Articles | Volume 17, issue 10
https://doi.org/10.5194/bg-17-2701-2020
© Author(s) 2020. 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-17-2701-2020
© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
Research article
| 
19 May 2020
Research article |
| 19 May 2020
| 19 May 2020
Quantifying the contributions of riverine vs. oceanic nitrogen to hypoxia in the East China Sea
Department of Oceanography, Dalhousie University, Halifax, NS, Canada
Department of Mathematics and Statistics, University of Strathclyde, Glasgow, UK
Katja Fennel
Department of Oceanography, Dalhousie University, Halifax, NS, Canada
Haiyan Zhang
Department of Oceanography, Dalhousie University, Halifax, NS, Canada
School of Marine Science and Technology, Tianjin University, Tianjin, China
Arnaud Laurent
Department of Oceanography, Dalhousie University, Halifax, NS, Canada
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Jonathan Lemay, Helmuth Thomas, Susanne E. Craig, William J. Burt, Katja Fennel, and Blair J. W. Greenan
Biogeosciences, 15, 2111–2123, https://doi.org/10.5194/bg-15-2111-2018, https://doi.org/10.5194/bg-15-2111-2018, 2018
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Fabian Große, Naomi Greenwood, Markus Kreus, Hermann-Josef Lenhart, Detlev Machoczek, Johannes Pätsch, Lesley Salt, and Helmuth Thomas
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A. Laurent, K. Fennel, R. Wilson, J. Lehrter, and R. Devereux
Biogeosciences, 13, 77–94, https://doi.org/10.5194/bg-13-77-2016, https://doi.org/10.5194/bg-13-77-2016, 2016
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L. Yu, K. Fennel, A. Laurent, M. C. Murrell, and J. C. Lehrter
Biogeosciences, 12, 2063–2076, https://doi.org/10.5194/bg-12-2063-2015, https://doi.org/10.5194/bg-12-2063-2015, 2015
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Biogeosciences, 11, 7061–7075, https://doi.org/10.5194/bg-11-7061-2014, https://doi.org/10.5194/bg-11-7061-2014, 2014
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Z. Xue, R. He, K. Fennel, W.-J. Cai, S. Lohrenz, and C. Hopkinson
Biogeosciences, 10, 7219–7234, https://doi.org/10.5194/bg-10-7219-2013, https://doi.org/10.5194/bg-10-7219-2013, 2013
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Biogeosciences, 10, 53–66, https://doi.org/10.5194/bg-10-53-2013, https://doi.org/10.5194/bg-10-53-2013, 2013
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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.
Mariche Bandibas Natividad, Jian-Jhih Chen, Hsin-Yu Chou, Lan-Feng Fan, Yi-Le Shen, and Wen-Chen Chou
EGUsphere, https://doi.org/10.5194/egusphere-2024-4000, https://doi.org/10.5194/egusphere-2024-4000, 2025
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Seagrass restoration serves as a nature-based solution for CO2 removal. We examined the organic carbon and carbonate dynamics of restored seagrasses (SG) and bare sediments (BS) using ex situ core incubations. SG exhibited higher net ecosystem metabolism compared to BS, while no significant difference was observed in net ecosystem calcification. Consequently, SG demonstrated a significantly enhanced overall capacity for carbon uptake.
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.
