Articles | Volume 13, issue 12
https://doi.org/10.5194/bg-13-3793-2016
© Author(s) 2016. This work is distributed under
the Creative Commons Attribution 3.0 License.
the Creative Commons Attribution 3.0 License.
https://doi.org/10.5194/bg-13-3793-2016
© Author(s) 2016. This work is distributed under
the Creative Commons Attribution 3.0 License.
the Creative Commons Attribution 3.0 License.
Research article
| 
01 Jul 2016
Research article |
| 01 Jul 2016
Dynamics of transparent exopolymer particles (TEP) during the VAHINE mesocosm experiment in the New Caledonian lagoon
Ilana Berman-Frank
CORRESPONDING AUTHOR
The Mina and Everard Goodman Faculty of Life Sciences, Bar-Ilan University, Ramat Gan, 5290002, Israel
Dina Spungin
The Mina and Everard Goodman Faculty of Life Sciences, Bar-Ilan University, Ramat Gan, 5290002, Israel
Eyal Rahav
The Mina and Everard Goodman Faculty of Life Sciences, Bar-Ilan University, Ramat Gan, 5290002, Israel
National Institute of Oceanography, Israel Oceanographic and Limnological Research, Haifa, 31080, Israel
France Wambeke
Aix Marseille Université, CNRS/INSU, Université de Toulon, IRD, Mediterranean Institute of Oceanography (MIO) UM110, 13288,
Marseille, France
Kendra Turk-Kubo
Ocean Sciences Department, University of California, Santa Cruz, 1156 High Street, Santa Cruz, CA 95064, USA
Thierry Moutin
Aix Marseille Université, CNRS/INSU, Université de Toulon, IRD, Mediterranean Institute of Oceanography (MIO) UM110, 13288,
Marseille, France
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Christos Panagiotopoulos, Mireille Pujo-Pay, Mar Benavides, France Van Wambeke, and Richard Sempéré
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The OUTPACE cruise took place between New Caledonia and French Polynesia. The main purpose was to understand how micro-organisms can survive in a very poor environment. One main source of nutrients is at depth, below the euphotic layer where micro-organisms live. The purpose of the turbulence measurements was to determine to which extent turbulence may
upliftnutrients into the euphotic layer. The origin of the turbulence that was found contrasted along the transect was also determined.
Angela M. Kuhn, Katja Fennel, and Ilana Berman-Frank
Biogeosciences, 15, 7379–7401, https://doi.org/10.5194/bg-15-7379-2018, https://doi.org/10.5194/bg-15-7379-2018, 2018
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Recent studies demonstrate that marine N2 fixation can be carried out without light. However, direct measurements of N2 fixation in dark environments are relatively scarce. This study uses a model that represents biogeochemical cycles at a deep-ocean location in the Gulf of Aqaba (Red Sea). Different model versions are used to test assumptions about N2 fixers. Relaxing light limitation for marine N2 fixers improved the similarity between model results and observations of deep nitrate and oxygen.
Audrey Gimenez, Melika Baklouti, Thibaut Wagener, and Thierry Moutin
Biogeosciences, 15, 6573–6589, https://doi.org/10.5194/bg-15-6573-2018, https://doi.org/10.5194/bg-15-6573-2018, 2018
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During the OUTPACE cruise conducted in the oligotrophic to ultra-oligotrophic region of the western tropical South Pacific, two contrasted regions were sampled in terms of N2 fixation rates, primary production rates and nutrient availability. The aim of this work was to investigate the role of N2 fixation in the differences observed between the two contrasted areas by comparing two simulations only differing by the presence or not of N2 fixers using a 1-D biogeochemical–physical coupled model.
Thibaut Wagener, Nicolas Metzl, Mathieu Caffin, Jonathan Fin, Sandra Helias Nunige, Dominique Lefevre, Claire Lo Monaco, Gilles Rougier, and Thierry Moutin
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The western tropical South Pacific was sampled along a longitudinal 4000 km transect (OUTPACE cruise) for the measurement of carbonate parameters (total alkalinity and total inorganic carbon) between the Melanesian Archipelago and the western part of the South Pacific gyre. This paper reports this new dataset and derived properties. We also estimate anthropogenic carbon distribution in the water column using the TrOCA method.
