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Laboratory location

Sugimoto Campus

Research Areas 【 display / non-display

Ecosystem modeling, Aquatic Ecosystem Engineering, Social Ecosystem

Research subject summary 【 display / non-display

  • Promoting research with the theme of establishing ecological-social systems harmonized with aquatic environment - industrial economy - social culture based on two viewpoints, i.e., (1) interdisciplinary research to create new discoveries and values and (2) practical research useful in policies, plans and projects, In interdisciplinary research, we are exploring the mechanism, estimation and prediction for the ecosystem functions and biodiversity in the hydrosphere. In practical research, developing a science-based communication platform that contributes to the formulation of policies, plans and projects aimed at preserving and utilizing hydrosphere environment / ecosystem.

Research Interests 【 display / non-display

Numerical modeling, facilitation, Ecosystem, Aquatic Environment, Climate change

Research Career 【 display / non-display

  • Research on conservation and utilization of coastal ecosystem and construction of environmentally harmonious social system

    (Collaboration in Organization) Project Year :


    Keyword in research subject:  hypoxia, tidal flat ecosystem, nutrients cycle, biodiversity, numerical modeling

  • Research on mitigation and application capability of aquatic ecosystems for climate change

    (Collaboration in Japan) Project Year :


    Keyword in research subject:  Blue carbon, Carbon cycle, Numerical model

Education summary 【 display / non-display

  • Mathematical science, Mathematical modeling, Environmental ecology, Aquatic ecosystem engineering, Complex system

Association Memberships 【 display / non-display

  • American Geophysical Union

  • Japan Society of Civil Engineers

  • Japan Society on Water Environment

  • The Physical Society of Japan

  • Advanced Marine Science and Technology Society

Committee Memberships 【 display / non-display

  • 2019.04

    Advanced Marine and Science Technology   Director

  • 2004

    International Marine Environmental Modeling Seminar 2004   Session Co Chair Person

  • 2002

    International Marine Environmental Modeling Seminar 2002   Session Chair Person

  • 2001.04

    Journal Reviewer   Reviewer

Awards & Honors 【 display / non-display

  • The Hotta Memorial Encouragement Award, the Advanced Marine Science and Technology Society


Current Career 【 display / non-display

  • Osaka City University   Graduate School of Engineering   Urban Engineering Course   Professor  

Career 【 display / non-display

  • 2019.04

    Osaka City University   Graduate School of Engineering   Head of the Center for Urban Socio-Ecological Systems (CUES)

  • 2016.04

    Osaka City University   Engineering   Professor

  • 2014

    Mizuho Info. and Res Institute   Management & IT Consulting Div.   Research Director

  • 2010

    Mizuho Information and Research Institute   Env. and Energy Div.1   Research Director

  • 2005

    Mizuho Info. & Res. Inst.   Env., Natural Resources and Energy Div.   Principal Researcher/Senior Researcher

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Graduate School 【 display / non-display


    Aoyama Gakuin University  Graduate School, Division of Science and Engineering  Physics 


Published Papers 【 display / non-display

  • Modeling the life cycle of four types of phytoplankton and their bloom mechanisms in a benthic–pelagic coupled ecosystem

    Akio Sohma, Riku Imada, Tetsuya Nishikawa, Hisashi Shibuki

    Ecological Modelling ( in press)  2022.03  [Refereed]


    Akio SOHMA, Hayato KONISHI, Shinji TODA, Ryota NAKURA, Hisashi SHIBUKI, Hirotada MOKI and Tomohiro KUWAE

    Journal of Japan Society of Civil Engineers, Series B2 (Coastal Engineering)  76 ( 2 ) I_961 - I_966 2020.07  [Refereed]


  • Ecosystem functions in urban coastal areas– Considering our vision by ecosystem modeling

    Japan Society for Impact Assessment, Impact Assessment  18 ( 1 ) 33 - 38 2020  [Invited]

    DOI CiNii


    SOHMA Akio, NAKAI Mizuki, KUBO Atsushi, KUWAE Tomohiro

    Japan Society of Civil Engineers, Journal of Japan Society of Civil Engineers, Ser. B2 (Coastal Engineering)  74 ( 2 ) I_1267 - I_1272 2018.10  [Refereed]

