Articles | Volume 18, issue 3
Research article 16 Feb 2021
Research article | 16 Feb 2021
The seasonal phases of an Arctic lagoon reveal the discontinuities of pH variability and CO2 flux at the air–sea interface
Cale A. Miller et al.
Cale A. Miller, Katie Pocock, Wiley Evans, and Amanda L. Kelley
Ocean Sci., 14, 751–768,
Cale A. Miller, Katie Pocock, Wiley Evans, and Amanda L. Kelley
Ocean Sci., 14, 751–768,
Related subject area
Biogeochemistry: Coastal OceanThe 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 environmentA numerical model study of the main factors contributing to hypoxia and its interannual and short-term variability in the East China SeaThe 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 PeruWarming and ocean acidification may decrease estuarine dissolved organic carbon export to the oceanReconstructing 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 SeaCharacterizing the origin of excess dissolved organic carbon in coastal seawater using stable carbon isotope and light absorption characteristicsChemical characterization of Punta de Fuencaliente CO2 seeps system (La Palma Island, NE Atlantic Ocean): a new natural laboratory for ocean acidification studiesThe 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 BayAn observation-based evaluation and ranking of historical Earth System Model simulations for regional downscaling in the northwest North Atlantic OceanDecoupling 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 winterFe(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, AntarcticaENSO-driven fluctuations in oxygen supply and vertical extent of oxygen-poor waters in the oxygen minimum zone of the Eastern Tropical South PacificPatterns and drivers of dimethylsulfide concentration in the northeast subarctic Pacific across multiple spatial and temporal scalesPatterns of suspended particulate matter across the continental margin in the Canadian Beaufort Sea during summerReduced phosphorus loads from the Loire and Vilaine rivers were accompanied by increasing eutrophication in the Vilaine Bay (south Brittany, France)Carbon cycling in the North American coastal ocean: a synthesisContrasting effects of acidification and warming on dimethylsulfide concentrations during a temperate estuarine fall bloom mesocosm experimentInterannual variability in the summer dissolved organic matter inventory of the North Sea: implications for the continental shelf pumpRemineralization rate of terrestrial DOC as inferred from CO2 supersaturated coastal watersHigh-frequency variability of CO2 in Grand Passage, Bay of Fundy, Nova ScotiaSedimentary alkalinity generation and long-term alkalinity development in the Baltic Sea
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.
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.
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.
Michelle N. Simone, Kai G. Schulz, Joanne M. Oakes, and Bradley D. Eyre
Revised manuscript accepted for BGShort 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 (OA). 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.
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.
Heejun Han, Jeomshik Hwang, and Guebuem Kim
Revised manuscript accepted for BGShort summary
The main source of excess DOC occurring in coastal seawater off an artificial lake, which is semi-enclosed by a dyke, was determined using combination of various biogeochemical tools including DOC and nutrient concentrations, stable carbon isotope, and optical properties of colored dissolved organic matter (CDOM) in two different seasons (March 2017 and September 2018).
Sara González-Delgado, David González-Santana, Magdalena Santana-Casiano, Melchor González-Dávila, Celso A. Hernández, Carlos Sangil, and José Carlos Hernández
Revised manuscript accepted for BGShort summary
In this paper we describe the carbon system dynamics of a new CO2 seep system located off the coast of La Palma island. We explored 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. Its seeps are a key feature for robust experimental designs, aimed to comprehend how life has persisted through past Eras or to predict the consequences of Ocean Acidification in marine realm.
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.
Arnaud Laurent, Katja Fennel, and Angela Kuhn
Revised manuscript accepted for BGShort 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 an overall improvement in performance in CMIP6 from CMIP5. The regional model performed best.
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.
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.
Yonss Saranga José, Lothar Stramma, Sunke Schmidtko, and Andreas Oschlies
Revised manuscript accepted for BGShort summary
In situ observations along the Peruvian and Chilean coasts have exhibited variability in the water column oxygen concentration. This variability, which is attributed to the El Niño Southern Oscillation (ENSO), might have implication on the vertical extension of the Eastern Tropical South Pacific (ETSP) oxygen minimum zone. Here using a coupled physical-biogeochemical model, we provide new insights into how ENSO variability affects the vertical extension of the oxygen-poor waters of the ETSP.
Alysia E. Herr, Ronald P. Kiene, John W. H. Dacey, and Philippe D. Tortell
Biogeosciences, 16, 1729–1754,Short summary
Dimethylsulfide (DMS) is an essential component of the global sulfur cycle and a major source of climate-influencing aerosols. We examine the drivers of DMS concentration gradients along the British Columbia shelf by comparing DMS measurements to environmental variables and biological rates. We further combine new and existing data sets to provide a new summertime DMS climatology for the northeast subarctic Pacific. Our results highlight the importance of phytoplankton taxonomy to DMS cycling.
