Articles | Volume 15, issue 14
https://doi.org/10.5194/bg-15-4647-2018
© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
https://doi.org/10.5194/bg-15-4647-2018
© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
Seasonal development of iron limitation in the sub-Antarctic zone
Thomas J. Ryan-Keogh
CORRESPONDING AUTHOR
Southern Ocean Carbon and Climate Observatory, Natural Resources and
Environment, CSIR, Rosebank, Cape Town, 7700, South Africa
Department of Oceanography, University of Cape Town, Rondebosch, Cape
Town, 7701, South Africa
Sandy J. Thomalla
Southern Ocean Carbon and Climate Observatory, Natural Resources and
Environment, CSIR, Rosebank, Cape Town, 7700, South Africa
Marine Research Institute, University of Cape Town, Rondebosch, Cape
Town, 7701, South Africa
Thato N. Mtshali
Southern Ocean Carbon and Climate Observatory, Natural Resources and
Environment, CSIR, Rosebank, Cape Town, 7700, South Africa
Natasha R. van Horsten
Southern Ocean Carbon and Climate Observatory, Natural Resources and
Environment, CSIR, Rosebank, Cape Town, 7700, South Africa
Department of Earth Sciences, Stellenbosch University, Stellenbosch,
7600, South Africa
Hazel J. Little
Department of Oceanography, University of Cape Town, Rondebosch, Cape
Town, 7701, South Africa
Related authors
Thomas J. Ryan-Keogh, Sandy J. Thomalla, Nicolette Chang, and Tumelo Moalusi
Earth Syst. Sci. Data, 15, 4829–4848, https://doi.org/10.5194/essd-15-4829-2023, https://doi.org/10.5194/essd-15-4829-2023, 2023
Short summary
Short summary
Oceanic productivity has been highlighted as an important environmental indicator of climate change in comparison to other existing metrics. However, the availability of these data to assess trends and trajectories is plagued with issues, such as application to only a single satellite reducing the time period for assessment. We have applied multiple algorithms to the longest ocean colour record to provide a record for assessing climate-change-driven trends.
Asmita Singh, Susanne Fietz, Sandy J. Thomalla, Nicolas Sanchez, Murat V. Ardelan, Sébastien Moreau, Hanna M. Kauko, Agneta Fransson, Melissa Chierici, Saumik Samanta, Thato N. Mtshali, Alakendra N. Roychoudhury, and Thomas J. Ryan-Keogh
Biogeosciences, 20, 3073–3091, https://doi.org/10.5194/bg-20-3073-2023, https://doi.org/10.5194/bg-20-3073-2023, 2023
Short summary
Short summary
Despite the scarcity of iron in the Southern Ocean, seasonal blooms occur due to changes in nutrient and light availability. Surprisingly, during an autumn bloom in the Antarctic sea-ice zone, the results from incubation experiments showed no significant photophysiological response of phytoplankton to iron addition. This suggests that ambient iron concentrations were sufficient, challenging the notion of iron deficiency in the Southern Ocean through extended iron-replete post-bloom conditions.
Hanna M. Kauko, Philipp Assmy, Ilka Peeken, Magdalena Różańska-Pluta, Józef M. Wiktor, Gunnar Bratbak, Asmita Singh, Thomas J. Ryan-Keogh, and Sebastien Moreau
Biogeosciences, 19, 5449–5482, https://doi.org/10.5194/bg-19-5449-2022, https://doi.org/10.5194/bg-19-5449-2022, 2022
Short summary
Short summary
This article studies phytoplankton (microscopic
plantsin the ocean capable of photosynthesis) in Kong Håkon VII Hav in the Southern Ocean. Different species play different roles in the ecosystem, and it is therefore important to assess the species composition. We observed that phytoplankton blooms in this area are formed by large diatoms with strong silica armors, which can lead to high silica (and sometimes carbon) export to depth and be important prey for krill.
Natasha René van Horsten, Hélène Planquette, Géraldine Sarthou, Thomas James Ryan-Keogh, Nolwenn Lemaitre, Thato Nicholas Mtshali, Alakendra Roychoudhury, and Eva Bucciarelli
Biogeosciences, 19, 3209–3224, https://doi.org/10.5194/bg-19-3209-2022, https://doi.org/10.5194/bg-19-3209-2022, 2022
Short summary
Short summary
The remineralisation proxy, barite, was measured along 30°E in the southern Indian Ocean during early austral winter. To our knowledge this is the first reported Southern Ocean winter study. Concentrations throughout the water column were comparable to observations during spring to autumn. By linking satellite primary production to this proxy a possible annual timescale is proposed. These findings also suggest possible carbon remineralisation from satellite data on a basin scale.
Thomas J. Ryan-Keogh, Sandy J. Thomalla, Thato N. Mtshali, and Hazel Little
Biogeosciences, 14, 3883–3897, https://doi.org/10.5194/bg-14-3883-2017, https://doi.org/10.5194/bg-14-3883-2017, 2017
Short summary
Short summary
Primary production in the Southern Ocean is a key contributor to mitigating global anthropogenic carbon dioxide; however, the controlling mechanisms are poorly understood. A series of experiments were performed to look at whether the rates of primary production are limited by the biogeochemically important micronutrient iron. The results demonstrate that any global climate models that do not take into account the effect of iron availability could underestimate primary production by up to 80 %.
Thomas J. Ryan-Keogh, Sandy J. Thomalla, Nicolette Chang, and Tumelo Moalusi
Earth Syst. Sci. Data, 15, 4829–4848, https://doi.org/10.5194/essd-15-4829-2023, https://doi.org/10.5194/essd-15-4829-2023, 2023
Short summary
Short summary
Oceanic productivity has been highlighted as an important environmental indicator of climate change in comparison to other existing metrics. However, the availability of these data to assess trends and trajectories is plagued with issues, such as application to only a single satellite reducing the time period for assessment. We have applied multiple algorithms to the longest ocean colour record to provide a record for assessing climate-change-driven trends.
Asmita Singh, Susanne Fietz, Sandy J. Thomalla, Nicolas Sanchez, Murat V. Ardelan, Sébastien Moreau, Hanna M. Kauko, Agneta Fransson, Melissa Chierici, Saumik Samanta, Thato N. Mtshali, Alakendra N. Roychoudhury, and Thomas J. Ryan-Keogh
Biogeosciences, 20, 3073–3091, https://doi.org/10.5194/bg-20-3073-2023, https://doi.org/10.5194/bg-20-3073-2023, 2023
Short summary
Short summary
Despite the scarcity of iron in the Southern Ocean, seasonal blooms occur due to changes in nutrient and light availability. Surprisingly, during an autumn bloom in the Antarctic sea-ice zone, the results from incubation experiments showed no significant photophysiological response of phytoplankton to iron addition. This suggests that ambient iron concentrations were sufficient, challenging the notion of iron deficiency in the Southern Ocean through extended iron-replete post-bloom conditions.
Hanna M. Kauko, Philipp Assmy, Ilka Peeken, Magdalena Różańska-Pluta, Józef M. Wiktor, Gunnar Bratbak, Asmita Singh, Thomas J. Ryan-Keogh, and Sebastien Moreau
Biogeosciences, 19, 5449–5482, https://doi.org/10.5194/bg-19-5449-2022, https://doi.org/10.5194/bg-19-5449-2022, 2022
Short summary
Short summary
This article studies phytoplankton (microscopic
plantsin the ocean capable of photosynthesis) in Kong Håkon VII Hav in the Southern Ocean. Different species play different roles in the ecosystem, and it is therefore important to assess the species composition. We observed that phytoplankton blooms in this area are formed by large diatoms with strong silica armors, which can lead to high silica (and sometimes carbon) export to depth and be important prey for krill.
Mhlangabezi Mdutyana, Tanya Marshall, Xin Sun, Jessica M. Burger, Sandy J. Thomalla, Bess B. Ward, and Sarah E. Fawcett
Biogeosciences, 19, 3425–3444, https://doi.org/10.5194/bg-19-3425-2022, https://doi.org/10.5194/bg-19-3425-2022, 2022
Short summary
Short summary
Nitrite-oxidizing bacteria in the winter Southern Ocean show a high affinity for nitrite but require a minimum (i.e., "threshold") concentration before they increase their rates of nitrite oxidation significantly. The classic Michaelis–Menten model thus cannot be used to derive the kinetic parameters, so a modified equation was employed that also yields the threshold nitrite concentration. Dissolved iron availability may play an important role in limiting nitrite oxidation.
Natasha René van Horsten, Hélène Planquette, Géraldine Sarthou, Thomas James Ryan-Keogh, Nolwenn Lemaitre, Thato Nicholas Mtshali, Alakendra Roychoudhury, and Eva Bucciarelli
Biogeosciences, 19, 3209–3224, https://doi.org/10.5194/bg-19-3209-2022, https://doi.org/10.5194/bg-19-3209-2022, 2022
Short summary
Short summary
The remineralisation proxy, barite, was measured along 30°E in the southern Indian Ocean during early austral winter. To our knowledge this is the first reported Southern Ocean winter study. Concentrations throughout the water column were comparable to observations during spring to autumn. By linking satellite primary production to this proxy a possible annual timescale is proposed. These findings also suggest possible carbon remineralisation from satellite data on a basin scale.
Thomas J. Ryan-Keogh, Sandy J. Thomalla, Thato N. Mtshali, and Hazel Little
Biogeosciences, 14, 3883–3897, https://doi.org/10.5194/bg-14-3883-2017, https://doi.org/10.5194/bg-14-3883-2017, 2017
Short summary
Short summary
Primary production in the Southern Ocean is a key contributor to mitigating global anthropogenic carbon dioxide; however, the controlling mechanisms are poorly understood. A series of experiments were performed to look at whether the rates of primary production are limited by the biogeochemically important micronutrient iron. The results demonstrate that any global climate models that do not take into account the effect of iron availability could underestimate primary production by up to 80 %.
