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4. List of contributors

Author

Al-Kandari, Manal, primary, Allen, Andrew E., additional, Alves-de-Souza, Catharina, additional, Baird, Mark, additional, Berges, John A., additional, Bodrossy, Levente, additional, Bolch, Christopher J.S., additional, Bowler, Chris, additional, Bracher, Astrid, additional, Brewin, Robert J.W., additional, Burford, Michele A., additional, Campbell, Lisa, additional, Ciotti, Aurea M., additional, Clément, Alejandro, additional, Clementson, Lesley A., additional, Correa, Nicole, additional, Countway, Peter D., additional, Coyne, Kathryn J., additional, Craw, Pascal, additional, Dutkiewicz, Stephanie, additional, Gaonkar, Chetan C., additional, Garczarek, Laurence, additional, Gérikas Ribeiro, Catherine, additional, Greenlee, Sydney M., additional, Gutiérrez-Rodríguez, Andres, additional, Harke, Matthew J., additional, Henrichs, Darren W., additional, Hickman, Anna, additional, Highfield, Andrea, additional, Hirata, Takafumi, additional, Hook, Sharon E., additional, Ibarbalz, Federico M., additional, Kolody, Bethany C., additional, Kostadinov, Tihomir S., additional, Krock, Bernd, additional, Lopes dos Santos, Adriana, additional, Marcus, Lara, additional, Mardones, Jorge I., additional, McGregor, Glenn B., additional, Mongin, Mathieu, additional, Mouw, Colleen B., additional, Nagai, Satoshi, additional, Neilan, Brett A., additional, Nodder, Scott D., additional, Ong, Denise, additional, Organelli, Emanuele, additional, Paredes-Mella, Javier, additional, Richardson, Anthony, additional, Schroeder, Declan, additional, Sendall, Barbara C., additional, Shi, Xiao Li, additional, Silva, Sebastian, additional, Skerratt, Jennifer, additional, Smith, Matthew C., additional, Soja-Wozniak, Monika, additional, Stern, Rowena, additional, Steven, Andrew D.L., additional, Taylor, Alison R., additional, Thamatrakoln, Kimberlee, additional, Vaulot, Daniel, additional, Vezzulli, Luigi, additional, Vincent, Flora, additional, Von Dassow, Peter, additional, Wang, Yanfei, additional, Wild-Allen, Karen, additional, Willis, Anusuya, additional, Wood, Susanna A., additional, Woodhouse, Jason N., additional, Yarimizu, Kyoko, additional, and Young, Erica B., additional

Published
2022
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9. Concepts Toward a Global Mechanistic Mapping of Ocean Carbon Export

Author

Laurenceau-cornec, Emmanuel C., Mongin, Mathieu, Trull, Thoams W., Bressac, Matthieu, Cavan, Emma L., Bach, Lennart T., Le Moigne, Frédéric A.c., Planchon, Frédéric, Boyd, Philip W., Laurenceau-cornec, Emmanuel C., Mongin, Mathieu, Trull, Thoams W., Bressac, Matthieu, Cavan, Emma L., Bach, Lennart T., Le Moigne, Frédéric A.c., Planchon, Frédéric, and Boyd, Philip W.