Nicholas Bock, France Van Wambeke, Moïra Dion, and Solange Duhamel
Biogeosciences, 15, 3909–3925, https://doi.org/10.5194/bg-15-3909-2018, https://doi.org/10.5194/bg-15-3909-2018, 2018
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We report the distribution of major nano- and pico-plankton groups in the western tropical South Pacific. We found microbial community structure to be typical of highly stratified regions of the open ocean, with significant contributions to total biomass by picophytoeukaryotes, and N2 fixation playing a central role in regulating ecosystem processes. Our results also suggest a reduction in the importance of predation in regulating bacteria populations under nutrient-limited conditions.
Dina Spungin, Natalia Belkin, Rachel A. Foster, Marcus Stenegren, Andrea Caputo, Mireille Pujo-Pay, Nathalie Leblond, Cécile Dupouy, Sophie Bonnet, and Ilana Berman-Frank
Biogeosciences, 15, 3893–3908, https://doi.org/10.5194/bg-15-3893-2018, https://doi.org/10.5194/bg-15-3893-2018, 2018
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The way marine organisms die can determine the fate of organic matter (OM) in the ocean. We investigated whether a form of auto-induced programmed cell death (PCD) influenced phytoplankton mortality and fate of OM. Our results from high biomass blooms of the cyanobacterium Trichodesmium show evidence for PCD and high production of sticky carbon material termed transparent exopolymeric particles (TEP) that facilitates cellular aggregation and enhances the vertical flux of OM to depth.
Thierry Moutin, Thibaut Wagener, Mathieu Caffin, Alain Fumenia, Audrey Gimenez, Melika Baklouti, Pascale Bouruet-Aubertot, Mireille Pujo-Pay, Karine Leblanc, Dominique Lefevre, Sandra Helias Nunige, Nathalie Leblond, Olivier Grosso, and Alain de Verneil
Biogeosciences, 15, 2961–2989, https://doi.org/10.5194/bg-15-2961-2018, https://doi.org/10.5194/bg-15-2961-2018, 2018
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Surface waters of the western tropical South Pacific were sampled along a longitudinal 4000 km transect during the stratified period between the Melanesian Archipelago and the western part of the South Pacific gyre. We found a significant biological carbon pump sustained almost exclusively by N2 fixation and essentially controlled by phosphate availability in the iron-rich Melanesian Archipelago waters which appears to be a net sink for atmospheric CO2 while the gyre is in a quasi-steady state.
France Van Wambeke, Audrey Gimenez, Solange Duhamel, Cécile Dupouy, Dominique Lefevre, Mireille Pujo-Pay, and Thierry Moutin
Biogeosciences, 15, 2669–2689, https://doi.org/10.5194/bg-15-2669-2018, https://doi.org/10.5194/bg-15-2669-2018, 2018
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The western tropical South Pacific Ocean has recently been shown to be a hotspot for biological nitrogen fixation. In this study, we examined the horizontal and vertical distribution of heterotrophic prokaryotic production alongside photosynthetic rates, nitrogen fixation rates and phosphate turnover times across the western tropical South Pacific Ocean, in order to relate these fluxes to bottom–up controls (related to nitrogen, phosphate and labile C availability).
Angela N. Knapp, Kelly M. McCabe, Olivier Grosso, Nathalie Leblond, Thierry Moutin, and Sophie Bonnet
Biogeosciences, 15, 2619–2628, https://doi.org/10.5194/bg-15-2619-2018, https://doi.org/10.5194/bg-15-2619-2018, 2018
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The spatial distribution of biological N2 fixation fluxes to the ocean remains poorly constrained. Here we use nitrogen isotope budgets to identify significant N2 fixation inputs to the western tropical South Pacific (WTSP), where N2 fixation supports > 50 % of export production at stations proximal to iron sources. The significant N2 fixation inputs in the WTSP may offset nitrogen loss in the oxygen-deficient zones of the eastern tropical South Pacific.
Mathieu Caffin, Thierry Moutin, Rachel Ann Foster, Pascale Bouruet-Aubertot, Andrea Michelangelo Doglioli, Hugo Berthelot, Cécile Guieu, Olivier Grosso, Sandra Helias-Nunige, Nathalie Leblond, Audrey Gimenez, Anne Alexandra Petrenko, Alain de Verneil, and Sophie Bonnet
Biogeosciences, 15, 2565–2585, https://doi.org/10.5194/bg-15-2565-2018, https://doi.org/10.5194/bg-15-2565-2018, 2018
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We performed N budgets to assess the role of N2 fixation on production and export in the western tropical South Pacific Ocean. We deployed a combination of techniques including high-sensitivity measurements of N input and sediment traps deployment. We demonstrated that N2 fixation was the major source of new N before atmospheric deposition and upward nitrate fluxes. It contributed significantly to organic matter export, indicating a high efficiency of this region to export carbon.
