915-z, 2022.
Sarma, V. V. S. S. and Udaya Bhaskar, T. V. S.: Ventilation of Oxygen to Oxygen Minimum Zone Due to Anticyclonic Eddies in the Bay of Bengal, J. Geophys. Res.-Biogeo., 123, 2145–2153, https://doi.org/10.1029/2018JG004447, 2018.
Sarma, V. V. S. S., Krishna, M. S., Viswanadham, R., Rao, G. D., Rao, V. D., Sridevi, B., Kumar, B. S. K., Prasad, V. R., Subbaiah, C. V., Acharyya, T., and Bandopadhyay, D.: Intensified oxygen minimum zone on the western shelf of Bay of Bengal during summer monsoon: influence of river discharge, J. Oceanogr., 69, 45–55, https://doi.org/10.1007/s10872-012-0156-2, 2013.
Sarma, V. V. S. S., Rao, G. D., Viswanadham, R., Sherin, C. K., Salisbury, J., Omand, M. M., Mahadevan, A., Murty, V. S. N., Shroyer, E. L., Baumgartner, M., and Stafford, K. M.: Effects of Freshwater Stratification on Nutrients, Dissolved Oxygen, and Phytoplankton in the Bay of Bengal, Oceanography, 29, 222–231, 2016.
Saxena, H., Sahoo, D., Khan, M. A., Kumar, S., Sudheer, A. K., and Singh, A.: Dinitrogen fixation rates in the Bay of Bengal during summer monsoon, Environ. Res. Commun., 2, 051007, https://doi.org/10.1088/2515-7620/ab89fa, 2020.
Schott, F. A. and McCreary, J. P.: The monsoon circulation of the Indian Ocean, Prog. Oceanogr., 51, 1–123, https://doi.org/10.1016/S0079-6611(01)00083-0, 2001.
Schott, F. A., Xie, S.-P., and McCreary Jr., J. P.: Indian Ocean circulation and climate variability, Rev. Geophys., 47, RG1002, https://doi.org/10.1029/2007RG000245, 2009.
Schulz, G. and Penopp, J.: Dual Nitrate Stable Isotopes of SONNE 305 cruise in the East Equatorial Indian Ocean and Bay of Bengal, PANGAEA [data set], https://doi.org/10.1594/PANGAEA.983257, 2025.
Sen Gupta, R., De Sousa, S. N., and Joseph, T.: On nitrogen and phosphorus in the western Bay of Bengal, Indian J. Geo-Mar. Sci., 6, 107–110, 1977.
Sengupta, S., Parekh, A., Chakraborty, S., Ravi Kumar, K., and Bose, T.: Vertical variation of oxygen isotope in Bay of Bengal and its relationships with water masses, J. Geophys. Res.-Oceans, 118, 6411–6424, https://doi.org/10.1002/2013JC008973, 2013.
Shee, A., Sil, S., and Gangopadhyay, A.: Recent changes in the upper oceanic water masses over the Indian Ocean using Argo data, Sci. Rep.-UK, 13, 20252, https://doi.org/10.1038/s41598-023-47658-9, 2023.
Sheehan, P. M. F., Webber, B. G. M., Sanchez-Franks, A., Matthews, A. J., Heywood, K. J., and Vinayachandran, P. N.: Injection of Oxygenated Persian Gulf Water Into the Southern Bay of Bengal, Geophys. Res. Lett., 47, e2020GL087773, https://doi.org/10.1029/2020GL087773, 2020.
Shetye, S. R.: The movement and implications of the Ganges–Bramhaputra runoff on entering the Bay of Bengal, Curr. Sci. India, 64, 32–38, 1993.
Shiozaki, T., Ijichi, M., Kodama, T., Takeda, S., and Furuya, K.: Heterotrophic bacteria as major nitrogen fixers in the euphotic zone of the Indian Ocean, Global Biogeochem. Cy., 28, 1096–1110, https://doi.org/10.1002/2014GB004886, 2014.
