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  • Investigation on Bio-Geo-Chemical cycles and sedimentary processes at sediment-water

    interface under Oxygen Depleted Environments:

    Dive cruise at Indian Margin of the Arabian Sea

    Hiroshi Kitazato (IFREE, JAMSTEC)

  • Motivation-1 (Monitoring of material cycles at

    continental margins)

  • Carbon burial at continental margins

    Seibold and Berger, 1996

  • Sagami BaySagami Bay ーlong-term monitoringー


    For the purpose to know For the purpose to know how both material transportation how both material transportation

    and carbon burial occur inand carbon burial occur in bathyalbathyal basin at basin at

    active continental margin,active continental margin, longlong--term monitoring term monitoring

    of carbon budget of carbon budget both water column and both water column and

    basin floor basin floor have long been have long been

    carrying out at Sagami Bay carrying out at Sagami Bay since 1991.since 1991.

  • Monitoring: @Ocean color satellite @Natural fluorescent light @Chlorophyll-a measurement @sinking flux by sediment-

    trap @CTD-CMS water sampler @Observation of benthic

    nepheloid layer at long-term deep-sea observatory off Hatsushima Island

    @collection of surface sediments with multiple corer

    @in situ monitoring and experiments with submersible / ROV / profiling lander systems

    Kitazato, H. ed., 2003, Prog. Oceanogr.

  • Transportation pathways of organic carbonTransportation pathways of organic carbon ーーexemplified from Sagami Bayexemplified from Sagami Bayーー


    Organic/inorganic matter artificial compounds

    DownslopeDownslope inputinput (terrestrial, coastal)(terrestrial, coastal)

    Vertical inputVertical input (pelagic)(pelagic)

    Marine organic matter clay


    Tokyo Bay Sagami Bay

    Kitazato H. ed., 2003 ProOce

  • Carbon BudgetCarbon Budget at Sagami Bayat Sagami Bay

    Sinking organic carbon has consumed at

    benthic food webs. However, many of them are

    accumulated in the sediment.

    Carbon burials into sediment are forced

    both with terrestrial input of organic / inorganic materials

    and shallow RPD level at SWI




    megabenthosmegabenthos ++


    Kitazato, 2003; Nomaki et al., submitted


    Burial in sediment Burial in sediment 100mgC/m100mgC/m22/day/day central Sagami Baycentral Sagami Bay:: 0.1Gt / ye/ ye

  • Material cyclesMaterial cycles and strata formationand strata formation

    atat active ocean marginsactive ocean margins

    When we discussWhen we discuss material cyclesmaterial cycles and and

    strata formation strata formation at oceans,at oceans,

    biobio--geogeo--chemical activities chemical activities at SWIat SWI give important give important boundary conditionsboundary conditions for these processesfor these processes. .

  • Monitoring of Monitoring of material cyclesmaterial cycles

    at sedimentat sediment--waterwater interfaceinterface



  • Motivation-2 (anoxic environment)

  • Oceanic Anoxia • When we have taken an overview the Earth’s

    environmental history since 4.6Ba, we easily recognize two distinct environmental settings. Earlier half of the Earth’s history is characterized by anoxic and/or euxinic environments, whereas the later is well ventilated oxic environment. During the anoxic Earth’s environments, there may exist both different biogeochemical cycles and depositional processes even in the ocean.

    • Both banded iron formation and black shales are typically formed as sediments during the anoxic marine environments. Because, microbial ecosystem which is mainly composed of eubacteria, archaea and protists, may sustain primary production and material cycles in the anoxic ocean.

  • Changes in redox boundary since 4.6 Ba

    Oceanic Anoxic Event(OAE)


    OO22 OO22OO22

    Falkowski et al., 2004



    Origin of Life


  • Changes in EarthChanges in Earth’’s interior, climate and biotic evolutions interior, climate and biotic evolution Since 150 MaSince 150 Ma

  • Target

    1 m-thick finely laminated black shale Intercalated in pelagic limestone Duration: 350-800 ky

    (Arthur and Premoli-Silva, 1982; Ohkouchi et al., 1999)

    Cen oma


    lime ston


    Turon ian lim

    eston e

    Oceanic Anoxic Event-2 Livello Bonarelli at C/T boundary (94 Ma)

  • Schematic oceanic environments during the OAE-2, mid-Cretaceous

    Ohkouchi et al., 2006

    Diazotrophic cyanobacteria Green sulfur bacteria

  • Modern Analogue

    • Investigation of analogous environment at modern oceans may be the most effective approach to understand for elucidating ancient anoxic marine environmental systems and also for understanding mechanisms of biotic evolution.

