2019 Annual Meeting
The Oceanographic Society of Japan

19-F8: SCOR-GEOTRACES Joint Session

Biogeochemistry of trace elements and isotopes in the ocean- from GEOSECS to GEOTRACES

26 September 2019
TOYAMA INTERNATIONAL CONFERENCE CENTER

2019 Annual meeting, The Oceanographic Society of Japan

19-F8: SCOR-GEOTRACES Joint English Session

Biogeochemistry of trace elements and isotopes in the ocean~ from GEOSECS to GEOTRACES
Conveners: Jing Zhang, Hajime Obata, and Yuichiro Kumamoto
INTRODUCTION
This session includes 24 interdisciplinary talks related to GEOTRACES and
GEOSECS, and serves as a memorial to Wallace Broecker. Needless to say, the successof GEOTRACES today rests on the earlier success of GEOSECS. A few veterans of
GEOSECS and related successor programs including WOCE, CLIVAR, GO-SHIP,JGOFS, and SOLAS are represented as well.
GEOTRACES is one of the large-scale international research programs under
the auspices of SCOR, and began in 2005 as a succession program of GEOSECS that was
conducted in the 1970's. Today, nearly 40 countries are involved, performing cross-basin
sections, as well as many process studies in the global ocean, to clarify the role ofbiogeochemical cycles under on-going global environmental changes using traceelements and isotopes. Facing current rapid climate changes, it is essential to enhanceinterdisciplinary research and joint ocean surveys integrating physical, chemical, andbiological oceanography. Presentations cover a wide view of GEOTRACES and PaleoGEOTRACES topics in the international and regional oceans, as well as some in the
newly established international BioGeoSCAPES program.

19-F8: SCOR-GEOTRACES Joint Session

Biogeochemistry of trace elements and isotopes in the ocean- from GEOSECS to GEOTRACESOral26 September 2019, 9:00-12:00, 14:30-17:00

Oral26 September 2019,Oral26
9:00-12:00,
September
14:30-17:00
2019, 9:00-12:00, 14:30-17:00
9:00

INTRODUCTION

9:05

1.

WOCE – CLIVAR – GO-SHIP Masao FUKASAWA (Invited)

9:30

2.

Tidbits of JGOFS Chen Chen-Tung ARTHUR (Invited)

9:55

3.

Comparability of nutrients data and nutrients Certified Reference Materials: from GEOSECS- WOCE to GOSHIP/GEOTRACESMichio AOYAMA (Designated)

10:10

4.

Use of man-made geochemical transient tracers to oceanography in the past several decades (from GEOSECS
to GEOTRACES) (Designated)Yutaka W. WATANABE , Kenichi SASAKI

10:40

5.

Radiocarbon in the deep water and implications for large-scale circulation (Designated)
Yuichiro KUMAMOTO

10:55

6.

US GEOTRACES inception, strategy and outcomes (Invited)Mariko HATTA, Christopher I. MEASURES, Robert F. ANDERSON, William J. JENKINS

11:15

7.

Dissolved iron distribution in the subarctic Pacific - HNLC water formation and biogeochemical processes (Designated)Jun NISHIOKA, Hajime OBATA

11:30

8.

Distribution of lead isotopes in the North Pacific (Designated)Kazuhiro NORISUYE, Hajime OBATA, Toshitaka GAMO, Edward A. BOYLE

11:45

9.

Nickel and Copper Isotopes in Aerosols and Sinking Particles in the Northern South China Sea
Shotaro TAKANO, Yoshiki SOHRIN, Wen Hsuan LIAO, Tung-Yuan HO

Poster session (13:00-14:30)

14:30

10. Dissolved organic carbon (DOC) in the Indian Ocean
Masahito SHIGEMITSU, C. YOSHIKAWA, M. WAKITA, A. MURATA

14:45

11. Barium Isotope Geochemistry in a Large Estuarine System: the Pearl River Estuary, China (Invited)Zhimian CAO, Xinting RAO

15:05

12. Exploring marine biogeochemistry of molybdenum and tungsten
Makoto TSUJISAKA, Yuta FUJIWARA, Ayumi NAGAE, Yoshiki SOHRIN, Masafumi MURAYAMA, Gurumurthy G.
PUTTOJIRAO

15:20

13. Dissolved Nd isotope ratios along the GEOTRACES Eastern Pacific Zonal Transect (Invited)Chandranath BASAK, Yingzhe WU, Jesse M. MURATLI, Steven L. GOLDSTEIN, Brian A. HALEY, Leopoldo D.
PENA, Louise BOLGE

15:40

14. Tectonically induced formation of the semi-closed Japan Sea inferred from Nd isotopes (Designated)Keiji HORIKAWA, Yukiko KOZAKA, Yoshihiro ASAHARA, Hiroshi AMAKAWA, Yusuke OKAZAKI

16:10

15. Distribution and geochemical cycles of Pt in Ariake Sea, Japan
Asami S. MASHIO, Taiki TANIMURA, Hiroshi HASEGAWA, Teruya MAKI, Shigenobu TAKEDA, Hajime OBATA

16:25

16. Stimulated phosphorus utilization of microbes by zinc and iron addition in the western North PacificTamaha YAMAGUCHI, Kazutaka TAKAHASHI, Mitsuhide SATO, Ken FURUYA,

16:40

17. Global biogeography of giant viruses highlights their interplay with eukaryotic community
Hisashi ENDO, Yanze LI, Romain Blanc-MATHIEU, Hiroyuki OGARA

16:55

CLOSINGPoster26 September 2019, 13:00-14:30
P1. The change of material flux via SGD and its impact on coastal ocean
Saki KATAZAKAI, Jing ZHANG, Mai SUZUKI, Kazumi ASAI, Kota NOJIMA
P2. Transport of the upper Kuroshio Intermediate Water from northwestern Pacific to the Sea of Japan: using 137Cs as a tracer
Siteng J. ZHU, Jing ZHANG, Shota KAMBAYASHI, Takeshi MATSUNO, Eisuke TSUTSUMI, Shigenobu TAKEDA, Seiya NAGAO,
Mutsuo INOUE, Katsumi TAKAYAMA, Hiroshi OGAWA, Ichiro YASUDA
P3. Significance of Fukushima-derived radiocesium flux via river-estuary-coastal ocean system
Shota KAMBAYASHI, Jing ZHANG, Hisashi NARITA
P4. Atmospheric Nitrogen Deposition on The Sub-Tropic NWPO and Its Impact
Tadateru NOGUCHI, Jing ZHANG, Wenkai GUAN, Bingzhang CHEN, Meixun ZHAO, Yuanli ZHU, Joji ISHIZAKA, Takeshi
MATSUNO, Ichiro YASUDA
P5. Cu-binding organic ligands and dissolved organic matter in coastal waters
Wiwit1, Hajime OBATA, Kuo Hong WONG, Chia-Jung LU, Hiroshi OGAWA, Hideki FUKUDA, Shigenobu TAKEDA
P6. Factors affecting radiocesium concentration in sediment off Fukushima: Lateral transport of particles
S. OTOSAKA, T. SUZUKI, T. TSURUTA, T. MISONO, Y. MINO, T. ISHIMARU, J. KANDA, C. SUKIGARA, Y. ITO, N. M.
SUGIHARA, M.C. HONDA
P1. Applications of Radium Isotopes to Marine Flux Studies Guebuem KIM

19-F8-1

WOCE – CLIVAR – GO-SHIP○Masao Fukasawa1
1. JAMSTEC/NIPR
Keywords: Long Hydrography, World Ocean

1. Content
The history of Long Hydrographic Observation(LHO) is reviewed
2. Before WOCE
The history of LHO may be Meteor’s Expedition in
the Atlantic Ocean in 1932. An echo sounding wasintroduced firstly and seven zonal sections were
occupied, though interval of stations was so coarse. The
main purpose of the expedition was to know thestratification of seawater in the ocean. It is well known
that this expedition located Mid-Atlantic Ridge, North
Atlantic Deep Water, and Antarctic Bottom Water. Of
these findings, Antarctic Bottom Water had attracted
attentions of many chemical oceanographers to carry out
new program of Geochemical Ocean Sections Study(GEOSECS). GEOSECS expeditions were carried out
from 1972 to 1978 over the world ocean. The purpose of
GEOSECS was to investigate the thermohaline
circulation by measuring chemical tracers andradiotracers. So, the stations were lined up along
assumed pathway of NADW and AABW in each ocean.
GEOSECS succeeded to show schematic picture of
global thermohaline circulation as the first step of global
circulation study.
3. WOCE
After International Geophysical Year (IGY) from1957 to 1958, corresponding to the increasing sense ofcrisis for the climate change or Global Warming, World
Meteorological Organization (WMO) started World
Climate Program (WCP) in 1979. World Climate
Research Program (WCRP) was started in 1980 as a aubprogram of WCP sponsored by WMO and International
Council for Science (ICSU). IOC participated so late in
1993. Objectives of WCRP were to investigate thepredictability of climate and to promote scientificunderstandings of climate syste. World Ocean
Circulation Experiment (WOCE) was the stream III of
WCRP from 1990 to 2002 with proper objectives toknow ocean fluxes in the world ocean (1990-1998) andto develop a model for ocean data assimilation (1998 2002 AIMS phase). Former objective was the reason
why hydrographic lines were

set to form a “mesh” by land-to-land, surface tobottom sections. There are some special characteristics
of WOCE, e.g. 1. Essential Climate Variable (ECV)
which includes chemical and radio traces, wasintroduced as requirement to measure in hydrographic
program of WOCE (WHP). 2. International office wasestablished for each observational method (Data offices
and Data Accumulation Center for WHP, XBT, ADCPetc) to adjust observation plans of participating countries,
to prepare technical manuals of ECVs measurements in
UNESCO technical papers, to synthesis compiled data,
and to archive and open data within much shorter period
than before.
4.After WOCE
Data from WHP were quite “FAIR” supported by DOs
and DACs. Based on the “FAIR” characteristic of WHP,
World Ocean Atlas (WOA) of NOAA (USA) andeWOCE of Scripps Institution of Oceanography couldarchive “epoch-making” progress. After WOCE era, theframework of WHP was taken over by CRIVAR and
Carbon Hydrographic Program (CCHDP) incorporate
with Joint Global Flux Study (JGOFS). In 2007, CCHDP
was renewed as Global Ocean Ship-Based Hydrographic
Investigation Program (GO-SHIP) under Global Ocean
Observing System (GOOS) including biological study
so far with a unique objective to develop a strategy for asustained hydrography program.
5.Remark
There have been quite a few innovations in ocean
observation. Argo float is one of such innovations. Now,
Argo may be the most appropriate measuring platformof ocean monitoring. However, it should be noted herethat ship based hydrography continues to give alloceanographers unrestricted possibility to understandocean and seawater state INTERDISCIPLINARY withHIGHEST ACCURATE data which will be a historical
record of our ocean and the Earth19-F8-2

