hiroshi kitazato (ifree, jamstec) (ifree, jamstec) motivation-1 (monitoring of material cycles at...
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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
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
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)
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
1 m-thick finely laminated black shale Intercalated in pelagic limestone Duration: 350-800 ky
(Arthur and Premoli-Silva, 1982; Ohkouchi et al., 1999)
Turon ian lim
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
• 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
ForaminifersForaminifers live inlive in
Both sulfur oxidizing bacteria and sequestered
chloroplast are housed in
cytoplasm as symbionts
Nitrogen oxidation from NH4+ to N2 under
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.
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
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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