Abstract

The gravitational sinking of organic debris from ocean ecosystems is a dominant mechanism of the biological carbon pump (BCP) that regulates global climate. The fraction of primary production exported downward, the e-ratio, is an important but poorly constrained BCP metric. In mid- and high-latitude oceans, seasonal and local variations of sinking particle fluxes modulate strongly the e-ratio. These locally-specific e-ratio variations and their ecological foundations are here encapsulated in the term ‘export systems’ (ES). ES have been partly characterized for a few ocean locations, but remain largely ignored over most of ocean's surface. Here, in a fully conceptual approach and with the primary aim to understand rather than to estimate ocean carbon export, we combine biogeochemical (BGC) modeling with satellite observations to map ES at fine spatio-temporal scales. We identify four plausible ES with distinct e-ratio seasonalities across mid- and high-latitude oceans. The ES map confirms the outlines of traditional BGC provinces, and unveils new boundaries indicating where (and how) the annual relationship between carbon export and production changes markedly. At six sites where ES features can be partially inferred from in situ data, we test our approach and propose key ecological processes driving carbon export. In the light of our findings, a re-examination of 1,841 field-based e-ratios could challenge the conventional wisdom that e-ratios change strongly with latitude, suggesting a possible seasonal artefact caused by the timing of observations. By deciphering carbon export mechanistically, our conceptual ES map gives timely directions to emergent ocean robotic explorations of the BCP. Key Points A plausible mechanistic map of ocean carbon export is derived from spatio-temporal changes of the e-ratio in mid and high-latitude oceans The map unveils the possible distribution and boundaries of four main systems of export and explains their potential ecological driv

Published
2023
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12. Ecological Forecasting and Operational Information Systems Support Sustainable Ocean Management

Author

Sun, Chaojiao, primary, Hobday, Alistair J., additional, Condie, Scott A., additional, Baird, Mark E., additional, Eveson, J. Paige, additional, Hartog, Jason R., additional, Richardson, Anthony J., additional, Steven, Andrew D. L., additional, Wild-Allen, Karen, additional, Babcock, Russell C., additional, Yang, Dezhou, additional, Yu, Rencheng, additional, and Mongin, Mathieu, additional

Published
2022
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18. CSIRO Environmental Modelling Suite (EMS): Scientific description of the optical and biogeochemical models (vB3p0)

Author

Baird, Mark, Wild-Allen, Karen, Parslow, John, Mongin, Mathieu, Robson, Barbara, Skerratt, Jennifer, Rizwi, Farhan, Soja-Wozniak, Monika, Jones, Emlyn, Herzfeld, Mike, Margvelashvili, Nugzar, Andrewartha, John, Langlais, Clothilde, Adams, Matthew, Cherukuru, Nagur, Gustafsson, Malin, Hadley, Scott, Ralph, Peter, Rosebrock, Uwe, Schroeder, Thomas, Laiolo, Leonardo, Harrison, Daniel, Steven, Andrew, Baird, Mark, Wild-Allen, Karen, Parslow, John, Mongin, Mathieu, Robson, Barbara, Skerratt, Jennifer, Rizwi, Farhan, Soja-Wozniak, Monika, Jones, Emlyn, Herzfeld, Mike, Margvelashvili, Nugzar, Andrewartha, John, Langlais, Clothilde, Adams, Matthew, Cherukuru, Nagur, Gustafsson, Malin, Hadley, Scott, Ralph, Peter, Rosebrock, Uwe, Schroeder, Thomas, Laiolo, Leonardo, Harrison, Daniel, and Steven, Andrew

Abstract

Since the mid-1990s, Australia's Commonwealth Science Industry and Research Organisation (CSIRO) has been developing a biogeochemical (BGC) model for coupling with a hydrodynamic and sediment model for application in estuaries, coastal waters and shelf seas. The suite of coupled models is referred to as the CSIRO Environmental Modelling Suite (EMS) and has been applied at tens of locations around the Australian continent. At a mature point in the BGC model's development, this paper presents a full mathematical description, as well as links to the freely available code and user guide. The mathematical description is structured into processes so that the details of new parameterisations can be easily identified, along with their derivation. In EMS, the underwater light field is simulated by a spectrally resolved optical model that calculates vertical light attenuation from the scattering and absorption of 20+ optically active constituents. The BGC model itself cycles carbon, nitrogen, phosphorous and oxygen through multiple phytoplankton, zooplankton, detritus and dissolved organic and inorganic forms in multiple water column and sediment layers. The water column is dynamically coupled to the sediment to resolve deposition, resuspension and benthic-pelagic biogeochemical fluxes. With a focus on shallow waters, the model also includes detailed representations of benthic plants such as seagrass, macroalgae and coral polyps. A second focus has been on, where possible, the use of geometric derivations of physical limits to constrain ecological rates. This geometric approach generally requires population-based rates to be derived from initially considering the size and shape of individuals. For example, zooplankton grazing considers encounter rates of one predator on a prey field based on summing relative motion of the predator with the prey individuals and the search area; chlorophyll synthesis includes a geom