Tidbits of JGOFS○Chen Chen-Tung Arthur
Department of Oceanography, National Sun Yat-Sen University, Kaohsiung 80424
Former executive member of JGOFS SSC and former vice chair of IGBP SC
Keywords: JGOFS, SCOR, IGBP, Carbon cycle, climate change

1. Abstract
The oceans contain about 50 times as much CO2 as theatmosphere. As a result, even a two percent change inthe oceanic carbon budget would cause a 100% change
in the CO2 concentration in the atmosphere. Yet, in theearly eighties, marine geochemists and biologists wereconcerned that the physical transport model available atthe time would be inadequate to determine the role of theocean in the atmospheric carbon budget and hence theprediction of climate change. The Scientific Committeeof Oceanic Research (SCOR) took the problem into its
hands and initiated the Joint Global Ocean Flux Study(JGOFS) programme in 1987 to study the fluxes ofcarbon between the atmosphere and ocean, and within
the ocean interior. In 1989 JGOFS became one of theearly core projects of the International Geosphere
Biosphere Programme (IGBP).
The objectives of JGOFS were:• To determine and understand on a global scale theprocesses controlling the time-varying fluxes of carbon
and associated biogenic elements in the ocean, and toevaluate the related exchanges with the atmosphere, sea
floor and continental boundaries• To develop a capacity to predict on a global scale
the response to anthropogenic perturbations, inparticular those related to climate change.
As a result of these two projects as well as a global
network ofobservations temporal increases of oceanic CO2
concentration and inventory, but a decrease of pH, arequantified. JGOFS was completed in 2003 and left thefollowing legacy in the eyes of IGBP.

• The role of the Ocean Carbon Cycle in Global
Change. Fasham, Michael J.R. (Ed.) Springer Verlag,
Heidelberg, Germany, 2003, 297 pp. (A synthesis of
JGOFS science).
• The Changing Ocean Carbon Cycle: A midterm
synthesis of the Joint Global Ocean Flux Study. Hanson,
R.B., Ducklow, H.W. and Field, J.G. (eds). IGBP Book
Series No. 5. Cambridge University Press, UK, 2000,
520 pp.
• Ocean Biogeochemistry and global change, 2001.
IGBP Science no. 2 (A popular summary of JGOFS mainachievements).
In addition, before JGOFS the conventional wisdom
was that the continental margins are sources of CO2 tothe atmosphere. The late S. Tsunogai was among the firstto point out otherwise based on the study in the East
China Sea. To tackle the controversial problem JGOFS
teamed up with the Land Ocean Interactions in the
Coastal Zone project (LOICZ) of IGBP in 1994 to form
the JGOFS/LOICZ Task Team on Continental Margin
Studies. Partly due to the effort of the Task Team now
we know that outside of estuaries most continental
margins are actually sinks of CO2.

19-F8-3

Comparability of nutrients data and nutrients Certified
ReferenceMaterials: from GEOSECS- WOCE to GOSHIP/GEOTRACESMichio AOYAMARIGC, JAMSTEC and CRiED, Univ. of Tsukuba

Keywords:

words: Nutrients, CRM, WOCE, hydrography

1. Introduction
In seawater, nitrogen, phosphorus and silicon exist as
so-called nutrients e. g. nitrate, phosphate and silicate,and spatial distribution and temporal variation ofnutrients regulate the productivity of the ocean.
Therefore, nutrients had been measuring as an importantparameter of oceanography for long time. In addition,
because it is closely linked to the carbon cycle throughbiological activities such as photosynthesis andrespiration via the C: O: N: P stoichiometry, so-called
Redfield ratio, nutrients are also regarded as importantfrom the viewpoint of global warming and ocean
acidification. In addition, nutrients are also linked to theoxygen circulation through same C: O: N: P
stoichiometry as well as carbon cycle. Oxygen, likenutrients, is an essential part of life in the ocean, and not
only is it necessary for each of the organisms to live, butalso the circulation of the nutrients and carbons on theearth. The global nutrient data set GND13(http://www.godac.jamstec.go.jp/resource/data_catalo
g/GND13/GND13.zip), which was created based on the
nutrients data of which traceability and comparability
are ensured published by the author, may give us moreaccurate ocean general circulation pattern in deep layersof the Pacific Ocean. Therefore it is very important tokeep comparability and traceability of high quality
nutrients, carbonate system parameters and dissolved
oxygen data, those enable us to study changes andvariability of carbon, nutrients and dissolved oxygen and
C: O: N: P stoichiometry accurately.
2. History of effort to keep comparability andtraceability of nutrients concentration
GEOSECS was carried out 1972-1978 and preWOCE and WOCE era was late 1980s to 1990s. Nutrient
CRM was needed during the WOCE era but no one
could supply natural seawater base nutrients CRM while
IAPSO salinity standards and Dickson’s DIC standards
were available and had been working well at that time.

Inter laboratories comparison exercises of nutrientsmeasurements were carried out by ICES since 1965 until
1993, and WHPO encouraged participants of WOCE
cruises to participate the IC exercises to improvecomparability of nutrients data in the world instead ofusing CRMs. Some European laboratories also usedfresh deep sea water as tracking standard solution.
MRI/JMA, JMATEC and KANSO also started to
produce nutrients RM since 1993. Aoyama et al.
reported at the OSM2002 about new seawater basenutrient RM of which life is four years and have good
homogeneity, the number of bottles per lot was 300
bottles. Some guy told me that “I cannot believe”.
Although certification of the RM was not available in2002, we pointed out about the issue of who and how tocertify them. The IPCC 2007 reported, however, thatinability to study nutrient variability in the deep ocean isdue to lack of comparability of nutrients data (Bindoff etal., 2007). Aoyama at MRI started to use RM in cruises
conducted 2000s until now. Aoyama also organized IC
exercise since 2003 until 2012. Hereafter IOCCPJAMSTEC IC exercises were carried out 2014/15 and2017/18.
3, SCOR-JAMSTEC CRM, KANSO CRM and NMIJCRM
Now SCOR-JAMSTEC CRM, KANSO CRM and
NMIJ CRM are available and people can use CRMs
more globally in the cruises of GO-SHIP and
GEOTRACES. IOCCP encouraged the use of CRM fornutrients in 2017 (Tanhua et al., 2017). Recent IC results
indicated that comparability of nutrients data in ourworld becomes better especially for nitrate andphosphate, but we need to do more to improvecomparability for silicate. It is also important to have SI
traceability throughout carbon, nutrients and dissolved
oxygen.

19-F8-4

Use of man-made geochemical transient tracers tooceanography in the past several decades (from GEOSECS
to GEOTRACES)○Yutaka W. WATANABE1, Kenichi SASAKI2
1. Hokkaido Univ. , 2. JAMSTEC
Keywords: transient tracers, CFCs, SF6

1. Abstract
Time-dependent tracers are important tools to clarify
the ocean physical dynamics along with ocean
biogeochemical
cycles.
Especially,
man-madegeochemical transient tracers such as tritium (3H),
bomb-radiocarbon (bomb-14C), chlorofluorocarbons(CFCs) and sulfur hexafluoride (SF6) can allow us toelucidate the ocean physical and biogeochemical
dynamics on decadal time-scale.
In the 1970s, the Geochemical Ocean Section Study(GEOSECS) as the first global ocean survey for thethree-dimensional
distributionsofphysicalbiogeochemical properties was carried out.
GEOSECS used 3H and 14C as transiet tracers [Broecker
and Peng, 1982] although these data were sparse due totheir complicated measurements.
In the late-1980s, developing the analytical methodof CFCs in seawater [Bullister and Weiss, 1998] made it
possible to enforce the extensive ocean field survey tostudy detailed water movement s such as the World
Ocean Circulation Experiment (WOCE). Especially,using the CFCs data with their atmospheric time history
and solubilities could evaluate the apparent ages of watermass from when the water mass left the surface during
the past decades, bringing many collaborations withphysical and chemical oceanographers (Fig. 1).
However, due to the world-wide ban on the
production of CFCs in industrial countries, theatmospheric increasing rate of CFCs after the mid1990s
have been gradually decrease, so that it was almost
impossible to use CFCs dating techniques. To overcome
this problem, it is essential to use SF6 as a potential timedependent ocean tracer [Law et al., 1994]. Furthermore,
SF6 was focused by biological oceanography in the ironfertilization experiment [e.g., Tsuda et al., 2003], as a
tracer of iron-injected surface water mass.
Recently, these tracer observation data are used inorder to study the ocean carbon dynamics and to evaluate

the changes in ocean ventilation and circulation due toclimate change. We will introduce some examples using

CFCs and SF6 in our presentation.
Fig.1: The atmospheric time history of anthropogenic
geochemical transient tracers [Sarmiento and Gruber,
2006]
2. Reference
Broecker WS, Peng TH (1982). Tracers in the Sea.
Elgigio Press, New York.
Bullister JL, Weiss RF (1988). Determination of CCl3F
and CCl2F2 in seawater and air. Deep-Sea Res. 35: 839853.
Law CS, Watson AJ, Liddicoat MI (1994). Automatedvacuum of analysis of sulphur hexafluoride in seawater:
derivation of the atmospheric trend (1970-1993) andpotential as a transient racer. Mar. Chem. 48: 57-59.
Sarmiento JL, Gruber
N (2006). Ocean
Biogeochemical Dynamics. Princeton University Press,
New Jersey.
Tsuda A et al. (2003). A mesoscale iron enrichment in
the western subarctic Pacific induces a large centric
diatom bloom. Science 300: 958-961.

