Articles | Volume 18, issue 18
Biogeosciences, 18, 5247–5264, 2021
https://doi.org/10.5194/bg-18-5247-2021
© Author(s) 2021. This work is distributed under
the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
Biogeosciences, 18, 5247–5264, 2021
https://doi.org/10.5194/bg-18-5247-2021
© Author(s) 2021. This work is distributed under
the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
Research article
28 Sep 2021
Research article
| 28 Sep 2021
Long-term spatiotemporal variations in and expansion of low-oxygen conditions in the Pearl River estuary: a study synthesizing observations during 1976–2017
Jiatang Hu et al.
Related authors
Zheng Chen, Bin Wang, Chuang Xu, Zhongren Zhang, Shiyu Li, and Jiatang Hu
Biogeosciences Discuss., https://doi.org/10.5194/bg-2021-358, https://doi.org/10.5194/bg-2021-358, 2022
Preprint under review for BG
Short summary
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Deterioration of low-oxygen conditions in eastern Pearl River Estuary (PRE) was revealed by monitoring data over 25 years. The declining wind forcing and increasing nutrient input contributed significantly to areal expansion and intensity deterioration of low oxygen. Besides, the exacerbated eutrophication drove a shift in the dominant source of organic matter from terrestrial inputs to in situ primary production, which has probably led to an earlier onset of hypoxia in summer.
Bin Wang, Jiatang Hu, Shiyu Li, Liuqian Yu, and Jia Huang
Biogeosciences, 15, 6105–6125, https://doi.org/10.5194/bg-15-6105-2018, https://doi.org/10.5194/bg-15-6105-2018, 2018
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A physical–biogeochemical model was applied to study the response of hypoxia and oxygen dynamics to different riverine inputs. Results showed that the hypoxia in the Pearl River estuary was most sensitive to riverine inputs of POC, followed by DO and nutrients. This study also highlighted the significance of re-aeration for its buffering effects; i.e. the re-aeration responded rapidly to the perturbations of riverine inputs and in turn moderated the DO changes impacted by these perturbations.
Bin Wang, Jiatang Hu, Shiyu Li, and Dehong Liu
Biogeosciences, 14, 2979–2999, https://doi.org/10.5194/bg-14-2979-2017, https://doi.org/10.5194/bg-14-2979-2017, 2017
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We proposed a novel method named the physical modulation method to quantify the contributions of boundary conditions, the source and sink processes occurring in local and adjacent waters to DO conditions. A mass balance analysis of DO based on the physical modulation method indicated that the DO conditions were mainly controlled by source and sink processes, among which the sediment oxygen demand and re-aeration were two main processes controlling the spatial extent and the duration of hypoxia.
Zheng Chen, Bin Wang, Chuang Xu, Zhongren Zhang, Shiyu Li, and Jiatang Hu
Biogeosciences Discuss., https://doi.org/10.5194/bg-2021-358, https://doi.org/10.5194/bg-2021-358, 2022
Preprint under review for BG
Short summary
Short summary
Deterioration of low-oxygen conditions in eastern Pearl River Estuary (PRE) was revealed by monitoring data over 25 years. The declining wind forcing and increasing nutrient input contributed significantly to areal expansion and intensity deterioration of low oxygen. Besides, the exacerbated eutrophication drove a shift in the dominant source of organic matter from terrestrial inputs to in situ primary production, which has probably led to an earlier onset of hypoxia in summer.
Bin Wang, Katja Fennel, and Liuqian Yu
Ocean Sci., 17, 1141–1156, https://doi.org/10.5194/os-17-1141-2021, https://doi.org/10.5194/os-17-1141-2021, 2021
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We demonstrate that even sparse BGC-Argo profiles can substantially improve biogeochemical prediction via a priori model tuning. By assimilating satellite surface chlorophyll and physical observations, subsurface distributions of physical properties and nutrients were improved immediately. The improvement of subsurface chlorophyll was modest initially but was greatly enhanced after adjusting the parameterization for light attenuation through further a priori tuning.
