Articles | Volume 11, issue 10
Biogeosciences, 11, 2771–2791, 2014
© Author(s) 2014. This work is distributed under
the Creative Commons Attribution 3.0 License.
the Creative Commons Attribution 3.0 License.
Research article 27 May 2014
Research article | 27 May 2014
Benthic mineralization and nutrient exchange over the inner continental shelf of western India
A. K. Pratihary et al.
No articles found.
Parvathi Vallivattathillam, Suresh Iyyappan, Matthieu Lengaigne, Christian Ethé, Jérôme Vialard, Marina Levy, Neetu Suresh, Olivier Aumont, Laure Resplandy, Hema Naik, and Wajih Naqvi
Biogeosciences, 14, 1541–1559,Short summary
During late boreal summer and fall, the west coast of India (WCI) experiences hypoxia, which turns into anoxia during some years. We analyze a coupled physical–biogeochemical simulation over the 1960–2012 period to investigate the physical processes influencing oxycline interannual variability off the WCI. We show that fall WCI oxycline fluctuations are strongly related to Indian Ocean Dipole (IOD), with positive IODs preventing anoxia, while negative IODs do not necessarily result in anoxia.
Pratirupa Bardhan, Syed Wajih Ahmad Naqvi, Supriya G. Karapurkar, Damodar M. Shenoy, Siby Kurian, and Hema Naik
Biogeosciences, 14, 767–779,Short summary
Although India has the third highest number of dams globally, there is a knowledge gap on the cycling of bioessential elements in such systems. This study (first of its kind) investigates the stable isotopes of nitrate and particulate organic matter in a pristine Indian reservoir. Nitrogen transformations in the anaerobic bottom waters were isotopically characterised. Overall, solar intensity, water depth and redox conditions are the major controls on the biogeochemical cycling in this system.
G. Cowie, S. Mowbray, S. Kurian, A. Sarkar, C. White, A. Anderson, B. Vergnaud, G. Johnstone, S. Brear, C. Woulds, S. W. A. Naqvi, and H. Kitazato
Biogeosciences, 11, 6683–6696,
Related subject area
Biogeochemistry: Coastal OceanCoastal processes modify projections of some climate-driven stressors in the California Current SystemUpwelling-induced trace gas dynamics in the Baltic Sea inferred from 8 years of autonomous measurements on a ship of opportunityDestruction and reinstatement of coastal hypoxia in the South China Sea off the Pearl River estuaryHypersaline tidal flats as important “blue carbon” systems: a case study from three ecosystemsDrivers and impact of the seasonal variability of the organic carbon offshore transport in the Canary upwelling systemOrganic carbon densities and accumulation rates in surface sediments of the North Sea and SkagerrakAn observation-based evaluation and ranking of historical Earth system model simulations in the northwest North Atlantic OceanCharacterizing the origins of dissolved organic carbon in coastal seawater using stable carbon isotope and light absorption characteristicsWarming and ocean acidification may decrease estuarine dissolved organic carbon export to the oceanChemical characterization of the Punta de Fuencaliente CO2-enriched system (La Palma, NE Atlantic Ocean): a new natural laboratory for ocean acidification studiesThe seasonal phases of an Arctic lagoon reveal the discontinuities of pH variability and CO2 flux at the air–sea interfaceThe northern European shelf as an increasing net sink for CO2Impacts of biogenic polyunsaturated aldehydes on metabolism and community composition of particle-attached bacteria in coastal hypoxiaA Lagrangian study of the contribution of the Canary coastal upwelling to the nitrogen budget of the open North AtlanticDenitrification by benthic foraminifera and their contribution to N-loss from a fjord environmentThe impact of land-fast ice on the distribution of terrestrial dissolved organic matter in the Siberian Arctic shelf seasA numerical model study of the main factors contributing to hypoxia and its interannual and short-term variability in the East China SeaSources of Fe-binding organic ligands in surface waters of the western Antarctic PeninsulaThe effects of decomposing invasive jellyfish on biogeochemical fluxes and microbial dynamics in an ultra-oligotrophic seaUsing 226Ra and 228Ra isotopes to distinguish water mass distribution in the Canadian Arctic ArchipelagoFactors controlling plankton community production, export flux, and particulate matter stoichiometry in the coastal upwelling system off PeruReconstructing extreme climatic and geochemical conditions during the largest natural mangrove dieback on recordTechnical note: Measurements and data analysis of sediment–water oxygen flux using a new dual-optode eddy covariance instrumentThe impact of intertidal areas on the carbonate system of the southern North SeaThe recent state and variability of the carbonate system of the Canadian Arctic Archipelago and adjacent basins in the context of ocean acidificationA regional hindcast model simulating ecosystem dynamics, inorganic carbon chemistry, and ocean acidification in the Gulf of AlaskaRelative impacts of global changes and regional watershed changes