19-F8-5

Radiocarbon in the deep water and implications for largescale circulation
Yuichiro Kumamoto
Japan Agency for Marine-Earth Science and Technology
Keywords: radiocarbon, deep circulation, GEOSECS, WOCE

1. Introduction
The application of

the deep and abyssal ocean could be described by a
14

C (radiocarbon) for thevertical (1D) advection–diffusion equation.

oceanography is to date objects or to determine various

3. GEOSECS

process rates in the ocean. Atmospheric radiocarbon is

During the 1970s the Geochemical Ocean Sectionstransferred to the ocean primarily by air–sea gas(GEOSECS) program provided the first full waterexchange. Once in the ocean, radiocarbon is subject tocolumn global survey of the oceanic radiocarbon

the same physical, chemical, and biological processes

distribution. About 2200 data were obtained bythat affect total dissolved inorganic carbon (DIC). Thereradioactivity measurement. When the GEOSECS data

are two major sources, natural and bombproduced

became available, box models were again used toradiocarbon. Natural radiocarbon is produced by cosmic

estimate residence times and mass fluxes for the abyssal

ray and its production rate has been constant in a longocean. In this case, the model had only four boxes, one

time-scale. Bomb radiocarbon was produced mainly infor the deep region of each ocean. Results from thisthe late 1950s and early 1960s by nuclear weapon testing.

calculation gave mean replacement times of 510, 250,

In surface water, approximately shallower than 1000m,

275, and 85 years for the deep Pacific, Indian, Atlantic,

the distribution of natural radiocarbon has been masked

and Southern Ocean, respectively.

by the bomb radiocarbon. Here I review studies on large-

4. WOCEscale circulation in deep water by means of natural

In the World Ocean Circulation Experiment (WOCE)

radiocarbon in DIC (DI14C).

conducted in the world ocean in the 1990's, more than

2. Pre-GEOSECS

15,000 of seawater samples were collected at 785

Soon after the radiocarbon dating method wasstations and DI14C was measured using the accelerator

developed in the early 1950s, it was applied to seawatermass spectrometer, which can measure radiocarbon withsamples. During the 1950s and 1960s, most of thea sample amount of 1/1000 or less as compared to thatseawater samples were limited to the shallow layers

for the traditional radioactivity measurement. Aboutowing to the difficulty of deep water sampling. Just Afterseven times larger number of WOCE radiocarbon data

the first subsurface measurements of radiocarbon, one ofclearly show the deep path of the wellknown global

the primary applications has been the determination ofthermohaline circulation. As a result, the map of the

deep ocean ventilation rates. Most of these calculations

WOCE radiocarbon was used to assess ocean carbon

have used a box model. The first such estimates yielded

cycle models and it was found that many of them weremean residence times for the various deep and abyssal

inconsistent with the new databased metrics of deep andocean basins of 350–900 years. A solution of theseabyssal radiocarbon. In addition, the WOCE radiocarbon

models generally assumes a steadystate circulation,

revealed that an observed 14C-age, which is the time

identifiable source water regions with known DI14C, noelapsed, is dominated by two equally important

mixing between water masses, and no significant

components, an elapsed time since a body of water has

biological sources or sinks. Another early approach

been in contact with the atmosphere and with aassumed that the vertical distribution of radiocarbon in“preformed 14C-age

19-F8-6

US GEOTRACES inception, strategy and outcomes○Mariko Hatta1, Christopher I. Measures1, Robert F. Anderson2,
William J. Jenkins3
1. University of Hawaii, USA, 2. Lamont-Doherty Earth Observatory of Colombia
University, USA. 3, Woods Hole Oceanographic Institution, USA.
Keywords: US GEOTRACES, strategy, trace elements, iron

1. Abstract
The assembly of vertical profiles of a large number oftrace elements determined in the North Pacific Ocean by
Nozaki (2001) depicted visually the variety of ways inwhich these elements interact with, and thus trace,
oceanographic processes. However, those profiles had
been collected individually. There had been no large
chemistry focused coordinated section program since
GEOSECS in the 1970’s. It was the need for such a
program that brought Catherine Jeandel and RobertAnderson together at a JGOFS meeting in Bergen
Norway in April 2000. They were concerned about theslow rate of progress of trace elements and isotopes(TEIs) research and the necessity to build a large
program such as "GEOSECS for TEIs" to capitalize on
the tremendous advances that had been made in both
sampling technology and analytical methodology,
therefore it seemed like an appropriate time to launch a
new initiative.
Six marine geochemists, Gideon
Henderson (UK), Martin Frank (Germany), Roger
Francois (Canada), Mukul Sharma (USA), Catherine(France) and Robert (USA) initiated the first
GEOTRACES meeting (it gained that name later) at a
special “Town Hall” at the 2001 Fall AGU.
Encouraged by the enthusiastic turnout for this event, theorganizers submitted a proposal for a planning workshop
to the US National Science Foundation. This in turnled to the first open science workshop held in Toulouse,
France (April 2003). Subsequently individual countries
formed their own national groups that held planningmeetings to raise interest, define goals, and provide
volunteers for a 30 person group representing 12
countries that wrote the Science Plan that was approvedby the International GeosphereBiosphere Programme
and published in 2006. The first International Scientific
Steering Committee, convened by SCOR, met for firsttime in Fall 2006 in San Francisco and organized theocean basin planning workshops. The first of theseworkshops was held in Hawaii in 2007 (Pacific), and thiswas followed by one in Oxford, UK (Atlantic) and Goa,
India (Indian). These workshops, which attracted
international participation, established basin priorities,
and proposed cruise tracks for each basin. The concept
was that individual
countries would then volunteer to occupy various
sections depending on national interests and logisticalconstraints.
The US GEOTRACES SSC prioritized their chosen
study regions based on several criteria: scientific interest
for TEIs, logistics (cost/length/risks), leaders, links with
CLIVAR and other country’s plans. The US has now
completed 4 basin-scale cruise tracks (North Atlantic
zonal transect, Eastern Pacific zonal transect EPZT,
Arctic Ocean, and North Pacific Meridional Transect).
An example of the value that the program has brought
to understanding of biogeochemical cycles is during the
Sept 2018 PMT GP15 cruise, where large water column
anomalies of helium isotopes and iron (Fe)concentrations were found at intermediate depths above
Loihi Seamount. The observation of the export ofthese anomalies as far as 1000 km along the 152° W
transect provides an insight into the significance ofhydrothermal Fe input at intermediate depths in theocean. Furthermore numerical dye-release modelingpredicts that this flux supplies Fe to the dominant
upwelling signature off the west coast of N. America,
indicating that processes in the middle of the Pacific playa role in supplying this limiting micronutrient.
To date the US GEOTRACES program has funded 79
Principal
Investigators(PIs).
Eachtransectaccommodated about 40 PIs, many postdocs andstudents, resulting in 235 publications and 27
dissertations, with more to come.

19-F8-7

Dissolved iron distribution in the subarctic Pacific- HNLC water formation and biogeochemical processes      ○Jun Nishioka1, Hajime Obata2
1. Institute of Low Temperature Science, Hokkaido University
2. Atmosphere and Ocean Research Institute, The University of Tokyo
Keywords: subarctic Pacific, iron, HNLC, biogeochemical processes

1. Introduction
It is well known that phytoplankton growth is broadly
limited by iron (Fe) availability in the subarctic Pacific.
To investigate which Fe sources control the amplitude ofseasonal variation in biogeochemical parameters in thesubarctic Pacific, we examined the spatial variation in
the west-to-east distribution of dissolved Fe (DFe)across the western and eastern subarctic Pacific throughthe Japanese GEOTRACES program.
2. Methods
The KH-12-4 and KH17-3 cruises of R/V Hakuhomaru
made zonal vertical section observations from west toeast across the subarctic Pacific (around 47°N; GP 02)
from August to October 2012 and June to August 2017.
To obtain the full depth vertical profiles of DFe, we
conducted sampling and sub-sampling in accordancewith the GEOTRACES protocol. Hydrographic data andseawater samples were collected using a clean CTDcarousel multiple sampler system, on which 24 acidcleaned Teflon-coated 12-L Niskin-X bottles were
mounted. We connected a 0.2 µm Acropak filter (Pall
Corporation) to the Niskin-X spigot, then, the filtrate
was collected in acid-cleaned 125-mL LDPE bottles(Nalgene Co., Ltd). The filtrate (<0.2 µm) was adjusted
to pH < 2 by the addition of ultrapure HCl and thenallowed to stand for approximately 24 h at room
temperature. It was then adjusted to pH 3.2 just before
the sample measurements. Then, DFe was analyzed
onboard by using a flowinjection analysis (FIA)chemiluminescence detection system (Obata et al. 1993,1997). All sample treatments were performed underlaminar flow in the onboard clean-air laboratory.
3. Results and Discussion
The vertical section profile of the western subarctic
Pacific gyre showed high dissolved Fe concentrations

from the bottom of the surface mixed layer to as deep asapproximately 3000 m, suggesting that Fe-richintermediate water is transported laterally anddistributed across the western subarctic gyre, over2000 km. The section data also indicate that the
influence of the western Fe-rich intermediate water does
not reach the Alaskan gyre. The profiles of DFe reflect
the influence of Fe supplied from several potential
external sources (external Fe), such as atmospheric Fe
and laterally transported Fe, along with internallyrecycled Fe (internal Fe), such as remineralization andrelease of Fe from organic particles settling in the watercolumn. Therefore, to understand the controlling sourcesof Fe in the subarctic Pacific, it is necessary to evaluate
both external and internal Fe sources. We used the Fe*concept for quantitative evaluation of the spatial patternof the contributions of internal and external DFe in asection profile.
Fe* = external DFe = [DFe] (observed) – [PO4] (observed) ×
RFe:P
The Fe* index distribution clearly indicates that thewestern Fe-rich intermediate water is well explained byexternal sedimentary Fe sources and water transportsystems from a subpolar marginal sea, the Sea of
Okhotsk, and the continental margin. The spatial patternof Fe to nutrient stoichiometry supplied from theintermediate water to the surface, in comparison with
reported Fe and nutrient demand in surface
phytoplankton, quantitatively explains the differences insurface macronutrient consumption between the westernand eastern gyre as well as the formation of the highnutrient and low chlorophyll region in the wholesubarctic Pacific.

Distribution of lead isotopes in the North Pacific19-F8-8○Kazuhiro Norisuye 1,Hajime Obata2,Toshitaka Gamo2,Edward A. Boyle 3
1. Faculty of Science, Niigata University, 2.Atmosphere and Ocean Research Institute,
the University of Tokyo, 3. Massachusetts Institute of Technology
Keywords: Lead isotopes, GEOTRACES, Pacific Ocean, biogeochemical cycles
1. Purpose

cartridge filter, transferred to HDPE bottles and acidified

Humans have been injecting lead (Pb) to the marinewith ultra-high purity HCl after the sampling. The

environment through mining, smelting, burning of fossil

samples were brought to our laboratory and chemical

fuels and consumption of leaded gasoline for more thanseparation was carried out: briefly, acetic acid/acetatea century (Boyle et al., 2014). Anthropogenic Pb

buffer solution was added to 400 g of the acidified

overwhelms that of natural origin in the modern ocean.

seawater samples. The sample solution of pH 4.75 was

Pb globally dispersed as such is a tracer forpassed through a chelating resin column (NOBIAS

anthropogenic contaminants in the ocean and assigned

CHELATE PA-1F, Hitachi-High Technologies, Japan) to

as a key parameter in the ongoing international

preconcentrate and separate Pb from interfering

GEOTRACES program. Ratios of four isotopes (
206

204

Pb,

elements. After the elution of Pb with nitric acid solution,Pb, 207Pb, 208Pb) are especially useful in characterizing

secondary column procedure was carried out to attainanthropogenic

mutualcomplete removal of the interfering heavy metals andtransformation of Pb isotopes between particulate andsourcesandinvestigating

almost quantitative recovery of Pb isotopes. The final

dissolved forms (Sherrell et al., 1992). Pb isotope ratios

solution was evaporated to dryness, Pb in the residual

display characteristic values in mode water masses (Leewas redissolved with dilute nitric acid and Tl standard

et al., 2015), which play an important role in heatsolution was spiked to the solution (NIST 997 with atransfer between surface ocean and lower atmosphere.

certified 205Tl/203Tl ratio of 2.3871). Pb isotope ratios in

Pb isotopes in the Atlantic and Indian Oceans have been

the final solution were measured with Neptune multi-

investigated (Echegoyen et al., 2014; Noble et al., 2015),

collector ICPMS. Reliability of our method was verified

while knowledge of Pb isotopes in the deep Pacific isusing intercalibration samples.

sparse partly because analysis is difficult for Pacific deep
waters with high silicate contents (Boyle et al., 2012).