Published
2020

20. CSIRO Environmental Modelling Suite (EMS): scientific description of the optical and biogeochemical models (vB3p0)

Author

Baird, Mark E., primary, Wild-Allen, Karen A., additional, Parslow, John, additional, Mongin, Mathieu, additional, Robson, Barbara, additional, Skerratt, Jennifer, additional, Rizwi, Farhan, additional, Soja-Woźniak, Monika, additional, Jones, Emlyn, additional, Herzfeld, Mike, additional, Margvelashvili, Nugzar, additional, Andrewartha, John, additional, Langlais, Clothilde, additional, Adams, Matthew P., additional, Cherukuru, Nagur, additional, Gustafsson, Malin, additional, Hadley, Scott, additional, Ralph, Peter J., additional, Rosebrock, Uwe, additional, Schroeder, Thomas, additional, Laiolo, Leonardo, additional, Harrison, Daniel, additional, and Steven, Andrew D. L., additional

Published
2020
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23. A mechanistic model of coral bleaching due to temperature-mediated light-driven reactive oxygen build-up in zooxanthellae

Author

Mongin, Mathieu, Bay, Line, Skerratt, Jennifer, Baird, Mark, Soja-Wozniak, Monika, Cantin, Neal, and Rizwi, Farhan

Subjects
bepress|Life Sciences, bepress|Life Sciences|Marine Biology, MarXiv|Life Sciences, MarXiv|Life Sciences|Marine Biology
Abstract

Mass coral bleaching has emerged in the 21st century as the greatest threat to the health of the world's reefs. A sophisticated process understanding of bleaching at the polyp scale has now been achieved through laboratory and field studies, but this knowledge is yet to be applied in mechanistic models of shelf-scale reef systems. In this study we develop a mechanistic model of the coral-symbiont relationship that considers temperature-mediated build-up of reactive oxygen species due to excess light, leading to zooxanthellae expulsion. The model explicitly represents the coral host biomass, as well as zooxanthellae biomass, intracellular pigment concentration, nutrient status, and the dynamics of reaction centres and the xanthophyll cycle. Photophysiological processes represented include photoadaptation, xanthophyll cycle dynamics, and reaction centre state transitions. The mechanistic model of the coral-symbiont relationship is incorporated into a $\sim$1 km resolution coupled hydrodynamic - biogeochemical model that encompasses the entire $\sim$2000 km length of the Great Barrier Reef. A simulation of the 2016 bleaching event shows the model is able to capture the broadscale features of the observed bleaching, but fails to capture bleaching on offshore reefs due to the model's grid being unable to resolve the bathymetry of shallow platforms surrounded by deep water. To further analyse the model behaviour, a $\sim$200 m resolution nested simulation of Davies Reef (18$^{\circ}$49'S, 147$^{\circ}$38'E) is undertaken. We use this nested model to demonstrate the depth gradient in zooxanthellae response to thermal stress. Finally, we discuss the uncertainties in the bleaching model, which lie primarily in quantifying the link between reactive oxygen build-up and the expulsion process. Through the mechanistic representation of environmental forcing, this model of coral bleaching applied in realistic environmental conditions has the potential to generate more detailed predictions than the presently-available satellite-based coral bleaching metrics, and can be used to evaluate proposed management strategies.