W. R. Joubert, S. Swart, A. Tagliabue, S. J. Thomalla, and P. M. S. Monteiro
Biogeosciences Discuss., https://doi.org/10.5194/bgd-11-4335-2014, https://doi.org/10.5194/bgd-11-4335-2014, 2014
Revised manuscript not accepted
Related subject area
Biogeochemistry: Open Ocean
The fingerprint of climate variability on the surface ocean cycling of iron and its isotopes
Reconstructing the ocean's mesopelagic zone carbon budget: sensitivity and estimation of parameters associated with prokaryotic remineralization
Seasonal cycles of biogeochemical fluxes in the Scotia Sea, Southern Ocean: a stable isotope approach
Absence of photophysiological response to iron addition in autumn phytoplankton in the Antarctic sea-ice zone
Optimal parameters for the ocean's nutrient, carbon, and oxygen cycles compensate for circulation biases but replumb the biological pump
Importance of multiple sources of iron for the upper-ocean biogeochemistry over the northern Indian Ocean
Exploring the role of different data types and timescales in the quality of marine biogeochemical model calibration
All about nitrite: exploring nitrite sources and sinks in the eastern tropical North Pacific oxygen minimum zone
Fossil coccolith morphological attributes as a new proxy for deep ocean carbonate chemistry
Reconstructing ocean carbon storage with CMIP6 Earth system models and synthetic Argo observations
Using machine learning and Biogeochemical-Argo (BGC-Argo) floats to assess biogeochemical models and optimize observing system design
The representation of alkalinity and the carbonate pump from CMIP5 to CMIP6 Earth system models and implications for the carbon cycle
Characteristics of Physical and Biochemical Parameters within Mesoscale Eddies in the Southern Ocean
Model estimates of metazoans' contributions to the biological carbon pump
Reviews and syntheses: Expanding the global coverage of gross primary production and net community production measurements using BGC-Argo floats
Tracing differences in iron supply to the Mid-Atlantic Ridge valley between hydrothermal vent sites: implications for the addition of iron to the deep ocean
Nitrite cycling in the primary nitrite maxima of the eastern tropical North Pacific
Hotspots and drivers of compound marine heatwaves and low net primary production extremes
Ecosystem impacts of marine heat waves in the northeast Pacific
Tracing the role of Arctic shelf processes in Si and N cycling and export through the Fram Strait: insights from combined silicon and nitrate isotopes
Controls on the relative abundances and rates of nitrifying microorganisms in the ocean
The response of diazotrophs to nutrient amendment in the South China Sea and western North Pacific
Seasonal dynamics and annual budget of dissolved inorganic carbon in the northwestern Mediterranean deep convection region
Influence of GEOTRACES data distribution and misfit function choice on objective parameter retrieval in a marine zinc cycle model
Physiological flexibility of phytoplankton impacts modelled chlorophyll and primary production across the North Pacific Ocean
Observation-constrained estimates of the global ocean carbon sink from Earth system models
Early winter barium excess in the southern Indian Ocean as an annual remineralisation proxy (GEOTRACES GIPr07 cruise)
Controlling factors on the global distribution of a representative marine non-cyanobacterial diazotroph phylotype (Gamma A)
Summer trends and drivers of sea surface fCO2 and pH changes observed in the southern Indian Ocean over the last two decades (1998–2019)
Global nutrient cycling by commercially targeted marine fish
Major processes of the dissolved cobalt cycle in the North and equatorial Pacific Ocean
The impact of the South-East Madagascar Bloom on the oceanic CO2 sink
Nitrite regeneration in the oligotrophic Atlantic Ocean
Bridging the gaps between particulate backscattering measurements and modeled particulate organic carbon in the ocean
Biological production in two contrasted regions of the Mediterranean Sea during the oligotrophic period: an estimate based on the diel cycle of optical properties measured by BioGeoChemical-Argo profiling floats
Acidification of the Nordic Seas
Reconstruction of global surface ocean pCO2 using region-specific predictors based on a stepwise FFNN regression algorithm
Biogeochemical controls on ammonium accumulation in the surface layer of the Southern Ocean
Oxygen export to the deep ocean following Labrador Sea Water formation
N2 fixation in the Mediterranean Sea related to the composition of the diazotrophic community and impact of dust under present and future environmental conditions
Dissolution of a submarine carbonate platform by a submerged lake of acidic seawater
Seasonal flux patterns and carbon transport from low-oxygen eddies at the Cape Verde Ocean Observatory: lessons learned from a time series sediment trap study (2009–2016)
Subsurface iron accumulation and rapid aluminum removal in the Mediterranean following African dust deposition
Long-distance particle transport to the central Ionian Sea
Deep chlorophyll maximum and nutricline in the Mediterranean Sea: emerging properties from a multi-platform assimilated biogeochemical model experiment
Phosphorus cycling in the upper waters of the Mediterranean Sea (PEACETIME cruise): relative contribution of external and internal sources
Fast local warming is the main driver of recent deoxygenation in the northern Arabian Sea
Influence of atmospheric deposition on biogeochemical cycles in an oligotrophic ocean system
Impact of dust addition on the metabolism of Mediterranean plankton communities and carbon export under present and future conditions of pH and temperature
Comparing CLE-AdCSV applications using SA and TAC to determine the Fe-binding characteristics of model ligands in seawater
Daniela König and Alessandro Tagliabue
Biogeosciences, 20, 4197–4212, https://doi.org/10.5194/bg-20-4197-2023, https://doi.org/10.5194/bg-20-4197-2023, 2023
Short summary
Short summary
Using model simulations, we show that natural and anthropogenic changes in the global climate leave a distinct fingerprint in the isotopic signatures of iron in the surface ocean. We find that these climate effects on iron isotopes are often caused by the redistribution of iron from different external sources to the ocean, due to changes in ocean currents, and by changes in algal growth, which take up iron. Thus, isotopes may help detect climate-induced changes in iron supply and algal uptake.
Chloé Baumas, Robin Fuchs, Marc Garel, Jean-Christophe Poggiale, Laurent Memery, Frédéric A. C. Le Moigne, and Christian Tamburini
Biogeosciences, 20, 4165–4182, https://doi.org/10.5194/bg-20-4165-2023, https://doi.org/10.5194/bg-20-4165-2023, 2023
Short summary
Short summary
Through the sink of particles in the ocean, carbon (C) is exported and sequestered when reaching 1000 m. Attempts to quantify C exported vs. C consumed by heterotrophs have increased. Yet most of the conducted estimations have led to C demands several times higher than C export. The choice of parameters greatly impacts the results. As theses parameters are overlooked, non-accurate values are often used. In this study we show that C budgets can be well balanced when using appropriate values.
Anna Belcher, Sian F. Henley, Katharine Hendry, Marianne Wootton, Lisa Friberg, Ursula Dallman, Tong Wang, Christopher Coath, and Clara Manno
Biogeosciences, 20, 3573–3591, https://doi.org/10.5194/bg-20-3573-2023, https://doi.org/10.5194/bg-20-3573-2023, 2023
Short summary
Short summary
The oceans play a crucial role in the uptake of atmospheric carbon dioxide, particularly the Southern Ocean. The biological pumping of carbon from the surface to the deep ocean is key to this. Using sediment trap samples from the Scotia Sea, we examine biogeochemical fluxes of carbon, nitrogen, and biogenic silica and their stable isotope compositions. We find phytoplankton community structure and physically mediated processes are important controls on particulate fluxes to the deep ocean.
Asmita Singh, Susanne Fietz, Sandy J. Thomalla, Nicolas Sanchez, Murat V. Ardelan, Sébastien Moreau, Hanna M. Kauko, Agneta Fransson, Melissa Chierici, Saumik Samanta, Thato N. Mtshali, Alakendra N. Roychoudhury, and Thomas J. Ryan-Keogh
Biogeosciences, 20, 3073–3091, https://doi.org/10.5194/bg-20-3073-2023, https://doi.org/10.5194/bg-20-3073-2023, 2023
Short summary
Short summary
Despite the scarcity of iron in the Southern Ocean, seasonal blooms occur due to changes in nutrient and light availability. Surprisingly, during an autumn bloom in the Antarctic sea-ice zone, the results from incubation experiments showed no significant photophysiological response of phytoplankton to iron addition. This suggests that ambient iron concentrations were sufficient, challenging the notion of iron deficiency in the Southern Ocean through extended iron-replete post-bloom conditions.
Benoît Pasquier, Mark Holzer, Matthew A. Chamberlain, Richard J. Matear, Nathaniel L. Bindoff, and François W. Primeau
Biogeosciences, 20, 2985–3009, https://doi.org/10.5194/bg-20-2985-2023, https://doi.org/10.5194/bg-20-2985-2023, 2023
Short summary
Short summary
Modeling the ocean's carbon and oxygen cycles accurately is challenging. Parameter optimization improves the fit to observed tracers but can introduce artifacts in the biological pump. Organic-matter production and subsurface remineralization rates adjust to compensate for circulation biases, changing the pathways and timescales with which nutrients return to the surface. Circulation biases can thus strongly alter the system’s response to ecological change, even when parameters are optimized.
Priyanka Banerjee
Biogeosciences, 20, 2613–2643, https://doi.org/10.5194/bg-20-2613-2023, https://doi.org/10.5194/bg-20-2613-2023, 2023
Short summary
Short summary
This study shows that atmospheric deposition is the most important source of iron to the upper northern Indian Ocean for phytoplankton growth. This is followed by iron from continental-shelf sediment. Phytoplankton increase following iron addition is possible only with high background levels of nitrate. Vertical mixing is the most important physical process supplying iron to the upper ocean in this region throughout the year. The importance of ocean currents in supplying iron varies seasonally.
Iris Kriest, Julia Getzlaff, Angela Landolfi, Volkmar Sauerland, Markus Schartau, and Andreas Oschlies
Biogeosciences, 20, 2645–2669, https://doi.org/10.5194/bg-20-2645-2023, https://doi.org/10.5194/bg-20-2645-2023, 2023
Short summary
Short summary
Global biogeochemical ocean models are often subjectively assessed and tuned against observations. We applied different strategies to calibrate a global model against observations. Although the calibrated models show similar tracer distributions at the surface, they differ in global biogeochemical fluxes, especially in global particle flux. Simulated global volume of oxygen minimum zones varies strongly with calibration strategy and over time, rendering its temporal extrapolation difficult.
John C. Tracey, Andrew R. Babbin, Elizabeth Wallace, Xin Sun, Katherine L. DuRussel, Claudia Frey, Donald E. Martocello III, Tyler Tamasi, Sergey Oleynik, and Bess B. Ward
Biogeosciences, 20, 2499–2523, https://doi.org/10.5194/bg-20-2499-2023, https://doi.org/10.5194/bg-20-2499-2023, 2023
Short summary
Short summary
Nitrogen (N) is essential for life; thus, its availability plays a key role in determining marine productivity. Using incubations of seawater spiked with a rare form of N measurable on a mass spectrometer, we quantified microbial pathways that determine marine N availability. The results show that pathways that recycle N have higher rates than those that result in its loss from biomass and present new evidence for anaerobic nitrite oxidation, a process long thought to be strictly aerobic.