on the inorganic carbon balance of the Chesapeake BayDecoupling of ΔO2∕Ar and particulate organic carbon dynamics in nearshore surface ocean watersWind-driven stratification patterns and dissolved oxygen depletion off the Changjiang (Yangtze) EstuaryRemoval of phosphorus and nitrogen in sediments of the eutrophic Stockholm archipelago, Baltic SeaQuantifying the contributions of riverine vs. oceanic nitrogen to hypoxia in the East China SeaMacroalgal metabolism and lateral carbon flows can create significant carbon sinksRegulation of nitrous oxide production in low-oxygen waters off the coast of PeruAcrylic acid and related dimethylated sulfur compounds in the Bohai and Yellow seas during summer and winterThe fate of upwelled nitrate off Peru shaped by submesoscale filaments and frontsFe(II) stability in coastal seawater during experiments in Patagonia, Svalbard, and Gran CanariaDistribution and behaviour of dissolved selenium in tropical peatland-draining rivers and estuaries of MalaysiaAnomalies in the carbonate system of Red Sea coastal habitatsTracing terrestrial versus marine sources of dissolved organic carbon in a coastal bay using stable carbon isotopesMajor role of ammonia-oxidizing bacteria in N2O production in the Pearl River estuaryLong-term trends in pH in Japanese coastal seawaterNitric oxide (NO) in the Bohai Sea and the Yellow SeaNet heterotrophy and carbonate dissolution in two subtropical seagrass meadowsShifts in dimethylated sulfur concentrations and microbiome composition in the red-tide causing dinoflagellate Alexandrium minutum during a simulated marine heatwaveControls on redox-sensitive trace metals in the Mauritanian oxygen minimum zoneSeasonal and spatial patterns of primary production in a high-latitude fjord affected by Greenland Ice Sheet run-offSpring net community production and its coupling with the CO2 dynamics in the surface water of the northern Gulf of MexicoDistribution, seasonality, and fluxes of dissolved organic matter in the Pearl River (Zhujiang) estuary, ChinaDissolved organic matter at the fluvial–marine transition in the Laptev Sea using in situ data and ocean colour remote sensingCollection of large benthic invertebrates in sediment traps in the Amundsen Sea, Antarctica
Samantha A. Siedlecki, Darren Pilcher, Evan M. Howard, Curtis Deutsch, Parker MacCready, Emily L. Norton, Hartmut Frenzel, Jan Newton, Richard A. Feely, Simone R. Alin, and Terrie Klinger
Biogeosciences, 18, 2871–2890,Short summary
Future ocean conditions can be simulated using projected trends in fossil fuel use paired with Earth system models. Global models generally do not include local processes important to coastal ecosystems. These coastal processes can alter the degree of change projected. Higher-resolution models that include local processes predict modified changes in carbon stressors when compared to changes projected by global models in the California Current System.
Erik Jacobs, Henry C. Bittig, Ulf Gräwe, Carolyn A. Graves, Michael Glockzin, Jens D. Müller, Bernd Schneider, and Gregor Rehder
Biogeosciences, 18, 2679–2709,Short summary
We use a unique data set of 8 years of continuous carbon dioxide (CO2) and methane (CH4) surface water measurements from a commercial ferry to study upwelling in the Baltic Sea. Its seasonality and regional and interannual variability are examined. Strong upwelling events drastically increase local surface CO2 and CH4 levels and are mostly detected in late summer after long periods of impaired mixing. We introduce an extrapolation method to estimate regional upwelling-induced trace gas fluxes.
Yangyang Zhao, Khanittha Uthaipan, Zhongming Lu, Yan Li, Jing Liu, Hongbin Liu, Jianping Gan, Feifei Meng, and Minhan Dai
Biogeosciences, 18, 2755–2775,Short summary
In situ oxygen consumption rates were estimated for the first time during destruction of coastal hypoxia as disturbed by a typhoon and its reinstatement in the South China Sea off the Pearl River estuary. The reinstatement of summer hypoxia was rapid with a comparable timescale with that of its initial disturbance from frequent tropical cyclones, which has important implications for better understanding the intermittent nature of coastal hypoxia and its prediction in a changing climate.
Dylan R. Brown, Humberto Marotta, Roberta B. Peixoto, Alex Enrich-Prast, Glenda C. Barroso, Mario L. G. Soares, Wilson Machado, Alexander Pérez, Joseph M. Smoak, Luciana M. Sanders, Stephen Conrad, James Z. Sippo, Isaac R. Santos, Damien T. Maher, and Christian J. Sanders
Biogeosciences, 18, 2527–2538,Short summary
Hypersaline tidal flats (HTFs) are coastal ecosystems with freshwater deficits often occurring in arid or semi-arid regions near mangrove supratidal zones with no major fluvial contributions. This study shows that HTFs are important carbon and nutrient sinks which may be significant given their extensive coverage. Our findings highlight a previously unquantified carbon as well as a nutrient sink and suggest that coastal HTF ecosystems could be included in the emerging blue carbon framework.