Cited articles
Bian, C., Jiang, W., and Greatbatch, R. J.: An exploratory model study of
sediment transport sources and deposits in the Bohai Sea, Yellow Sea, and
East China Sea, J. Geophys. Res.-Oceans, 118, 5908–5923,
https://doi.org/10.1002/2013JC009116, 2013. a, b, c
Bopp, L., Resplandy, L., Untersee, A., Le Mezo, P., and Kageyama, M.: Ocean
(de)oxygenation from the Last Glacial Maximum to the twenty-first century:
insights from Earth System models, Philos. T. R. Soc. A, 375, 20160323,
https://doi.org/10.1098/rsta.2016.0323, 2017. a, b, c, d
Carton, J. A. and Giese, B. S.: A Reanalysis of Ocean Climate Using Simple
Ocean Data Assimilation (SODA), Mon. Weather Rev., 136, 2999–3017,
https://doi.org/10.1175/2007MWR1978.1, 2008. a
Chen, C.-T. A., Hsing, L.-Y., Liu, C.-L., and Wang, S.-L.: Degree of nutrient
consumption of upwelled water in the Taiwan Strait based on dissolved organic
phosphorus or nitrogen, Mar. Chem., 87, 73–86,
https://doi.org/10.1016/j.marchem.2004.01.006, 2004. a
Chi, L., Song, X., Yuan, Y., Wang, W., Zhou, P., Fan, X., Cao, X., and Yu, Z.:
Distribution and key influential factors of dissolved oxygen off the
Changjiang River Estuary (CRE) and its adjacent waters in China, Mar.
Pollut. Bull., 125, 440–450, https://doi.org/10.1016/j.marpolbul.2017.09.063, 2017. a, b
Dee, D. P., Uppala, S. M., Simmons, A. J., Berrisford, P., Poli, P., Kobayashi,
S., Andrae, U., Balmaseda, M. A., Balsamo, G., Bauer, P., Bechtold, P.,
Beljaars, A. C. M., van de Berg, L., Bidlot, J., Bormann, N., Delsol, C.,
Dragani, R., Fuentes, M., Geer, A. J., Haimberger, L., Healy, S. B.,
Hersbach, H., Hólm, E. V., Isaksen, L., Kållberg, P., Köhler,
M., Matricardi, M., McNally, A. P., Monge-Sanz, B. M., Morcrette, J.-J.,
Park, B.-K., Peubey, C., de Rosnay, P., Tavolato, C., Thépaut, J.-N.,
and Vitart, F.: The ERA-Interim reanalysis: configuration and performance of
the data assimilation system, Q. J. Roy. Meteor. Soc., 137, 553–597,
https://doi.org/10.1002/qj.828, 2011. a
Egbert, G. D. and Erofeeva, S. Y.: Efficient Inverse Modeling of Barotropic
Ocean Tides, J. Atmos. Ocean. Tech., 19, 183–204,
https://doi.org/10.1175/1520-0426(2002)019<0183:EIMOBO>2.0.CO;2, 2002. a
Fan, W. and Song, J.: A numerical study of the seasonal variations of
nutrients in the Changjiang River estuary and its adjacent sea area, Ecol.
Model., 291, 69–81, https://doi.org/10.1016/j.ecolmodel.2014.07.026, 2014. a, b
Feng, Y., Fennel, K., Jackson, G. A., DiMarco, S. F., and Hetland, R. D.: A
model study of the response of hypoxia to upwelling-favorable wind on the
northern Gulf of Mexico shelf, J. Marine Syst., 131, 63–73,
https://doi.org/10.1016/j.jmarsys.2013.11.009, 2014. a
Fennel, K. and Testa, J. M.: Biogeochemical Controls on Coastal Hypoxia,
Annu. Rev. Mar. Sci., 11, 105–130,
https://doi.org/10.1146/annurev-marine-010318-095138, 2019. a
Fennel, K., Wilkin, J., Levin, J., Moisan, J., O'Reilly, J., and Haidvogel, D.:
Nitrogen cycling in the Middle Atlantic Bight: Results from a
three-dimensional model and implications for the North Atlantic nitrogen
budget, Global Biogeochem. Cy., 20, 1–14, https://doi.org/10.1029/2005GB002456, 2006. a, b, c, d, e