Bin Wang, Katja Fennel, Liuqian Yu, and Christopher Gordon
Biogeosciences, 17, 4059–4074, https://doi.org/10.5194/bg-17-4059-2020, https://doi.org/10.5194/bg-17-4059-2020, 2020
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We assess trade-offs between different types of biological observations, specifically satellite ocean color and BGC-Argo profiles and the benefits of combining both for optimizing a biogeochemical model of the Gulf of Mexico. Using all available observations leads to significant improvements in observed and unobserved variables (including primary production and C export). Our results highlight the significant benefits of BGC-Argo measurements for biogeochemical model optimization and validation.
Bin Wang, Jiatang Hu, Shiyu Li, Liuqian Yu, and Jia Huang
Biogeosciences, 15, 6105–6125, https://doi.org/10.5194/bg-15-6105-2018, https://doi.org/10.5194/bg-15-6105-2018, 2018
Short summary
Short summary
A physical–biogeochemical model was applied to study the response of hypoxia and oxygen dynamics to different riverine inputs. Results showed that the hypoxia in the Pearl River estuary was most sensitive to riverine inputs of POC, followed by DO and nutrients. This study also highlighted the significance of re-aeration for its buffering effects; i.e. the re-aeration responded rapidly to the perturbations of riverine inputs and in turn moderated the DO changes impacted by these perturbations.
Bin Wang, Jiatang Hu, Shiyu Li, and Dehong Liu
Biogeosciences, 14, 2979–2999, https://doi.org/10.5194/bg-14-2979-2017, https://doi.org/10.5194/bg-14-2979-2017, 2017
Short summary
Short summary
We proposed a novel method named the physical modulation method to quantify the contributions of boundary conditions, the source and sink processes occurring in local and adjacent waters to DO conditions. A mass balance analysis of DO based on the physical modulation method indicated that the DO conditions were mainly controlled by source and sink processes, among which the sediment oxygen demand and re-aeration were two main processes controlling the spatial extent and the duration of hypoxia.
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Mixed layer depth dominates over upwelling in regulating the seasonality of ecosystem functioning in the Peruvian upwelling system
Temporal dynamics of surface ocean carbonate chemistry in response to natural and simulated upwelling events during the 2017 coastal El Niño near Callao, Peru
Pelagic primary production in the coastal Mediterranean Sea: variability, trends, and contribution to basin-scale budgets
Contrasting patterns of carbon cycling and dissolved organic matter processing in two phytoplankton–bacteria communities
Biophysical controls on seasonal changes in the structure, growth, and grazing of the size-fractionated phytoplankton community in the northern South China Sea
Seasonal dispersal of fjord meltwaters as an important source of iron and manganese to coastal Antarctic phytoplankton
Modeling cyanobacteria life cycle dynamics and historical nitrogen fixation in the Baltic Proper
Simultaneous assessment of oxygen- and nitrate-based net community production in a temperate shelf sea from a single ocean glider
Drought recorded by Ba/Ca in coastal benthic foraminifera
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Fe-binding organic ligands in coastal and frontal regions of the western Antarctic Peninsula
Temporal variability and driving factors of the carbonate system in the Aransas Ship Channel, TX, USA: a time series study
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Retracing hypoxia in Eckernförde Bight (Baltic Sea)
The impact of the freeze–melt cycle of land-fast ice on the distribution of dissolved organic matter in the Laptev and East Siberian seas (Siberian Arctic)
The fate of upwelled nitrate off Peru shaped by submesoscale filaments and fronts
Coastal processes modify projections of some climate-driven stressors in the California Current System
Upwelling-induced trace gas dynamics in the Baltic Sea inferred from 8 years of autonomous measurements on a ship of opportunity
Destruction and reinstatement of coastal hypoxia in the South China Sea off the Pearl River estuary
Hypersaline tidal flats as important “blue carbon” systems: a case study from three ecosystems
Drivers and impact of the seasonal variability of the organic carbon offshore transport in the Canary upwelling system
Organic carbon densities and accumulation rates in surface sediments of the North Sea and Skagerrak
An observation-based evaluation and ranking of historical Earth system model simulations in the northwest North Atlantic Ocean
Characterizing the origins of dissolved organic carbon in coastal seawater using stable carbon isotope and light absorption characteristics