Giulia Bonino, Elisa Lovecchio, Nicolas Gruber, Matthias Münnich, Simona Masina, and Doroteaciro Iovino
Biogeosciences, 18, 2429–2448,Short summary
Seasonal variations of processes such as upwelling and biological production that happen along the northwestern African coast can modulate the temporal variability of the biological activity of the adjacent open North Atlantic hundreds of kilometers away from the coast thanks to the lateral transport of coastal organic carbon. This happens with a temporal delay, which is smaller than a season up to roughly 500 km from the coast due to the intense transport by small-scale filaments.
Markus Diesing, Terje Thorsnes, and Lilja Rún Bjarnadóttir
Biogeosciences, 18, 2139–2160,Short summary
The upper 10 cm of the seafloor of the North Sea and Skagerrak contain 231×106 t of carbon in organic form. The Norwegian Trough, the deepest sedimentary basin in the studied area, stands out as a zone of strong organic carbon accumulation with rates on par with neighbouring fjords. Conversely, large parts of the North Sea are characterised by rapid organic carbon degradation and negligible accumulation. This dual character is likely typical for continental shelf sediments worldwide.
Arnaud Laurent, Katja Fennel, and Angela Kuhn
Biogeosciences, 18, 1803–1822,Short summary
CMIP5 and CMIP6 models, and a high-resolution regional model, were evaluated by comparing historical simulations with observations in the northwest North Atlantic, a climate-sensitive and biologically productive ocean margin region. Many of the CMIP models performed poorly for biological properties. There is no clear link between model resolution and skill in the global models, but there is an overall improvement in performance in CMIP6 from CMIP5. The regional model performed best.
Heejun Han, Jeomshik Hwang, and Guebuem Kim
Biogeosciences, 18, 1793–1801,Short summary
The main source of excess DOC occurring in coastal seawater off an artificial lake, which is enclosed by a dike along the western coast of South Korea, was determined using a combination of various biogeochemical tools including DOC and nutrient concentrations, stable carbon isotope, and optical properties (absorbance and fluorescence) of dissolved organic matter in two different seasons (March 2017 and September 2018).
Michelle N. Simone, Kai G. Schulz, Joanne M. Oakes, and Bradley D. Eyre
Biogeosciences, 18, 1823–1838,Short summary
Estuaries are responsible for a large contribution of dissolved organic carbon (DOC) to the global C cycle, but it is unknown how this will change in the future. DOC fluxes from unvegetated sediments were investigated ex situ subject to conditions of warming and ocean acidification. The future climate shifted sediment fluxes from a slight DOC source to a significant sink, with global coastal DOC export decreasing by 80 %. This has global implications for C cycling and long-term C storage.
Sara González-Delgado, David González-Santana, Magdalena Santana-Casiano, Melchor González-Dávila, Celso A. Hernández, Carlos Sangil, and José Carlos Hernández
Biogeosciences, 18, 1673–1687,Short summary
We describe the carbon system dynamics of a new CO2 seep system located off the coast of La Palma. We explored for over a year, finding points with lower levels of pH and alkalinity; high levels of carbon; and poorer levels of aragonite and calcite, both essential for calcifying species. The seeps are a key feature for robust experimental designs, aimed at comprehending how life has persisted through past eras or at predicting the consequences of ocean acidification in the marine realm.
Cale A. Miller, Christina Bonsell, Nathan D. McTigue, and Amanda L. Kelley
Biogeosciences, 18, 1203–1221,Short summary
We report here the first year-long high-frequency pH data set for an Arctic lagoon that captures ice-free and ice-covered seasons. pH and salinity correlation varies by year as we observed positive correlation and independence. Photosynthesis is found to drive high pH values, and small changes in underwater solar radiation can result in rapid decreases in pH. We estimate that arctic lagoons may act as sources of CO2 to the atmosphere, potentially offsetting the Arctic Ocean's CO2 sink capacity.
Meike Becker, Are Olsen, Peter Landschützer, Abdirhaman Omar, Gregor Rehder, Christian Rödenbeck, and Ingunn Skjelvan
Biogeosciences, 18, 1127–1147,Short summary
We developed a simple method to refine existing open-ocean maps towards different coastal seas. Using a multi-linear regression, we produced monthly maps of surface ocean fCO2 in the northern European coastal seas (the North Sea, the Baltic Sea, the Norwegian Coast and the Barents Sea) covering a time period from 1998 to 2016. Based on this fCO2 map, we calculate trends in surface ocean fCO2, pH and the air–sea gas exchange.
Zhengchao Wu, Qian P. Li, Zaiming Ge, Bangqin Huang, and Chunming Dong
Biogeosciences, 18, 1049–1065,Short summary
Seasonal hypoxia in the nearshore bottom waters frequently occurs in the Pearl River estuary. Aerobic respiration is the ultimate cause of local hypoxia. We found an elevated level of polyunsaturated aldehydes in the bottom water outside the estuary, which promoted the growth and metabolism of special groups of particle-attached bacteria and thus contributed to oxygen depletion in hypoxic waters. Our results may be important for understanding coastal hypoxia and its linkages to eutrophication.