Fennel, K., Hetland, R., Feng, Y., and DiMarco, S.: A coupled physical-biological model of the Northern Gulf of Mexico shelf: model description, validation and analysis of phytoplankton variability, Biogeosciences, 8, 1881–1899, https://doi.org/10.5194/bg-8-1881-2011, 2011. a, b
Fennel, K., Hu, J., Laurent, A., Marta-Almeida, M., and Hetland, R.:
Sensitivity of hypoxia predictions for the northern Gulf of Mexico to
sediment oxygen consumption and model nesting, J. Geophys. Res.-Oceans, 118,
990–1002, https://doi.org/10.1002/jgrc.20077, 2013. a, b
Gao, L., Li, D., Ishizaka, J., Zhang, Y., Zong, H., and Guo, L.: Nutrient
dynamics across the river-sea interface in the Changjiang (Yangtze River)
estuary–East China Sea region, Limnol. Oceanogr., 60, 2207–2221,
https://doi.org/10.1002/lno.10196, 2015. a
Garcia, H. E., Boyer, T. P., Locarnini, R. A., Antonov, J. I., Mishonov, A. V.,
Baranova, O. K., Zweng, M. M., Reagan, J. R., Johnson, D. R., and Levitus,
S.: World Ocean Atlas 2013. Volume 3: Dissolved oxygen, apparent oxygen
utilization, and oxygen saturation, Tech. rep., National Oceanic and
Atmospheric Administration (NOAA), Silver Spring, MD, https://doi.org/10.7289/V5XG9P2W,
2013a. a
Garcia, H. E., Locarnini, R. A., Boyer, T. P., Antonov, J. I., Baranova, O. K.,
Zweng, M. M., Reagan, J. R., Johnson, D. R., Mishonov, A. V., and Levitus,
S.: World Ocean Atlas 2013. Volume 4: Dissolved inorganic nutrients
(phosphate, nitrate, silicate), Tech. rep., National Oceanic and Atmospheric
Administration (NOAA), Silver Spring, MD, https://doi.org/10.7289/V5J67DWD, 2013b. a
Große, F.:
Regional Ocean Modeling System (ROMS), version 3.7, with added capability to produce output for the ETRAC software,
available at: https://github.com/FabianGrosse/ROMS_3.7_for_ETRAC,
(last access: 20 August 2019), 2018a. a
Große, F.:
Element TRACing software for numerical models (ETRAC), available at: https://github.com/FabianGrosse/ETRAC (last access: 20 August 2019), 2018b. a
Große, F., Kreus, M., Lenhart, H.-J., Pätsch, J., and Pohlmann, T.:
A Novel Modeling Approach to Quantify the Influence of Nitrogen Inputs on
the Oxygen Dynamics of the North Sea, Front. Mar. Sci., 4, 383,
https://doi.org/10.3389/fmars.2017.00383, 2017. a, b, c
Große, F., Fennel, K., and Laurent, A.: Quantifying the Relative
Importance of Riverine and Open-Ocean Nitrogen Sources for Hypoxia Formation
in the Northern Gulf of Mexico, J. Geophys. Res.-Oceans, 124, 5451–5467,
https://doi.org/10.1029/2019JC015230, 2019. a, b, c, d
Guo, X., Miyazawa, Y., and Yamagata, T.: The Kuroshio onshore intrusion along
the shelf break of the East China Sea: The origin of the Tsushima Warm
Current, J. Phys. Oceanogr., 36, 2205–2231, https://doi.org/10.1175/JPO2976.1, 2006. a, b, c
Haidvogel, D. B., Arango, H., Budgell, W. P., Cornuelle, B. D., Curchitser, E.,
Di Lorenzo, E., Fennel, K., Geyer, W. R., Hermann, A. J., Lanerolle, L.,
Levin, J., McWilliams, J. C., Miller, A. J., Moore, A. M., Powell, T. M.,
Shchepetkin, A. F., Sherwood, C. R., Signell, R. P., Warner, J. C., and
Wilkin, J.: Ocean forecasting in terrain-following coordinates: Formulation
and skill assessment of the Regional Ocean Modeling System, J. Comput.