Published
2018

25. Supplementary material to "CSIRO Environmental Modelling Suite (EMS): Scientific description of the optical and biogeochemical models (vB3p0)"

Author

Baird, Mark E., primary, Wild-Allen, Karen A., additional, Parslow, John, additional, Mongin, Mathieu, additional, Robson, Barbara, additional, Skerratt, Jennifer, additional, Rizwi, Farhan, additional, Soja-Woznaik, Monika, additional, Jones, Emlyn, additional, Herzfeld, Mike, additional, Margvelashvili, Nugzar, additional, Andrewartha, John, additional, Langlais, Clothilde, additional, Adams, Matthew P., additional, Cherukuru, Nagur, additional, Gustafsson, Malin, additional, Hadley, Scott, additional, Ralph, Peter J., additional, Rosebrock, Uwe, additional, Schroeder, Thomas, additional, Laiolo, Leonardo, additional, Harrison, Daniel, additional, and Steven, Andrew D. L., additional

Published
2019
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26. CSIRO Environmental Modelling Suite (EMS): Scientific description of the optical and biogeochemical models (vB3p0)

Author

Baird, Mark E., primary, Wild-Allen, Karen A., additional, Parslow, John, additional, Mongin, Mathieu, additional, Robson, Barbara, additional, Skerratt, Jennifer, additional, Rizwi, Farhan, additional, Soja-Woznaik, Monika, additional, Jones, Emlyn, additional, Herzfeld, Mike, additional, Margvelashvili, Nugzar, additional, Andrewartha, John, additional, Langlais, Clothilde, additional, Adams, Matthew P., additional, Cherukuru, Nagur, additional, Gustafsson, Malin, additional, Hadley, Scott, additional, Ralph, Peter J., additional, Rosebrock, Uwe, additional, Schroeder, Thomas, additional, Laiolo, Leonardo, additional, Harrison, Daniel, additional, and Steven, Andrew D. L., additional

Published
2019
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28. Shifts in coralline algae, macroalgae, and coral juveniles in the Great Barrier Reef associated with present‐day ocean acidification.

Author

Smith, Joy N., Mongin, Mathieu, Thompson, Angus, Jonker, Michelle J., De'ath, Glenn, and Fabricius, Katharina E.

Subjects
*OCEAN acidification, *CORALLINE algae, *CORAL reef conservation, *CORAL bleaching, *CORAL reefs & islands, *REEFS, *CORALS, *WORLD Heritage Sites
Abstract

Seawater acidification from increasing CO2 is often enhanced in coastal waters due to elevated nutrients and sedimentation. Our understanding of the effects of ocean and coastal acidification on present‐day ecosystems is limited. Here we use data from three independent large‐scale reef monitoring programs to assess coral reef responses associated with changes in mean aragonite saturation state (Ωar) in the Great Barrier Reef World Heritage Area (GBR). Spatial declines in mean Ωar are associated with monotonic declines in crustose coralline algae (up to 3.1‐fold) and coral juvenile densities (1.3‐fold), while non‐calcifying macroalgae greatly increase (up to 3.2‐fold), additionally to their natural changes across and along the GBR. These three key groups of organisms are important proxies for coral reef health. Our data suggest a tipping point at Ωar 3.5–3.6 for these coral reef health indicators. Suspended sediments acted as an additive stressor. The latter suggests that effective water quality management to reduce suspended sediments might locally and temporarily reduce the pressure from ocean acidification on these organisms. [ABSTRACT FROM AUTHOR]

Published
2020
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31. Towards evidence-based parameter values and priors for aquatic ecosystem modelling

Author

Robson, Barbara J., primary, Arhonditsis, George B., additional, Baird, Mark E., additional, Brebion, Jerome, additional, Edwards, Kyle F., additional, Geoffroy, Leonie, additional, Hébert, Marie-Pier, additional, van Dongen-Vogels, Virginie, additional, Jones, Emlyn M., additional, Kruk, Carla, additional, Mongin, Mathieu, additional, Shimoda, Yuko, additional, Skerratt, Jennifer H., additional, Trevathan-Tackett, Stacey M., additional, Wild-Allen, Karen, additional, Kong, Xiangzhen, additional, and Steven, Andy, additional