Sigman, D. M. and Fripiat, F.: Nitrogen Isotopes in the Ocean, in: Encyclopedia of Ocean Sciences, 3rd edn., edited by: Cochran, J. K., Bokuniewicz, H. J., and Yager, P. L., Academic Press, vol. 1, 263–278, https://doi.org/10.1016/B978-0-12-409548-9.11605-7, 2019.
Sigman, D. M., Altabet, M. A., McCorkle, D. C., Francois, R., and Fischer, G.: The δ15N of nitrate in the Southern Ocean: Nitrogen cycling and circulation in the ocean interior, J. Geophys. Res.-Oceans, 105, 19599–19614, https://doi.org/10.1029/2000JC000265, 2000.
Sigman, D. M., Casciotti, K. L., Andreani, M., Barford, C., Galanter, M., and Böhlke, J. K.: A Bacterial Method for the Nitrogen Isotopic Analysis of Nitrate in Seawater and Freshwater, Anal. Chem., 73, 4145–4153, https://doi.org/10.1021/ac010088e, 2001.
Sigman, D. M., Granger, J., DiFiore, P. J., Lehmann, M. M., Ho, R., Cane, G., and van Geen, A.: Coupled nitrogen and oxygen isotope measurements of nitrate along the eastern North Pacific margin, Global Biogeochem. Cy., 19, https://doi.org/10.1029/2005GB002458, 2005.
Sigman, D. M., DiFiore, P. J., Hain, M. P., Deutsch, C., Wang, Y., Karl, D. M., Knapp, A. N., Lehmann, M. F., and Pantoja, S.: The dual isotopes of deep nitrate as a constraint on the cycle and budget of oceanic fixed nitrogen, Deep-Sea Res. Pt. I, 56, 1419–1439, https://doi.org/10.1016/j.dsr.2009.04.007, 2009.
Snider, D. M., Spoelstra, J., Schiff, S. L., and Venkiteswaran, J. J.: Stable Oxygen Isotope Ratios of Nitrate Produced from Nitrification: 18O-Labeled Water Incubations of Agricultural and Temperate Forest Soils, Environ. Sci. Technol., 44, 5358–5364, https://doi.org/10.1021/es1002567, 2010.
South, A., Michael, S., and Massicotte, P.: rnaturalearthdata: World Vector Map Data from Natural Earth Used in “rnaturalearth”, CRAN [code], https://doi.org/10.32614/CRAN.package.rnaturalearthdata, 2025.
Sprintall, J. and Tomczak, M.: On the formation of central water and thermocline ventilation in the southern hemisphere, Deep-Sea Res. Pt. I, 40, 827–848, https://doi.org/10.1016/0967-0637(93)90074-D, 1993.
Sprintall, J., Wijffels, S. E., Molcard, R., and Jaya, I.: Direct estimates of the Indonesian Throughflow entering the Indian Ocean: 2004–2006, J. Geophys. Res.-Oceans, 114, C07001, https://doi.org/10.1029/2008JC005257, 2009.
Sridevi, B. and Sarma, V. V. S. S.: A revisit to the regulation of oxygen minimum zone in the Bay of Bengal, J. Earth Syst. Sci., 129, 107, https://doi.org/10.1007/s12040-020-1376-2, 2020.
Srivastava, R., Ramesh, R., Prakash, S., Anilkumar, N., and Sudhakar, M.: Oxygen isotope and salinity variations in the Indian sector of the Southern Ocean, Geophys. Res. Lett., 34, https://doi.org/10.1029/2007GL031790, 2007.
Strous, M., Fuerst, J. A., Kramer, E. H. M., Logemann, S., Muyzer, G., van de Pas-Schoonen, K. T., Webb, R., Kuenen, J. G., and Jetten, M. S. M.: Missing lithotroph identified as new planctomycete, Nature, 400, 446–449, https://doi.org/10.1038/22749, 1999.