Phys., 227, 3595–3624, https://doi.org/10.1016/j.jcp.2007.06.016, 2008. a, b
Hetland, R. D. and Zhang, X.: Interannual Variation in Stratification over the
Texas–Louisiana Continental Shelf and Effects on Seasonal Hypoxia, in:
Modeling Coastal Hypoxia, edited by: Dubravko, J., Rose, K. A., Hetland,
R. D., and Fennel, K., 49–60, Springer, Cham, Switzerland,
https://doi.org/10.1007/978-3-319-54571-4_3, 2017. a
Laurent, A., Fennel, K., Hu, J., and Hetland, R.: Simulating the effects of phosphorus limitation in the Mississippi and Atchafalaya River plumes, Biogeosciences, 9, 4707–4723, https://doi.org/10.5194/bg-9-4707-2012, 2012. a
Laurent, A., Fennel, K., Cai, W.-J., Huang, W.-J., Barbero, L., and Wanninkhof,
R.: Eutrophication-induced acidification of coastal waters in the northern
Gulf of Mexico: Insights into origin and processes from a coupled
physical-biogeochemical model, Geophys. Res. Lett., 44, 946–956,
https://doi.org/10.1002/2016GL071881, 2017. a
Laurent, A., Fennel, K., Ko, D. S., and Lehrter, J.: Climate Change Projected
to Exacerbate Impacts of Coastal Eutrophication in the Northern Gulf of
Mexico, J. Geophys. Res.-Oceans, 123, 3408–3426, https://doi.org/10.1002/2017JC013583,
2018. a
Li, X., Bianchi, T., Yang, Z., Osterman, L. E., Allison, M. E., DiMarco,
S. F., and Yang, H.: Historical trends of hypoxia in Changjiang River
estuary: Applications of chemical biomarkers and microfossils, J. Marine
Syst., 86, 57–68, https://doi.org/10.1016/j.jmarsys.2011.02.003, 2011. a
Liu, S. M., Zhang, J., Chen, H. T., Wu, Y., Xiong, H., and Zhang, Z. F.:
Nutrients in the Changjiang and its tributaries, Biogeochemistry, 62,
1–18, https://doi.org/10.1023/A:1021162214304, 2003. a
Liu, S. M., Hong, G.-H., Zhang, J., Ye, X. W., and Jiang, X. L.: Nutrient budgets for large Chinese estuaries, Biogeosciences, 6, 2245–2263, https://doi.org/10.5194/bg-6-2245-2009, 2009. a
Liu, S. M., Qi, X. H., Li, X., Ye, H. R., Wu, Y., Ren, J. L., Zhang, J., and
Xu, W. Y.: Nutrient dynamics from the Changjiang (Yangtze River) estuary to
the East China Sea, J. Marine Syst., 154, 15–27,
https://doi.org/10.1016/j.jmarsys.2015.05.010, 2016. a
Locarnini, R. A., Mishonov, A. V., Antonov, J. I., Boyer, T. P., Garcia, H. E.,
Baranova, O. K., Zweng, M. M., Paver, C. R., Reagan, J. R., Johnson, D. R.,
Hamilton, M., Seidov, D., and Levitus, S.: World Ocean Atlas 2013. Volume 1:
Temperature, Tech. rep., National Oceanic and Atmospheric Administration
(NOAA), Silver Spring, MD, https://doi.org/10.7289/V55X26VD, 2013. a
McDougall, T. J. and Barker, P. M.: Getting started with TEOS-10 and the Gibbs
Seawater (GSW) oceanographic toolbox, Tech. rep., SCOR/IAPSO, available at:
http://www.teos-10.org/pubs/gsw/v3_04/pdf/Getting_Started.pdf (last access: 20 August 2019),
2011. a
Ménesguen, A., Cugier, P., and Leblond, I.: A new numerical technique
for tracking chemical species in a multi-source, coastal ecosystem, applied
to nitrogen causing Ulva blooms in the Bay of Brest (France), Limnol.