Derara Hailegeorgis, Zouhair Lachkar, Christoph Rieper, and Nicolas Gruber
Biogeosciences, 18, 303–325,Short summary
Using a Lagrangian modeling approach, this study provides a quantitative analysis of water and nitrogen offshore transport in the Canary Current System. We investigate the timescales, reach and structure of offshore transport and demonstrate that the Canary upwelling is a key source of nutrients to the open North Atlantic Ocean. Our findings stress the need for improving the representation of the Canary system and other eastern boundary upwelling systems in global coarse-resolution models.
Constance Choquel, Emmanuelle Geslin, Edouard Metzger, Helena L. Filipsson, Nils Risgaard-Petersen, Patrick Launeau, Manuel Giraud, Thierry Jauffrais, Bruno Jesus, and Aurélia Mouret
Biogeosciences, 18, 327–341,Short summary
Marine microorganisms such as foraminifera are able to live temporarily without oxygen in sediments. In a Swedish fjord subjected to seasonal oxygen scarcity, a change in fauna linked to the decrease in oxygen and the increase in an invasive species was shown. The invasive species respire nitrate until 100 % of the nitrate porewater in the sediment and could be a major contributor to nitrogen balance in oxic coastal ecosystems. But prolonged hypoxia creates unfavorable conditions to survive.
Jens A. Hölemann, Bennet Juhls, Dorothea Bauch, Markus Janout, Boris P. Koch, and Birgit Heim
Revised manuscript accepted for BGShort summary
The Arctic Ocean receive enormous amounts of river water, which is rich in dissolved organic matter (tDOM) and an important component of the Arctic carbon cycle. Our analysis shows that mixing of three major freshwater sources is the main factor that regulates the distribution of tDOM concentrations in the Siberian shelf seas. In this context, the formation and melting of the land-fast ice in the Laptev Sea and the peak spring discharge of the Lena River are of particular importance.
Haiyan Zhang, Katja Fennel, Arnaud Laurent, and Changwei Bian
Biogeosciences, 17, 5745–5761,Short summary
In coastal seas, low oxygen, which is detrimental to coastal ecosystems, is increasingly caused by man-made nutrients from land. This is especially so near mouths of major rivers, including the Changjiang in the East China Sea. Here a simulation model is used to identify the main factors determining low-oxygen conditions in the region. High river discharge is identified as the prime cause, while wind and intrusions of open-ocean water modulate the severity and extent of low-oxygen conditions.
Indah Ardiningsih, Kyyas Seyitmuhammedov, Sylvia G. Sander, Claudine H. Stirling, Gert-Jan Reichart, Kevin R. Arrigo, Loes J. A. Gerringa, and Rob Middag
Revised manuscript accepted for BGShort summary
Organic Fe speciation is investigated along a natural gradient of the western Antarctic Peninsula, from an ice-covered shelf to the open ocean. The two major fronts in the region affect the distribution of ligands. The excess ligands not bound to DFe comprised up to 80 % of the total ligand concentrations, implying the potential to solubilize additional Fe input. The ligands on the shelf can increase the DFe residence time and fuel local primary production upon ice melt.
Tamar Guy-Haim, Maxim Rubin-Blum, Eyal Rahav, Natalia Belkin, Jacob Silverman, and Guy Sisma-Ventura
Biogeosciences, 17, 5489–5511,Short summary
The availability of nutrients in oligotrophic marine ecosystems is limited. Following jellyfish blooms, large die-off events result in the release of high amounts of nutrients to the water column and sediment. Our study assessed the decomposition effects of an infamous invasive jellyfish in the ultra-oligotrophic Eastern Mediterranean Sea. We found that jellyfish decomposition favored heterotrophic bacteria and altered biogeochemical fluxes, further impoverishing this nutrient-poor ecosystem.
Chantal Mears, Helmuth Thomas, Paul B. Henderson, Matthew A. Charette, Hugh MacIntyre, Frank Dehairs, Christophe Monnin, and Alfonso Mucci
Biogeosciences, 17, 4937–4959,Short summary
Major research initiatives have been undertaken within the Arctic Ocean, highlighting this area's global importance and vulnerability to climate change. In 2015, the international GEOTRACES program addressed this importance by devoting intense research activities to the Arctic Ocean. Among various tracers, we used radium and carbonate system data to elucidate the functioning and vulnerability of the hydrographic regime of the Canadian Arctic Archipelago, bridging the Pacific and Atlantic oceans.