Alain de Verneil, Louise Rousselet, Andrea M. Doglioli, Anne A. Petrenko, Christophe Maes, Pascale Bouruet-Aubertot, and Thierry Moutin
Biogeosciences, 15, 2125–2147, https://doi.org/10.5194/bg-15-2125-2018, https://doi.org/10.5194/bg-15-2125-2018, 2018
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Oceanographic campaigns to measure biogeochemical processes popularly deploy drifters with onboard incubations to stay in a single body of water. Here, we aggregate physical data taken during such a cruise, OUTPACE, to independently test in a new approach whether the drifter really stayed in what can be considered a single biological or chemical environment. This study concludes that future campaigns would benefit from similar data collection and analysis to validate their sampling strategy.
Alain Fumenia, Thierry Moutin, Sophie Bonnet, Mar Benavides, Anne Petrenko, Sandra Helias Nunige, and Christophe Maes
Biogeosciences Discuss., https://doi.org/10.5194/bg-2017-557, https://doi.org/10.5194/bg-2017-557, 2018
Revised manuscript not accepted
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The Melanesian archipelago waters between 160° E and 170° W are characterized by a significant N2 fixation rates and an excess of particulate organic nitrogen compared to the canonical ratio of Redfield and a positive N*. We hypothesize that the southern branch of the subtropical gyre is probably the main vector of excess nitrogen transport in the thermocline waters showing an influence of nitrogen fixation occurring in the western tropical in a large part of the South Pacific.
Alain de Verneil, Louise Rousselet, Andrea M. Doglioli, Anne A. Petrenko, and Thierry Moutin
Biogeosciences, 14, 3471–3486, https://doi.org/10.5194/bg-14-3471-2017, https://doi.org/10.5194/bg-14-3471-2017, 2017
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A surface summer plankton bloom in the western tropical South Pacific was sampled during the Oligotrophy to UlTra-oligotrophy PACific Experiment (OUTPACE) cruise. We characterize the bloom's properties and the circulation responsible for its evolution. Nitrogen fixation helped sustain the bloom, and larger-scale flows, rather than the smaller ones, explain its movements. Future studies of blooms in this region can make use of these findings to track the horizontal export of plankton production.
Thierry Moutin, Andrea Michelangelo Doglioli, Alain de Verneil, and Sophie Bonnet
Biogeosciences, 14, 3207–3220, https://doi.org/10.5194/bg-14-3207-2017, https://doi.org/10.5194/bg-14-3207-2017, 2017
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The overall goal of OUTPACE was to obtain a successful representation of the interactions between planktonic organisms and the cycle of biogenic elements in the western tropical South Pacific Ocean across trophic and N2 fixation gradients. The international OUTPACE cruise took place between 18 February and 3 April 2015 aboard the RV L’Atalante and involved 60 scientists. The transect covered ~4 000 km from the western part of the Melanesian archipelago to the western boundary of the gyre.
Audrey Gimenez, Melika Baklouti, Sophie Bonnet, and Thierry Moutin
Biogeosciences, 13, 5103–5120, https://doi.org/10.5194/bg-13-5103-2016, https://doi.org/10.5194/bg-13-5103-2016, 2016
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In the context of the VAHINE mesocosm experiment in the Nouméa lagoon (New Caledonia), a 1-D vertical biogeochemical mechanistic model was used together with the in situ experiment to complement our comprehension of the planktonic ecosystem dynamics and the main biogeochemical carbon, nitrogen and phosphate fluxes. The model also showed the fate of fixed N2 by providing, over time, the proportion of diazotroph-derived nitrogen (DDN) in each compartment (mineral and organic) of the model.
Angela N. Knapp, Sarah E. Fawcett, Alfredo Martínez-Garcia, Nathalie Leblond, Thierry Moutin, and Sophie Bonnet
Biogeosciences, 13, 4645–4657, https://doi.org/10.5194/bg-13-4645-2016, https://doi.org/10.5194/bg-13-4645-2016, 2016
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The goal of this manuscript was to track the fate of newly fixed nitrogen (N) in large volume mesocosms in the coastal waters of New Caledonia. We used a N isotope ("δ15N") budget and found a shift in the δ15N of sinking particulate N over the 23-day experiment, indicating that nitrate supported export production at the beginning of the experiment, but that nitrogen fixation supported export at the end. We infer that nitrogen fixation supported export production by a release of dissolved N.