3. Results and discussion

We have been developing a new method for

The concentration of Pb in the North Pacific ispreconcentration and separation of Pb isotopes to obtaingenerally high in subsurface water and decreases with

distributions of Pb and Pb isotope ratios in the vast area

depth, comparable to previous results in the Northof the North Pacific. In this presentation, we will

Pacific (Wu et al., 2010; Zheng et al., 2019). 206Pb/207Pb

describe the distribution of Pb isotope ratios in the North

isotope ratios increase with depth and are lower than the

Pacific determined by the method.

values for hemipelagic sediments (206Pb/207Pb = 1.2117,
Jones et al., 2000) due to the dominant anthropogenic

2. Method

influence on the water column, consistent with theWater samples were collected during the R/V Hakuho-

previous study (Zurbrick et al., 2017). We will discuss

Maru KH-12-4 cruise and R/V Shinsei-Maru KS-13-T3

regional difference of Pb isotope ratios between thecruise using a CTD carousel multi-sampling system andwestern, central and eastern North Pacific and compare

Niskin-X samplers. Samples were filtered through a 0.2

our dataset with coral time series data (Inoue andµm AcroPak

Tanimizu, 2008).

19-F8-9

Nickel and Copper Isotopes in Aerosols and Sinking
Particles in the Northern South China Sea○Shotaro Takano1, Yoshiki Sohrin1, Wen Hsuan Liao2, Tung-Yuan Ho2
1. Institute for Chemical Research, Kyoto University
2. Research Center for Environmental Changes, Academia Sinica
Keywords: source identification, aerosols, biogenic particles

1. Introduction
Nickel and Copper are bio-essential trace metals in theocean. The oceanic cycle of Ni and Cu is controlled bybiogeochemical processes. Sinking particles play animportant role in biogeochemical cycling of trace metals
by transporting them from the surface to the deep ocean,and provide a direct information on the oceanic sink of
trace metals. Recent advances of mass spectrometers andchemical separation techniques have enabled us todetermine isotope ratios of trace metals in geochemical
samples. The isotope ratios of trace metals are powerfultools to identify sources and transformation processes.
Here, we present the isotope ratios of Ni and Cu in
sinking particles, aerosols, and seawater collected in the
Northern South China Sea.
2. Method
Sinking particle samples were collected from April
2014 to March 2015 at the SouthEast Asian Time-series
Study (SEATS) station located at 18.0°N, 116.0°E in the
Northern South China Sea. Seawater samples werecollected at the same station in October 2006. Aerosol
samples were collected from January to December 2011
at Dongsha Atoll, which is located at 20.7°N, 116.7°E
with a distance of 300 km from the SEATS station.
Isotope ratios of Ni and Cu in the seawater samples were
determined using a previously published method(Takano et al., 2017): Ni and Cu in the samples were preconcentrated and purified by chelating extraction andanion exchange, and their isotopic ratios were measured
using MC-ICPMS. For the analysis of Ni and Cu
isotopes in sinking particle and aerosol samples, we havemodified the previous method to remove Al, Fe, and Mn.
These elements are enriched in aerosols and sinking
particles. The isotope ratios of Ni and Cu are expressedin δ60Ni and δ65Cu as follows:δ60Ni=[(60Ni/58Ni)Sample/(60Ni/58Ni)NIST SRM 986−1]×1000
δ65Cu=[ 65Cu/ 63Cu)Sample/65Cu/63Cu)NIST SRM 976−1]×1000

3.

Results and Discussion
In the aerosol samples, δ60Ni is in a range from −0.08
to +0.56‰ and δ65Cu is in a range from −0.33 to +0.83‰.
These are largely different from those of lithogenic
materials, suggesting that Ni and Cu in the aerosols are
dominated by anthropogenic sources. In the sinking
particle samples, δ60Ni is in a range from +0.01 to+0.54 ‰ at a depth of 2000 m and from −0.18 to +0.54‰
at a depth of 3500 m. δ65Cu is in a range from +0.15 to+0.35‰ at a depth of 2000 m and from +0.01 to +0.35‰
at a depth of 3500 m. We estimate sources of Ni and Cu
in sinking particles based on a combination of theirisotope ratios and elemental ratios to Ti, Mn, and P. The
δ60Ni in the sinking particles is linearly correlated with
the P/Ni ratio, suggesting two sources for Ni in sinking
particles. One of the sources has low δ60Ni and P/Ni,
which is considered to be lithogenic particles supplied
via resuspension of marine sediments off the southwest
Taiwan. The other source has high δ60Ni and P/Ni. The
candidate for this source is biogenic particles, which
preferentially adsorb heavy Ni isotopes on their surface.
For Cu, δ65Cu and P/Cu in the sinking particles are
between those of marine sediments and labile fractionsof suspended particles. The previous study suggested
that Cu in the labile fractions is associated with organic
matter (Little et al., 2018). Therefore, Cu in sinking
particles is derived from resuspended marine sediments
and biogenic particles as well as Ni. The correlation
between Cu and P is weaker than that for Ni, suggesting
the Cu concentrations in biogenic particles are notconstant due to scavenging of Cu through the watercolumn.
References
Little, S.H. et al., 2018. Paired dissolved and particulate
phase Cu isotope distributions in the South Atlantic.
Chemical Geology. Takano, S. et al., 2017. A simple andrapid method for isotopic analysis of nickel, copper, andzinc in seawater using chelating extraction and anion
exchange. Analytica Chimica Acta, 967: 111

19-F8-10

Dissolved organic carbon (DOC) in the Indian Ocean○Masahito Shigemitsu1, C. Yoshikawa1, M. Wakita1, A. Murata1
1. JAMSTEC
Keywords: DOC, Indian Ocean, Indonesian throughflow

1. Introduction
In the meridional overturning circulation, theIndonesian throughflow (ITF) enters the Indian Ocean
from the Pacific and moves to the Atlantic, and thisinflow influences basin-scale biogeochemistry (Talley
and Sprintall, 2005).
Dissolved organic carbon (DOC) is the largest reservoir(~662 Pg C) of reduced carbon in the ocean (Hansell etal., 2009), and understanding the basin-scale behavior isimportant.
In this study, we aim to gain insights into the amountof DOC transported via the ITF from the Pacific to theIndian Oceans. To this end, we measure DOC
concentrations for the seawater samples obtained in arevisit cruise along the World Ocean Circulation
Experiment Hydrographic Programme (WHP) section
I10 between Indonesia and Australia (Figure). Then, we
estimate the velocity field across the I10 section using ageostrophic inverse box model. Finally, the DOC flux tothe Indian Ocean through the ITF is estimated, with thevelocity field and the DOC data.
2. Methods
We conducted a revisit cruise along the WHP section
I10 from December 2015 to January 2016. At eachstation, a CTD profile was obtained with temperature,salinity and pressure, and bottle sampling was also
carried out. Concentrations of DOC were measured byusing a Shimadzu TOC-L for the water samples, and therepeatability of DOC was ~1.0 µmol kg-1. In addition to
our data, we also used the data from the WHP section I5
conducted from March 2009 to May 2009 (Figure). The
data of temperature, salinity, pressure and DOC were
downloaded from the Carbon Hydrographic Data Office(CCHDO) website (http://cchdo.ucsd.edu/) .
In order to estimate the velocity fields
across the sections, the steady geostrophic box inversion
was considered:

where ρ(j,q) is the density in station pair j at depth
interval q, bj is the reference-level velocity, Δa(j,q) is thearea in depth interval q in station pair j, δj is the unit
normal (±1) for pair j forthe volume under consideration, and vR is the thermal
wind velocity. ρi, wi , and Ai are the density, pseudovertical velocity and corresponding horizontal area
across each isopycnal layer, respectively. ni is the noise,and FEj is the Ekman mass flux. The Ekman transport
was calculated from an average wind stress of
NCEP/NCAR reanalysis (Kalnay et al., 1996) over theperiod 1981 to 2010. All unknowns, bj , wi, and ni were
estimated by using the Gauss-Markov estimator(Wunsch, 1996).
3. Results
Along the section I10, DOC concentrations ranged
from ~38 µmol kg-1 in the deep waters to ~80µmol kg1 in the shallow waters.
Using the steady geostrophic box inversion, the ITF
was estimated at 12±8 Sv. With the measured DOC
concentrations and the estimated volume transport of
ITF, the DOC flux via the ITF was estimated at 573 ±223 kmol/s. In the presentation, we will discuss thesources and sinks of DOC associated with thebiogeochemical processes in the Indian Ocean.

19-F8-11

Barium Isotope Geochemistry in a Large Estuarine
System: the Pearl River Estuary, China○Zhimian Cao1, Xinting Rao1
1. State Key Laboratory of Marine Environmental Science, Xiamen University,
Xiamen, China
Keywords: stable barium isotopes, estuarine mixing, sediment pore-water, proxy

1. Abstract

generally showing a shift to lighter values from theBarium (Ba) is a widely used proxy in oceanography

topmost layer down to 15 cm depth, were observed infor tracing water mass mixing, river inputs, and

the PRE surface sediments. These gradients primarily

biologicaltheresults from Ba isotope fractionation caused by various

determination of stable Ba isotopic compositions

productivity.