Lennart Thomas Bach, Allanah Joy Paul, Tim Boxhammer, Elisabeth von der Esch, Michelle Graco, Kai Georg Schulz, Eric Achterberg, Paulina Aguayo, Javier Arístegui, Patrizia Ayón, Isabel Baños, Avy Bernales, Anne Sophie Boegeholz, Francisco Chavez, Gabriela Chavez, Shao-Min Chen, Kristin Doering, Alba Filella, Martin Fischer, Patricia Grasse, Mathias Haunost, Jan Hennke, Nauzet Hernández-Hernández, Mark Hopwood, Maricarmen Igarza, Verena Kalter, Leila Kittu, Peter Kohnert, Jesus Ledesma, Christian Lieberum, Silke Lischka, Carolin Löscher, Andrea Ludwig, Ursula Mendoza, Jana Meyer, Judith Meyer, Fabrizio Minutolo, Joaquin Ortiz Cortes, Jonna Piiparinen, Claudia Sforna, Kristian Spilling, Sonia Sanchez, Carsten Spisla, Michael Sswat, Mabel Zavala Moreira, and Ulf Riebesell
Biogeosciences, 17, 4831–4852,Short summary
The eastern boundary upwelling system off Peru is among Earth's most productive ocean ecosystems, but the factors that control its functioning are poorly constrained. Here we used mesocosms, moored ~ 6 km offshore Peru, to investigate how processes in plankton communities drive key biogeochemical processes. We show that nutrient and light co-limitation keep productivity and export at a remarkably constant level while stoichiometry changes strongly with shifts in plankton community structure.
James Z. Sippo, Isaac R. Santos, Christian J. Sanders, Patricia Gadd, Quan Hua, Catherine E. Lovelock, Nadia S. Santini, Scott G. Johnston, Yota Harada, Gloria Reithmeir, and Damien T. Maher
Biogeosciences, 17, 4707–4726,Short summary
In 2015–2016, a massive mangrove dieback event occurred along ~1000 km of coastline in Australia. Multiple lines of evidence from climate data, wood and sediment samples suggest low water availability within the dead mangrove forest. Wood and sediments also reveal a large increase in iron concentrations in mangrove sediments during the dieback. This study supports the hypothesis that the forest dieback was associated with low water availability driven by a climate-change-related ENSO event.
Markus Huettel, Peter Berg, and Alireza Merikhi
Biogeosciences, 17, 4459–4476,Short summary
Oxygen fluxes are a valued proxy for organic carbon production and mineralization at the seafloor. These fluxes can be measured non-invasively with the aquatic eddy covariance instrument, but the fast, fragile oxygen sensor it uses often causes questionable flux data. We developed a dual-O2-optode instrument and data evaluation method that allow improved flux measurements. Deployments over carbonate sands in the shallow shelf demonstrate that the instrument can produce reliable oxygen flux data.
Fabian Schwichtenberg, Johannes Pätsch, Michael Ernst Böttcher, Helmuth Thomas, Vera Winde, and Kay-Christian Emeis
Biogeosciences, 17, 4223–4245,Short summary
Ocean acidification has a range of potentially harmful consequences for marine organisms. It is related to total alkalinity (TA) mainly produced in oxygen-poor situations like sediments in tidal flats. TA reduces the sensitivity of a water body to acidification. The decomposition of organic material and subsequent TA release in the tidal areas of the North Sea (Wadden Sea) is responsible for reduced acidification in the southern North Sea. This is shown with the results of an ecosystem model.
Alexis Beaupré-Laperrière, Alfonso Mucci, and Helmuth Thomas
Biogeosciences, 17, 3923–3942,Short summary
Ocean acidification is the process by which the oceans are changing due to carbon dioxide emissions from human activities. Studying this process in the Arctic Ocean is essential as this ocean and its ecosystems are more vulnerable to the effects of acidification. Water chemistry measurements made in recent years show that waters in and around the Canadian Arctic Archipelago are considerably affected by this process and show dynamic conditions that might have an impact on local marine organisms.
Claudine Hauri, Cristina Schultz, Katherine Hedstrom, Seth Danielson, Brita Irving, Scott C. Doney, Raphael Dussin, Enrique N. Curchitser, David F. Hill, and Charles A. Stock
Biogeosciences, 17, 3837–3857,Short summary
The coastal ecosystem of the Gulf of Alaska (GOA) is especially vulnerable to the effects of ocean acidification and climate change. To improve our conceptual understanding of the system, we developed a new regional biogeochemical model setup for the GOA. Model output suggests that bottom water is seasonally high in CO2 between June and January. Such extensive periods of reoccurring high CO2 may be harmful to ocean acidification-sensitive organisms.
Pierre St-Laurent, Marjorie A. M. Friedrichs, Raymond G. Najjar, Elizabeth H. Shadwick, Hanqin Tian, and Yuanzhi Yao
Biogeosciences, 17, 3779–3796,Short summary
Over the past century, estuaries have experienced global (atmospheric CO2 concentrations and temperature) and regional changes (river inputs, land use), but their relative impact remains poorly known. In the Chesapeake Bay, we find that global and regional changes have worked together to enhance how much atmospheric CO2 is taken up by the estuary. The increased uptake is roughly equally due to the global and regional changes, providing crucial perspective for managers of the bay's watershed.