Dina Spungin, Ulrike Pfreundt, Hugo Berthelot, Sophie Bonnet, Dina AlRoumi, Frank Natale, Wolfgang R. Hess, Kay D. Bidle, and Ilana Berman-Frank
Biogeosciences, 13, 4187–4203, https://doi.org/10.5194/bg-13-4187-2016, https://doi.org/10.5194/bg-13-4187-2016, 2016
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The marine cyanobacterium Trichodesmium spp. forms massive blooms important to carbon and nitrogen cycling in the oceans that often collapse abruptly. We investigated a Trichodesmium bloom in the lagoon waters of New Caledonia to specifically elucidate the cellular processes mediating the bloom decline. We demonstrate physiological, biochemical, and genetic evidence for nutrient and oxidative stress that induced a genetically controlled programmed cell death (PCD) pathway leading to bloom demise.
Ulrike Pfreundt, Dina Spungin, Sophie Bonnet, Ilana Berman-Frank, and Wolfgang R. Hess
Biogeosciences, 13, 4135–4149, https://doi.org/10.5194/bg-13-4135-2016, https://doi.org/10.5194/bg-13-4135-2016, 2016
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The VAHINE experiment in the New Caledonia lagoon (SW Pacific) targeted the dynamics of nutrient pools and fluxes, N2 fixation, and the composition and productivity of the microbial communities. To connect this information to the actual activities of diverse microbial taxa, we present the analysis of the community-wide gene expression for 23 days. The results from this experiment provide insight into the microbial activities in a low-nutrient, low-chlorophyll ecosystem and within a mesocosm.
Marc Tedetti, Lauriane Marie, Rüdiger Röttgers, Martine Rodier, France Van Wambeke, Sandra Helias, Mathieu Caffin, Véronique Cornet-Barthaux, and Cécile Dupouy
Biogeosciences, 13, 3283–3303, https://doi.org/10.5194/bg-13-3283-2016, https://doi.org/10.5194/bg-13-3283-2016, 2016
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In the framework of the VAHINE project, we investigated the spectral characteristics and the variability of dissolved and particulate chromophoric materials throughout a 23-day mesocosm experiment conducted in the south-west Pacific at the mouth of the New Caledonian coral lagoon. We found that the dynamics of CDOM and particulate matter absorption were strongly coupled with those of cyanobacteria Synechococcus spp. and bacterial production.
France Van Wambeke, Ulrike Pfreundt, Aude Barani, Hugo Berthelot, Thierry Moutin, Martine Rodier, Wolfgang R. Hess, and Sophie Bonnet
Biogeosciences, 13, 3187–3202, https://doi.org/10.5194/bg-13-3187-2016, https://doi.org/10.5194/bg-13-3187-2016, 2016
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The phytoplankton is at the base of the plankton food web in large parts of oceanic "deserts" such as the South Pacific Ocean, where nitrogen sources limit activity. Mesocosms were fertilized with phosphorus to stimulate diazotrophy (atmospheric N2 fixation). Mostly diazotroph-derived nitrogen fuelled the heterotrophic bacterial community through indirect processes generating dissolved organic matter and detritus, such as mortality, lysis and grazing of both diazotrophs and non-diazotrophs.
Sophie Bonnet, Thierry Moutin, Martine Rodier, Jean-Michel Grisoni, Francis Louis, Eric Folcher, Bertrand Bourgeois, Jean-Michel Boré, and Armelle Renaud
Biogeosciences, 13, 2803–2814, https://doi.org/10.5194/bg-13-2803-2016, https://doi.org/10.5194/bg-13-2803-2016, 2016
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e main goal of the VAHINE project was to study the fate of N2 fixation in the ocean. Three large-volume (~ 50 m3) mesocosms were deployed in a tropical oligotrophic ecosystem (the New Caledonia lagoon, south-eastern Pacific). This introductory paper describes the scientific objectives of the project in detail as well as the implementation plan: the mesocosm description and deployment, the selection of the study site, and the logistical and sampling strategy.