Warming and ocean acidification may decrease estuarine dissolved organic carbon export to the ocean
Chemical characterization of the Punta de Fuencaliente CO2-enriched system (La Palma, NE Atlantic Ocean): a new natural laboratory for ocean acidification studies
The seasonal phases of an Arctic lagoon reveal the discontinuities of pH variability and CO2 flux at the air–sea interface
The northern European shelf as an increasing net sink for CO2
Impacts of biogenic polyunsaturated aldehydes on metabolism and community composition of particle-attached bacteria in coastal hypoxia
A Lagrangian study of the contribution of the Canary coastal upwelling to the nitrogen budget of the open North Atlantic
Denitrification by benthic foraminifera and their contribution to N-loss from a fjord environment
A reactive nitrogen budget of the Bohai Sea based on an isotope mass balance model
A numerical model study of the main factors contributing to hypoxia and its interannual and short-term variability in the East China Sea
The effects of decomposing invasive jellyfish on biogeochemical fluxes and microbial dynamics in an ultra-oligotrophic sea
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Factors controlling plankton community production, export flux, and particulate matter stoichiometry in the coastal upwelling system off Peru
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The recent state and variability of the carbonate system of the Canadian Arctic Archipelago and adjacent basins in the context of ocean acidification
A regional hindcast model simulating ecosystem dynamics, inorganic carbon chemistry, and ocean acidification in the Gulf of Alaska
Relative impacts of global changes and regional watershed changes on the inorganic carbon balance of the Chesapeake Bay
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Gesa Schulz, Tina Sanders, Justus E. E. van Beusekom, Yoana G. Voynova, Andreas Schöl, and Kirstin Dähnke
Biogeosciences, 19, 2007–2024, https://doi.org/10.5194/bg-19-2007-2022, https://doi.org/10.5194/bg-19-2007-2022, 2022
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Estuaries can significantly alter nutrient loads before reaching coastal waters. Our study of the heavily managed Ems estuary (Northern Germany) reveals three zones of nitrogen turnover along the estuary with water-column denitrification in the most upstream hyper-turbid part, nitrate production in the middle reaches and mixing/nitrate uptake in the North Sea. Suspended particulate matter was the overarching control on nitrogen cycling in the hyper-turbid estuary.
Wiley Evans, Geoffrey T. Lebon, Christen D. Harrington, Yuichiro Takeshita, and Allison Bidlack
Biogeosciences, 19, 1277–1301, https://doi.org/10.5194/bg-19-1277-2022, https://doi.org/10.5194/bg-19-1277-2022, 2022
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Information on the marine carbon dioxide system along the northeast Pacific Inside Passage has been limited. To address this gap, we instrumented an Alaskan ferry in order to characterize the marine carbon dioxide system in this region. Data over a 2-year period were used to assess drivers of the observed variability, identify the timing of severe conditions, and assess the extent of contemporary ocean acidification as well as future levels consistent with a 1.5 °C warmer climate.
Melissa Ward, Tye L. Kindinger, Heidi K. Hirsh, Tessa M. Hill, Brittany M. Jellison, Sarah Lummis, Emily B. Rivest, George G. Waldbusser, Brian Gaylord, and Kristy J. Kroeker
Biogeosciences, 19, 689–699, https://doi.org/10.5194/bg-19-689-2022, https://doi.org/10.5194/bg-19-689-2022, 2022
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Here, we synthesize the results from 62 studies reporting in situ rates of seagrass metabolism to highlight spatial and temporal variability in oxygen fluxes and inform efforts to use seagrass to mitigate ocean acidification. Our analyses suggest seagrass meadows are generally autotrophic and variable in space and time, and the effects on seawater oxygen are relatively small in magnitude.
Tianfei Xue, Ivy Frenger, A. E. Friederike Prowe, Yonss Saranga José, and Andreas Oschlies
Biogeosciences, 19, 455–475, https://doi.org/10.5194/bg-19-455-2022, https://doi.org/10.5194/bg-19-455-2022, 2022
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The Peruvian system supports 10 % of the world's fishing yield. In the Peruvian system, wind and earth’s rotation bring cold, nutrient-rich water to the surface and allow phytoplankton to grow. But observations show that it grows worse at high upwelling. Using a model, we find that high upwelling happens when air mixes the water the most. Then phytoplankton is diluted and grows slowly due to low light and cool upwelled water. This study helps to estimate how it might change in a warming climate.