Sarah Z. Rosengard, Robert W. Izett, William J. Burt, Nina Schuback, and Philippe D. Tortell
Biogeosciences, 17, 3277–3298,Short summary
Net community production sets the maximum quantity of phytoplankton carbon available for the marine food web and longer-term storage in the deep ocean. We compared two approaches to estimate this critical variable from autonomous measurements of mixed-layer dissolved oxygen and particulate organic carbon, observing a significant discrepancy between estimates in an upwelling zone near the Oregon coast. We use this discrepancy to assess the fate of organic carbon produced in the mixed layer.
Taavi Liblik, Yijing Wu, Daidu Fan, and Dinghui Shang
Biogeosciences, 17, 2875–2895,Short summary
Multiple factors have been accused of triggering coastal hypoxia off the Changjiang Estuary. In situ observations, remote sensing and numerical simulation data were used to study dissolved oxygen depletion in the area. Oxygen distributions can be explained by wind forcing and river discharge, as well as concurrent features in surface and deep layer circulation. If summer monsoon prevails, hypoxia more likely occurs in the north while hypoxia in the south appears if the summer monsoon is weaker.
Niels A. G. M. van Helmond, Elizabeth K. Robertson, Daniel J. Conley, Martijn Hermans, Christoph Humborg, L. Joëlle Kubeneck, Wytze K. Lenstra, and Caroline P. Slomp
Biogeosciences, 17, 2745–2766,Short summary
We studied the removal of phosphorus (P) and nitrogen (N) in the eutrophic Stockholm archipelago (SA). High sedimentation rates and sediment P contents lead to high P burial. Benthic denitrification is the primary nitrate-reducing pathway. Together, these mechanisms limit P and N transport to the open Baltic Sea. We expect that further nutrient load reduction will contribute to recovery of the SA from low-oxygen conditions and that the sediments will continue to remove part of the P and N loads.
Fabian Große, Katja Fennel, Haiyan Zhang, and Arnaud Laurent
Biogeosciences, 17, 2701–2714,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.
Kenta Watanabe, Goro Yoshida, Masakazu Hori, Yu Umezawa, Hirotada Moki, and Tomohiro Kuwae
Biogeosciences, 17, 2425–2440,Short summary
Macroalgal beds are among the vegetated coastal ecosystems that take up atmospheric CO2. We investigated the relationships between macroalgal metabolism and inorganic and organic carbon fluxes in a temperate macroalgal bed during the productive time of year. The macroalgal metabolism formed water with low CO2 and high dissolved organic carbon concentrations that was then exported offshore. This export process potentially enhances CO2 uptake in and around macroalgal beds.
Claudia Frey, Hermann W. Bange, Eric P. Achterberg, Amal Jayakumar, Carolin R. Löscher, Damian L. Arévalo-Martínez, Elizabeth León-Palmero, Mingshuang Sun, Xin Sun, Ruifang C. Xie, Sergey Oleynik, and Bess B. Ward
Biogeosciences, 17, 2263–2287,Short summary
The production of N2O via nitrification and denitrification associated with low-O2 waters is a major source of oceanic N2O. We investigated the regulation and dynamics of these processes with respect to O2 and organic matter inputs. The transcription of the key nitrification gene amoA rapidly responded to changes in O2 and strongly correlated with N2O production rates. N2O production by denitrification was clearly stimulated by organic carbon, implying that its supply controls N2O production.
Xi Wu, Pei-Feng Li, Hong-Hai Zhang, Mao-Xu Zhu, Chun-Ying Liu, and Gui-Peng Yang
Biogeosciences, 17, 1991–2008,Short summary
Acrylic acid (AA) exhibited obvious spatial and temporal variations in the Bohai and Yellow seas. Strong biological production and abundant terrestrial inputs led to high AA in summer. Extremely high AA in sediments might result from the cleavage of intracellular DMSP and reduce bacterial metabolism. Degradation experiments of AA and DMSP proved other sources of AA and microbial consumption to be the key removal source. This study provided insightful information on the sulfur cycle these seas.
Jaard Hauschildt, Soeren Thomsen, Vincent Echevin, Andreas Oschlies, Yonss Saranga José, Gerd Krahmann, Laura A. Bristow, and Gaute Lavik
Revised manuscript accepted for BGShort summary
In this paper we quantify the subduction of upwelled nitrate due to physical processes on the order of several kilometers in the coastal upwelling off Peru and its effect on primary production. We also compare the prepresentation of these processes in a high-resolution simulation (~2.5 km) with a more coarsely resolved simulation (~12 km). To do this, we combine high-resolution shipboard observations of physical and biogeochemical parameters with a complex biogeochemical model configuration.