Sophie Bonnet, Hugo Berthelot, Kendra Turk-Kubo, Sarah Fawcett, Eyal Rahav, Stéphane L'Helguen, and Ilana Berman-Frank
Biogeosciences, 13, 2653–2673, https://doi.org/10.5194/bg-13-2653-2016, https://doi.org/10.5194/bg-13-2653-2016, 2016
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N2 fixation rates were measured daily in ~ 50 m3 mesocosms deployed in New Caledonia to investigate the high-frequency dynamics of diazotrophy and the fate of diazotroph-derived nitrogen (DDN) oligotrophic ecosystems. ~ 10 % of UCYN-C from the water column were exported daily to the traps, representing as much as 22.4 ± 5.5 % of the total POC exported at the height of the UCYN-C bloom. 16 ± 6 % of the DDN was released to the dissolved pool and 21 ± 4 % was transferred to non-diazotrophic plankton.
Ulrike Pfreundt, France Van Wambeke, Mathieu Caffin, Sophie Bonnet, and Wolfgang R. Hess
Biogeosciences, 13, 2319–2337, https://doi.org/10.5194/bg-13-2319-2016, https://doi.org/10.5194/bg-13-2319-2016, 2016
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The Southwest Pacific has one of the highest N2 fixation rates in the global ocean, yet information is scarce on the bacterioplankton interrelationships. We detected high microbial diversity in the New Caledonia lagoon and inside a 50 000 L experimental enclosure of the same water mass over 3 weeks and give evidence for previously unknown niche partitioning. Phosphate fertilization promoted the growth of efficient N2 fixing cyanobacteria triggering the growth of most heterotrophic bacteria.
A. Guyennon, M. Baklouti, F. Diaz, J. Palmieri, J. Beuvier, C. Lebaupin-Brossier, T. Arsouze, K. Béranger, J.-C. Dutay, and T. Moutin
Biogeosciences, 12, 7025–7046, https://doi.org/10.5194/bg-12-7025-2015, https://doi.org/10.5194/bg-12-7025-2015, 2015
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Dissolved organic carbon (DOC) has already been identified as a potentially significant source of carbon export in the Mediterranean Sea, though in situ export estimations are scarce. This work provides a thorough analysis at basin scale of carbon export with the coupled model NEMO-MED12/Eco3M-MED model. The seasonality and the processes of particulate and dissolved carbon production are also investigated. DOC export appears to be dominant in most regions, especially in the eastern basin.
H. Berthelot, T. Moutin, S. L'Helguen, K. Leblanc, S. Hélias, O. Grosso, N. Leblond, B. Charrière, and S. Bonnet
Biogeosciences, 12, 4099–4112, https://doi.org/10.5194/bg-12-4099-2015, https://doi.org/10.5194/bg-12-4099-2015, 2015
A. Talarmin, F. Van Wambeke, P. Lebaron, and T. Moutin
Biogeosciences, 12, 1237–1247, https://doi.org/10.5194/bg-12-1237-2015, https://doi.org/10.5194/bg-12-1237-2015, 2015
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Along a transect in the warm nutrient-depleted Mediterranean Sea, we found that microorganisms shared phosphate resources by using different uptake strategies. Heterotrophic prokaryotes dominated phosphate uptake in the upper layers while cyanobacteria dominated uptake fluxes around the deep chlorophyll maximum depth. Synechococcus seemed well equipped to respond to pulses of phosphate, whereas Prochlorococcus and heterotrophs were more adapted to very low concentrations.
E. Rahav, B. Herut, M. R. Mulholland, B. Voß, D. Stazic, C. Steglich, W. R. Hess, and I. Berman-Frank
Biogeosciences Discuss., https://doi.org/10.5194/bgd-10-10327-2013, https://doi.org/10.5194/bgd-10-10327-2013, 2013
Revised manuscript has not been submitted
S. Efrati, Y. Lehahn, E. Rahav, N. Kress, B. Herut, I. Gertman, R. Goldman, T. Ozer, M. Lazar, and E. Heifetz
Biogeosciences, 10, 3349–3357, https://doi.org/10.5194/bg-10-3349-2013, https://doi.org/10.5194/bg-10-3349-2013, 2013
E. Rahav, B. Herut, A. Levi, M. R. Mulholland, and I. Berman-Frank
Ocean Sci., 9, 489–498, https://doi.org/10.5194/os-9-489-2013, https://doi.org/10.5194/os-9-489-2013, 2013
Related subject area
Biogeochemistry: Open Ocean
Model estimates of metazoans' contributions to the biological carbon pump
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
Influence of GEOTRACES data distribution and misfit function choice on objective parameter retrieval in a marine zinc cycle model
The representation of alkalinity and the carbonate pump from CMIP5 to CMIP6 ESMs and implications for the ocean carbon cycle
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
Reconstructing ocean carbon storage with CMIP6 models and synthetic Argo observations
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
Impact of dust addition on Mediterranean plankton communities under present and future conditions of pH and temperature: an experimental overview
Reviews and syntheses: Trends in primary production in the Bay of Bengal – is it at a tipping point?