Shao-Min Chen, Ulf Riebesell, Kai G. Schulz, Elisabeth von der Esch, Eric P. Achterberg, and Lennart T. Bach
Biogeosciences, 19, 295–312, https://doi.org/10.5194/bg-19-295-2022, https://doi.org/10.5194/bg-19-295-2022, 2022
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Oxygen minimum zones in the ocean are characterized by enhanced carbon dioxide (CO2) levels and are being further acidified by increasing anthropogenic atmospheric CO2. Here we report CO2 system measurements in a mesocosm study offshore Peru during a rare coastal El Niño event to investigate how CO2 dynamics may respond to ongoing ocean deoxygenation. Our observations show that nitrogen limitation, productivity, and plankton community shift play an important role in driving the CO2 dynamics.
Paula Maria Salgado-Hernanz, Aurore Regaudie-de-Gioux, David Antoine, and Gotzon Basterretxea
Biogeosciences, 19, 47–69, https://doi.org/10.5194/bg-19-47-2022, https://doi.org/10.5194/bg-19-47-2022, 2022
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For the first time, this study presents the characteristics of primary production in coastal regions of the Mediterranean Sea based on satellite-borne observations for the period 2002–2016. The study concludes that there are significant spatial and temporal variations among different regions. Quantifying primary production is of special importance in the marine food web and in the sequestration of carbon dioxide from the atmosphere to the deep waters.
Samu Elovaara, Eeva Eronen-Rasimus, Eero Asmala, Tobias Tamelander, and Hermanni Kaartokallio
Biogeosciences, 18, 6589–6616, https://doi.org/10.5194/bg-18-6589-2021, https://doi.org/10.5194/bg-18-6589-2021, 2021
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Dissolved organic matter (DOM) is a significant carbon pool in the marine environment. The composition of the DOM pool, as well as its interaction with microbes, is complex, yet understanding it is important for understanding global carbon cycling. This study shows that two phytoplankton species have different effects on the composition of the DOM pool and, through the DOM they produce, on the ensuing microbial community. These communities in turn have different effects on DOM composition.
Yuan Dong, Qian P. Li, Zhengchao Wu, Yiping Shuai, Zijia Liu, Zaiming Ge, Weiwen Zhou, and Yinchao Chen
Biogeosciences, 18, 6423–6434, https://doi.org/10.5194/bg-18-6423-2021, https://doi.org/10.5194/bg-18-6423-2021, 2021
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Temporal change of plankton growth and grazing are less known in the coastal ocean, not to mention the relevant controlling mechanisms. Here, we performed monthly size-specific dilution experiments outside a eutrophic estuary over a 1-year cycle. Phytoplankton growth was correlated to nutrients and grazing mortality to total chlorophyll a. A selective grazing on small cells may be important for maintaining high abundance of large-chain-forming diatoms in this eutrophic system.
Kiefer O. Forsch, Lisa Hahn-Woernle, Robert M. Sherrell, Vincent J. Roccanova, Kaixuan Bu, David Burdige, Maria Vernet, and Katherine A. Barbeau
Biogeosciences, 18, 6349–6375, https://doi.org/10.5194/bg-18-6349-2021, https://doi.org/10.5194/bg-18-6349-2021, 2021
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We show that for an unperturbed cold western Antarctic Peninsula fjord, the seasonality of iron and manganese is linked to the dispersal of metal-rich meltwater sources. Geochemical measurements of trace metals in meltwaters, porewaters, and seawater, collected during two expeditions, showed a seasonal cycle of distinct sources. Finally, model results revealed that the dispersal of surface meltwater and meltwater plumes originating from under the glacier is sensitive to katabatic wind events.
Jenny Hieronymus, Kari Eilola, Malin Olofsson, Inga Hense, H. E. Markus Meier, and Elin Almroth-Rosell
Biogeosciences, 18, 6213–6227, https://doi.org/10.5194/bg-18-6213-2021, https://doi.org/10.5194/bg-18-6213-2021, 2021
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Dense blooms of cyanobacteria occur every summer in the Baltic Proper and can add to eutrophication by their ability to turn nitrogen gas into dissolved inorganic nitrogen. Being able to correctly estimate the size of this nitrogen fixation is important for management purposes. In this work, we find that the life cycle of cyanobacteria plays an important role in capturing the seasonality of the blooms as well as the size of nitrogen fixation in our ocean model.