Recentsuccessinsolution-solid phase interactions. Both formation ofprovides a novel tool to study the biogeochemical

authigenic barite and Ba precipitation associated withcycling of Ba and evaluate the reliability of the Ba proxy

the redox cycling of manganese preferentially remove

for reconstruction of paleosalinity and paleoproductivity.

light Ba isotopes from the pore-water. These processes

In this study, we present a new dataset of dissolved Ba

induce the heaviest δ138/134BaDBa (0.5-0.7‰) in the(DBa) isotopes (δ138/134BaDBa) in the water column andtopmostsediment pore-water from the upper reaches to the lower

significantly contribute to the bottom waters of the PRE

seaside of the Pearl River Estuary (PRE) in Southerncharacterized by lighter δ138/134BaDBa (0.1-0.3‰). This

China.

contrast suggests that Ba isotopes in sediments are

pore-water,which,

however,

does

not

DBa concentrations in the surface waters of the PRE

potentially a more robust proxy of paleosalinity than Ba

showed non-conservative distributions along salinity

concentrations because even considerable benthic fluxes

gradients in both summer (July 2015) and winterof Ba would not significantly influence the conservative(January 2017). A maximum concentration of DBa

δ138/134BaDBa-salinity relationship in the water column(DBamax) was observed in both seasons with values ofof estuaries. On the other hand, barite dissolution in

224.7 and 230.3 nmol kg-1 corresponding to salinities of

sulfate-depleted sediments and subsequent precipitation

2.3 and 4.9, respectively. AfterDBamax, DBaof authigenic barite most likely alter the original

concentrations decreased linearly with increasing

sedimentary Ba isotopic compositions, implying that in

138/134

salinity till the sea end. Surface δ

BaDBa signatures

overall increased from the river water (~0.20‰) to theseawater endmember (~0.60‰), generally mirroring the
distribution of DBa concentrations. δ138/134BaDBa also
behaved conservatively against salinity after the DBamax,
suggesting that Ba isotopes are a potential new tracer of
paleosalinity in proximity to large river plumes. We
speculate that particle adsorption of Ba preferentiallyremoves lighter Ba isotopes, which results in relatively
low DBa concentrations and heavy δ138/134BaDBa
signatures for the river water endmember at zero salinityof the PRE.
In the winter season of January 2017, pronounced
depth-dependent variations of pore-water δ138/134BaDBa,

this case the Ba isotope proxy data need to be consideredwith caution.

19-F8-12

Exploring marine biogeochemistry of molybdenum
and tungsten
Makoto Tsujisaka1, Yuta Fujiwara1, Ayumi Nagae1, ○Yoshiki Sohrin1, Masafumi
Murayama2, Gurumurthy Gundiga Puttojirao3
1.Kyoto University, 2. Kochi University, 3. Birbal Sahni Institute of Paleoscience, India

Keywords: Stable isotopes, Biogeochemical cycle, Paleoceanography, GEOTRACESA Group 6 element molybdenum (Mo) form molybdate

applying this method to paleoceanographic study on

MoO42–and is conservatively distributed with amarine sediment cores that had been collected from theconcentration of ~107 nmol/kg in the oxic modern

Sea of Japan and the northeastern Arabian Sea. We will1

ocean . In sulfidic waters, MoO42– is transformed into

report the present status and overview of our study in thethiomolybdate MoOxS4–x2–, which is fixed in sulfidic

presentation.

2

sediments . Since the sulfide concentration causes alarge shift in the concentration and stable isotope ratio of

1 Nakagawa, Y. et al. The molybdenum isotopic

Mo in sediments, Mo has been extensively studied as acomposition of the modern ocean. Geochem. J. 46,

proxy for paleoceanography3,4.

131-141 (2012).

Tungsten (W) is located just below Mo on the periodic

2 Mohajerin, T. J. et al. Tungsten–molybdenum

table. Although W forms tungstate WO42– and isfractionation in estuarine environments. Geochim.

conservatively distributed in the oxic modern ocean as

Cosmochim. Acta 177, 105-119 (2016).

well as Mo, the concentration of W is as low as ~49

3 Anbar, A. D. & Rouxel, O. Metal stable isotopes inpmol/kg5,6. Since the transformation of WO42– into

paleoceanography. Annu. Rev. Earth Planet. Sci. 35,

thiotungstate WOxS4–x2– requires about a ten times

717-746 (2007).

2

higher concentration of sulfide than that for Mo , W andMoaresignificantly

fractionatedinmarineenvironments, such as hydrothermal systems

7

and4 Robbins, L. J. et al. Trace elements at the intersectionof marine biological and geochemical evolution.
Earth-Sci. Rev. 163, 323-348, (2016).

estuarine2. Thus, we expect that the Mo/W concentration

5 Firdaus, M. L. et al. Dissolved and labile particulate Zr,

ratio and the stable isotope ratio of W will be promising

Hf, Nb, Ta, Mo and W in the western North Pacificproxies for paleoceanography.

Ocean. J. Oceanogr. 64, 247-257, (2008).

To establish a reliable proxy in paleoceanography, it isessential to understand the biogeochemical cycles of Mo

6 Sohrin, Y. et al. Tungsten in north Pacific waters. Mar.
Chem. 22, 95-103 (1987).

and W in the modern ocean. So far we have developed

7 Kishida, K. et al. Tungsten enriched in submarine

an analytical method to determine the isotopic ratio ofhydrothermal fluids. Earth Planet. Sci. Lett. 222, 819-

8

dissolved Mo in seawater and proved that Mo isotopes

827 (2004).

are uniformly distributed in the modern ocean1. Now we

8 Nakagawa, Y. et al. Precise isotopic analysis of Mo inare developing a new analytical method to determine theseawater using multiple collector-inductively coupledisotopic ratio of dissolved W in seawater.

mass spectrometry coupled with a chelating resin

For solid samples, such as sediments and rocks, we havecolumn preconcentration method. Anal. Chem. 80,

developed a method for precise analysis of the9213-9219 (2008).

9

concentration and isotopic composition of Mo and W .

9 Tsujisaka, M. et al. Precise analysis of the

In this method, we realized an effective and simple

concentration and isotopic composition of molybdenum

removal of interfering elements by using a combinationand tungsten in geochemical reference materials. Anal.

of chelating extraction and anion exchange. Now we are

Chim. Acta (submitted).

19-F8-13

Dissolved Nd isotope ratios along the GEOTRACES
Eastern Pacific Zonal Transect○Chandranath Basak 1,2 ,Yingzhe Wu 1, Jesse M. Muratli 3, Steven L. Goldstein 1, Brian A.
Haley 3, Leopoldo D. Pena 4, Louise Bolge 1
1. Lamont-Doherty Earth Observatory of Columbia University, 2. Department of Earth Sciences,
University of Delaware, 3. Oregon State University, 4. GRC Geociències Marines, Departmentof Earth and Ocean Dynamics, University of Barcelona
Keywords: GEOTRACES, EPZT, Ocean Circulation, Neodymium

 The GEOTRACES Eastern Pacific Zonal Transect(EPZT, GP 16) encompasses a wide variety of ocean
environments including a near shore oxygen minimum
zone and Earth’s most active ocean ridge, thereby
offering a unique opportunity to study thebiogeochemical cycling of Nd and the impacts on Nd
isotopes. We report dissolved Nd isotopes with emphasison whether it behaves as a conservative water mass
tracer in the region, and the effects of hydrothermal input.
 The EPZT can be broadly divided into two segments
east and west of the mid-ocean ridge. The easternsegment shows εNd ~ -2 from the surface to 1000 m, withvalues decreasing to εNd ~ -4 to -5 with increasing depth.
The western segment shows slightly lower εNd values of~ -3 in upper 1000 m. Below 1000 m, like the easternsegment, εNd generally decreases with depth, typically tovalues of ~ -5 to -7. However, western profiles, both over
the ridge and farther west, show a prominent increase at
3000 m depth of ~1 εNd-unit, both at the ridge and along
the western segment.
 The surface signal can be attributed to particle
contributions from continent and/or dust. Within thesubsurface to upper 1000 m the εNd data can be explained
as variable mixtures of Equatorial Subsurface Water (~1.6, ESW) and Antarctic Intermediate Water (~ -7,
AAIW) with ESW dominating majority of the stations.
Pacific Deep Water (~ -4) and Lower Circumpolar Deep
Water (~ -8) dominate at depths >1000 m. The higher
εNd values within the upper 1000 m of the westernsegment suggest higher proportions of AAIW. The inputof hydrothermal Nd to the ocean is generally considered
to benegligible due to scavenging at the ridge. The EPZT
results indicate that hydrothermal Nd can alter theseawater Nd isotope composition near the ridge.

19-F8-14

Tectonically induced formation of the semi-closed Japan
Sea inferred from Nd isotopes○Keiji Horikawa1, Yukiko Kozaka1, Yoshihiro Asahara2, Hiroshi Amakawa3, Yusuke Okazaki4
1.University of Toyama, 2. Nagoya Univ., 3. JAMSTEC, 4. Kyushu Univ.
Keywords: Lead isotopes, GEOTRACES, Pacific Ocean, biogeochemical cycles

1. Abstract
Abstract The Japan Sea in the western North Pacific wasconnected to the deep Pacific via deep seaways before it
became a semi-closed marginal sea. However, the timingof the semi-closure and its cause(s) remain debatable. To
further constrain the timing, for the first time weanalyzed Nd isotopic compositions of fossil fish teeth
and fish debris deposited in the Japan Sea (Integrated
Ocean Drilling Program [IODP] Site U1425, ~2000 m
water depth) over the past 10 m.y. Neodymium isotope
values (–4.5 to –3.2 εNd) in the Japan Sea prior to 4.5
Ma illustrate that the deep Japan Sea was composed ofan admixture of less-radiogenic Lower Circumpolar
Deep Water (avg. –4.3 εNd) and more-radiogenic North
Pacific Deep Water (avg. –2.2εNd), potentially withinflow from the Okhotsk Sea. At 4.5 Ma, εNd values fell
to –5.5 εNd within a span of 140 k.y., suggesting that the
deep-water communication between the Japan Sea andthe North Pacific rapidly declined. We argue that active
mountain building in the northern Japan arc, initiated byaccelerated Pacific plate motion from the late Miocene
to mid-Pliocene, caused the shallowing/narrowing of theJapan Sea–Pacific seaways and rapidly made the Japan
Sea semi-closed at 4.5 Ma. As a result, the Japan Sea
circulation patterns were realigned; a cyclonic
circulation was developed and drew less-radiogenic
Amur River–influenced Okhotsk Sea water into theJapan Sea..

Fig. 1 C: Ten-million-year Nd isotope records from IODP Site U1425 and DSDP Site 296 and Fe-Mn crust 13D-27A(van de Flierdt et al., 2004). Detrital εNd from Site U1425 is also shown. D: Semiquantitative abundance ofradiolarian Siphocampe arachnea (Ehrenberg) group from cores at Sites U1425B (black line) and U1430A (blueshading) in Japan Sea (Kamikuri et al., 2017). E–G: Schematic paleogeographic maps (modified from Sato, 1994),with intermediate- and deep-water circulation patterns inferred from Nd isotope records.