Incorporating the stable carbon isotope 13C in the ocean biogeochemical component of the Max Planck Institute Earth System Model
Seasonal cycling of zinc and cobalt in the south-eastern Atlantic along the GEOTRACES GA10 section
Carbon export and fate beneath a dynamic upwelled filament off the California coast
Contrasted release of insoluble elements (Fe, Al, rare earth elements, Th, Pa) after dust deposition in seawater: a tank experiment approach
On the barium–oxygen consumption relationship in the Mediterranean Sea: implications for mesopelagic marine snow remineralization
Compound high-temperature and low-chlorophyll extremes in the ocean over the satellite period
Can machine learning extract the mechanisms controlling phytoplankton growth from large-scale observations? – A proof-of-concept study
Reviews and syntheses: The biogeochemical cycle of silicon in the modern ocean
Oxygen budget of the north-western Mediterranean deep- convection region
Cross-basin differences in the nutrient assimilation characteristics of induced phytoplankton blooms in the subtropical Pacific waters
Dynamics of the deep chlorophyll maximum in the Black Sea as depicted by BGC-Argo floats
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
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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.
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
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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
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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
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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
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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
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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
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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
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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.
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
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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.
Alban Planchat, Lester Kwiatkwoski, 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
EGUsphere, https://doi.org/10.5194/egusphere-2022-1041, https://doi.org/10.5194/egusphere-2022-1041, 2022
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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.
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
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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
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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.
Katherine E. Turner, Doug M. Smith, Anna Katavouta, and Richard G. Williams
Biogeosciences Discuss., https://doi.org/10.5194/bg-2022-166, https://doi.org/10.5194/bg-2022-166, 2022
Revised manuscript accepted for BG
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We present a new method for reconstructing ocean carbon using climate models and temperature and salinity fields. We test this method by reconstructing modelled carbon fields using synthetic observations consistent with current sampling programmes. Sensitivity tests find that the method can reproduce both trends and variability in upper-ocean carbon. Our results indicate that this method can provide a new estimate for ocean carbon stocks and can be used to compare with existing carbon products.
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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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.
Frédéric Gazeau, Céline Ridame, France Van Wambeke, Samir Alliouane, Christian Stolpe, Jean-Olivier Irisson, Sophie Marro, Jean-Michel Grisoni, Guillaume De Liège, Sandra Nunige, Kahina Djaoudi, Elvira Pulido-Villena, Julie Dinasquet, Ingrid Obernosterer, Philippe Catala, and Cécile Guieu
Biogeosciences, 18, 5011–5034, https://doi.org/10.5194/bg-18-5011-2021, https://doi.org/10.5194/bg-18-5011-2021, 2021
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This paper shows that the impacts of Saharan dust deposition in different Mediterranean basins are as strong as those observed in coastal waters but differed substantially between the three tested stations, differences attributed to variable initial metabolic states. A stronger impact of warming and acidification on mineralization suggests a decreased capacity of Mediterranean surface communities to sequester CO2 following the deposition of atmospheric particles in the coming decades.
Carolin R. Löscher
Biogeosciences, 18, 4953–4963, https://doi.org/10.5194/bg-18-4953-2021, https://doi.org/10.5194/bg-18-4953-2021, 2021
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The Bay of Bengal (BoB) is classically seen as an ocean region with low primary production, which has been predicted to decrease even further. Here, the importance of such a trend is used to explore what could happen to the BoB's low-oxygen core waters if primary production decreases. Lower biological production leads to less oxygen loss in deeper waters by respiration; thus it could be that oxygen will not further decrease and the BoB will not become anoxic, different to other low-oxygen areas.