    • Black Sea, Red Sea, Northern Arabian Sea and California Border Land should be typical cases for oceanic dysoxic/anoxic environments.

  • Four probable origins for the creation of anoxic environments

    • Permanent ocean stratification covered with fresh water on sea surface cf. Black Sea, Japan Sea

    • High surface productivity under upwelling area cf. Arabian Sea, off Namibia

    • High input of terrestrial organic carbon cf. coastal anoxic environments

    • Permanent ocean stratification due to Megaplume or brine water inputs

    cf. Red Sea

  • Modified from Herrle, Tuebinger Mikropal. Mitteil., 2002

    Modern Anoxic Environments cf. Black Sea cf. Red Sea

    cf. Arabian Sea Coastal Anoxia

  • What kind of organisms does dwell in anoxic environments ?

    • Eubacteria, Archaea and Protista dwell in anoxic/euxinic environments.

    • Bacterial ecto- and endosymbiosis is commonly observed in anoxic protists. In particular, endosymbiosis may be important for thinking about evolution of eukaryotes.

  • Anoxic ciliates house Endosymbiotic Bacteria in cell

    Methane producing bacteria +hydrogenosome

    Fenchel and Finley, 1995

  • Bernhard, 2003

    ForaminifersForaminifers live inlive in

    euxiniceuxinic environmentenvironment

    Both sulfur oxidizing bacteria and sequestered

    diatom -originated

    chloroplast are housed in

    cytoplasm as symbionts

  • Nitrogen cycle

  • AnammoxAnammox

    Nitrogen oxidation from NH4+ to N2 under

    anoxic environment

    Kuypers et al., 2003

  • By courtesy of A. Gooday

  • Questions and Purpose

    • What kinds of sedimentary processes do take place at oxygen minimum zone and the surrounded environments? How do biogeochemical cycles exist at anoxic seas? What kinds of biotic activities do exist under oxygen depleted environments?

    • For the purpose to elucidate depositional processes and biogeochemical cycles at sediment-water interface (SWI) under oxygen depleted environment, we plan to carry out multidisciplinary research cruise at Indian sector of the Arabian Sea.

  • Research Tactics

  • In situ approaches

    In situ experiments In situ measurement, monitoring and


  • in situin situ feeding experimentsfeeding experiments

  • 1) Settle culture cores on the seafloor by ROV Hyper-dolphin.

    2) Introduce 13C-15N labeled food (Dunaliella, diatom, bacteria and glucose) on the seafloor into semi-closed culture devices.

    3) After injection of foods, recover culture devices after days of incubation.

    4) Cut sediment surface and sort living foraminifera from the sediments.

    Outline of in situ 13C-15N feeding experiments

    Bulk analyses → After decalcify tests,

    EA:TOC content IRMS:Carbon isotopic composition

    Lipid analyses → After extracting organic compounds,

    GC/MS:identification, quantification GC/C/MS: Carbon isotopic composition

    Permanent station 1450mPermanent station 1450m

  • Changes in seasonal assimilation of organic carbon Changes in seasonal assimilation of organic carbon by benthic foraminifers at SWIby benthic foraminifers at SWI

    Nomaki et al., 2005Most POC has been consumed for respiration

  • In situIn situ Measurements and Measurements and MonitoringMonitoring (O(O22, pH , pH ))

  • Laboratory observation Intertidal sediment with harpacticoid copepods

    and nematodes

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  • 2D2D--OO22 optode system for optode system for in situin situ observationobservation collaborative cruise with IFREE, JAMSTEC / Univ. Copenhagen collaborative cruise with IFREE, JAMSTEC / Univ. Copenhagen

    / MPI/ MPI--Bremen Bremen / Univ. / Univ. TTüübingenbingen (200


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