Amanda Gerotto, Hongrui Zhang, Renata Hanae Nagai, Heather M. Stoll, Rubens César Lopes Figueira, Chuanlian Liu, and Iván Hernández-Almeida
Biogeosciences, 20, 1725–1739, https://doi.org/10.5194/bg-20-1725-2023, https://doi.org/10.5194/bg-20-1725-2023, 2023
Short summary
Short summary
Based on the analysis of the response of coccolithophores’ morphological attributes in a laboratory dissolution experiment and surface sediment samples from the South China Sea, we proposed that the thickness shape (ks) factor of fossil coccoliths together with the normalized ks variation, which is the ratio of the standard deviation of ks (σ) over the mean ks (σ/ks), is a robust and novel proxy to reconstruct past changes in deep ocean carbon chemistry.
Katherine E. Turner, Doug M. Smith, Anna Katavouta, and Richard G. Williams
Biogeosciences, 20, 1671–1690, https://doi.org/10.5194/bg-20-1671-2023, https://doi.org/10.5194/bg-20-1671-2023, 2023
Short summary
Short summary
We present a new method for reconstructing ocean carbon using climate models and temperature and salinity observations. To test this method, we reconstruct modelled carbon using synthetic observations consistent with current sampling programmes. Sensitivity tests show skill in reconstructing carbon trends and variability within the upper 2000 m. Our results indicate that this method can be used for a new global estimate for ocean carbon content.
Alexandre Mignot, Hervé Claustre, Gianpiero Cossarini, Fabrizio D'Ortenzio, Elodie Gutknecht, Julien Lamouroux, Paolo Lazzari, Coralie Perruche, Stefano Salon, Raphaëlle Sauzède, Vincent Taillandier, and Anna Teruzzi
Biogeosciences, 20, 1405–1422, https://doi.org/10.5194/bg-20-1405-2023, https://doi.org/10.5194/bg-20-1405-2023, 2023
Short summary
Short summary
Numerical models of ocean biogeochemistry are becoming a major tool to detect and predict the impact of climate change on marine resources and monitor ocean health. Here, we demonstrate the use of the global array of BGC-Argo floats for the assessment of biogeochemical models. We first detail the handling of the BGC-Argo data set for model assessment purposes. We then present 23 assessment metrics to quantify the consistency of BGC model simulations with respect to BGC-Argo data.
Alban Planchat, Lester Kwiatkowski, Laurent Bopp, Olivier Torres, James R. Christian, Momme Butenschön, Tomas Lovato, Roland Séférian, Matthew A. Chamberlain, Olivier Aumont, Michio Watanabe, Akitomo Yamamoto, Andrew Yool, Tatiana Ilyina, Hiroyuki Tsujino, Kristen M. Krumhardt, Jörg Schwinger, Jerry Tjiputra, John P. Dunne, and Charles Stock
Biogeosciences, 20, 1195–1257, https://doi.org/10.5194/bg-20-1195-2023, https://doi.org/10.5194/bg-20-1195-2023, 2023
Short summary
Short summary
Ocean alkalinity is critical to the uptake of atmospheric carbon and acidification in surface waters. We review the representation of alkalinity and the associated calcium carbonate cycle in Earth system models. While many parameterizations remain present in the latest generation of models, there is a general improvement in the simulated alkalinity distribution. This improvement is related to an increase in the export of biotic calcium carbonate, which closer resembles observations.
Qian Liu, Yingjie Liu, and Xiaofeng Li
Biogeosciences Discuss., https://doi.org/10.5194/bg-2023-39, https://doi.org/10.5194/bg-2023-39, 2023
Revised manuscript accepted for BG
Short summary
Short summary
In the Southern Ocean, abundant eddies behave opposite to our expectations. That is, anticyclonic (cyclonic) eddies are cold (warm). By investigating the variations of physical and biochemical parameters in eddies, we find that abnormal eddies have unique and significant effects on modulating the parameters. This study fills a gap in understanding the effects of abnormal eddies on physical and biochemical parameters in the Southern Ocean.
Jérôme Pinti, Tim DeVries, Tommy Norin, Camila Serra-Pompei, Roland Proud, David A. Siegel, Thomas Kiørboe, Colleen M. Petrik, Ken H. Andersen, Andrew S. Brierley, and André W. Visser
Biogeosciences, 20, 997–1009, https://doi.org/10.5194/bg-20-997-2023, https://doi.org/10.5194/bg-20-997-2023, 2023
Short summary
Short summary
Large numbers of marine organisms such as zooplankton and fish perform daily vertical migration between the surface (at night) and the depths (in the daytime). This fascinating migration is important for the carbon cycle, as these organisms actively bring carbon to depths where it is stored away from the atmosphere for a long time. Here, we quantify the contributions of different animals to this carbon drawdown and storage and show that fish are important to the biological carbon pump.
Robert W. Izett, Katja Fennel, Adam C. Stoer, and David P. Nicholson
Biogeosciences Discuss., https://doi.org/10.5194/bg-2023-46, https://doi.org/10.5194/bg-2023-46, 2023
Revised manuscript accepted for BG
Short summary
Short summary
This manuscript provides an overview of the capacity to expand the global coverage of marine primary production estimates using autonomous ocean-going instruments, called Biogeochemical-Argo floats. We review existing approaches to quantifying primary production using floats, provide examples of the current implementation of the methods, and offer insights into how they can be better exploited. This paper is timely, given the ongoing expansion of the biogeochemical Argo array.
Alastair J. M. Lough, Alessandro Tagliabue, Clément Demasy, Joseph A. Resing, Travis Mellett, Neil J. Wyatt, and Maeve C. Lohan
Biogeosciences, 20, 405–420, https://doi.org/10.5194/bg-20-405-2023, https://doi.org/10.5194/bg-20-405-2023, 2023
Short summary
Short summary
Iron is a key nutrient for ocean primary productivity. Hydrothermal vents are a source of iron to the oceans, but the size of this source is poorly understood. This study examines the variability in iron inputs between hydrothermal vents in different geological settings. The vents studied release different amounts of Fe, resulting in plumes with similar dissolved iron concentrations but different particulate concentrations. This will help to refine modelling of iron-limited ocean productivity.
Nicole M. Travis, Colette L. Kelly, Margaret R. Mulholland, and Karen L. Casciotti
Biogeosciences, 20, 325–347, https://doi.org/10.5194/bg-20-325-2023, https://doi.org/10.5194/bg-20-325-2023, 2023
Short summary
Short summary
The primary nitrite maximum is a ubiquitous upper ocean feature where nitrite accumulates, but we still do not understand its formation and the co-occurring microbial processes involved. Using correlative methods and rates measurements, we found strong spatial patterns between environmental conditions and depths of the nitrite maxima, but not the maximum concentrations. Nitrification was the dominant source of nitrite, with occasional high nitrite production from phytoplankton near the coast.
Natacha Le Grix, Jakob Zscheischler, Keith B. Rodgers, Ryohei Yamaguchi, and Thomas L. Frölicher
Biogeosciences, 19, 5807–5835, https://doi.org/10.5194/bg-19-5807-2022, https://doi.org/10.5194/bg-19-5807-2022, 2022
Short summary
Short summary
Compound events threaten marine ecosystems. Here, we investigate the potentially harmful combination of marine heatwaves with low phytoplankton productivity. Using satellite-based observations, we show that these compound events are frequent in the low latitudes. We then investigate the drivers of these compound events using Earth system models. The models share similar drivers in the low latitudes but disagree in the high latitudes due to divergent factors limiting phytoplankton production.
Abigale M. Wyatt, Laure Resplandy, and Adrian Marchetti
Biogeosciences, 19, 5689–5705, https://doi.org/10.5194/bg-19-5689-2022, https://doi.org/10.5194/bg-19-5689-2022, 2022
Short summary
Short summary
Marine heat waves (MHWs) are a frequent event in the northeast Pacific, with a large impact on the region's ecosystems. Large phytoplankton in the North Pacific Transition Zone are greatly affected by decreased nutrients, with less of an impact in the Alaskan Gyre. For small phytoplankton, MHWs increase the spring small phytoplankton population in both regions thanks to reduced light limitation. In both zones, this results in a significant decrease in the ratio of large to small phytoplankton.
Margot C. F. Debyser, Laetitia Pichevin, Robyn E. Tuerena, Paul A. Dodd, Antonia Doncila, and Raja S. Ganeshram
Biogeosciences, 19, 5499–5520, https://doi.org/10.5194/bg-19-5499-2022, https://doi.org/10.5194/bg-19-5499-2022, 2022
Short summary
Short summary
We focus on the exchange of key nutrients for algae production between the Arctic and Atlantic oceans through the Fram Strait. We show that the export of dissolved silicon here is controlled by the availability of nitrate which is influenced by denitrification on Arctic shelves. We suggest that any future changes in the river inputs of silica and changes in denitrification due to climate change will impact the amount of silicon exported, with impacts on Atlantic algal productivity and ecology.
Emily J. Zakem, Barbara Bayer, Wei Qin, Alyson E. Santoro, Yao Zhang, and Naomi M. Levine
Biogeosciences, 19, 5401–5418, https://doi.org/10.5194/bg-19-5401-2022, https://doi.org/10.5194/bg-19-5401-2022, 2022
Short summary
Short summary
We use a microbial ecosystem model to quantitatively explain the mechanisms controlling observed relative abundances and nitrification rates of ammonia- and nitrite-oxidizing microorganisms in the ocean. We also estimate how much global carbon fixation can be associated with chemoautotrophic nitrification. Our results improve our understanding of the controls on nitrification, laying the groundwork for more accurate predictions in global climate models.
Zuozhu Wen, Thomas J. Browning, Rongbo Dai, Wenwei Wu, Weiying Li, Xiaohua Hu, Wenfang Lin, Lifang Wang, Xin Liu, Zhimian Cao, Haizheng Hong, and Dalin Shi
Biogeosciences, 19, 5237–5250, https://doi.org/10.5194/bg-19-5237-2022, https://doi.org/10.5194/bg-19-5237-2022, 2022
Short summary
Short summary
Fe and P are key factors controlling the biogeography and activity of marine N2-fixing microorganisms. We found lower abundance and activity of N2 fixers in the northern South China Sea than around the western boundary of the North Pacific, and N2 fixation rates switched from Fe–P co-limitation to P limitation. We hypothesize the Fe supply rates and Fe utilization strategies of each N2 fixer are important in regulating spatial variability in community structure across the study area.