Tom Hull, Naomi Greenwood, Antony Birchill, Alexander Beaton, Matthew Palmer, and Jan Kaiser
Biogeosciences, 18, 6167–6180, https://doi.org/10.5194/bg-18-6167-2021, https://doi.org/10.5194/bg-18-6167-2021, 2021
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The shallow shelf seas play a large role in the global cycling of CO2 and also support large fisheries. We use an autonomous underwater vehicle in the central North Sea to measure the rates of change in oxygen and nutrients.
Using these data we determine the amount of carbon dioxide taken out of the atmosphere by the sea and measure how productive the region is.
These observations will be useful for improving our predictive models and help us predict and adapt to a changing ocean.
Inda Brinkmann, Christine Barras, Tom Jilbert, Tomas Naeraa, K. Mareike Paul, Magali Schweizer, and Helena L. Filipsson
Biogeosciences Discuss., https://doi.org/10.5194/bg-2021-310, https://doi.org/10.5194/bg-2021-310, 2021
Revised manuscript accepted for BG
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The concentration of the trace metal barium (Ba) in coastal seawater is a function of continental input, such as by riverine discharge. Our geochemical records of the severely hot and dry year 2018, and following wet year 2019, reveal that prolonged drought imprints with exceptionally low Ba concentrations in benthic foraminiferal calcium carbonates of coastal sediments. This highlights the potential of benthic Ba/Ca to trace past climate extremes and variability in coastal marine records.
Puthenveettil Narayana Menon Vinayachandran, Yukio Masumoto, Michael J. Roberts, Jenny A. Huggett, Issufo Halo, Abhisek Chatterjee, Prakash Amol, Garuda V. M. Gupta, Arvind Singh, Arnab Mukherjee, Satya Prakash, Lynnath E. Beckley, Eric Jorden Raes, and Raleigh Hood
Biogeosciences, 18, 5967–6029, https://doi.org/10.5194/bg-18-5967-2021, https://doi.org/10.5194/bg-18-5967-2021, 2021
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Upwelling in the coastal ocean triggers biological productivity and thus enhances fisheries. Therefore, understanding the phenomenon of upwelling and the underlying mechanisms is important. In this paper, the present understanding of the upwelling along the coastline of the Indian Ocean from the coast of Africa all the way up to the coast of Australia is reviewed. The review provides a synthesis of the physical processes associated with upwelling and its impact on the marine ecosystem.
Gaël Many, Caroline Ulses, Claude Estournel, and Patrick Marsaleix
Biogeosciences, 18, 5513–5538, https://doi.org/10.5194/bg-18-5513-2021, https://doi.org/10.5194/bg-18-5513-2021, 2021
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The Gulf of Lion shelf is one of the most productive areas in the Mediterranean. A model is used to study the mechanisms that drive the particulate organic carbon (POC). The model reproduces the annual cycle of primary production well. The shelf appears as an autotrophic ecosystem with a high production and as a source of POC for the adjacent basin. The increase in temperature induced by climate change could impact the trophic status of the shelf.
Alireza Merikhi, Peter Berg, and Markus Huettel
Biogeosciences, 18, 5381–5395, https://doi.org/10.5194/bg-18-5381-2021, https://doi.org/10.5194/bg-18-5381-2021, 2021
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The aquatic eddy covariance technique is a powerful method for measurements of solute fluxes across the sediment–water interface. Data measured by conventional eddy covariance instruments require a time shift correction that can result in substantial flux errors. We introduce a triple O2 sensor eddy covariance instrument that by design eliminates these errors. Deployments next to a conventional instrument in the Florida Keys demonstrate the improvements achieved through the new design.
Indah Ardiningsih, Kyyas Seyitmuhammedov, Sylvia G. Sander, Claudine H. Stirling, Gert-Jan Reichart, Kevin R. Arrigo, Loes J. A. Gerringa, and Rob Middag
Biogeosciences, 18, 4587–4601, https://doi.org/10.5194/bg-18-4587-2021, https://doi.org/10.5194/bg-18-4587-2021, 2021
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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 dissolved Fe (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.