19-F8-15

Distribution and geochemical cycles of Pt in Ariake Sea,Japan
○Asami S. Mashio1, Taiki Tanimura1, Hiroshi Hasegawa1, Teruya Maki1,
Shigenobu Takeda2, Hajime Obata3
1.Kanazawa University, 2.Nagasaki University, 3. The University of Tokyo
Keywords: Platinum, semi-closed sea, river water, sediment, fractional dissolution

1. Purpose

3. Results and Discussion

Platinum (Pt) belongs to the least abundant group of Pt concentrations ranged from 0.61 to 10.2 pmol/L inelements (platinum group elements, PGEs) in the earth’s

this study area. The highest Pt concentration, 10.2

crust (Wedepohl, 1995). Due to its specific and chemical

pmol/L, was observed at the deepest St. A7. Pt

properties, Pt has been used in a variety of industrial andconcentrations at all stations were higher than those of

medical applications, including automobile catalysis andopen ocean seawater (about 0.2 pmol/L; Suzuki et al.

anticancer drugs. At present, anthropogenic Pt has been2014). The concentrations increased with depth towardemitted and dispersed to the environment at a global

the bottom. We observed decreasing concentration trendscale.

from the Hayasaki-Seto Strait to inner central area in

Vertical profiles Pt in coastal seawaters indicatedAriake Sea. Pt concentrations in river water samples

increasing concentrations from surface to bottom

were about 0.2 pmol/L at the same level as those of open

(Mashio et al., 2017). Dissolved Pt might be supplied

ocean seawater. Higher Pt contents were found infrom seafloor sediment to seawater. However, theexchangeable phase (E4; 0.43 ng/g) or bound to Fe &process how Pt is supplied to seawater from sediment

Mn oxide phase (A11;1.26 ng/g) of the sediments. Pt

has remained unsolved.

contents in residual phases were 0.96 and 0.87 ng/g,

 In this study, our purpose was to reveal therespectively.

geochemical cycles of Pt between seawater and sediment Since there was little supply of dissolved Pt from riverin Ariake Sea. Ariake Sea is a semi-closed sea where weto in Ariake Sea, most of Pt was estimated to be supplied

can examine the interaction among seawater, sedimentsfrom sediments. Loosely adsorbed Pt onto sedimentand river water.

might be desorbed by complexing with chloride andemitted to seawater.

2. Methods
Seawater and sediment samples in this study werecollected from Tachibana Bay and Ariake Sea in Kyushu
area, Japan using Kakuyo-Maru (May 8 to 10, 2012,
May 18 to 20, 2015, May 7 to 9, 2018). Moreover, wecollected river water samples flowing into Ariake Seajust before the 2018 sampling time. We applied
fractional dissolution of sediments to understand thechemical form of Pt in sediments. Chemical sequential
extraction method included 5 steps (Tessier et al., 1979).
We determined sub-picomolar levels of dissolved Pt
using isotope-dilution Inductively Coupled Plasma Mass
Spectrometry (ICP-MS) after column preconcentration
with an anion exchange resin (Suzuki et al., 2014).

19-F8-16

Stimulated phosphorus utilization of microbes byzinc and iron addition in the western North PacificTamaha Yamaguchi1, Kazutaka Takahashi2, Mitsuhide Sato3, Ken Furuya4,
1.National Research Institute of Fisheries Science, 2. Department of Aquatic Bioscience, The
University of Tokyo, 3. Graduate School of Fisheries and Environmental Sciences, Nagasaki
University, 4. Graduate School of Engineering, Soka University
Keywords: alkaline phosphatase activity, phosphorus, trace metal, co-limitation

1. Purpose

phosphate limitation in these regions. The most

Phosphorus is one of the major growth limiting factors

significant positive response to zinc/iron addition ofof marine microbial communities in the ocean. Thus,

APA (maximum 2.5/1.5 folds higher than control) was

under phosphate depleted conditions, microbes express

observed at Stn. B. Moreover, enhancement of APA by aa metalloenzyme alkaline phosphatase in order tosingle addition of iron and zinc was also observed at Stn.

facilitate phosphorus acquisition from dissolved organic

A and C, respectively. These results suggest that limiting

matters. Because alkaline phosphatase superfamily

factors of APA gradually shifted from iron to zinc along

enzymes require either zinc or iron as a part of theirwith distance from the Asian Continent. However, noreaction center, co-limitation of phosphate and zinc/ironobvious changes in nutrient concentrations or microbial

is likely to occur in the surface layer of oligotrophic

community structures were observed in association withoceans, although the involvement of trace metals in thesuch enhancement of APA, except for an increase inmarine phosphorus cycle is not well understood. In thisheterotrophic bacteria abundance after zinc addition atcontext, we aimed to elucidate effects of zinc/ironStn. B. Such ambiguous results may be attributable toaddition on phosphorus acquisition of microbial

the short incubation period or deficiency of othercommunities in the subtropical North Pacific Ocean.

essential elements. In conclusion, we report the putative
co-limitation of phosphate and trace metals on microbial

2. Materials and Methods

communities for the first time in the western North

On-board enrichment incubation experiments were

Pacific Ocean. Our results suggest that phosphorus

conducted at 4 stations along a 23°N transect during theconsumption in this region will be stimulated by

R/V Hakuho-maru summer cruise (Figure 1). Either 2

sporadic supply of trace metals, leading to a progress innM of zinc, 2 nM of iron, or 200 nM of phosphate wasoligotrophication.

added to each of 5-L water samples pre-filtered with
100-µm mesh, and the samples were incubated for 2days in an on-deck running seawater bath. Alkaline
phosphatase activity (APA), dissolved inorganic andorganic phosphorus concentrations were measured, andmicrobial community structure was examined by flow
cytometry.
3. Results and Interpretation
Initially, phosphate was severely depleted (< 3 nM) at
the two western stations A and B, accompanied byincreasing APA towards the west. APA was suppressed
after phosphate addition at these stations, indicating

Figure 1 Station locations and the effect of reagent
addition on APA. White arrows show either significant
increase or decrease of APA in each treatment (p < 0.05),
whereas black bars show insignificant responses.

19-F8-17

Global biogeography of giant viruses highlights theirinterplay with eukaryotic community○Hisashi Endo1Yanze Li1Romain Blanc-Mathieu1Hiroyuki Ogata1
1. Kyoto University
Keywords: Nucleocytoplasmic large DNA viruses (NCLDVs), Biogeography, Metagenome, Arctic Ocean

1. Introduction
Nucleocytoplasmic large DNA viruses (NCLDVs)
constitute a monophyletic viral group infecting a wide
variety of eukaryotic lineages (Koonin and Yutin,2012). NCLDVs are ubiquitous in marine environmentswith extremely high species richness (Hingamp et al.,2013; Li et al., 2018, Mihara et al., 2018). However,their ecological and geographical characteristics arepoorly understood, due to the lack of knowledge about
the global patterns of distribution, diversity, and hostassociation. Here, we explore the distribution and thehost association of NCLDV community using the Tara
Oceans metagenomic data collected from the global
biomes.
2. Data and Methods
Metagenomic samples were collected from the Tara
Oceans expedition (2008–2013; Peasant et al., 2015) andthe Tara Oceans Polar Circle (TOPC) (2013; Gregory etal., 2019). We used the latest version of the nonredundant gene catalog of ocean metagenomes (OMRGC.v2; Salazar et al., submitted), which includes the
samples from Tara Oceans projects (0.2– 1.6/3.0 and<0.2 µm size fractions). We identified 7,020 NCLDVderived B type DNA polymerase (polB) genes fromOM-RGC.v2 using pplacer (Matsen et al., 2010). To
evaluate the diversity of NCLDVs in each sample,
Shannon’s
entropywasused.
Non-metricmultidimensional scaling (NMDS) based on Bray-Curtis
similarity was employed to assess compositionalvariation among samples. In addition, Partial Mantel test
(removing the effect of spatial autocorrelation) was
performed to evaluate the associations between NCLDVand eukaryotic community.
3. Results and Discussion
Community and phylogenetic analyses suggest that themarine NCLDVs were composed mostly ofalgaeinfecting lineages in the families Megaviridae andPhycodonaviridae in all samplingsites and depths. Although almost NCLDV phylotypes
were shared across world ocean, the Arctic Ocean had
higher proportion of unique NCLDVs, likely reflecting
the distribution of their specific host species.
Consequently, NCLDV communities in the Polarbiomes (Arctic and Antarctic Oceans) were clearly
distinct from others. The Shannon diversity of NCLDVs
peaked in tropical and subtropical regions and declined
toward the poleward, and this trend agreed well with thatof their known host community (Ibarbalz et al., inrevision). Significant correlations were found between
the community structures of NCLDVs and their known
hosts, especially phytoplankton lineages such as
chlorophytes and haptophytes, indicating the strong
interplay in structuring these communities. Our results
suggest that the NCLDVs follow the distribution of theirhosts, but would have significant roles on controlling the
local microbial structure in the ocean.

Figure 1. A synthesis map showing the numbers of total
and unique NCLDV polB phylotypes in each region. The
numbers of shared phylotypes between two regions arealso shown.

19-F8-P1

The change of material flux via SGD and its impact oncoastal ocean○Saki Katazakai1, Jing Zhang*1, Mai Suzuki1, Kazumi Asai2, and Kota Nojima1
1.University of Toyama, 2. Geo Science Laboratory Co., Ltd
Keywords: Submarine Groundwater Discharge(SGD) Climate Change

1. Introduction
Submarine Groundwater Discharge(SGD) is one ofthe processes of water and nutrient transport from theland to the ocean, and it is recognized worldwide that it
is important for basic production of the coastal ocean.
In Toyama Bay, Fresh SGD supply a large amount ofdissolved nutrients to coastal ocean, which have been
indicated to contribute significantly to primaryactivities on surface ocean (Hatta and Zhang, 2013).
However, in recent years, it reported that, the amountof snowfall decreased in the Hokuriku region including
Toyama Prefecture, while the amount of rainfall has
increased (Japan Meteorological Agency, 2015;
Yasunaga and Tomochika, 2017). As a result of thischange, the amount of SGD in Toyama Bay increased
by up to 30% in 30 years (Zhang et al. 2017). Thisquantitative change of the seafloor springs is
considered to bring about a qualitative change at thesame time. The aims of this study are (1) to understandthe changes of water quality associated with climatechange, and (2) to evaluate the impact on material
supply to the coastal ocean in Toyama Bay.