Caroline Ulses, Claude Estournel, Patrick Marsaleix, Karline Soetaert, Marine Fourrier, Laurent Coppola, Dominique Lefèvre, Franck Touratier, Catherine Goyet, Véronique Guglielmi, Fayçal Kessouri, Pierre Testor, and Xavier Durrieu de Madron
Biogeosciences Discuss., https://doi.org/10.5194/bg-2022-219, https://doi.org/10.5194/bg-2022-219, 2022
Revised manuscript accepted for BG
Short summary
Short summary
Deep convection plays a key role in the circulation, thermodynamics and biogeochemical cycles in the Mediterranean Sea, considered as a hotspot of biodiversity and climate change. In this study, we investigate the seasonal cycle and annual budget of dissolved inorganic carbon in the deep convection area of the northwestern Mediterranean Sea.
Claudia Eisenring, Sophy E. Oliver, Samar Khatiwala, and Gregory F. de Souza
Biogeosciences, 19, 5079–5106, https://doi.org/10.5194/bg-19-5079-2022, https://doi.org/10.5194/bg-19-5079-2022, 2022
Short summary
Short summary
Given the sparsity of observational constraints on micronutrients such as zinc (Zn), we assess the sensitivities of a framework for objective parameter optimisation in an oceanic Zn cycling model. Our ensemble of optimisations towards synthetic data with varying kinds of uncertainty shows that deficiencies related to model complexity and the choice of the misfit function generally have a greater impact on the retrieval of model Zn uptake behaviour than does the limitation of data coverage.
Yoshikazu Sasai, Sherwood Lan Smith, Eko Siswanto, Hideharu Sasaki, and Masami Nonaka
Biogeosciences, 19, 4865–4882, https://doi.org/10.5194/bg-19-4865-2022, https://doi.org/10.5194/bg-19-4865-2022, 2022
Short summary
Short summary
We have investigated the adaptive response of phytoplankton growth to changing light, nutrients, and temperature over the North Pacific using two physical-biological models. We compare modeled chlorophyll and primary production from an inflexible control model (InFlexPFT), which assumes fixed carbon (C):nitrogen (N):chlorophyll (Chl) ratios, to a recently developed flexible phytoplankton functional type model (FlexPFT), which incorporates photoacclimation and variable C:N:Chl ratios.
Jens Terhaar, Thomas L. Frölicher, and Fortunat Joos
Biogeosciences, 19, 4431–4457, https://doi.org/10.5194/bg-19-4431-2022, https://doi.org/10.5194/bg-19-4431-2022, 2022
Short summary
Short summary
Estimates of the ocean sink of anthropogenic carbon vary across various approaches. We show that the global ocean carbon sink can be estimated by three parameters, two of which approximate the ocean ventilation in the Southern Ocean and the North Atlantic, and one of which approximates the chemical capacity of the ocean to take up carbon. With observations of these parameters, we estimate that the global ocean carbon sink is 10 % larger than previously assumed, and we cut uncertainties in half.
Natasha René van Horsten, Hélène Planquette, Géraldine Sarthou, Thomas James Ryan-Keogh, Nolwenn Lemaitre, Thato Nicholas Mtshali, Alakendra Roychoudhury, and Eva Bucciarelli
Biogeosciences, 19, 3209–3224, https://doi.org/10.5194/bg-19-3209-2022, https://doi.org/10.5194/bg-19-3209-2022, 2022
Short summary
Short summary
The remineralisation proxy, barite, was measured along 30°E in the southern Indian Ocean during early austral winter. To our knowledge this is the first reported Southern Ocean winter study. Concentrations throughout the water column were comparable to observations during spring to autumn. By linking satellite primary production to this proxy a possible annual timescale is proposed. These findings also suggest possible carbon remineralisation from satellite data on a basin scale.
Zhibo Shao and Ya-Wei Luo
Biogeosciences, 19, 2939–2952, https://doi.org/10.5194/bg-19-2939-2022, https://doi.org/10.5194/bg-19-2939-2022, 2022
Short summary
Short summary
Non-cyanobacterial diazotrophs (NCDs) may be an important player in fixing N2 in the ocean. By conducting meta-analyses, we found that a representative marine NCD phylotype, Gamma A, tends to inhabit ocean environments with high productivity, low iron concentration and high light intensity. It also appears to be more abundant inside cyclonic eddies. Our study suggests a niche differentiation of NCDs from cyanobacterial diazotrophs as the latter prefers low-productivity and high-iron oceans.
Coraline Leseurre, Claire Lo Monaco, Gilles Reverdin, Nicolas Metzl, Jonathan Fin, Claude Mignon, and Léa Benito
Biogeosciences, 19, 2599–2625, https://doi.org/10.5194/bg-19-2599-2022, https://doi.org/10.5194/bg-19-2599-2022, 2022
Short summary
Short summary
Decadal trends of fugacity of CO2 (fCO2), total alkalinity (AT), total carbon (CT) and pH in surface waters are investigated in different domains of the southern Indian Ocean (45°S–57°S) from ongoing and station observations regularly conducted in summer over the period 1998–2019. The fCO2 increase and pH decrease are mainly driven by anthropogenic CO2 estimated just below the summer mixed layer, as well as by a warming south of the polar front or in the fertilized waters near Kerguelen Island.
Priscilla Le Mézo, Jérôme Guiet, Kim Scherrer, Daniele Bianchi, and Eric Galbraith
Biogeosciences, 19, 2537–2555, https://doi.org/10.5194/bg-19-2537-2022, https://doi.org/10.5194/bg-19-2537-2022, 2022
Short summary
Short summary
This study quantifies the role of commercially targeted fish biomass in the cycling of three important nutrients (N, P, and Fe), relative to nutrients otherwise available in water and to nutrients required by primary producers, and the impact of fishing. We use a model of commercially targeted fish biomass constrained by fish catch and stock assessment data to assess the contributions of fish at the global scale, at the time of the global peak catch and prior to industrial fishing.
Rebecca Chmiel, Nathan Lanning, Allison Laubach, Jong-Mi Lee, Jessica Fitzsimmons, Mariko Hatta, William Jenkins, Phoebe Lam, Matthew McIlvin, Alessandro Tagliabue, and Mak Saito
Biogeosciences, 19, 2365–2395, https://doi.org/10.5194/bg-19-2365-2022, https://doi.org/10.5194/bg-19-2365-2022, 2022
Short summary
Short summary
Dissolved cobalt is present in trace amounts in seawater and is a necessary nutrient for marine microbes. On a transect from the Alaskan coast to Tahiti, we measured seawater concentrations of dissolved cobalt. Here, we describe several interesting features of the Pacific cobalt cycle including cobalt sources along the Alaskan coast and Hawaiian vents, deep-ocean particle formation, cobalt activity in low-oxygen regions, and how our samples compare to a global biogeochemical model’s predictions.
Nicolas Metzl, Claire Lo Monaco, Coraline Leseurre, Céline Ridame, Jonathan Fin, Claude Mignon, Marion Gehlen, and Thi Tuyet Trang Chau
Biogeosciences, 19, 1451–1468, https://doi.org/10.5194/bg-19-1451-2022, https://doi.org/10.5194/bg-19-1451-2022, 2022
Short summary
Short summary
During an oceanographic cruise conducted in January 2020 in the south-western Indian Ocean, we observed very low CO2 concentrations associated with a strong phytoplankton bloom that occurred south-east of Madagascar. This biological event led to a strong regional CO2 ocean sink not previously observed.
Darren R. Clark, Andrew P. Rees, Charissa M. Ferrera, Lisa Al-Moosawi, Paul J. Somerfield, Carolyn Harris, Graham D. Quartly, Stephen Goult, Glen Tarran, and Gennadi Lessin
Biogeosciences, 19, 1355–1376, https://doi.org/10.5194/bg-19-1355-2022, https://doi.org/10.5194/bg-19-1355-2022, 2022
Short summary
Short summary
Measurements of microbial processes were made in the sunlit open ocean during a research cruise (AMT19) between the UK and Chile. These help us to understand how microbial communities maintain the function of remote ecosystems. We find that the nitrogen cycling microbes which produce nitrite respond to changes in the environment. Our insights will aid the development of models that aim to replicate and ultimately project how marine environments may respond to ongoing climate change.
Martí Galí, Marcus Falls, Hervé Claustre, Olivier Aumont, and Raffaele Bernardello
Biogeosciences, 19, 1245–1275, https://doi.org/10.5194/bg-19-1245-2022, https://doi.org/10.5194/bg-19-1245-2022, 2022
Short summary
Short summary
Part of the organic matter produced by plankton in the upper ocean is exported to the deep ocean. This process, known as the biological carbon pump, is key for the regulation of atmospheric carbon dioxide and global climate. However, the dynamics of organic particles below the upper ocean layer are not well understood. Here we compared the measurements acquired by autonomous robots in the top 1000 m of the ocean to a numerical model, which can help improve future climate projections.
Marie Barbieux, Julia Uitz, Alexandre Mignot, Collin Roesler, Hervé Claustre, Bernard Gentili, Vincent Taillandier, Fabrizio D'Ortenzio, Hubert Loisel, Antoine Poteau, Edouard Leymarie, Christophe Penkerc'h, Catherine Schmechtig, and Annick Bricaud
Biogeosciences, 19, 1165–1194, https://doi.org/10.5194/bg-19-1165-2022, https://doi.org/10.5194/bg-19-1165-2022, 2022
Short summary
Short summary
This study assesses marine biological production in two Mediterranean systems representative of vast desert-like (oligotrophic) areas encountered in the global ocean. We use a novel approach based on non-intrusive high-frequency in situ measurements by two profiling robots, the BioGeoChemical-Argo (BGC-Argo) floats. Our results indicate substantial yet variable production rates and contribution to the whole water column of the subsurface layer, typically considered steady and non-productive.
Filippa Fransner, Friederike Fröb, Jerry Tjiputra, Nadine Goris, Siv K. Lauvset, Ingunn Skjelvan, Emil Jeansson, Abdirahman Omar, Melissa Chierici, Elizabeth Jones, Agneta Fransson, Sólveig R. Ólafsdóttir, Truls Johannessen, and Are Olsen
Biogeosciences, 19, 979–1012, https://doi.org/10.5194/bg-19-979-2022, https://doi.org/10.5194/bg-19-979-2022, 2022
Short summary
Short summary
Ocean acidification, a direct consequence of the CO2 release by human activities, is a serious threat to marine ecosystems. In this study, we conduct a detailed investigation of the acidification of the Nordic Seas, from 1850 to 2100, by using a large set of samples taken during research cruises together with numerical model simulations. We estimate the effects of changes in different environmental factors on the rate of acidification and its potential effects on cold-water corals.