Sun, X., Frey, C., Garcia-Robledo, E., Jayakumar, A., and Ward, B. B.: Microbial niche differentiation explains nitrite oxidation in marine oxygen minimum zones, ISME J., 15, 1317–1329, https://doi.org/10.1038/s41396-020-00852-3, 2021.
Sun, X., Frey, C., and Ward, B. B.: Nitrite Oxidation Across the Full Oxygen Spectrum in the Ocean, Global Biogeochem. Cy., 37, e2022GB007548, https://doi.org/10.1029/2022GB007548, 2023.
Sverdrup, H. U., Johnson, M. W., and Fleming, R. H.: The Oceans Their Physics, Chemistry, and General Biology, Prentice-Hall, New York, 1060 pp., 1942.
Tiedje, J. M.: Ecology of denitrification and dissimilatory nitrate reduction to ammonium, in: Biology of anaerobic microorganisms, edited by: Zehnder, A. J. B., John Wiley and Sons, New York, 179–244, 1988.
Tomczak, M. and Godfrey, J. S.: Chapter 11 – The Indian Ocean, in: Regional Oceanography, edited by: Tomczak, M. and Godfrey, J. S., Pergamon, Amsterdam, 193–220, https://doi.org/10.1016/B978-0-08-041021-0.50015-1, 1994.
Trimmer, M., Nicholls, J. C., and Deflandre, B.: Anaerobic Ammonium Oxidation Measured in Sediments along the Thames Estuary, United Kingdom, Appl. Environ. Microb., 69, 6447–6454, https://doi.org/10.1128/AEM.69.11.6447-6454.2003, 2003.
Ummenhofer, C. C. and Hood, R. R. (Eds.): The Indian Ocean and its Role in the Global Climate System, 1st edn., Elsevier, ISBN 978-0-12-822698-8, 2024.
Vinayachandran, P. N., Masumoto, Y., Mikawa, T., and Yamagata, T.: Intrusion of the Southwest Monsoon Current into the Bay of Bengal, J. Geophys. Res.-Oceans, 104, 11077–11085, https://doi.org/10.1029/1999JC900035, 1999.
Wankel, S. D., Kendall, C., Pennington, J. T., Chavez, F. P., and Paytan, A.: Nitrification in the euphotic zone as evidenced by nitrate dual isotopic composition: Observations from Monterey Bay, California, Global Biogeochem. Cy., 21, https://doi.org/10.1029/2006GB002723, 2007.
Ward, B. B.: How Nitrogen Is Lost, Science, 341, 352–353, https://doi.org/10.1126/science.1240314, 2013.
Wickham, H., Chang, W., Henry, L., Pedersen, T. L., Takahashi, K., Wilke, C., Woo, K., Yutani, H., Dunnington, D., and van den Brand, T.: ggplot2: Elegant Graphics for Data Analysis, CRAN [code], https://doi.org/10.32614/CRAN.package.ggplot2, 2016.
Winkler, L. W.: Die Bestimmung des im Wasser gelösten Sauerstoffes, Ber. Dtsch. Chem. Ges., 21, 2843–2854, https://doi.org/10.1002/cber.188802102122, 1888.
Wyrtki, K.: Oceanographic atlas of the International Indian Ocean Expedition, National Science Foundation, Washington, DC, 531 pp., 1971.
Wyrtki, K.: An equatorial jet in the Indian ocean, Science, 181, 262–264, https://doi.org/10.1126/science.181.4096.262, 1973.
You, Y.: Seasonal variations of thermocline circulation and ventilation in the Indian Ocean, J. Geophys. Res.-Oceans, 102, 10391–10422, https://doi.org/10.1029/96JC03600, 1997.
You, Y. and Tomczak, M.: Thermocline circulation and ventilation in the Indian Ocean derived from water mass analysis, Deep-Sea Res. Pt. I, 40, 13–56, https://doi.org/10.1016/0967-0637(93)90052-5, 1993.
Short summary
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 the 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.
Oxygen-minimum zones (OMZs) are low-oxygen ocean areas that deplete nitrogen, a key marine...
Altmetrics
Final-revised paper
Preprint