Oceanogr., 51, 591–601, https://doi.org/10.4319/lo.2006.51.1_part_2.0591, 2006. a, b
Qian, W., Dai, M., Xu, M., Kao, S.-J., Du, C., Liu, J., Wang, H., Guo, L., and
Wang, L.: Non-local drivers of the summer hypoxia in the East China Sea off
the Changjiang Estuary, Estuar. Coast. Shelf S., 198, 393–399,
https://doi.org/10.1016/j.ecss.2016.08.032, 2017. a
Rabalais, N. N., Turner, R. E., and Wiseman Jr., W. J.: Gulf of Mexico
Hypoxia, A.K.A. “The Dead Zone”, Annu. Rev. Ecol. Syst., 33, 235–263,
https://doi.org/10.1146/annurev.ecolsys.33.010802.150513, 2002. a
Radtke, H., Neumann, T., Voss, M., and Fennel, W.: Modeling pathways of
riverine nitrogen and phosphorus in the Baltic Sea, J. Geophys.
Res.-Oceans, 117, 1–15, https://doi.org/10.1029/2012JC008119, 2012. a
Rutherford, K. and Fennel, K.: Diagnosing transit times on the northwestern North Atlantic continental shelf, Ocean Sci., 14, 1207–1221, https://doi.org/10.5194/os-14-1207-2018, 2018. a
Schmidtko, S., Stramma, L., and Visbeck, M.: Decline in global oceanic oxygen
content during the past five decades, Nature, 542, 335,
https://doi.org/10.1038/nature21399, 2017. a
Seitzinger, S. P., Harrison, J. A., Dumont, E., Beusen, A. H. W., and Bouwman,
A. F.: Sources and delivery of carbon, nitrogen, and phosphorus to the
coastal zone: An overview of Global Nutrient Export from Watersheds (NEWS)
models and their application, Global Biogeochem. Cy., 19, GB4S01,
https://doi.org/10.1029/2005GB002606, 2005. a
Shi, W., Wang, M., and Jiang, L.: Spring-neap tidal effects on satellite ocean
color observations in the Bohai Sea, Yellow Sea, and East China Sea, J.
Geophys. Res.-Oceans, 116, 1–13, https://doi.org/10.1029/2011JC007234, 2011. a
Simpson, J. H.: The shelf-sea fronts: implications of their existence and
behaviour, Philos. T. R. Soc. A, 302, 531–546,
https://doi.org/10.1098/rsta.1981.0181, 1981. a
Siswanto, E., Nakata, H., Matsuoka, Y., Tanaka, K., Kiyomoto, Y., Okamura, K.,
Zhu, J., and Ishizaka, J.: The long-term freshening and nutrient increases
in summer surface water in the northern East China Sea in relation to
Changjiang discharge variation, J. Geophys. Res.-Oceans, 113, C10030,
https://doi.org/10.1029/2008JC004812, 2008. a
Song, G., Liu, S., Zhu, Z., Zhai, W., Zhu, C., and Zhang, J.: Sediment oxygen
consumption and benthic organic carbon mineralization on the continental
shelves of the East China Sea and the Yellow Sea, Deep-Sea Res. Pt. II, 124,
53–63, https://doi.org/10.1016/j.dsr2.2015.04.012, 2016. a, b
Thyng, K. M., Greene, C. A., Hetland, R. D., Zimmerle, H. M., and DiMarco,
S. F.: True Colors of Oceanography: Guidelines for Effective and Accurate
Colormap Selection, Oceanography, 29, 9–13, https://doi.org/10.5670/oceanog.2016.66, 2016. a
Tong, Y., Zhao, Y., Zhen, G., Chi, J., Liu, X., Lu, Y., Wang, X., Yao, R.,
Chen, J., and Zhang, W.: Nutrient loads flowing into coastal waters from the
main rivers of China (2006–2012), Sci. Rep.-UK, 5, 16678,
https://doi.org/10.1038/srep16678, 2015. a
Wang, B.: Hydromorphological mechanisms leading to hypoxia off the Changjiang
estuary, Mar. Environ. Res., 67, 53–58,
https://doi.org/10.1016/j.marenvres.2008.11.001, 2009. a
Wang, B., Wei, Q., Chen, J., and Xie, L.: Annual cycle of hypoxia off the
Changjiang (Yangtze River) Estuary, Mar. Environ. Res., 77, 1–5,