     View Summary

    &nbsp;The carbon capture and storage in the coastal shallow ecosystem is a hot topic because of its high potential. The release and uptake of atmospheric CO<sub>2</sub> at the air-sea boundary is an important element consisting the series of carbon capture and storage of the shallow waters. In this study, we applied an ecosystem model, EMAGIN_B.C., considering carbonate chemistry, food-web, and Carbon-Nutrients-Oxygen cycling in the benthic-pelagic coupled system to Tokyo Bay, and analyzed the dynamics of air-sea CO<sub>2</sub> flux and its factors especially focusing on the river mouth area. As the result of the model analysis, CO<sub>2</sub> was released from the ocean to air at the river mouth area on an annual average basis, although CO<sub>2</sub> was taken up at other areas in Tokyo Bay. In addition, the CO<sub>2</sub> release and CO<sub>2</sub> uptake are repeated in the period from the end of April to the end of November. The CO<sub>2</sub> absorption period is thought to be dominated by the consumption of DIC by photosynthesis, and the release period is thought to be dominated by consumption of total alkalinity by nitrification.

    DOI CiNii


    SOHMA Akio, HARUTA Takuro

    Japan Society of Civil Engineers, Journal of Japan Society of Civil Engineers, Ser. B2 (Coastal Engineering)  74 ( 2 ) I_1273 - I_1278 2018.10  [Refereed]

     View Summary

    &nbsp;Hypoxia has been improving throughout Tokyo Bay, however, there are still seriously hypoxic areas. In this study, we analyzed the secular change of dissolved oxygen (DO) and consumption mechanism of the sea-floor due to reduction of nutrients and COD inflow from the land from 1979 to 2009, using the benthic-pelagic coupled ecosystem model, EMAGIN-H.P. As a result, the model demonstrated that there were at least three types of areas: zone A, in which DO increases; zone B, in which DO turns from a decrease to an increase; and zone C, where DO decreases. In addition, reduction of nutrients and COD inflow leads to (1) decrease of reduced substances (Mn<sup>2+</sup>, Fe<sup>2+</sup>, S<sup>2-</sup>) and increase of benthic fauna due to improvement of hypoxia at zone A, (2) decrease of reduced substances due to DO increase and decrease of benthic fauna due to food shortage at zone C, and (3) increase of benthic fauna until 1994 with the improvement of hypoxia and then a decrease due to food shortage at zone B. These results show that the optimal amount of nutrients and COD inflow in view of both the increase of benthic fauna and the improvement of hypoxia differs from area to area.

    DOI CiNii

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Books etc 【 display / non-display

  • Blue Carbon in Shallow Coastal Ecosystems, Carbon Dynamics, Policy, and Implementation.,Chapter 11: "CO2 Uptake in the Shallow Coastal Ecosystems Affected by Anthropogenic Impacts."

    Tomohiro Kuwae, Jota Kanda, Atsushi Kubo, Fumiyuki Nakajima, Hiroshi Ogawa, Akio Sohma, Masahiro Suzumura (Part: Contributor )

    Springer  2018.09

  • "Estuaries: Classification, Ecology, and Human Impacts” , Chapter 10: Modeling an Estuarine Ecosystem: How Tidal Flats and Benthic Ecosystems Affect the Eutrophic Estuary

    Akio Sohma (Part: Single Work )

    Nova Science Publishers  2015.01

  • Ecosystem Modeling and its Application for Seagrass Beds

    Akio Sohma (Part: Single Work )

    Nova Science Publishers  2011.03

  • Water Purification, Chapter 2: "Paradigm Shift from a Clean Ocean to a Bountiful Ocean -An essential vision revealed by ecological modeling of tidal flats - central bay area coupling and benthic-pelagic ecosystem coupling -

    (Part: Single Work )

    Nova Science Publishers  2009.12

Conference Activities & Talks 【 display / non-display

  • Effects of benthic biochemical processes on air-sea CO2 flux

    Akio Sohma, Daichi Okada

    ECSA 58 - EMECS 13: Estuaries and coastal seas in the Anthropocene – Structure, functions, services and management conference   (Online)  2021.09 