Bo Liu, Katharina D. Six, and Tatiana Ilyina
Biogeosciences, 18, 4389–4429, https://doi.org/10.5194/bg-18-4389-2021, https://doi.org/10.5194/bg-18-4389-2021, 2021
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We incorporate a new representation of the stable carbon isotope 13C in a global ocean biogeochemistry model. The model well reproduces the present-day 13C observations. We find a recent observation-based estimate of the oceanic 13C Suess effect (the decrease in 13C/12C ratio due to uptake of anthropogenic CO2; 13CSE) possibly underestimates 13CSE by 0.1–0.26 per mil. The new model will aid in better understanding the past ocean state via comparison to 13C/12C measurements from sediment cores.
Neil J. Wyatt, Angela Milne, Eric P. Achterberg, Thomas J. Browning, Heather A. Bouman, E. Malcolm S. Woodward, and Maeve C. Lohan
Biogeosciences, 18, 4265–4280, https://doi.org/10.5194/bg-18-4265-2021, https://doi.org/10.5194/bg-18-4265-2021, 2021
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Using data collected during two expeditions to the South Atlantic Ocean, we investigated how the interaction between external sources and biological activity influenced the availability of the trace metals zinc and cobalt. This is important as both metals play essential roles in the metabolism and growth of phytoplankton and thus influence primary productivity of the oceans. We found seasonal changes in both processes that helped explain upper-ocean trace metal cycling.
Hannah L. Bourne, James K. B. Bishop, Elizabeth J. Connors, and Todd J. Wood
Biogeosciences, 18, 3053–3086, https://doi.org/10.5194/bg-18-3053-2021, https://doi.org/10.5194/bg-18-3053-2021, 2021
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To learn how the biological carbon pump works in productive coastal upwelling systems, four autonomous carbon flux explorers measured carbon flux through the twilight zone beneath an offshore-flowing filament of biologically productive water. Strikingly different particle classes dominated the carbon fluxes during successive stages of the filament evolution over 30 d. Both flux and transfer efficiency were far greater than expected, suggesting an outsized filament impact in California waters.
Matthieu Roy-Barman, Lorna Foliot, Eric Douville, Nathalie Leblond, Fréderic Gazeau, Matthieu Bressac, Thibaut Wagener, Céline Ridame, Karine Desboeufs, and Cécile Guieu
Biogeosciences, 18, 2663–2678, https://doi.org/10.5194/bg-18-2663-2021, https://doi.org/10.5194/bg-18-2663-2021, 2021
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The release of insoluble elements such as aluminum (Al), iron (Fe), rare earth elements (REEs), thorium (Th) and protactinium (Pa) when Saharan dust falls over the Mediterranean Sea was studied during tank experiments under present and future climate conditions. Each element exhibited different dissolution kinetics and dissolution fractions (always lower than a few percent). Changes in temperature and/or pH under greenhouse conditions lead to a lower Th release and a higher light REE release.
Stéphanie H. M. Jacquet, Dominique Lefèvre, Christian Tamburini, Marc Garel, Frédéric A. C. Le Moigne, Nagib Bhairy, and Sophie Guasco
Biogeosciences, 18, 2205–2212, https://doi.org/10.5194/bg-18-2205-2021, https://doi.org/10.5194/bg-18-2205-2021, 2021
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We present new data concerning the relation between biogenic barium (Baxs, a tracer of carbon remineralization at mesopelagic depths), O2 consumption and prokaryotic heterotrophic production (PHP) in the Mediterranean Sea. The purpose of this paper is to improve our understanding of the relation between Baxs, PHP and O2 and to test the validity of the Dehairs transfer function in the Mediterranean Sea. This relation has never been tested in the Mediterranean Sea.
Natacha Le Grix, Jakob Zscheischler, Charlotte Laufkötter, Cecile S. Rousseaux, and Thomas L. Frölicher
Biogeosciences, 18, 2119–2137, https://doi.org/10.5194/bg-18-2119-2021, https://doi.org/10.5194/bg-18-2119-2021, 2021
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Marine ecosystems could suffer severe damage from the co-occurrence of a marine heat wave with extremely low chlorophyll concentration. Here, we provide a first assessment of compound marine heat wave and
low-chlorophyll events in the global ocean from 1998 to 2018. We reveal hotspots of these compound events in the equatorial Pacific and in the Arabian Sea and show that they mostly occur in summer at high latitudes and their frequency is modulated by large-scale modes of climate variability.