Published
2018
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32. Integrated modelling to support decision-making for marine social-ecological systems in Australia

Author

Melbourne-thomas, Jessica, Constable, Andrew J., Fulton, Elizabeth A., Corney, Stuart P., Trebilco, Rowan, Hobday, Alistair J., Blanchard, Julia L., Boschetti, Fabio, Bustamante, Rodrigo H., Cropp, Roger, Everett, Jason D., Fleming, Aysha, Galton-fenzi, Ben, Goldsworthy, Simon D., Lenton, Andrew, Lara-lopez, Ana, Little, Rich, Marzloff, Martin, Matear, Richard, Mongin, Mathieu, Plaganyi, Eva, Proctor, Roger, Risbey, James S., Robson, Barbara J., Smith, David C., Sumner, Michael D., Van Putten, E. Ingrid, Melbourne-thomas, Jessica, Constable, Andrew J., Fulton, Elizabeth A., Corney, Stuart P., Trebilco, Rowan, Hobday, Alistair J., Blanchard, Julia L., Boschetti, Fabio, Bustamante, Rodrigo H., Cropp, Roger, Everett, Jason D., Fleming, Aysha, Galton-fenzi, Ben, Goldsworthy, Simon D., Lenton, Andrew, Lara-lopez, Ana, Little, Rich, Marzloff, Martin, Matear, Richard, Mongin, Mathieu, Plaganyi, Eva, Proctor, Roger, Risbey, James S., Robson, Barbara J., Smith, David C., Sumner, Michael D., and Van Putten, E. Ingrid

Abstract

Policy- and decision-makers require assessments of status and trends for marine species, habitats, and ecosystems to understand if human activities in the marine environment are sustainable, particularly in the face of global change. Central to many assessments are statistical and dynamical models of populations, communities, ecosystems, and their socioeconomic systems and management frameworks. The establishment of a national system that could facilitate the development of such model-based assessments has been identified as a priority for addressing management challenges for Australia's marine environment. Given that most assessments require cross-scale information, individual models cannot capture all of the spatial, temporal, biological, and socioeconomic scales that are typically needed. Coupling or integrating models across scales and domains can expand the scope for developing comprehensive and internally consistent, system-level assessments, including higher-level feedbacks in social-ecological systems. In this article, we summarize: (i) integrated modelling for marine systems currently being undertaken in Australia, (ii) methods used for integration and comparison of models, and (iii) improvements to facilitate further integration, particularly with respect to standards and specifications. We consider future needs for integrated modelling of marine social-ecological systems in Australia and provide a set of recommendations for priority focus areas in the development of a national approach to integrated modelling. These recommendations draw on-and have broader relevance for-international efforts around integrated modelling to inform decision-making for marine systems.

Published
2017
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33. Integrated modelling to support decision-making for marine social–ecological systems in Australia

Author

Melbourne-Thomas, Jessica, primary, Constable, Andrew J, additional, Fulton, Elizabeth A, additional, Corney, Stuart P, additional, Trebilco, Rowan, additional, Hobday, Alistair J, additional, Blanchard, Julia L, additional, Boschetti, Fabio, additional, Bustamante, Rodrigo H, additional, Cropp, Roger, additional, Everett, Jason D, additional, Fleming, Aysha, additional, Galton-Fenzi, Ben, additional, Goldsworthy, Simon D, additional, Lenton, Andrew, additional, Lara-Lopez, Ana, additional, Little, Rich, additional, Marzloff, Martin P, additional, Matear, Richard, additional, Mongin, Mathieu, additional, Plagányi, Eva, additional, Proctor, Roger, additional, Risbey, James S, additional, Robson, Barbara J, additional, Smith, David C, additional, Sumner, Michael D, additional, and van Putten, E Ingrid, additional

Published
2017
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35. Use of remote-sensing reflectance to constrain a data assimilating marine biogeochemical model of the Great Barrier Reef