Jens K. Ehn, Rick A. Reynolds, Dariusz Stramski, David Doxaran, Bruno Lansard, and Marcel Babin
Biogeosciences, 16, 1583–1605,Short summary
Beam attenuation at 660 nm and suspended particle matter (SPM) relationships were determined during the MALINA cruise in August 2009 to the Canadian Beaufort Sea in order to expand our knowledge of particle distributions in Arctic shelf seas. The relationship was then used to determine SPM distributions for four other expeditions to the region. SPM patterns on the shelf were explained by an interplay between wind forcing, river discharge, and melting sea ice that controls the circulation.
Widya Ratmaya, Dominique Soudant, Jordy Salmon-Monviola, Martin Plus, Nathalie Cochennec-Laureau, Evelyne Goubert, Françoise Andrieux-Loyer, Laurent Barillé, and Philippe Souchu
Biogeosciences, 16, 1361–1380,Short summary
This work reports the consequences of nutrient management strategy, an example from southwestern Europe focused mainly on P reduction. Upstream rivers reveal indices of recoveries following the significant diminution of P, while eutrophication continues to increase downstream, especially when N is the limiting factor. This long-term ecosystem-scale analysis provides more arguments for a dual-nutrient (N and P) management strategy to mitigate eutrophication along the freshwater–marine continuum.
Katja Fennel, Simone Alin, Leticia Barbero, Wiley Evans, Timothée Bourgeois, Sarah Cooley, John Dunne, Richard A. Feely, Jose Martin Hernandez-Ayon, Xinping Hu, Steven Lohrenz, Frank Muller-Karger, Raymond Najjar, Lisa Robbins, Elizabeth Shadwick, Samantha Siedlecki, Nadja Steiner, Adrienne Sutton, Daniela Turk, Penny Vlahos, and Zhaohui Aleck Wang
Biogeosciences, 16, 1281–1304,Short summary
We review and synthesize available information on coastal ocean carbon fluxes around North America (NA). There is overwhelming evidence, compiled and discussed here, that the NA coastal margins act as a sink. Our synthesis shows the great diversity in processes driving carbon fluxes in different coastal regions, highlights remaining gaps in observations and models, and discusses current and anticipated future trends with respect to carbon fluxes and acidification.
Robin Bénard, Maurice Levasseur, Michael Scarratt, Sonia Michaud, Michel Starr, Alfonso Mucci, Gustavo Ferreyra, Michel Gosselin, Jean-Éric Tremblay, Martine Lizotte, and Gui-Peng Yang
Biogeosciences, 16, 1167–1185,Short summary
We present rare data on the combined effects of acidification and warming on dimethylsulfide (DMS) during a mesocosm experiment. Our results show a reduction of DMS under elevated pCO2, but warming the mesocosms by 5 °C translated into a positive offset in concentrations of DMS over the whole range of pCO2 tested. Our results suggest that warming could mitigate the expected reduction in DMS production due to OA, even increasing the net DMS production, with possible repercussions for the climate.
Saisiri Chaichana, Tim Jickells, and Martin Johnson
Biogeosciences, 16, 1073–1096,Short summary
Organic molecules dissolved in the waters of coastal seas (DOM) are a potentially important vector for carbon transport and storage in the open ocean. DOM carbon and nitrogen concentrations from two consecutive summers in the North Sea show a strong pattern of concentrations decreasing away from land. We also observe significant differences between the years in both the DOM concentration and C : N ratios, suggesting that carbon export from shelf seas might be mediated by organic matter cycling.
Filippa Fransner, Agneta Fransson, Christoph Humborg, Erik Gustafsson, Letizia Tedesco, Robinson Hordoir, and Jonas Nycander
Biogeosciences, 16, 863–879,Short summary
Although rivers carry large amounts of organic material to the oceans, little is known about what fate it meets when it reaches the sea. In this study we are investigating the fate of the carbon in this organic matter by the use of a numerical model in combination with ship measurements from the northern Baltic Sea. Our results suggests that there is substantial remineralization taking place, transforming the organic carbon into CO2, which is released to the atmosphere.
Rachel M. Horwitz, Alex E. Hay, William J. Burt, Richard A. Cheel, Joseph Salisbury, and Helmuth Thomas
Biogeosciences, 16, 605–616,Short summary
High-frequency CO2 measurements are used to quantify the daily and tidal cycles of dissolved carbon in the Bay of Fundy – home to the world's largest tides. The oscillating tidal flows drive a net carbon transport, and these results suggest that previously unaccounted for tidal variation could substantially modulate the coastal ocean's response to global ocean acidification. Evaluating the impact of rising atmospheric CO2 on coastal systems requires understanding this short-term variability.
Erik Gustafsson, Mathilde Hagens, Xiaole Sun, Daniel C. Reed, Christoph Humborg, Caroline P. Slomp, and Bo G. Gustafsson
Biogeosciences, 16, 437–456,Short summary
This work highlights that iron (Fe) dynamics plays a key role in the release of alkalinity from sediments, as exemplified for the Baltic Sea. It furthermore demonstrates that burial of Fe sulfides should be included in alkalinity budgets of low-oxygen basins. The sedimentary alkalinity generation may undergo large changes depending on both organic matter loads and oxygen conditions. Enhanced release of alkalinity from the seafloor can increase the CO2 storage capacity of seawater.
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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.
We report here the first year-long high-frequency pH data set for an Arctic lagoon that captures...