https://doi.org/10.1016/j.marenvres.2011.12.007, 2012. a
Wang, H., Yang, Z., Wang, Y., Saito, Y., and Liu, J. P.: Reconstruction of
sediment flux from the Changjiang (Yangtze River) to the sea since the
1860s, J. Hydrol., 349, 318–332, https://doi.org/10.1016/j.jhydrol.2007.11.005, 2008. a
Wang, J., Yan, W., Chen, N., Li, X., and Liu, L.: Modeled long-term changes of
DIN : DIP ratio in the Changjiang River in relation to Chl-α and DO
concentrations in adjacent estuary, Estuar. Coast. Shelf S., 166, 153–160,
https://doi.org/10.1016/j.ecss.2014.11.028, 2015. a
Wang, W., Yu, Z., Song, X., Yuan, Y., Wu, Z., Zhou, P., and Cao, X.: Intrusion
Pattern of the Offshore Kuroshio Branch Current and Its Effects on Nutrient
Contributions in the East China Sea, J. Geophys. Res.-Oceans, 123,
2116–2128, https://doi.org/10.1002/2017JC013538, 2018. a, b
Wu, G., Cao, W., Wang, F., Su, X., Yan, Y., and Guan, Q.: Riverine nutrient
fluxes and environmental effects on China's estuaries, Sci. Total Environ.,
661, 130–137, https://doi.org/10.1016/j.scitotenv.2019.01.120, 2019. a
Yan, W., Zhang, S., Sun, P., and Seitzinger, S. P.: How do nitrogen inputs to
the Changjiang basin impact the Changjiang River nitrate: A temporal analysis
for 1968–1997, Global Biogeochem. Cy., 17, 1091,
https://doi.org/10.1029/2002GB002029, 2003. a, b
Yang, D., Yin, B., Liu, Z., and Feng, X.: Numerical study of the ocean
circulation on the East China Sea shelf and a Kuroshio bottom branch
northeast of Taiwan in summer, J. Geophys. Res.-Oceans, 116, 1–20,
https://doi.org/10.1029/2010JC006777, 2011. a
Yang, D., Yin, B., Liu, Z., Bai, T., Qi, J., and Chen, H.: Numerical study on
the pattern and origins of Kuroshio branches in the bottom water of southern
East China Sea in summer, J. Geophys. Res.-Oceans, 117, 1–16,
https://doi.org/10.1029/2011JC007528, 2012. a, b
Yu, L., Fennel, K., Laurent, A., Murrell, M. C., and Lehrter, J. C.: Numerical analysis of the primary processes controlling oxygen dynamics on the Louisiana shelf, Biogeosciences, 12, 2063–2076, https://doi.org/10.5194/bg-12-2063-2015, 2015. a, b
Zhang, H., Zhao, L., Sun, Y., Wang, J., and Wei, H.: Contribution of sediment
oxygen demand to hypoxia development off the Changjiang Estuary, Estuar.
Coast. Shelf S., 192, 149–157, https://doi.org/10.1016/j.ecss.2017.05.006, 2017. a, b, c
Zhang, J.: Nutrient elements in large Chinese estuaries, Cont. Shelf Res.,
16, 1023–1045, https://doi.org/10.1016/0278-4343(95)00055-0, 1996. a
Zhang, J., Guo, X., and Zhao, L.: Tracing external sources of nutrients in the
East China Sea and evaluating their contributions to primary production,
Prog. Oceanogr., 176, 102122, https://doi.org/10.1016/j.pocean.2019.102122,
2019. a, b, c, d
Zhang, W., Wu, H., and Zhu, Z.: Transient Hypoxia Extent Off Changjiang River
Estuary due to Mobile Changjiang River Plume, J. Geophys. Res.-Oceans, 123,
9196–9211, https://doi.org/10.1029/2018JC014596, 2018. a, b
Zhang, W. G., Wilkin, J. L., and Schofield, O. M. E.: Simulation of Water Age
and Residence Time in New York Bight, J. Phys. Oceanogr., 40, 965–982,
https://doi.org/10.1175/2009JPO4249.1, 2010. a
Zhang, X., Hetland, R. D., Marta-Almeida, M., and DiMarco, S. F.: A
numerical investigation of the Mississippi and Atchafalaya freshwater
transport, filling and flushing times on the Texas-Louisiana Shelf, J.