Author

Jones, Emlyn M., primary, Baird, Mark E., additional, Mongin, Mathieu, additional, Parslow, John, additional, Skerratt, Jenny, additional, Lovell, Jenny, additional, Margvelashvili, Nugzar, additional, Matear, Richard J., additional, Wild-Allen, Karen, additional, Robson, Barbara, additional, Rizwi, Farhan, additional, Oke, Peter, additional, King, Edward, additional, Schroeder, Thomas, additional, Steven, Andy, additional, and Taylor, John, additional

Published
2016
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36. CSIRO Environmental Modelling Suite (EMS): Scientific description of the optical and biogeochemical models (vB3p0).

Author

Baird, Mark E., Wild-Allen, Karen A., Parslow, John, Mongin, Mathieu, Robson, Barbara, Skerratt, Jennifer, Rizwi, Farhan, Soja-Woznaik, Monika, Jones, Emlyn, Herzfeld, Mike, Margvelashvili, Nugzar, Andrewartha, John, Langlais, Clothilde, Adams, Matthew P., Cherukuru, Nagur, Gustafsson, Malin, Hadley, Scott, Ralph, Peter J., Rosebrock, Uwe, and Schroeder, Thomas

Subjects
BENTHIC plants, GEOMETRIC approach, CONTINENTAL shelf, TERRITORIAL waters, CHLOROPHYLL in water, SEDIMENTATION & deposition
Abstract

Since the mid 1990s, Australia's Commonwealth Science Industry and Research Organisation (CSIRO) has developed a biogeochemical (BGC) model for coupling with a hydrodynamic and sediment model for application in estuaries, coastal waters and shelf seas. The suite of coupled models is referred to as the CSIRO Environmental Modelling Suite (EMS) and has been applied at tens of locations around the Australian continent. At a mature point in the BGC model's development, this paper presents a full mathematical description, as well as links to the freely available code and User Guide. The mathematical description is structured into processes so that the details of new parameterisations can be easily identified, along with their derivation. The EMS BGC model cycles carbon, nitrogen, phosphorous and oxygen through multiple phytoplankton, zooplankton, detritus and dissolved organic and inorganic forms in multiple water column and sediment layers. The underwater light field is simulated by a spectrally-resolved optical model that includes the calculation of water-leaving reflectance for validation with remote sensing. The water column is dynamically coupled to the sediment to resolve deposition, resuspension and benthic-pelagic biogeochemical fluxes. With a focus on shallow waters, the model also includes particularly-detailed representations of benthic plants such as seagrass, macroalgae and coral polyps. A second focus has been on, where possible, the use of geometric derivations of physical limits to constrain ecological rates, which generally requires population-based rates to be derived from initially considering the size and shape of individuals. For example, zooplankton grazing considers encounter rates of one predator on a prey field based on summing relative motion of the predator with the prey individuals and the search area, chlorophyll synthesis includes a geometrically-derived self-shading term, and the bottom coverage of benthic plants is generically-related to their biomass using an exponential form derived from geometric arguments. This geometric approach has led to a more algebraically-complicated set of equations when compared to more empirical biogeochemical model formulations. But while being algebraically-complicated, the model has fewer unconstrained parameters and is therefore simpler to move between applications than it would otherwise be. The version of the biogeochemistry described here is implemented in the eReefs project that is delivering a near real time coupled hydrodynamic, sediment and biogeochemical simulation of the Great Barrier Reef, northeast Australia, and its formulation provides an example of the application of geometric reasoning in the formulation of aquatic ecological processes. [ABSTRACT FROM AUTHOR]

Published
2019
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37. Remote-sensing reflectance and true colour produced by a coupled hydrodynamic, optical, sediment, biogeochemical model of the Great Barrier Reef, Australia: Comparison with satellite data