Mark J. Hopwood, Carolina Santana-González, Julian Gallego-Urrea, Nicolas Sanchez, Eric P. Achterberg, Murat V. Ardelan, Martha Gledhill, Melchor González-Dávila, Linn Hoffmann, Øystein Leiknes, Juana Magdalena Santana-Casiano, Tatiana M. Tsagaraki, and David Turner
Biogeosciences, 17, 1327–1342,Short summary
Fe is an essential micronutrient. Fe(III)-organic species are thought to account for > 99 % of dissolved Fe in seawater. Here we quantified Fe(II) during experiments in Svalbard, Gran Canaria, and Patagonia. Fe(II) was always a measurable fraction of dissolved Fe up to 65 %. Furthermore, when Fe(II) was allowed to decay in the dark, it remained present longer than predicted by kinetic equations, suggesting that Fe(II) is a more important fraction of dissolved Fe in seawater than widely recognized.
Yan Chang, Moritz Müller, Ying Wu, Shan Jiang, Wan Wan Cao, Jian Guo Qu, Jing Ling Ren, Xiao Na Wang, En Ming Rao, Xiao Lu Wang, Aazani Mujahid, Mohd Fakharuddin Muhamad, Edwin Sien Aun Sia, Faddrine Holt Ajon Jang, and Jing Zhang
Biogeosciences, 17, 1133–1145,Short summary
Selenium (Se) is an essential micronutrient for many organisms. Our knowledge of dissolved Se biogeochemical cycling in tropical estuaries is limited. We have found that dissolved organic Se (DOSe) was the major speciation in the peat-draining rivers and estuaries. The DOSe fractions may be associated with high molecular weight peatland-derived carbon compounds and may photodegrade to more bioavailable forms once transported to oligotrophic coastal water, where they may promote productivity.
Kimberlee Baldry, Vincent Saderne, Daniel C. McCorkle, James H. Churchill, Susana Agusti, and Carlos M. Duarte
Biogeosciences, 17, 423–439,Short summary
The carbon cycling of coastal ecosystems over large spatial scales is not well measured relative to the open ocean. In this study we measure the carbonate system in the three habitats, to measure ecosystem-driven changes compared to offshore waters. We find (1) 70 % of seagrass meadows and mangrove forests show large ecosystem-driven changes, and (2) mangrove forests show strong and consistent trends over large scales, while seagrass meadows display more variability.
Shin-Ah Lee, Tae-Hoon Kim, and Guebuem Kim
Biogeosciences, 17, 135–144,Short summary
We differentiate between sources of dissolved organic matter (DOM) (terrestrial, marine autochthonous production, and artificial island and seawater interaction) in coastal bay waters surrounded by large cities using multiple DOM tracers, including dissolved organic carbon (DOC) and nitrogen (DON), stable carbon isotopes, fluorescent DOM, and the DOC/DON ratio.
Li Ma, Hua Lin, Xiabing Xie, Minhan Dai, and Yao Zhang
Biogeosciences, 16, 4765–4781,Short summary
The major microbial process producing N2O in estuarine ecosystems remains controversial. Combining the concentrations and isotopic compositions of N2O, distributions and transcript levels of ammonia-oxidizing bacterial and archaeal amoA and denitrifier nirS genes, and in situ incubation estimates of nitrification rates and N2O production rates, we clarified that ammonia-oxidizing bacteria contributed the major part in N2O production in the upper Pearl River estuary despite their low abundance.
Miho Ishizu, Yasumasa Miyazawa, Tomohiko Tsunoda, and Tsuneo Ono
Biogeosciences, 16, 4747–4763,Short summary
Using water quality data collected at 289 monitoring sites as part of the Water Pollution Control Program, we evaluated the long-term trends of pH in Japanese coastal seawater at ambient temperature from 1978 to 2009. We found that the annual maximum pH, which generally represents the pH of surface waters in winter, had decreased at 75 % of the sites, but had increased at the remaining sites. The annual maximum pH decreased at an average rate of −0.0024 yr−1, with relatively large deviations.
Ye Tian, Chao Xue, Chun-Ying Liu, Gui-Peng Yang, Pei-Feng Li, Wei-Hua Feng, and Hermann W. Bange
Biogeosciences, 16, 4485–4496,Short summary
Nitric oxide (NO) seems to be widespread, with different functions in the marine ecosystem, but we know little about it. Concentrations of NO were in a range from below the limit of detection to 616 pmol L−1 at the surface and 482 pmol L−1 at the bottom of the Bohai and Yellow seas. The study region was a source of atmospheric NO. Net NO sea-to-air fluxes were much lower than NO photoproduction rates, implying that the NO produced in the mixed layer was rapidly consumed before entering the air.