Nutrient and Carbon flux

concentrations of major chemical components (nutrients,
cations, anions, etc.) were measured in the laboratory.
We also measured hydrogen and oxygen stable
isotopes(δD, δ18O) using water isotope ratio analyzers(Picarro L2120-i, L2130-i) owned by the ResearchInstitute for Humanity and Nature.
3. Results and Discussion
Comparing the past (2000-2003) and present (20172018), it was confirmed that the concentration ofbicarbonate increased, while the nutrient concentration
decreased. In addition, the isotope values (δD, δ18O) of
SGD, shallow groundwater, and river water also
decreased. These results mean that the residence time
was more shorter, which was supported by the results oftritium concentration.
Furthermore, we calculated the amount of material
supply from the land to Toyama Bay via the river and
SGD using the results of previous studies and this study.
As a result, nutrient flux decreased by from 40 to 80%
and the carbon flux increased two times over the past 10
years.

2. Data and Methods
SGD samples were collected at the water depth ofabout 8 m. We also conducted shallow groundwater andthe upstream rivers in the Katakai River Alluvial Fan
linked to SGD. In addition, in order to understand theoverview of the water and material transport from theland to Toyama Bay, we investigated five First-classrivers. SGD was collected directly by scuba diving andabout 1L sample was successfully collected bysuctioning with the syringe attached to the device shownin figure 1.
Samples of SGD, groundwater, and river water wereimmediately measured for water temperature, pH, andelectrical conductivity at the each sites, and theFig1. Sampling for SGD

19-F8-P2

Transport of the upper Kuroshio Intermediate Waterfrom northwestern Pacific to the Sea of Japan: using 137Cs
as a tracer○J Siteng J. Zhu1, Jing Zhang*1, Shota Kambayashi2, Takeshi Matsuno3, Eisuke Tsutsumi6,
Shigenobu Takeda4, Seiya Nagao5, Mutsuo Inoue5, Katsumi Takayama3, Hiroshi Ogawa6,
Ichiro Yasuda6
1.Univ. Toyama, 2. Central Laboratory, Marine Ecology Research Institute, Japan, 3. RIAM,
Kyushu Univ., 4. Nagasaki Univ., 5. Kanazawa Univ., 6. AORI, Univ. Tokyo
Keywords: 137Cs, subtropical mode water, water masses, KIW, nutrients

1. Abstract
Kuroshio is the western boundary current of the Pacificproviding abundant nutrients from its intermediate water(KIW). However, vary lack research, especially using
direct chemical tracers to track the transport and quantify
the nutrients flux of the KIW, which contains abundantnutrients, was in the previous studies. 137Cs in thesubtropical mode water (STMW) that originated in the
Fukushima Dai-ichi Nuclear Power Station (FDNPS)
accident is an excellent tracer and it can also be useful toresearch the transport of the KIW. In this study, transportof the upper Kuroshio intermediate water from
northwestern Pacific to the Sea of Japan was shown
approached using the direct evidence 137Cs.
Data and water samples were collected from the
Hakuho-Maru KH-17-5 Cruise and Nagasaki-Maru 464
Cruise in November and July 2017 respectively. Data
from KH-17-5 Cruise was used for the study of areaaround the Luzon Strait and those of the Nagasaki-maru
464 Cruise was used for the study of area around outer
shelf region of the East China Sea (ECS) and theTsushima Strait. The 137Cs active concentration was
analyzed by the γ-Ray spectrometry after
preconcentration. The turbulence intensity wasmeasured using TurboMAP and VMP2000.
137
Cs from the FDNPS accident inked onto the STMW
in the North Pacific at a depth of 300-400 m, and then
STMW was observed in the Luzon strait after mixing
with the origin of the Kuroshio through diffusion andvertical mixing which is consistent with Vigan Mensah’s
research. The KIW is transported from Luzon Strait
northward to Tokara Strait via the continental shelf
margin of the East China Sea, and part of it is transported
to the Sea of Japan via Tsushima Strait traced using 137Cs.
The water mass with the maximum value of 137Cs was
identified as STMW, the upper layer of KIW, and its
depth gradually decreases from 400 m in Luzon to 150

m in ECS, and finally about 100 m in Tsushima Strait.
The Tsushima warm current in depth of 100 m can be
identified as KIW, rich in nutrients, by our analysis of137
Cs and potential density. The flux and contribution of
KIW to the west channel of the Tsushima warm current
and to the whole Tsushima warm current were calculatedusing current velocity and nutrients data in the same
season, which is about 22% and 8% of the DIN in
Tsushima warm current from KIW. It is the first timethat the transport of the upper Kuroshio intermediatewater from northwestern Pacific to the Sea of Japan was
intuitively shown19-F8-P3

Significance of Fukushima-derived radiocesium flux
via river-estuary-coastal ocean system○Shota Kambayashi1, Jing Zhang2, Hisashi Narita3
1. Central Laboratory, Marine Ecology Research Institute, Japan , 2. Graduate School of Sci. andEng., Univ. of Toyama, Japan , 3. School of Marine Sci. and Tech., Tokai Univ., Japan
Keywords: Fukushima-derived radiocesium; Submarine groundwater discharge; Recycled saline
groundwater discharge; Export flux into the ocean

1. Introduction
Riverine input is a major pathway for discharge fromland to the ocean. Furthermore, submarine groundwater
discharge (SGD) has been recognized as an importantsource flowing into the ocean. The concentration ofradionuclides in SGD are often dramatically higher thanin river water. Moreover, Charette et al. (2013) raised thepossibility that the SGD-derived radiocesium flux to theocean increases due to seawater intrusion driven by tidal
pumping or seasonal changes in the hydraulic gradient.
However, few reports have been published on
subsurface pathways as a source of radiocesium. The
major goals of this study are to explore the distributionof Fukushima-derived radiocesium in riverestuarycoastal ocean system and to evaluate the export
flux from land to coastal ocean, including SGD. To
accomplish these goals, we investigated activity
concentration of radiocesium in Matsukawa-ura Lagoon,
the largest lagoon in Fukushima.
2. Materials and Methods
Water samples (river water, groundwater and estuarine
water) were collected from October, 2014 to October,2016. The salinity was also measured with a sensor.
Water samples were filtered through a 0.45-µm
membrane filter. In addition, sediment samples (fromsurface to 5 cm below lagoon bottom) for obtaining porewater were collected on October, 2016. Sediment
samples were squeezed by a centrifuge (3,000 rpm, 30
min). After centrifugation, a pore water sample wasfiltered through a 0.20-µm membrane filter. Dissolved
radiocesium was concentrated on ammonium
phosphomolybdate (AMP). The activity concentration
was measured with Ge detectors. All of the activity
concentration values were decay-corrected to thesampling date.

3. Results and Discussion
Activity concentration of dissolved 137Cs showedexcess from low to intermediate salinity (<0.1 - 18) inthe estuarine water. This increase in activity
concentration of dissolved 137Cs was most likely the
result of desorption from particles when the riverine
particles mixed with seawater. In the polyhaline andeuhaline zone (> 18.0), the activity concentration ofdissolved 137Cs gradually decreased due to dilution
caused by seawater. These results suggest that dissolved
radiocesium behaved non-conservatively via riverestuary-coastal ocean system. Moreover, activity
concentration of 137Cs in pore water was much higher
than in overlying water, suggesting that a significant
amount of radiocesium in sediment desorb into porewater. From results of mass balance model, dissolved
137
Cs flux from lagoon bottom such as recycled saline
groundwater discharge (RSGD) is about 15 times greaterthan riverine input including desorption from particles.
This result implies that RSGD is the major radiocesium
source flowing into the lagoon. Moreover, the export
fluxes of dissolved 137Cs, including RSGD from the
Pacific coast of eastern Japan to the coastal environment,
were estimated to be up to 4 times greater than the sumof the values for riverine input and ongoing release fromthe Fukushima Daiichi Nuclear Power Station harbor.
Thus, RSGD plays an important role in the system ofradiocesium discharge from land to coastal ocean.

19-F8-P4

Atmospheric Nitrogen Deposition on The Sub-Tropic
NWPO and Its Impact○Tadateru Noguchi1, Jing Zhang1*, Wenkai Guan2, Bingzhang Chen3, Meixun Zhao2,
Yuanli Zhu4, Joji Ishizaka4, Takeshi Matsuno5, Ichiro Yasuda6
1. University of Toyama, 2. Ocean University of China, 3. JAMSTEC, 4. Nagoya University, 5.
Kyusyu University, 6. The University of Tokyo
Keywords: Pacific oceanAerosolPhytoplanktonNutrients

1. Introduction
It has been suggested that aerosols (particulates in theatmosphere) such as continent-derived loess andanthropogenic dust carried by the monsoon wind and thewesterly wind play a very important role in surface
ocean primary production(Yuan et al., 2006). Previous
study report that spring dust events in Asia increase thebase production of the western North Pacific by morethan 70%(Yoon et al., 2017). There is a need to evaluate
the impact of aerosols on marine phytoplankton and themarine environment. However, there are not manyobservation researches at these sites today, and there are
few observations especially on the ocean. Observation
research in the field is important for model creation andthe model’s accuracy improvement. Therefore, in thisstudy, we aimed material transport between theatmosphere and the ocean focusing on nutrients
deposition and surface primary production.
2. Methods
In this study, aerosols and surface seawater werecollected during the R/V Hakuho-maru KH-17-5 cruise(2017.11.14-12.18). Nutrients and REEs in the aerosol
sample. The aerosols were collected using a high volume
air sampler (SHIBATA HV1000-F). Major chemicalcomponents, nutrients and rare earth elements in theaerosol, were extracted into MilliQ water and measured.
Surface water was collected using a pump during thecruise. The Chl-a samples were extracted using D MF
after filtering during the cruise, and later were measured
using a fluorometer(Turnerdesigns 10-AU). The
biomarkers were measured at the Ocean University of
China.
3. Results & Discussions
Analyses of REEs in the aerosols showed that theatmospheric dust (aerosol) is a mixture of loess, coalsmoke and sea salt. Their ratios were calculated as 60%,
26%, and 14%, respectively. From this, it was inferredthat the majority of aerosols flying to the Pacific Ocean
originated from or passed through the Chines e continentrich in loess and dust, and the actual amount of
sedimentation could be quantified.
A positive correlation was found between TDIN
deposition and the surface Chl-a concentration(R=0.8 9).