Christopher Holder and Anand Gnanadesikan
Biogeosciences, 18, 1941–1970, https://doi.org/10.5194/bg-18-1941-2021, https://doi.org/10.5194/bg-18-1941-2021, 2021
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A challenge for marine ecologists in studying phytoplankton is linking small-scale relationships found in a lab to broader relationships observed on large scales in the environment. We investigated whether machine learning (ML) could help connect these small- and large-scale relationships. ML was able to provide qualitative information about the small-scale processes from large-scale information. This method could help identify important relationships from observations in future research.
Paul J. Tréguer, Jill N. Sutton, Mark Brzezinski, Matthew A. Charette, Timothy Devries, Stephanie Dutkiewicz, Claudia Ehlert, Jon Hawkings, Aude Leynaert, Su Mei Liu, Natalia Llopis Monferrer, María López-Acosta, Manuel Maldonado, Shaily Rahman, Lihua Ran, and Olivier Rouxel
Biogeosciences, 18, 1269–1289, https://doi.org/10.5194/bg-18-1269-2021, https://doi.org/10.5194/bg-18-1269-2021, 2021
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Silicon is the second most abundant element of the Earth's crust. In this review, we show that silicon inputs and outputs, to and from the world ocean, are 57 % and 37 % higher, respectively, than previous estimates. These changes are significant, modifying factors such as the geochemical residence time of silicon, which is now about 8000 years and 2 times faster than previously assumed. We also update the total biogenic silica pelagic production and provide an estimate for sponge production.
Caroline Ulses, Claude Estournel, Marine Fourrier, Laurent Coppola, Fayçal Kessouri, Dominique Lefèvre, and Patrick Marsaleix
Biogeosciences, 18, 937–960, https://doi.org/10.5194/bg-18-937-2021, https://doi.org/10.5194/bg-18-937-2021, 2021
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We analyse the seasonal cycle of O2 and estimate an annual O2 budget in the north-western Mediterranean deep-convection region, using a numerical model. We show that this region acts as a large sink of atmospheric O2 and as a major source of O2 for the western Mediterranean Sea. The decrease in the deep convection intensity predicted in recent projections may have important consequences on the overall uptake of O2 in the Mediterranean Sea and on the O2 exchanges with the Atlantic Ocean.
Fuminori Hashihama, Hiroaki Saito, Taketoshi Kodama, Saori Yasui-Tamura, Jota Kanda, Iwao Tanita, Hiroshi Ogawa, E. Malcolm S. Woodward, Philip W. Boyd, and Ken Furuya
Biogeosciences, 18, 897–915, https://doi.org/10.5194/bg-18-897-2021, https://doi.org/10.5194/bg-18-897-2021, 2021
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We investigated the nutrient assimilation characteristics of deep-water-induced phytoplankton blooms across the subtropical North and South Pacific Ocean. Nutrient drawdown ratios of dissolved inorganic nitrogen to phosphate were anomalously low in the western North Pacific, likely due to the high phosphate uptake capability of low-phosphate-adapted phytoplankton. The anomalous phosphate uptake might influence the maintenance of chronic phosphate depletion in the western North Pacific.
Florian Ricour, Arthur Capet, Fabrizio D'Ortenzio, Bruno Delille, and Marilaure Grégoire
Biogeosciences, 18, 755–774, https://doi.org/10.5194/bg-18-755-2021, https://doi.org/10.5194/bg-18-755-2021, 2021
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This paper addresses the phenology of the deep chlorophyll maximum (DCM) in the Black Sea (BS). We show that the DCM forms in March at a density level set by the winter mixed layer. It maintains this location until June, suggesting an influence of the DCM on light and nutrient profiles rather than mere adaptation to external factors. In summer, the DCM concentrates ~55 % of the chlorophyll in a 10 m layer at ~35 m depth and should be considered a major feature of the BS phytoplankton dynamics.
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Short summary
In the marine environment, sticky sugar-containing gels, termed transparent exopolymeric particles (TEP), are produced from biological sources and physical and chemical processes. These compounds are essential vectors enhancing downward flow of organic matter and its storage at depth. Spatial and temporal dynamics of TEPs were followed for 23 days during the VAHINE mesocosm experiment that investigated the fate of nitrogen and carbon derived from organisms fixing atmospheric N2 (diazotrophs).
In the marine environment, sticky sugar-containing gels, termed transparent exopolymeric...
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