Guorong Zhong, Xuegang Li, Jinming Song, Baoxiao Qu, Fan Wang, Yanjun Wang, Bin Zhang, Xiaoxia Sun, Wuchang Zhang, Zhenyan Wang, Jun Ma, Huamao Yuan, and Liqin Duan
Biogeosciences, 19, 845–859, https://doi.org/10.5194/bg-19-845-2022, https://doi.org/10.5194/bg-19-845-2022, 2022
Short summary
Short summary
A predictor selection algorithm was constructed to decrease the predicting error in the surface ocean partial pressure of CO2 (pCO2) mapping by finding better combinations of pCO2 predictors in different regions. Compared with previous research using the same combination of predictors in all regions, using different predictors selected by the algorithm in different regions can effectively decrease pCO2 predicting errors.
Shantelle Smith, Katye E. Altieri, Mhlangabezi Mdutyana, David R. Walker, Ruan G. Parrott, Sedick Gallie, Kurt A. M. Spence, Jessica M. Burger, and Sarah E. Fawcett
Biogeosciences, 19, 715–741, https://doi.org/10.5194/bg-19-715-2022, https://doi.org/10.5194/bg-19-715-2022, 2022
Short summary
Short summary
Ammonium is a crucial yet poorly understood component of the Southern Ocean nitrogen cycle. We attribute our finding of consistently high ammonium concentrations in the winter mixed layer to limited ammonium consumption and sustained ammonium production, conditions under which the Southern Ocean becomes a source of carbon dioxide to the atmosphere. From similar data collected over an annual cycle, we propose a seasonal cycle for ammonium in shallow polar waters – a first for the Southern Ocean.
Jannes Koelling, Dariia Atamanchuk, Johannes Karstensen, Patricia Handmann, and Douglas W. R. Wallace
Biogeosciences, 19, 437–454, https://doi.org/10.5194/bg-19-437-2022, https://doi.org/10.5194/bg-19-437-2022, 2022
Short summary
Short summary
In this study, we investigate oxygen variability in the deep western boundary current in the Labrador Sea from multiyear moored records. We estimate that about half of the oxygen taken up in the interior Labrador Sea by air–sea gas exchange during deep water formation is exported southward the same year. Our results underline the complexity of the oxygen uptake and export in the Labrador Sea and highlight the important role this region plays in supplying oxygen to the deep ocean.
Céline Ridame, Julie Dinasquet, Søren Hallstrøm, Estelle Bigeard, Lasse Riemann, France Van Wambeke, Matthieu Bressac, Elvira Pulido-Villena, Vincent Taillandier, Fréderic Gazeau, Antonio Tovar-Sanchez, Anne-Claire Baudoux, and Cécile Guieu
Biogeosciences, 19, 415–435, https://doi.org/10.5194/bg-19-415-2022, https://doi.org/10.5194/bg-19-415-2022, 2022
Short summary
Short summary
We show that in the Mediterranean Sea spatial variability in N2 fixation is related to the diazotrophic community composition reflecting different nutrient requirements among species. Nutrient supply by Saharan dust is of great importance to diazotrophs, as shown by the strong stimulation of N2 fixation after a simulated dust event under present and future climate conditions; the magnitude of stimulation depends on the degree of limitation related to the diazotrophic community composition.
Matthew P. Humphreys, Erik H. Meesters, Henk de Haas, Szabina Karancz, Louise Delaigue, Karel Bakker, Gerard Duineveld, Siham de Goeyse, Andreas F. Haas, Furu Mienis, Sharyn Ossebaar, and Fleur C. van Duyl
Biogeosciences, 19, 347–358, https://doi.org/10.5194/bg-19-347-2022, https://doi.org/10.5194/bg-19-347-2022, 2022
Short summary
Short summary
A series of submarine sinkholes were recently discovered on Luymes Bank, part of Saba Bank, a carbonate platform in the Caribbean Netherlands. Here, we investigate the waters inside these sinkholes for the first time. One of the sinkholes contained a body of dense, low-oxygen and low-pH water, which we call the
acid lake. We use measurements of seawater chemistry to work out what processes were responsible for forming the acid lake and discuss the consequences for the carbonate platform.
Gerhard Fischer, Oscar E. Romero, Johannes Karstensen, Karl-Heinz Baumann, Nasrollah Moradi, Morten Iversen, Götz Ruhland, Marco Klann, and Arne Körtzinger
Biogeosciences, 18, 6479–6500, https://doi.org/10.5194/bg-18-6479-2021, https://doi.org/10.5194/bg-18-6479-2021, 2021
Short summary
Short summary
Low-oxygen eddies in the eastern subtropical North Atlantic can form an oasis for phytoplankton growth. Here we report on particle flux dynamics at the oligotrophic Cape Verde Ocean Observatory. We observed consistent flux patterns during the passages of low-oxygen eddies. We found distinct flux peaks in late winter, clearly exceeding background fluxes. Our findings suggest that the low-oxygen eddies sequester higher organic carbon than expected for oligotrophic settings.
Matthieu Bressac, Thibaut Wagener, Nathalie Leblond, Antonio Tovar-Sánchez, Céline Ridame, Vincent Taillandier, Samuel Albani, Sophie Guasco, Aurélie Dufour, Stéphanie H. M. Jacquet, François Dulac, Karine Desboeufs, and Cécile Guieu
Biogeosciences, 18, 6435–6453, https://doi.org/10.5194/bg-18-6435-2021, https://doi.org/10.5194/bg-18-6435-2021, 2021
Short summary
Short summary
Phytoplankton growth is limited by the availability of iron in about 50 % of the ocean. Atmospheric deposition of desert dust represents a key source of iron. Here, we present direct observations of dust deposition in the Mediterranean Sea. A key finding is that the input of iron from dust primarily occurred in the deep ocean, while previous studies mainly focused on the ocean surface. This new insight will enable us to better represent controls on global marine productivity in models.
Léo Berline, Andrea Michelangelo Doglioli, Anne Petrenko, Stéphanie Barrillon, Boris Espinasse, Frederic A. C. Le Moigne, François Simon-Bot, Melilotus Thyssen, and François Carlotti
Biogeosciences, 18, 6377–6392, https://doi.org/10.5194/bg-18-6377-2021, https://doi.org/10.5194/bg-18-6377-2021, 2021
Short summary
Short summary
While the Ionian Sea is considered a nutrient-depleted and low-phytoplankton biomass area, it is a crossroad for water mass circulation. In the central Ionian Sea, we observed a strong contrast in particle distribution across a ~100 km long transect. Using remote sensing and Lagrangian simulations, we suggest that this contrast finds its origin in the long-distance transport of particles from the north, west and east of the Ionian Sea, where phytoplankton production was more intense.
Anna Teruzzi, Giorgio Bolzon, Laura Feudale, and Gianpiero Cossarini
Biogeosciences, 18, 6147–6166, https://doi.org/10.5194/bg-18-6147-2021, https://doi.org/10.5194/bg-18-6147-2021, 2021
Short summary
Short summary
During summer, maxima of phytoplankton chlorophyll concentration (DCM) occur in the subsurface of the Mediterranean Sea and can play a relevant role in carbon sequestration into the ocean interior. A numerical model based on in situ and satellite observations provides insights into the range of DCM conditions across the relatively small Mediterranean Sea and shows a western DCM that is 25 % shallower and with a higher phytoplankton chlorophyll concentration than in the eastern Mediterranean.
Elvira Pulido-Villena, Karine Desboeufs, Kahina Djaoudi, France Van Wambeke, Stéphanie Barrillon, Andrea Doglioli, Anne Petrenko, Vincent Taillandier, Franck Fu, Tiphanie Gaillard, Sophie Guasco, Sandra Nunige, Sylvain Triquet, and Cécile Guieu
Biogeosciences, 18, 5871–5889, https://doi.org/10.5194/bg-18-5871-2021, https://doi.org/10.5194/bg-18-5871-2021, 2021
Short summary
Short summary
We report on phosphorus dynamics in the surface layer of the Mediterranean Sea. Highly sensitive phosphate measurements revealed vertical gradients above the phosphacline. The relative contribution of diapycnal fluxes to total external supply of phosphate to the mixed layer decreased towards the east, where atmospheric deposition dominated. Taken together, external sources of phosphate contributed little to total supply, which was mainly sustained by enzymatic hydrolysis of organic phosphorus.
Zouhair Lachkar, Michael Mehari, Muchamad Al Azhar, Marina Lévy, and Shafer Smith
Biogeosciences, 18, 5831–5849, https://doi.org/10.5194/bg-18-5831-2021, https://doi.org/10.5194/bg-18-5831-2021, 2021
Short summary
Short summary
This study documents and quantifies a significant recent oxygen decline in the upper layers of the Arabian Sea and explores its drivers. Using a modeling approach we show that the fast local warming of sea surface is the main factor causing this oxygen drop. Concomitant summer monsoon intensification contributes to this trend, although to a lesser extent. These changes exacerbate oxygen depletion in the subsurface, threatening marine habitats and altering the local biogeochemistry.
France Van Wambeke, Vincent Taillandier, Karine Desboeufs, Elvira Pulido-Villena, Julie Dinasquet, Anja Engel, Emilio Marañón, Céline Ridame, and Cécile Guieu
Biogeosciences, 18, 5699–5717, https://doi.org/10.5194/bg-18-5699-2021, https://doi.org/10.5194/bg-18-5699-2021, 2021
Short summary
Short summary
Simultaneous in situ measurements of (dry and wet) atmospheric deposition and biogeochemical stocks and fluxes in the sunlit waters of the open Mediterranean Sea revealed complex physical and biological processes occurring within the mixed layer. Nitrogen (N) budgets were computed to compare the sources and sinks of N in the mixed layer. The transitory effect observed after a wet dust deposition impacted the microbial food web down to the deep chlorophyll maximum.
Frédéric Gazeau, France Van Wambeke, Emilio Marañón, Maria Pérez-Lorenzo, Samir Alliouane, Christian Stolpe, Thierry Blasco, Nathalie Leblond, Birthe Zäncker, Anja Engel, Barbara Marie, Julie Dinasquet, and Cécile Guieu
Biogeosciences, 18, 5423–5446, https://doi.org/10.5194/bg-18-5423-2021, https://doi.org/10.5194/bg-18-5423-2021, 2021
Short summary
Short summary
Our study shows that the impact of dust deposition on primary production depends on the initial composition and metabolic state of the tested community and is constrained by the amount of nutrients added, to sustain both the fast response of heterotrophic prokaryotes and the delayed one of phytoplankton. Under future environmental conditions, heterotrophic metabolism will be more impacted than primary production, therefore reducing the capacity of surface waters to sequester anthropogenic CO2.