     View Summary

    Shallow-coastal ecosystems (SCE) have the function of climate change mitigation (CCM). CO2 gas exchange between the atmosphere and the ocean (CO2 air-sea flux) is an important factor of CCM that constitutes a series of processes in which coastal ecosystems take up, secure, and store carbon from the atmospheric CO2. CO2 air-sea flux is governed by the partial pressure of CO2 (pCO2), and it fluctuates due to the biochemical production/consumption of dissolved inorganic carbon (DIC) and total alkalinity (TA). In SCE with high biological productivity, biochemical DIC and TA production/consumption are large in both pelagic and benthic systems, however, it is unclear how much they contribute to pCO2. The purpose of our study is to elucidate the dominant factors of biochemical processes on the CO2 air-sea flux from the viewpoint of the comprehensive carbon cycle in the pelagic-benthic coupled ecosystem. To achieve this purpose, we used the benthic-pelagic coupled ecosystem model (EMAGIN-B.C) describing (1) carbon secures associated with planktons/benthic faunas metabolism, (2) carbon storage through sedimentation/burial of carbon to the benthic system, (3) carbonate dynamics among pCO2, pH, DIC, and TA driven by biochemical processes. The model was applied to Tokyo bay, an urbanized SCE in Japan. As a result of analysis, if pelagic DIC biochemical production/consumption were eliminated, CO2 air-sea flux changes from the absorption of 5.5 mol/m2/yr to the emission of 10.1 mol/m2/yr in average, annually. If benthic TA biochemical production/consumption were eliminated, CO2 air-sea flux changed from the absorption of 5.5 mol/m2/yr to the emission of 7.3 mol/m2/yr. The main causes of the changes of pelagic DIC and benthic TA are DIC consumption by phytoplankton photosynthesis, and TA production by anoxic mineralization of benthic detritus respectively. These results suggest that DIC and TA dynamics both in the pelagic and benthic ecosystems strongly affects CO2 air-sea flux.

  • Ecosystem model study on the cause of oligotrophication in Harima-nada sea -the effect on nutrient concentration by rivers, bivalves and surrounding sea

    Momoko Annna Furukawa, Akio Sohma

    Water and Environment Technology Conference Online 2021  (Online)  2021.08  Japan Society on Water Environment

     View Summary

    The Harima-nada sea, a part of the Seto Inland Sea in Japan, has been suffering from the fishery damages, e. g.
    discoloration of Pyrophia yezonesis and decrease of ammodytes personatus. One cause is thought to be the decrease in
    dissolved inorganic nitrogen (DIN) over the past decades from the 1980s-2000s.
    The objective of this study is to clarify the key factor of the decrease in DIN from the perspective of nutrients cycle
    comprised of the benthic-pelagic ecosystem network. We used the benthic-pelagic ecosystem model, EMAGIN-L.P.,
    which analyzes the nutrients cycles driven by biogeochemical-physical processes and metabolisms of benthic faunas,
    zooplankton, and 4 types of phytoplankton. By this, we analyzed the effect of the decrease in DIN inflow from rivers and
    from the surrounding sea area, Osaka bay, and the decrease of bivalves from 1980 and 2000 on DIN in Harima-nada sea.
    From the analysis, the DIN decreases in the Harima-nada sea since the 1980s was affected by all of the above, However,
    most significantly affected by the decrease in DIN inflow from Osaka Bay. Further, the decrease in the number of bivalves
    did not cause only the decrease in DIN concentration, but also the increase in phytoplankton.

  • Effects of River Water Quality on Carbon Uptake, Capture and Storage in Mangrove and Seagrass Coupled Ecosystems

    Akihito Ryogoku, Akio Sohma


  • The Effect of Changes in the Amount of Inorganic Nitrogen Flowing in from Rivers and Osaka Bay and existing Bivalves on Oligotrophication in Harima-nada Sea

    Momoko Anna Furukawa, Akio Sohma


  • Influence of Marine Organisms' pH dependency on Carbon Uptake, Capture and Storage Functions

    Keishi Omachi, Akio Sohma


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Grant-in-Aid for Scientific Research 【 display / non-display

  • Development of a blue carbon ecosystem model to reveal carbon capture and storage function in urban shallow waters

    Grant-in-Aid for Scientific Research(C) Representative

    Project Year :


Other external funds procured 【 display / non-display

  • Research for Climate Change and Ecosystem Function

    System name: (Commissioned Project)  Representative

    Project Year :



Charge of on-campus class subject 【 display / non-display

  • Environmental ecology

    (2021) University, Special course

  • Geo Environmental Engineering

    (2021) University, Special course

  • Aquatic Ecology

    (2021) University, Special course

  • Hydrosphere ecosystem engineering

    (2021) Graduate school, Special course

  • Transport phenomena

    (2021) University, Special course

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Social Contribution 【 display / non-display

  • Connectedness between Numerical Modeling and Coastal Environmental Problems ~ History and Prospects ~

    Role : Lecturer

     Audience : Graduate students, Teachers, Researchesrs, General, Scientific organization, Company, Civic organization, Governmental agency 


    Sponsor, Organizer, Publisher : Committee on Hydroscience and Hydraulic Engineering, Coastal Engineering Committee, JSCE  Lecture Notes of the 54rd Summer Seminar on Hydraulic Engineering, 2018, Course B