Geophys. Res.-Oceans, 117, C11009, https://doi.org/10.1029/2012JC008108, 2012. a
Zhao, L. and Guo, X.: Influence of cross-shelf water transport on nutrients and phytoplankton in the East China Sea: a model study, Ocean Sci., 7, 27–43, https://doi.org/10.5194/os-7-27-2011, 2011. a, b
Zheng, J., Gao, S., Liu, G., Wang, H., and Zhu, X.: Modeling the impact of river discharge and wind on the hypoxia off Yangtze Estuary, Nat. Hazards Earth Syst. Sci., 16, 2559–2576, https://doi.org/10.5194/nhess-16-2559-2016, 2016. a
Zhou, F., Chai, F., Huang, D., Xue, H., Chen, J., Xiu, P., Xuan, J., Li, J.,
Zeng, D., Ni, X., and Wang, K.: Investigation of hypoxia off the Changjiang
Estuary using a coupled model of ROMS-CoSiNE, Prog. Oceanogr., 159,
237–254, https://doi.org/10.1016/j.pocean.2017.10.008, 2017. a, b
Zhou, P., Song, X., Yuan, Y., Wang, W., Cao, X., and Yu, Z.: Intrusion pattern
of the Kuroshio Subsurface Water onto the East China Sea continental shelf
traced by dissolved inorganic iodine species during the spring and autumn of
2014, Mar. Chem., 196, 24–34, https://doi.org/10.1016/j.marchem.2017.07.006, 2017.
a, b, c, d
Zhou, P., Song, X., Yuan, Y., Wang, W., Chi, L., Cao, X., and Yu, Z.:
Intrusion of the Kuroshio Subsurface Water in the southern East China Sea
and its variation in 2014 and 2015 traced by dissolved inorganic iodine
species, Prog. Oceanogr., 165, 287–298, https://doi.org/10.1016/j.pocean.2018.06.011,
2018. a, b, c
Zhu, Z.-Y., Wu, H., Liu, S.-M., Wu, Y., Huang, D.-J., Zhang, J., and Zhang,
G.-S.: Hypoxia off the Changjiang (Yangtze River) estuary and in the
adjacent East China Sea: Quantitative approaches to estimating the tidal
impact and nutrient regeneration, Mar. Pollut. Bull., 125, 103–114,
https://doi.org/10.1016/j.marpolbul.2017.07.029, 2017. a, b, c
Zweng, M. M., Reagan, J. R., Antonov, J. I., Locarnini, R. A., Mishonov, A. V.,
Boyer, T. P., Garcia, H. E., Baranova, O. K., Johnson, D. R., Seidov, D.,
Biddle, M. M., and Levitus, S.: World Ocean Atlas 2013. Volume 2: Salinity,
Tech. rep., National Oceanic and Atmospheric Administration (NOAA), Silver
Spring, MD, https://doi.org/10.7289/V5251G4D, 2013. a
Short summary
In the East China Sea, hypoxia occurs frequently from spring to fall due to high primary production and subsequent decomposition of organic matter. Nitrogen inputs from the Changjiang and the open ocean have been suggested to contribute to hypoxia formation. We used a numerical modelling approach to quantify the relative contributions of these nitrogen sources. We found that the Changjiang dominates, which suggests that nitrogen management in the watershed would improve oxygen conditions.
In the East China Sea, hypoxia occurs frequently from spring to fall due to high primary...
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