Bryce R. Van Dam, Christian Lopes, Christopher L. Osburn, and James W. Fourqurean
Biogeosciences, 16, 4411–4428,Short summary
We report on direct measurements of net ecosystem productivity (NEP) and net ecosystem calcification (NEC) in a Florida Bay seagrass ecosystem. We found notable differences between our carbon-based NEP and similar determinations made using oxygen. Over the study period, both NEP and NEC were negative, revealing that these sites are net heterotrophic and have dissolved CaCO3. Our findings point to sediments maintaining negative NEP and NEC despite high seagrass above-ground primary production.
Elisabeth Deschaseaux, James O'Brien, Nachshon Siboni, Katherina Petrou, and Justin R. Seymour
Biogeosciences, 16, 4377–4391,Short summary
Here we report that abrupt increases in temperature–simulating marine heatwaves might have the potential to shape the physiological state and biogenic sulfur production in microalgae involved in harmful algal blooms. Changes in physiology and biochemistry seem to trigger a shift in the bacteria community associated with these microalgae. Since microalgae and associated bacteria play an important role in climate regulation, this could have serious consequences for our future ocean and climate.
Insa Rapp, Christian Schlosser, Jan-Lukas Menzel Barraqueta, Bernhard Wenzel, Jan Lüdke, Jan Scholten, Beat Gasser, Patrick Reichert, Martha Gledhill, Marcus Dengler, and Eric P. Achterberg
Biogeosciences, 16, 4157–4182,Short summary
The availability of iron (Fe) affects phytoplankton growth in large parts of the ocean. Shelf sediments, particularly in oxygen minimum zones, are a major source of Fe and other essential micronutrients, such as cobalt (Co) and manganese (Mn). We observed enhanced concentrations of Fe, Co, and Mn corresponding with low oxygen concentrations along the Mauritanian shelf, indicating that the projected future decrease in oxygen concentrations may result in increases in Fe, Mn, and Co concentrations.
Johnna M. Holding, Stiig Markager, Thomas Juul-Pedersen, Maria L. Paulsen, Eva F. Møller, Lorenz Meire, and Mikael K. Sejr
Biogeosciences, 16, 3777–3792,Short summary
Phytoplankton sustain important fisheries along the coast of Greenland. However, climate change is causing severe melting of the Greenland Ice Sheet, and continued melting has the potential to alter fjord ecosystems. We investigate how freshwater from the ice sheet is impacting the environment of one fjord in northeast Greenland, causing a low production of phytoplankton. This fjord may be a model for how some fjord ecosystems will be altered following increased melting and glacial retreat.
Zong-Pei Jiang, Wei-Jun Cai, John Lehrter, Baoshan Chen, Zhangxian Ouyang, Chengfeng Le, Brian J. Roberts, Najid Hussain, Michael K. Scaboo, Junxiao Zhang, and Yuanyuan Xu
Biogeosciences, 16, 3507–3525,Short summary
The biological production and air–sea CO2 exchange in the surface water of the northern Gulf of Mexico during springtime were mainly controlled by the changes in the availability of light and nutrients during the river–ocean mixing process, with strong CO2 uptake occurring in the river plume regions. The slow air–sea CO2 exchange rate and buffering effect of the CO2 system may result in decoupling between biological production and CO2 flux.
Yang Li, Guisheng Song, Philippe Massicotte, Fangming Yang, Ruihuan Li, and Huixiang Xie
Biogeosciences, 16, 2751–2770,Short summary
We surveyed the spatial and seasonal variations and estimated the seaward export of DOM in the of Pearl River estuary (PRE), China. The concentration of DOM in this estuary decreases from land to sea but the change in its chemical character is marginal. The concentration and export of DOM are the lowest among the world's major rivers. Yet DOM delivered from the PRE is protein-rich and can be readily used by microbes, thereby exerting a potentially important impact on the local marine ecosystem.
Bennet Juhls, Pier Paul Overduin, Jens Hölemann, Martin Hieronymi, Atsushi Matsuoka, Birgit Heim, and Jürgen Fischer
Biogeosciences, 16, 2693–2713,Short summary
In this article, we present the variability and characteristics of dissolved organic matter at the fluvial–marine transition in the Laptev Sea from a unique dataset collected during 11 Arctic expeditions. We develop a new relationship between dissolved organic carbon (DOC) and coloured dissolved organic matter absorption, which is used to estimate surface water DOC concentration from space. We believe that our findings help current efforts to monitor ongoing changes in the Arctic carbon cycle.
Minkyoung Kim, Eun Jin Yang, Hyung Jeek Kim, Dongseon Kim, Tae-Wan Kim, Hyoung Sul La, SangHoon Lee, and Jeomshik Hwang
Biogeosciences, 16, 2683–2691,Short summary
Unexpectedly, in sediment traps deployed in the Antarctic Amundsen Sea to catch small sinking particles in the water, large benthic invertebrates such as long and slender worms, baby sea urchins, and small scallops were found. We suggest three hypotheses: lifting of these animals by anchor ice formation and subsequent transport by ice rafting, spending their juvenile period in a habitat underneath the sea ice and subsequent falling, or their active use of the current as a means of dispersal.
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