Loes J. A. Gerringa, Martha Gledhill, Indah Ardiningsih, Niels Muntjewerf, and Luis M. Laglera
Biogeosciences, 18, 5265–5289, https://doi.org/10.5194/bg-18-5265-2021, https://doi.org/10.5194/bg-18-5265-2021, 2021
Short summary
Short summary
For 3 decades, competitive ligand exchange–adsorptive cathodic stripping voltammetry was used to estimate the Fe-binding capacity of organic matter in seawater. In this paper the performance of the competing ligands is compared through the analysis of a series of model ligands.
The main finding of this paper is that the determined speciation parameters are not independent of the application, making interpretation of Fe speciation data more complex than it was thought before.
Cited articles
Behrenfeld, M. J., Worthington, K., Sherrell, R. M., Chavez, F. P., Strutton,
P., McPhaden, M., and Shea, D. M.: Controls on tropical Pacific Ocean
productivity revealed through nutrient stress diagnostics, Nature, 442,
1025–1028, https://doi.org/10.1038/nature05083, 2006.
Behrenfeld, M. J., O'Malley, R. T., Boss, E. S., Westberry, T. K., Graff,
J. R., Halsey, K. H., Milligan, A. J., Siegel, D. A., and Brown, M. B.:
Reevaluating ocean warming impacts on global phytoplankton, Nat. Clim. Change, 6, 323–330, https://doi.org/10.1038/nclimate2838, 2016.
Bellacicco, M., Volpe, G., Colella, S., Pitarch, J., and Santoleri, R.:
Influence of photoacclimation on the phytoplankton seasonal cycle in the
Mediterranean Sea as seen by satellite, Remote Sens. Environ., 184, 595–604,
https://doi.org/10.1016/j.rse.2016.08.004, 2016.
Bopp, L., Aumont, O., Cadule, P., Alvain, S., and Gehlen, M.: Response of
diatoms distribution to global warming and potential implications: A global
model study, Geophys. Res. Lett., 32, L19606, https://doi.org/10.1029/2005GL023653, 2005.
Boyd, P. W.: Environmental factors controlling phytoplankton processes in the
Southern Ocean, J. Phycol., 38, 844–861,
https://doi.org/10.1046/j.1529-8817.2002.t01-1-01203.x, 2002.
Boyd, P. W., Jickells, T., Law, C. S., Blain, S., Boyle, E. A., Buesseler, K.
O., Coale, K. H., Cullen, J. J., de Baar, H. J. W., Follows, M., Harvey, M.,
Lancelot, C., Levasseur, M., Owens, N. P. J., Pollard, R., Rivkin, R. B.,
Sarmiento, J., Schoemann, V., Smetacek, V., Takeda, S., Tsuda, A., Turner,
S., and Watson, A. J.: Mesoscale iron enrichment experiments 1993–2005:
Synthesis and future directions, Science, 315, 612–617,
https://doi.org/10.1126/science.1131669, 2007.
Boyd, P. W., Strzepek, R., Fu, F. X., and Hutchins, D. A.: Environmental
control of open-ocean phytoplankton groups: Now and in the future, Limnol.
Oceanogr., 55, 1353–1376, https://doi.org/10.4319/lo.2010.55.3.1353, 2010.
Boyd, P. W., Arrigo, K. R., Strzepek, R., and van Dijken, G. L.: Mapping
phytoplankton iron utilization: Insights into Southern Ocean supply
mechanisms, J. Geophys. Res., 117, C06009, https://doi.org/10.1029/2011JC007726, 2012.
Boyer, T. P., Antonov, J. I., Baranova, O. K., Coleman, C., Garcia, H. E.,
Grodsky, A., Johnson, D. R., Locarnini, R. A., Mishonov, A. V., and O'Brien,
T. D.: World Ocean Database 2013, NOAA Printing Office, Silver Spring, Maryland,
USA, 2013.
Braun, A. V.: A comparison of subtropical storms in the South Atlantic basin
with Australian east-coast cyclones, 28th Conference on Hurricanes and Tropical Meteorology, 5,
2008.
Brody, S. R., Lozier, M. S., and Dunne, J. P.: A comparison of methods to
determine phytoplankton bloom initiation, J. Geophys. Res., 118, 2345–2357,
https://doi.org/10.1002/jgrc.20167, 2013.
Browning, T. J., Bouman, H. A., Moore, C. M., Schlosser, C., Tarran, G. A.,
Woodward, E. M. S., and Henderson, G. M.: Nutrient regimes control
phytoplankton ecophysiology in the South Atlantic, Biogeosciences, 11,
463–479, https://doi.org/10.5194/bg-11-463-2014, 2014
Carranza, M. M. and Gille, S. T.: Southern Ocean wind-driven entrainment
enhances satellite chlorophyll-a through the summer, J. Geophys. Res.-Oceans, 120, 304–323, https://doi.org/10.1002/2014JC010203, 2015.
Coale, K. H.: Effects of iron, manganese, copper, and zinc enrichments on
productivity and biomass in the subarctic Pacific, Limnol. Oceanogr., 36,
1851–1864, https://doi.org/10.4319/lo.1991.36.8.1851, 1991.
Cochlan, W. P.: Nitrogen Uptake in the Southern Ocean, in: Nitrogen in the
Marine Environment, Elsevier, Amsterdam, 2008.
Cullen, J. J. and Davis, R. F.: The blank can make a big difference in
oceanographic measurements, Limnol. Oceanogr., 12, 29–35,
https://doi.org/10.1002/lob.200312229, 2003.
de Baar, H. J. W., Buma, A. G. J., Nolting, R. F., Cadee, G. C., Jacques, G.,
and Treguer, P. J.: On iron limitation of the Southern Ocean: Experimental
observations in the Weddell and Scotia Seas, Mar. Ecol. Prog. Ser., 65, 105–122,
https://doi.org/10.3354/meps065105, 1990.
de Baar, H. J. W., Boyd, P. W., Coale, K. H., Landry, M. R., Tsuda, A.,
Assmy, P., Bakker, D. C. E., Bozec, Y., Barber, R. T., Brezinski, M. A.,
Buesseler, K. O., Boyé, M., Croot, P. L., Gervais, F., Gorbunov, M. Y.,
Harrison, P. J., Hiscock, W. T., Laan, P., Lancelot, C., Law, C. S.,
Levasseur, M., Marchetti, A., Millero, F. J., Nishioka, J., Nojiri, Y., van
Oijen, T., Riebesell, U., Rijkenberg, M. J. A., Saito, H., Takeda, S.,
Timmermans, K. R., Veldhuis, M. J. W., Waite, A. M., and Wong, C. S.:
Synthesis of iron fertilization experiments: From the iron age in the age of
enlightenment, J. Geophys. Res., 110, C09S16, https://doi.org/10.1029/2004JC002601, 2005.
de Boyer Montégut, C., Madec, G., Fischer, A. S., Lazar, A., and
Iudicone, D.: Mixed layer depth over the global ocean: an examination of
profile data and a profile-based climatology, J. Geophys. Res., 109, C12003,
https://doi.org/10.1029/2004JC002378, 2004.
Dubischar, C. D. and Bathmann, U. V.: Grazing impacts of copepods and salps
on phytoplankton in the Atlantic sector of the Southern Ocean, Deep.-Sea. Res. Pt. 1, 44, 415–433, https://doi.org/10.1016/S0967-0645(96)00064-1, 1997.
Duce, R. A. and Tindale, N. W.: Atmospheric Transport of Iron and Its
Deposition in the Ocean, Limnol. Oceanogr., 36, 1715–1726,
https://doi.org/10.4319/lo.1991.36.8.1715, 1991.
Egan, L.: QuickChem Method 31-107-04-1-C – Nitrate and/or Nitrite in brackish
or seawater, Lachat Instruments, Colorado, USA, 2008.
Fauchereau, N., Tagliabue, A., Bopp, L., and Monteiro, P. M. S.: The response
of phytoplankton biomass to transient mixing events in the Southern Ocean,
Geophys. Res. Lett., 38, L17601, https://doi.org/10.1029/2011GL048498, 2011.
Gibberd, M.-J., Kean, E., Barlow, R., Thomalla, S., and Lucas, M.:
Phytoplankton chemotaxonomy in the Atlantic sector of the Southern Ocean
during late summer 2009, Deep.-Sea. Res. Pt. 1, 78, 70–78,
https://doi.org/10.1016/j.dsr.2013.04.007, 2013.
Grasshoff, K., Ehrhardt, M., and Kremling, K.: Methods of seawater analysis,
Verlag Chemie, Wienheim, Germany, 1983.
Hiscock, M. R., Lance, V. P., Apprill, A. M., Johnson, Z., Bidigare, R. R.,
Mitchell, B. G., Smith, W. O. J., and Barber, R. T.: Photosynthetic maximum
quantum yield increases are an essential component of Southern Ocean
phytoplankton iron response, P. Natl. Acad. Sci. USA, 105, 4775–4780,
https://doi.org/10.1073/pnas.0705006105, 2008.
Hutchins, D. A., Sedwick, P. N., DiTullio, G. R., Boyd, P. W., Quéguiner,
B., Griffiths, F. B., and Crossely, C.: Control of phytoplankton growth by
iron and silicic acid availability in the subantarctic Southern Ocean:
Experimental results from the SAZ Project, J. Geophys. Res., 106,
31559–31572, https://doi.org/10.1029/2000JC000333, 2001.
Irwin, J. S.: A theoretical variation of the wind profile power-law exponent
as a function of surface roughness and stability, Atmos. Environ., 13, 191–194,
https://doi.org/10.1016/0004-6981(79)90260-9, 1967.
Johnson, K. S., Elrod, V. A., Fitzwater, S. E., Plant, J., Boyle, E.,
Bergquist, B., Bruland, K. W., Aguilar-Islas, A. M., Buck, K., Lohan, M. C.,
Smith, G. J., Sohst, B. M., Coale, K. H., Gordon, M., Tanner, S., Measures,
C. I., Moffett, J., Barbeau, K. A., King, A., Bowie, A. R., Chase, Z.,
Cullen, J. J., Laan, P., Landing, W., Mendez, J., Milne, A., Obata, H., Doi,
T., Ossiander, L., Sarthou, G., Sedwick, P. N., Van den Berg, S.,
Laglera-Baquer, L., Wu, J.-F., and Cai, Y.: Developing standards for
dissolved iron in seawater, Eos, Transactions American Geophysical Union, 88,
131–132, https://doi.org/10.1029/2007EO110003, 2007.