Author

Baird, Mark E., primary, Cherukuru, Nagur, additional, Jones, Emlyn, additional, Margvelashvili, Nugzar, additional, Mongin, Mathieu, additional, Oubelkheir, Kadija, additional, Ralph, Peter J., additional, Rizwi, Farhan, additional, Robson, Barbara J., additional, Schroeder, Thomas, additional, Skerratt, Jennifer, additional, Steven, Andrew D.L., additional, and Wild-Allen, Karen A., additional

Published
2016
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38. A biophysical representation of seagrass growth for application in a complex shallow-water biogeochemical model

Author

Baird, Mark E., primary, Adams, Matthew P., additional, Babcock, Russell C., additional, Oubelkheir, Kadija, additional, Mongin, Mathieu, additional, Wild-Allen, Karen A., additional, Skerratt, Jennifer, additional, Robson, Barbara J., additional, Petrou, Katherina, additional, Ralph, Peter J., additional, O’Brien, Katherine R., additional, Carter, Alex B., additional, Jarvis, Jessie C., additional, and Rasheed, Michael A., additional

Published
2016
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40. The exposure of the Great Barrier Reef to ocean acidification

Author

Mongin, Mathieu, primary, Baird, Mark E., additional, Tilbrook, Bronte, additional, Matear, Richard J., additional, Lenton, Andrew, additional, Herzfeld, Mike, additional, Wild-Allen, Karen, additional, Skerratt, Jenny, additional, Margvelashvili, Nugzar, additional, Robson, Barbara J., additional, Duarte, Carlos M., additional, Gustafsson, Malin S. M., additional, Ralph, Peter J., additional, and Steven, Andrew D. L., additional

Published
2016
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42. Potential phytoplankton responses to iron and stratification changes in the Southern Ocean based on a flexible-composition phytoplankton model

Author

Mongin, Mathieu, Nelson, David, Pondaven, Philippe, Tréguer, Paul, Antarctic Climate and Ecosystems Cooperative Research Centre (ACE-CRC), College of Oceanography, Oregon State University (OSU), Laboratoire des Sciences de l'Environnement Marin (LEMAR) (LEMAR), Institut de Recherche pour le Développement (IRD)-Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Université de Brest (UBO)-Institut Universitaire Européen de la Mer (IUEM), Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS), and Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS)

Subjects
EXPORT PRODUCTION, LIGHT, FERTILIZATION, GROWTH, BLOOM, SI, ECOSYSTEM MODEL, BIOGEOCHEMISTRY, PACIFIC SECTOR, [SDU.STU.OC]Sciences of the Universe [physics]/Earth Sciences/Oceanography, PRIMARY PRODUCTIVITY
Abstract

International audience; Under present climatic conditions, primary production in the Southern Ocean is limited by a combination of grazing pressure, the light/mixing regime, and iron. The response of the ecosystem to a permanent increase of iron supply and/or changes in the mixing regime is analyzed with a flexible-composition phytoplankton model that includes C, N, Si, and Fe cycling. Limitation of phytoplankton growth by light and nutrients ( Si, N, and Fe) is treated through their effects on cellular elemental composition. The model is applied to the KERFIX time series in the subantarctic region. Two physical scenarios are considered, normal and reduced mixed layer depth, with four different aeolian inputs of Fe in each case ranging from 1 to 1000 times the estimated present input. These simulations suggest that Fe supply via dust and rain must be increased by more than a factor of 10 to produce significant changes. Increased Fe supply alone causes the bloom to occur later in the season ( summer rather than spring), and coupled with a decrease in the mixed layer depth it produces drastic changes in the bloom intensity while preserving its present temporal development. Seasonal interaction between light and Fe limitation plays a critical role in controlling the primary and export production. If aeolian Fe input is increased by a factor of 1000, and mixed layer depth is reduced at the same time, export of carbon increases by a factor of 3. Light limitation prevents complete drawdown of nitrate, even if Fe limitation is removed and mixed layer depth reduced. This sets an upper limit on the primary production that can be achieved under the present meteorological conditions in this sector of the Southern Ocean.

Published
2007

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