Melissa R. McCutcheon, Hongming Yao, Cory J. Staryk, and Xinping Hu
Biogeosciences, 18, 4571–4586, https://doi.org/10.5194/bg-18-4571-2021, https://doi.org/10.5194/bg-18-4571-2021, 2021
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We used 5+ years of discrete samples and 10 months of hourly sensor measurements to explore temporal variability and environmental controls on pH and pCO2 at the Aransas Ship Channel. Seasonal and diel variability were both present but small compared to other regions in the literature. Despite the small tidal range, tidal control often surpassed biological control. In comparison with sensor data, discrete samples were generally representative of mean annual and seasonal carbonate chemistry.
Kai G. Schulz, Eric P. Achterberg, Javier Arístegui, Lennart T. Bach, Isabel Baños, Tim Boxhammer, Dirk Erler, Maricarmen Igarza, Verena Kalter, Andrea Ludwig, Carolin Löscher, Jana Meyer, Judith Meyer, Fabrizio Minutolo, Elisabeth von der Esch, Bess B. Ward, and Ulf Riebesell
Biogeosciences, 18, 4305–4320, https://doi.org/10.5194/bg-18-4305-2021, https://doi.org/10.5194/bg-18-4305-2021, 2021
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Upwelling of nutrient-rich deep waters to the surface make eastern boundary upwelling systems hot spots of marine productivity. This leads to subsurface oxygen depletion and the transformation of bioavailable nitrogen into inert N2. Here we quantify nitrogen loss processes following a simulated deep water upwelling. Denitrification was the dominant process, and budget calculations suggest that a significant portion of nitrogen that could be exported to depth is already lost in the surface ocean.
Heiner Dietze and Ulrike Löptien
Biogeosciences, 18, 4243–4264, https://doi.org/10.5194/bg-18-4243-2021, https://doi.org/10.5194/bg-18-4243-2021, 2021
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In recent years fish-kill events caused by oxygen deficit have been reported in Eckernförde Bight (Baltic Sea). This study sets out to understand the processes causing respective oxygen deficits by combining high-resolution coupled ocean circulation biogeochemical modeling, monitoring data, and artificial intelligence.
Jens A. Hölemann, Bennet Juhls, Dorothea Bauch, Markus Janout, Boris P. Koch, and Birgit Heim
Biogeosciences, 18, 3637–3655, https://doi.org/10.5194/bg-18-3637-2021, https://doi.org/10.5194/bg-18-3637-2021, 2021
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The Arctic Ocean receives large amounts of river water rich in terrestrial dissolved organic matter (tDOM), which is 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.
Jaard Hauschildt, Soeren Thomsen, Vincent Echevin, Andreas Oschlies, Yonss Saranga José, Gerd Krahmann, Laura A. Bristow, and Gaute Lavik
Biogeosciences, 18, 3605–3629, https://doi.org/10.5194/bg-18-3605-2021, https://doi.org/10.5194/bg-18-3605-2021, 2021
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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.
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, https://doi.org/10.5194/bg-18-2871-2021, https://doi.org/10.5194/bg-18-2871-2021, 2021
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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, https://doi.org/10.5194/bg-18-2679-2021, https://doi.org/10.5194/bg-18-2679-2021, 2021
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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, https://doi.org/10.5194/bg-18-2755-2021, https://doi.org/10.5194/bg-18-2755-2021, 2021
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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, https://doi.org/10.5194/bg-18-2527-2021, https://doi.org/10.5194/bg-18-2527-2021, 2021
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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, https://doi.org/10.5194/bg-18-2429-2021, https://doi.org/10.5194/bg-18-2429-2021, 2021
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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, https://doi.org/10.5194/bg-18-2139-2021, https://doi.org/10.5194/bg-18-2139-2021, 2021
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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, https://doi.org/10.5194/bg-18-1803-2021, https://doi.org/10.5194/bg-18-1803-2021, 2021
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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, https://doi.org/10.5194/bg-18-1793-2021, https://doi.org/10.5194/bg-18-1793-2021, 2021
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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, https://doi.org/10.5194/bg-18-1823-2021, https://doi.org/10.5194/bg-18-1823-2021, 2021
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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, https://doi.org/10.5194/bg-18-1673-2021, https://doi.org/10.5194/bg-18-1673-2021, 2021
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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, https://doi.org/10.5194/bg-18-1203-2021, https://doi.org/10.5194/bg-18-1203-2021, 2021
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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.