Khatiwala, S., Primeua, F., and Hall, T.: Reconstruction of the history of
anthropogenic CO2 concentrations in the ocean, Nature, 462,
346–349, https://doi.org/10.1038/nature08526, 2009.
Kolber, Z. S. and Falkowski, P. G.: Use of active fluorescence to estimate
phytoplankton photosynthesis in situ, Limnol. Oceanogr., 38, 1646–1665,
https://doi.org/10.4319/lo.1993.38.8.1646, 1993.
Kolber, Z. S., Prášil, O., and Falkowski, P. G.: Measurements of
variable chlorophyll fluorescence using fast repetition rate techniques:
defining methodology and experimental protocols, Biochim. Biophys. Acta., 1367,
88–106, https://doi.org/10.1016/S0005-2728(98)00135-2, 1998.
Kruskopf, M. and Flynn, K. J.: Chlorophyll content and fluorescence responses
cannot be used to gauge reliably phytoplankton biomass, nutrient status or
growth rate, New. Phytol., 169, 525–536, https://doi.org/10.1111/j.1469-8137.2005.01601.x,
2006.
Le Quéré, C., Raupach, M. R., Canadell, J. G., Marland, G., Bopp, L.,
Ciais, P., Conway, T. J., Doney, S. C., Feely, R. A., Foster, P.,
Friendlingstein, P., Gurney, K., Houghton, R. A., House, J. I., Huntingford,
C., Levy, P. E., Lomas, M. R., Majkut, J., Metzl, N., Ometto, J. P., Peters,
G. P., Prentice, I. C., Randerson, J. T., Running, S. W., Sarmiento, J. L.,
Schuster, U., Sitch, S., Takahashi, T., Viovy, N., van der Werf, G. R., and
Woodward, F. I.: Trends in the sources and sinks of carbon dioxide, Nat. Geosci., 2, 831–836, https://doi.org/10.1038/ngeo689, 2009.
Lin, H., Kuzimov, F. I., Park, J., Lee, S., Falkowski, P. G., and Gorbunov,
M. Y.: The fate of photons absorbed by phytoplankton in the global ocean,
Science, 351, 264–267, https://doi.org/10.1126/science.aab2213, 2016.
Little, H., Vichi, M., Thomalla, S. J., and Swart, S.: Spatial and temporal
scales of chlorophyll variability using high-resolution glider data, J. Marine
Syst., 187, 1–12, https://doi.org/10.1016/j.marsys.2018.06.011, 2018.
Loisel, H., Nicolas, J. M., Deschamps, P. Y., and Frouin, R.: Seasonal and
inter-annual variability of particulate organic matter in the global ocean,
Geophys. Res. Lett., 29, 2196, https://doi.org/10.1029/2002GL015948,
2002.
Lucas, M., Seeyave, S., Sanders, R., Moore, C. M., Williamson, R., and
Stinchcombe, M.: Nitrogen uptake responses to a naturally Fe-fertilised
phytoplankton bloom during the 2004/2005 CROZEX study, Deep.-Sea. Res. Pt. 1,
54, 2138–2173, https://doi.org/10.4319/lo.2007.52.6.2540, 2007.
Macey, A. I., Ryan-Keogh, T. J., Richier, S., Moore, C. M., and Bibby, T. S.:
Photosynthetic protein stoichiometry and photophysiology in the high latitude
North Atlantic, Limnol. Oceanogr., 59, 1853–1864, https://doi.org/10.4319/lo.2014.59.6.1853,
2014.
Mackey, M. D., Mackey, D. J., Higgins, H. W., and Wright, S. W.: CHEMTAX – a
program for estimating class abundances from chemical markers: application to
HPLC measurements of phytoplankton, Mar. Ecol. Prog. Ser., 144, 265–283,
https://doi.org/10.3354/meps144265, 1996.
Mackie, D. S., Boyd, P. W., McTainsh, G. H., Tindale, N. W., Westberry, T.
K., and Hunter, K. A.: Biogeochemistry of iron in Australian dust: From
eolian uplift to marine uptake, Geochem. Geophy. Geosy., 9,
Q03Q08, https://doi.org/10.1029/2007GC001813, 2008.
Maldonado, M. T., Boyd, P. W., Harrison, P. J., and Price, N. M.:
Co-limitation of phytoplankton growth by light and Fe during winter in the NE
subarctic Pacific Ocean, Deep.-Sea. Res. Pt. 1, 46, 2475–2485,
https://doi.org/10.1016/S0967-0645(99)00072-7, 1999.
Marinov, I., Gnanadesikan, A., Toggweiler, J. R., and Sarmiento, J. L.: The
Southern Ocean biogeochemical divide, Nature, 441, 964–967,
https://doi.org/10.1038/nature04883, 2006.
Martin, J. H. and Fitzwater, S. E.: Iron deficiency limits phytoplankton
growth in the northeast Pacific subarctic, Nature, 331, 341–343,
https://doi.org/10.1038/331341a0, 1988.
Martin, J. H., Gordon, R. M., and Fitzwater, S. E.: Iron in Antarctic waters,
Nature, 345, 156–158, https://doi.org/10.1038/345156a0, 1990.
Massom, R. A. and Stammerjohn, S. E.: Antarctic sea ice change and
variability – Physical and ecological implications, Polar Sci., 4,
149–186, https://doi.org/10.1016/j.polar.2010.05.001, 2010.
Mignot, A., Claustre, H., Uitz, J., Poteau, A., D'Ortenzio, F., and Xing, X.:
Understanding the seasonal dynamics of phytoplankton biomass and the deep
chlorophyll maximum in oligotrophic environments: A Bio-Argo float
investigation, Global Biogeochem. Cy., 28, 856–876,
https://doi.org/10.1002/2013GB004781, 2014.
Mikaloff Fletcher, S. E., Gruber, N., Jacobson, A. R., Doney, S. C.,
Dutkiewicz, S., Gerber, M., Follows, M., Joos, F., Lindsay, K., Menemenlis,
D., Mouchet, A., Müller, S. A., and Sarmiento, J. L.: Inverse estimates
of anthropogenic CO2 uptake, transport, and storage by the
ocean, Global Biogeochem. Cy., 20, GB2002, https://doi.org/10.1029/2005GB002530, 2006.
Milligan, A. J. and Harrison, P. J.: Effects of non-steady-state iron
limitation on nitrogen assimilatory enzymes in the marine diatom
Thalassiosira weissflogii (Bacillariophyceae), J. Phycol., 36, 78–86,
https://doi.org/10.1046/j.1529-8817.2000.99013.x, 2000.
Moore, C. M., Seeyave, S., Hickman, A. E., Allen, J. T., Lucas, M. I.,
Planquette, H., Pollard, R. T., and Poulton, A. J.: Iron-light interactions
during the CROZet natural iron bloom and EXport experiment (CROZEX) I:
Phytoplankton growth and photophysiology, Deep.-Sea. Res. Pt. 1, 54,
2045–2065, https://doi.org/10.1016/j.dsr2.2007.06.011, 2007.
Moore, C. M., Mills, M. M., Arrigo, K. R., Berman-Frank, I., Bopp, L., Boyd,
P. W., Galbraith, E. D., Geider, R. J., Guieu, C., Jaccard, S. L., Jickells,
T. D., La Roche, J., Lenton, T. M., Mahowald, N. M., Marañón, E.,
Marinov, I., Moore, J. K., Nakatsuka, T., Oschlies, A., Saito, M. A.,
Thingstad, T. F., Tsuda, A., and Ulloa, O.: Processes and patterns of oceanic
nutrient limitation, Nat. Geosci., 6, 701–710, https://doi.org/10.1038/NGEO1765, 2013.
Nelson, D. M. and Smith, W. O. J.: Sverdrup revisited: Critical depths,
maximum chlorophyll levels and the control of Southern Ocean productivity by
the irradiance-mixing regime, Limnol. Oceanogr., 36, 1650–1661, 1991.
Nicholson, S.-A., Lévy, M., Llort, J., Swart, S., and Monteiro, P. M. S.:
Investigation into the impact of storms on sustaining summer primary
productivity in the Sub-Antarctic Ocean, Geophys. Res. Lett., 43, 9192–9199,
https://doi.org/10.1002/2016GL069973, 2016.
Nielsdóttir, M. C., Bibby, T. S., Moore, C. M., Hinz, D. J., Sanders, R.,
Whitehouse, M., Korb, R., and Achterberg, E. P.: Seasonal and spatial
dynamics of iron availability in the Scotia Sea, Mar. Chem., 130, 62–72,
https://doi.org/10.1038/345156a0, 2012.
Nowlin, W. D. and Klinck, J. M.: The physics of the Antarctic Circumpolar
Current, Rev. Geophys., 24, 469–491, https://doi.org/10.1029/RG024i003p00469, 1986.
Obata, H., Karatani, H., and Nakayama, E.: Automated determination of iron in
seawater by chelating resin concentration and chemiluminescence detection,
Anal. Chem., 65, 1524–1528, https://doi.org/10.1021/ac00059a007, 1993.
Orsi, A. H., Whitworth III, T. W., and Nowlin, W. D.: On the meridional
extent and front of the Antarctic Circumpolar Current, Deep.-Sea. Res. Pt. 1,
42, 641–673, https://doi.org/10.1016/0967-0637(95)00021-W, 1995.
Pakhomov, E. A. and Froneman, P. W.: Zooplankton dynamics in the eastern
Atlantic sector of the Southern Ocean during austral summer 1997/1998,
Deep.-Sea. Res. Pt. 1, 51, 2599–2616, https://doi.org/10.1016/j.dsr2.2000.11.001, 2004.
Parkhill, J., Maillet, G., and Cullen, J. J.: Fluorescence-based maximal
quantum yield for PSII as a diagnostic of nutrient stress, J. Phycol., 37,
517–529, https://doi.org/10.1046/j.1529-8817.2001.037004517.x, 2001.
Price, N. M.: The elemental stoichiometry and composition of an iron-limited
diatom, Limnol. Oceanogr., 50, 1149–1158, 2005.
Price, N. M., Ahner, B. A., and Morel, F. M. M.: The equatorial Pacific
Ocean: Grazer-controlled phytoplankton populations in an iron-limited
ecosystem, Limnol. Oceanogr., 39, 520–534, https://doi.org/10.4319/lo.1994.39.3.0520, 1994.
Racault, M.-F., Le Quéré, C., Buitenhuis, E., Sathyendranath, S., and
Platt, T.: Phytoplankton phenology in the global ocean, Ecol. Indic., 14, 152–163, https://doi.org/10.1016/j.ecolind.2011.07.010, 2012.
