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

1991〜2006

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 inbathyalbathyal 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

Advection?

Organic/inorganic matterartificial compounds

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

Vertical inputVertical input(pelagic)(pelagic)

Marine organic matterclay

mgC/m2/day

Tokyo Bay Sagami Bay

Kitazato H. ed., 2003 ProOce

Carbon BudgetCarbon Budgetat 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 sedimentare forced

both with terrestrial inputof organic / inorganic materials

andshallow RPD level at SWI

RespirationRespiration

productioproductionn

depositiondeposition

megabenthosmegabenthos＋＋

advectionadvection

Kitazato, 2003; Nomaki et al., submitted

MeiobenthosMeiobenthos

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

Material cyclesMaterial cyclesand strata formationand strata formation

atatactive ocean marginsactive ocean margins

When we discussWhen we discussmaterial 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 conditionsfor these processesfor these processes. .

Monitoring of Monitoring of material cyclesmaterial cycles

at sedimentat sediment--waterwaterinterfaceinterface

炭素サイクル

Wada，2002

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 euxinicenvironments, whereas the later is well ventilated oxicenvironment. 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)

HH++

OO22 OO22OO22

Falkowski et al., 2004

Kitazato、2005

HH++

Origin of Life

HH++

Changes in EarthChanges in Earth’’s interior, climate and biotic evolutions interior, climate and biotic evolutionSince 150 MaSince 150 Ma

Target

1 m-thick finely laminated black shaleIntercalated in pelagic limestoneDuration: 350-800 ky

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

Cenomanian

limestone

Turonian limestone

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 cyanobacteriaGreen 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 areacf. Arabian Sea, off Namibia

• High input of terrestrial organic carboncf. coastal anoxic environments

• Permanent ocean stratification due to Megaplumeor brine water inputs

cf. Red Sea

Modified from Herrle, Tuebinger Mikropal. Mitteil., 2002

Modern Anoxic Environmentscf. 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 houseEndosymbioticBacteria in cell

Methane producing bacteria＋hydrogenosome

Fenchel and Finley, 1995

Bernhard, 2003

ForaminifersForaminiferslive inlive in

euxiniceuxinicenvironmentenvironment

Both sulfur oxidizing bacteria and sequestered

diatom-originated

chloroplast arehoused 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 experimentsIn situ measurement, monitoring and

observations

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 contentIRMS：Carbon isotopic composition

Lipid analyses → After extracting organic compounds,

GC/MS：identification, quantificationGC/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 observationIntertidal sediment with harpacticoid copepods

and nematodes

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

/ MPI/ MPI--Bremen Bremen / Univ. / Univ. TTüübingenbingen (2003)(2003)

ElinorElinor--typetypeLanderLander

CCD CCD cameracamera

LEDsLEDs

MirrorMirrorOptodeOptode filmfilm

FilterFilter

DichroicDichroicmirrormirror

LensLens

Time-lapse optode images obtained from NT06-05 cruisegive us more information about sediment dynamics and

behavioral ecology of micro-benthos dwelled in the deep-sea sediment

1 cm

Courtesy from Glud and Staahl

Bioirrigation by polychaete

Courtesy from Glud and Staahl

R/V YokosukaShinkai 6500

Target Area

• High productivity anoxic oceanenvironment at Arabian Sea: Indian continental margin close to Goa is a target field for dive cruise. Because Indian continental margin is known as the most oxygen-depleted OMZ at Arabian Sea.

Arabian Sea

Off Goa

Cowie, 2005

500900

15002000

3000

Cruise

@ Season: post monsoon period (October - November)

@ Ship/submersible: Yokosuka / Shinkai6500

@ Dives: 30 dives at five stations (500, 900, 1500, 2000, 3000m)

Dive plan

• 6 dives at one station• First dive: set profiling lander /

feeding devices / benthic chambers• Second~fifth dives: collecting cores,

benthic organisms and recover feeding devices → on board experiments

• Sixth dive: recover lander system

Connection to the International Program

• COMARGE Project, Census of Marine Life (CoML)

• IMBER ?