Meike Becker, Are Olsen, Peter Landschützer, Abdirhaman Omar, Gregor Rehder, Christian Rödenbeck, and Ingunn Skjelvan
Biogeosciences, 18, 1127–1147, https://doi.org/10.5194/bg-18-1127-2021, https://doi.org/10.5194/bg-18-1127-2021, 2021
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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, https://doi.org/10.5194/bg-18-1049-2021, https://doi.org/10.5194/bg-18-1049-2021, 2021
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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, https://doi.org/10.5194/bg-18-303-2021, https://doi.org/10.5194/bg-18-303-2021, 2021
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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, https://doi.org/10.5194/bg-18-327-2021, https://doi.org/10.5194/bg-18-327-2021, 2021
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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.
Shichao Tian, Birgit Gaye, Jianhui Tang, Yongming Luo, Wenguo Li, Niko Lahajnar, Kirstin Dähnke, Tina Sanders, Tianqi Xiong, Weidong Zhai, and Kay-Christian Emeis
Biogeosciences Discuss., https://doi.org/10.5194/bg-2020-471, https://doi.org/10.5194/bg-2020-471, 2020
Revised manuscript accepted for BG
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We constraint the nitrogen budget and in particular the internal sources and sinks of nitrate in the Bohai Sea by using a mass-based and dual stable-isotope approach based on δ15N and δ18O of nitrate. Based on the available mass fluxes and isotope data an updated nitrogen budget is proposed. Compared to previous estimates, it is more complete and includes the impact of interior cycling (nitrification) on the nitrate pool. The main external nitrogen sources are rivers contributing 17.5 %–20.6 %.
Haiyan Zhang, Katja Fennel, Arnaud Laurent, and Changwei Bian
Biogeosciences, 17, 5745–5761, https://doi.org/10.5194/bg-17-5745-2020, https://doi.org/10.5194/bg-17-5745-2020, 2020
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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, https://doi.org/10.5194/bg-17-5489-2020, https://doi.org/10.5194/bg-17-5489-2020, 2020
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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, https://doi.org/10.5194/bg-17-4937-2020, https://doi.org/10.5194/bg-17-4937-2020, 2020
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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, https://doi.org/10.5194/bg-17-4831-2020, https://doi.org/10.5194/bg-17-4831-2020, 2020
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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, https://doi.org/10.5194/bg-17-4707-2020, https://doi.org/10.5194/bg-17-4707-2020, 2020
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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, https://doi.org/10.5194/bg-17-4459-2020, https://doi.org/10.5194/bg-17-4459-2020, 2020
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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, https://doi.org/10.5194/bg-17-4223-2020, https://doi.org/10.5194/bg-17-4223-2020, 2020
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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, https://doi.org/10.5194/bg-17-3923-2020, https://doi.org/10.5194/bg-17-3923-2020, 2020
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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, https://doi.org/10.5194/bg-17-3837-2020, https://doi.org/10.5194/bg-17-3837-2020, 2020
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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, https://doi.org/10.5194/bg-17-3779-2020, https://doi.org/10.5194/bg-17-3779-2020, 2020
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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, https://doi.org/10.5194/bg-17-3277-2020, https://doi.org/10.5194/bg-17-3277-2020, 2020
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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, https://doi.org/10.5194/bg-17-2875-2020, https://doi.org/10.5194/bg-17-2875-2020, 2020
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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, https://doi.org/10.5194/bg-17-2745-2020, https://doi.org/10.5194/bg-17-2745-2020, 2020
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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.
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Short summary
In situ observations over 42 years were used to explore the long-term changes to low-oxygen conditions in the Pearl River estuary. Apparent expansion of the low-oxygen conditions in summer was identified, primarily due to the combined effects of increased anthropogenic inputs and decreased sediment load. Large areas of severe low-oxygen events were also observed in early autumn and were formed by distinct mechanisms. The estuary seems to be growing into a seasonal, estuary-wide hypoxic zone.
In situ observations over 42 years were used to explore the long-term changes to low-oxygen...
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