Ras, J., Claustre, H., and Uitz, J.: Spatial variability of phytoplankton
pigment distributions in the Subtropical South Pacific Ocean: comparison
between in situ and predicted data, Biogeosciences, 5, 353–369,
https://doi.org/10.5194/bg-5-353-2008, 2008.
Raven, J. A.: Predictions of Mn and Fe use efficiencies of phototrophic
growth as a function of light availability for growth and C assimilation
pathway, New. Phytol., 116, 1–18, https://doi.org/10.1111/j.1469-8137.1990.tb00505.x, 1990.
Raven, J. A., Evans, M. C., and Korb, R. E.: The role of trace metals in
photosynthetic electron transport in O2-evolving organisms, Photosynth. Res., 60, 111–150, https://doi.org/10.1023/A:1006282714942, 1999.
Rio, M. H., Guinehut, S., and Larnicol, G.: New CNES-CLS09 global mean
dynamic topography computed from the combination of GRACE data, altimetry,
and in situ measurements, J. Geophys. Res., 116, C07018,
https://doi.org/10.1029/2010JC006505, 2011.
Roháček, K.: Chlorophyll Fluorescence Parameters: The Definitions,
Photosynthetic Meaning, and Mutual Relationships, Photosynthetica, 40, 13–29,
https://doi.org/10.1023/A:1020125719386, 2002.
Ryan-Keogh, T. J., Macey, A. I., Cockshutt, A. M., Moore, C. M., and Bibby,
T. S.: The cyanobacterial chlorophyll-binding-protein IsiA acts to increase
the in vivo effective absorption cross-section of photosystem I
under iron limitation, J. Phycol., 48, 145–154,
https://doi.org/10.1111/j.1529-8817.2011.01092.x, 2012.
Ryan-Keogh, T. J., Macey, A. I., Nielsdóttir, M., Lucas, M. I.,
Steigenberger, S. S., Stinchcombe, M. C., Achterberg, E. P., Bibby, T. S.,
and Moore, C. M.: Spatial and temporal development of phytoplankton iron
stress in relation to bloom dynamics in the high-latitude North Atlantic
Ocean, Limnol. Oceanogr., 58, 533–545, https://doi.org/10.4319/lo.2013.58.2.0533, 2013.
Ryan-Keogh, T. J., DeLizo, L. M., Smith Jr., W. O., Sedwick, P. N.,
McGillicuddy Jr., D. J., Moore, C. M., and Bibby, T. S.: Temporal
progression of photosynthetic strategy by phytoplankton in the Ross Sea,
Antarctica, J. Marine Syst., 166, 87–96,
https://doi.org/10.1016/j.jmarsys.2016.08.014, 2017a.
Ryan-Keogh, T. J., Thomalla, S. J., Mtshali, T. N., and Little, H.: Modelled
estimates of spatial variability of iron stress in the Atlantic sector of the
Southern Ocean, Biogeosciences, 14, 3883–3897,
https://doi.org/10.5194/bg-14-3883-2017, 2017b.
Sarthou, G., Baker, A. R., Blain, S., Achterberg, E. P., Boye, M., Bowie, A.
R., Croot, P., Laan, P., de Baar, H. J. W., Jickells, T. D., and Worsfold, P.
J.: Atmospheric iron deposition and sea-surface dissolved iron concentrations
in the eastern Atlantic Ocean, Deep-Sea Res. Pt. I, 50, 1339–1352, https://doi.org/10.1016/S0967-0637(03)00126-2, 2003.
Schlitzer, R.: Carbon export fluxes in the Southern Ocean: results from
inverse modeling and comparion with satellite-based estimates, Deep.-Sea. Res. Pt. 1, 49, 1623–1644, https://doi.org/10.4319/lo.1994.39.3.0520, 2002.
Schrader, P. S., Milligan, A. J., and Behrenfeld, M. J.: Surplus
Photosynthetic Antenna Complexes Underlie Diagnostics of Iron Limitation in a
Cyanobacterium, PLoS ONE, 6, e18753, https://doi.org/10.1371/journal.pone.0018753, 2011.
Shi, T., Sun, Y., and Falkowski, P. G.: Effects of iron limitation on the
expression of metabolic genes in the marine cyanobacterium
Trichodesmium erythraeum IMS101, Environ. Microbiol., 9,
2945–2956, https://doi.org/10.1111/j.1462-2920.2007.01406.x, 2007.
Siegel, D. A., Doney, S. C., and Yoder, J. A.: The North Atlantic spring
phytoplankton bloom and Sverdrup's critical depth hypothesis, Science, 296,
730–733, https://doi.org/10.1126/science.1069174, 2002.
Smetacek, V., Assmy, P., and Henjes, J.: The role of grazing in structuring
Southern Ocean pelagic ecosystems and biogeochemical cycles, Antarct. Sci., 16,
541–558, https://doi.org/10.1017/S0954102004002317, 2004.
Stramski, D., Reynolds, R. A., Kahru, M., and Mitchell, B. G.: Estimation of
Particulate Organic Carbon in the Ocean from Satellite Remote Sensing,
Science, 285, 239–242, https://doi.org/10.1126/science.285.5425.239, 1999.
Strzepek, R. F. and Harrison, P. J.: Photosynthetic architecture differs in
coastal and oceanic diatoms, Nature, 431, 689–692, https://doi.org/10.1038/nature02954, 2004.
Strzepek, R. F., Hunter, K. A., Frew, R. D., Harrison, P. J., and Boyd, P.
W.: Iron-light interactions differ in Southern Ocean phytoplankton, Limnol. Oceanogr., 57, 1182–1200, https://doi.org/10.4319/lo.2012.57.4.1182, 2012.
Strzepek, R. F., Maldonado, M. T., Hunter, K. A., Frew, R. D., and Boyd, P.
W.: Adaptive strategies by Southern Ocean phytoplankton to lessen iron
limitation: Uptake of organically complexed iron and reduced cellular iron
requirements, Limnol. Oceanogr., 56, 1983–2002, https://doi.org/10.4319/lo.2011.56.6.1983,
2011.
Suggett, D. J., Moore, C. M., Hickman, A. E., and Geider, R. J.:
Interpretation of fast repetition rate (FRR) fluorescence: signatures of
phytoplankton community structure versus physiological state, Mar. Ecol. Prog. Ser., 376, 1–19, https://doi.org/10.3354/meps07830, 2009.
Sunda, W. G. and Huntsman, S. A.: Interrelated influence of iron, light and
cell size on marine phytoplankton growth, Nature, 390, 389–392,
https://doi.org/10.1038/37093, 1997.
Sverdrup, H. U.: On conditions for the vernal blooming of phytoplankton,
Journal du Conseil International pour l'Exploration de la Mer, 18, 287–295,
1953.
Swart, S., Speich, S., Ansorge, I. J., and Lutjeharms, J. R. E.: An
altimetry-based gravest empirical mode south of Africa: 1. Development and
validation, J. Geophys. Res., 115, C03002, https://doi.org/10.1029/2009JC005299,
2010.
Swart, S., Chang, N., Fauchereau, N., Joubert, W. R., Lucas, M., Mtshali, T.,
Roychoudhury, A., Tagliabue, A., Thomalla, S., Waldron, H. N., and Monteiro,
P. M. S.: Southern Ocean Seasonal Cycle Experiment 2012: Seasonal scale
climate and carbon cycle links, S. Afr. J. Sci., 108, 11–13,
https://doi.org/10.4102/sajs.v108i3/4.1089, 2012.
Swart, S., Thomalla, S. J., and Monteiro, P. M. S.: The seasonal cycle of
mixed layer dynamics and phytoplankton biomass in the Sub-Antarctic Zone: A
high-resolution glider experiment, J. Marine Syst., 147, 103–115,
https://doi.org/10.1016/j.jmarsys.2014.06.002, 2015.
Tagliabue, A., Sallée, J.-B., Bowie, A. R., Lévy, M., Swart, S., and
Boyd, P. W.: Surface-water iron supplies in the Southern Ocean sustained by
deep winter mixing, Nat. Geosci., 7, 314–320, https://doi.org/10.1038/ngeo2101, 2014.
Thomalla, S. J., Fauchereau, N., Swart, S., and Monteiro, P. M. S.: Regional
scale characteristics of the seasonal cycle of chlorophyll in the Southern
Ocean, Biogeosciences, 8, 2849–2866, https://doi.org/10.5194/bg-8-2849-2011,
2011
Thomalla, S. J., Racault, M.-F., Swart, S., and Monteiro, P. M. S.:
High-resolution view of the spring bloom initiation and net community
production in the Subantarctic Southern Ocean using glider data, ICES, J.
Mar. Sci., 72, 1999–2020, https://doi.org/10.1093/icesjms/fsv105, 2015.
Thomalla, S. J., Moutier, W., Ryan-Keogh, T. J., Gregor, L., and Schütt,
J.: An optimized method for correcting fluorescence quenching using optical
backscattering on autonomous platforms, Limnol. Oceanogr.-Meth.,
16, 132–144, https://doi.org/10.1002/lom3.10324, 2017.
Welschmeyer, N. A.: Fluorometric analysis of chlorophyll-a in the presence
of chlorophyll-b and pheopigments, Limnol. Oceanogr., 39, 1985–1992,
https://doi.org/10.4319/lo.1994.39.8.1985, 1994.
Westberry, T., Behrenfeld, M. J., Siegel, D. A., and Boss, E.: Carbon-based
primary productivity modeling with vertically resolved photoacclimation,
Global Biogeochem. Cy., 22, GB2024, https://doi.org/10.1029/2007GB003078, 2008.
Westberry, T. K., Schultz, P., Behrenfeld, M. J., Dunne, J. P., Hiscock, M.
R., Maritorena, S., Sarmiento, J. L., and Siegel, D. A.: Annual cycles of
phytoplankton biomass in the subarctic Atlantic and Pacific Ocean, Global Biogeochem. Cy., 30, 175–190, https://doi.org/10.1002/2015GB005276, 2016.
Wolters, M.: Quickchem Method 31-114-27-1-D – Silicate in Brackish or
Seawater, Lachat Instruments, Colorado, USA, 2002.
Short summary
The availability of iron in the Southern Ocean constrains the overall extent and magnitude of the phytoplankton bloom. Uncertainty remains over the dominant supply mechanisms, which are expected to be altered by climate change. Nutrient addition experiments confirm that iron limitation is seasonal in nature, with increased responses to iron addition in late summer. This is driven by variability in the supply mechanisms across the growing season, which fail to meet the phytoplankton demand.
The availability of iron in the Southern Ocean constrains the overall extent and magnitude of...
Altmetrics
Final-revised paper
Preprint