Furthermore, the ratio of different phytoplankton specieschanged according to the amount of nutrients deposition.
The change in the proportion of brassica sterol shows theamount of diatoms increases with NO3 − deposition. The
value of NH4+ do not fluctuate. It is suggested that not
only the amount of nutrients deposition but also the kindof nutrient influence the composition of phytoplankton
species. We focused on the Luzon Strait to compare
winter vertical mixing, which is one of the major sourcesof nutrient supply in the open ocean, and nutrient
deposition from the atmosphere. The required amount of
nitrogen nutrient determined from the integrated value(17-24 µmol / m3) of 0-80 m of the Chl-a concentration
was approximately 2.3-3.6 µmol / m3. The amount of
nitrogen deposition in the Luzon Strait was 25 µmol / m2
/ day. We found that nutrient sedimentation completely
met the phytoplankton requirements. These results provethat nitrogen from the atmosphere plays an importantrole in this area.
4. Conclusions
About half of the aerosols in the subtropical area ofNorthwestern Pacific comes from loess, then 30% an dless than 20% from coal smoke and sea salt
respectively, estimated by using dissolved Rare EarthElements in aerosols. A positive correlation was found
bet ween the nutrient deposition and Chlorophyll-aconcentration in surface sea water. The phytoplankton
specie s composition is influenced by the amount of
nutrient deposition and different speciation of nutrients.
The estimation of consumed nutrient from C-Chl-a
integration (<80m) is N=2.2±0.59 µmol/m3,
P=0.13±0.05 µmol/ m3 in surface water column.
However, the deposition of N from atmosphere into thesurface ocean was estimated 25 µmol/m2/day in thisstudy. Furthermore, in the Luzon Strait area, theintegrated N (<80m) is 1.7 times higher, where strong
vertical mixing observed, comparing with those stations
with very wake vertical mixing. In summary, thenutrient deposited from atmosphere plays as animportant role in the phytoplankton on the surface subtropic western north pacific ocean.

19-F8-P5

Cu-binding organic ligands and dissolved organic matterin coastal waters○Wiwit1, Hajime Obata1, Kuo Hong Wong1, Chia-Jung Lu1, Hiroshi Ogawa1, Hideki Fukuda1,
Shigenobu Takeda2
1. Atmosphere and Ocean Research Institute, The University of Tokyo, Kashiwa, Japan, 2.
Graduate School of Fisheries and Environmental sciences, Nagasaki University, Nagasaki, Japan
Keywords: organic ligand, dissolved copper, dissolved organic matter, incubation experiments

Copper is a bio-essential element to mostmicroorganism at low concentrations, but at highconcentrations free copper (Cu2+) can be toxic. Copper
in seawater is predominantly complexed by strongorganic ligands exuded by phytoplankton to reduce toxic
Cu2+ concentrations. Previous studies showed Cubinding organic ligands were correlated with terrestrial
humic substances in seawater (e.g., Kogut and Voelker,
2001). Therefore, in order to understand how organic
ligands for Cu were produced in seawater, weinvestigated the relationship between Cu-bindingorganic ligands (concentrations and conditional stability
constants) and dissolved organic matter (DOM) by
incubation experiments.
 Seawater samples used for the incubations werecollected from Ariake Sea (A11 in Fig. 1) and Otsuchi
Bay, Japan in May 2019. These experiments wereconducted at constant temperature (200C) under lightand dark conditions. For some samples, adequate
amounts of nitrate and phosphate were added. One extra
set of the incubation experiment using Otsuchi Bay
water was conducted in the presence of zooplankton.
The samples were incubated for 1, 3, 5, 7, and 14 days.
Copper speciation parameters were determined bycompetitive ligand exchange adsorptive cathodic
strippingvoltammetry(CLEadCSV)
using
salicylaldoxime (SA) as the competing ligand (Campos
and van den Berg, 1994; Wong et al., 2018).
Chromophoric DOM (CDOM) absorbances were
measured at 200–800 nm using a dual beam
spectrophotometer, while fluorescent DOM (FDOM)
patterns were measured in the range of 250–500 nm and
280–600 nm for the excitation and emission by using aspectrofluorometer.
Preliminary data showed total dissolved copper
concentrations gradually decreased with incubation time.
CDOM absorption coefficient at 440 nm (a440) increased
under nutrient-rich condition compared to other samples.

FDOM results for Ariake Sea samples showed that there
are four components including two protein-like and two
humic-like components. Using CLE-adCSV, organic
ligands were detected in both Ariake Sea and Otsuchi
Bay samples, whose conditional stability constants wereapproximately 1014. The relationship between theorganic ligands and DOM (CDOM and FDOM) werebeing investigated in this study.
Fig. 1. Map of the sampling location in Ariake Sea

References
Campos, M.L.A.M., van den Berg, C.M.G., 1994.
Determination of copper complexation in sea
water by cathodic stripping voltammetry andligand competition with saliclyaldoxime. Anal.
Chim. Acta 284, 481–496.
Kogut, M. B., Voelker, B. M., 2001. Strong copperbinding behavior of terrestrial humic substancesin seawater. Environ. Sci. Technol., 35, 1149–
1156.
Wong, K.H., Obata, H., Kim, T., Mashio, A.S., Ogawa,
H., Fukuda, H., 2018. Organic complexation ofcopper in estuarine waters: an assessment of themulti-detection window approach. Mar. Chem.
204, 144–151.

19-F8-P6

Factors affecting radiocesium concentration in sediment
off Fukushima: Lateral transport of particles
S. Otosaka 1, T. Suzuki 2, T. Tsuruta 2, T. Misono 2, Y. Mino 3, T. Ishimaru 4, J. Kanda 4,
C. Sukigara 4, Y. Ito 4, N. Murakami-Sugihara 1, M.C. Honda 5
1. AORI UTokyo, 2. JAEA, 3. Nagoya Univ, 4. TUMSAT, 5 JAMSTEC

Keywords: Radiocesium, Sinking particles, Seabed sediment, Fukushima Daiichi NPPIntroduction
The accident of Fukushima Daiichi Nuclear Power
Plant (FDNNP) that occurred in March 2011 is anunusual event in which a large amount of radionuclides
was released directly to the ocean.
At present,
accurately understanding the dynamics of theradionuclide in the ocean on a decadal scale andclarifying the factors are one of the issues that marine
chemists should be addressed. It is known that a few
percent of the radiocesium released to the ocean by theaccident has deposited on the coastal seabed. Although
the concentration of radiocesium in the seabed showed agradual decreasing trend with time, the decreasing rate
was not always constant, and it is pointed out thatvarious processes affected the behavior of radionuclides
near the seabed. In this study, in order to clarify thetransport process of suspended radiocesium from thecoast to the offshore area, which is one of the processes
that change the inventory of radionuclides in sediments,
a sediment trap experiment was conducted for one year
at the southeast station of the FDNNP.
Materials and Methods
From May 2017 to June 2018, a time-series sediment
trap was deployed 10 m above the seafloor at the station
located at about 50 km (37° 00’ N, 141° 25’ E, bottom
depth 210 m) offshore of Iwaki City. Sinking particles
for 39 periods were collected at intervals of 5 to 30 days.
The activity concentrations of two radiocesium isotopes(134Cs, 137Cs) were measured as accident-derived
radionuclides and the major components (biogenic opal,
biogenic carbonates, lithogenics, organic matter) andlead-210 (210Pb) activity concentrations were measured
as indicators of the characteristics of sinking particles.
Seabed sediment samples collected from the mooring
station and the surrounding area were also analyzed in
the same manner as sinking particles. A current meter
was installed at the same depth as the sediment trap, andwater temperature, current direction, and current
velocity were observed during the sampling period.
Results and Discussion
137
Cs was detected from sinking particles throughout
the observation period, and the 137Cs activity
concentration showed clear seasonal variation. The
137
Cs concentration in the sinking particles showed amaximum value during the period in December 2017(110 Bq kg-1, decay corrected to March 11, 2011). This
concentration was an order of magnitude higher than the137
Cs concentration in the surface sediment (0-1 cm
layer) at the same station. On the other hand, the 137Csconcentration in summer (May to September) was about
1 to 15 Bq kg-1, and showed a similar to or lower thanthat of surface sediments. Although 134Cs was below
the detection limit in many periods due to the small
amount of samples and fast radioactive decay of 134Cs,
most of the radiocesium detected in this study ispresumed to be accident-derived. The total mass flux
observed with the sediment trap ranged between 143 and1732 mg m-2 day-1, and several maxima exceeding
1000 mg m-2 day-1 occur from March to June wereobserved. Since the major component of the sinking
particles during this period was lithogenics, it can beconsidered that the high mass flux was mainly due to the
supply of riverine particles and the resuspension of
sediments. In this season, contentious southward flow
was observed near the seafloor. From these results, it
was found that 137Cs-bound particles were laterallytransported in this season from coastal area including thevicinity of the FDNNP. From the mass balance of 210Pb(particle-reactive natural radionuclide) in the watercolumn at the mooring station, it was estimated that thestation is located in the area where particles are imported
from the surrounding area. Nevertheless, the observed
annual 137Cs particle flux was less than 3% of the 137Cs
inventory in the seabed (1250 Bq m-2) at the mooring
station. From these results, it can be concluded that thetransport of 137Csbound particles from the coastal area
has a relatively small effect of changing the abundanceof 137Cs in sediments. Regarding the detailed process,relatively high concentrations of 137Cs were detectedfrom the settling particles from late fall to winter(November to February). Sinking particles collected inthis period had a slightly higher proportion of organic
matter. These results are considered to indicate thatorganic matter particles which incorporate 137Cs
accumulated on the seabed were remobilized by
disturbance near the seafloor in late autumn. Although
the magnitude is quite small, the transport ofradionuclides associated with organic matter is aremarkable process in consideration of the migration ofbioavailable radionuclides near the seafloor.

Applications of Radium Isotopes to Marine Flux Studies
Guebuem Kim
School of Earth and Environmental Sciences, Seoul National University,

Keywords: Radium, Ocean, Flux, Elements

1. Abstract
Combinations of radium isotopes (226Ra, 228Ra, 224Ra,
and 223Ra) have been successfully used to trace water
mixing and transport in the ocean. Due to theirdifference in half lives, 224Ra (half life: 3.4 d) and 223Ra(half life: 11.3 d) are suitable for application to thecoastal ocean, while 228Ra (5.8 y) and 226Ra (1622 y) are
more useful for basin-scale studies. In the ocean, Ra
isotopes are produced primarily from marine sediments
enriched with their parents. There are additional sourcesfrom groundwater and river water where the isotopes are
an order of magnitude enriched relative to open-ocean
seawater. Amongst these Ra isotopes, 228Ra is an ideal
tracer of fluxes on a basin scale since its decay andtransport/mixing of sedimentary sources produce large

gradients across important oceanic interfaces: crosscontinental-shelves, upper-deep oceans, and benthic
boundary layers. However, such applications of Ra
isotopes have been hampered mainly by difficulties
resulting from their extremely low-level activities in theocean. In this study, I demonstrate how we can more
efficiently measure Ra isotopes in the ocean and how the
scarcity of Ra data can be complemented byextrapolation of available data using an inverse model.
Then, I will briefly introduce how we can apply these Radata (observed and modeled) to hot issues in modern
marinebiogeochemistry
includingsubmarine
groundwater discharge, cross-shelf fluxes of chemical
constituents, and carbon sequestration in the ocean.