ACG33-01

Room:202

Time:May 26 09:00-09:18

Iron and spring water which have been ignored in material cycles in coastal marine
ecosystems
YAMAMOTO, Tamiji1∗
1

Grad Sch Biosph Sci, Hiroshima Univ.

Material cycles in coastal areas can be calculated by freshwater and salinity budgets using a standardized method proposed by
LOICZ (Land-Ocean Interaction in the Coastal Zones) Working Group if the targetted area is estuaries with an obvious salinity
gradient. In the manual, material loads from spring water can be ignored in case no data are available. However, it is assumed
that bottom spring water contains higher concentration of dissolved matter particularly minerals than that of river water, because
it passes through the underground lithosphere. Eventhough the water volume is smaller than that of river water, it may contribute
greatly to the material budget in coastal areas.
In enclosed coastal seas of Japan, the number of red tide occurrence has been decreased and the transparency has also significantly been increased by reduction measures of material loads from land. There are several areas in which the growth of fish andother organisms is depressed by nutrient depletion, which is called ”oligotrophication”.
Unexpectedly, the anoxic water mass is still formed in the bottom layer of coastal areas whereas the material loads was reduced.
This evidenced that the anoxic water mass may be formed not only by decomposition of organic matter but also by chemical
oxidation of hydrogen sulfide. This also suggests that depletion of iron which is an essential element for the growth of algae.
The author recently determined the concentration of dissolved iron from the upper area of the Ohta River which flowing into
Hiroshima Bay to lower river and seawater of the bay. Iron and nutrient concentrations in a spring in the bay were also investigated. The author hopes the presentation would be a hook to promote material cycle study of coastal seas.
Keywords: nutrient, material cycle, iron, spring

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ACG33-02

Room:202

Time:May 26 09:18-09:36

Estimation of distribution and discharge flux of submarine groundwater using Rn-222 in
the Yatsushiro Bay
HOSONO, Takahiro1∗ ; NIKPEYMAN, Yaser2 ; ONO, Masahiko3 ; YANG, Heejun2 ; SHIMADA, Jun2 ;TAKIKAWA, Kiyoshi4
1

Priority Organization for Innovation and Excellence, Kumamoto University, 2 Department of Earth Sciences, GSST, Kumamoto
University, 3 The National Institute of Advanced Industrial Science and Technology, 4 Center for Marine Environment Studies,
Kumamoto University
Continuous Rn-222 monitoring method has been developed around a decade ago, and with this method, evaluation of spatial
distribution and flux of submarine groundwater discharge (SGD) in/along ocean coastal bay/line is becoming popular worldwide.
In this presentation, we will introduce a case study in Yatsushiro Bay, describing distribution and flux properties of SGD, deduced
by Rn-222 data collected during recent four years. We try to show and confirm the merit and limit of Rn-222 monitoring method
and propose a new approach to solve several potential problems on Rn-222 study.
Yatsushiro Bay is one of the largest inland sea in Japan, surrounded by Kyushu mainland to the east and Amakusa Islands tothe west. Its total area is around 1,200 km2 with a total coastal line of around 220 km. The hinterland of this bay is composedof watersheds with various topographic and geological features. Therefore, Yatsushiro Bay should provide an ideal setting tounderstand the factors, i.e., watershed area, topographical gradient, presence of tidal flat, geological constituent materials andgeological structure, controlling SGD distribution properties in wide scale coastal sea area. By summarizing these features, we
can confirm interesting SGD distributing natures in coastal environments.
After analyzing Rn-222 samples of 61 flowing rivers into Yatsushiro Bay, we realized that river waters contain considerable Rn222, which value cannot be ignored when interpreting Rn-222 signal in the sea. In order to evaluate the effect of river-originatedRn-222 in the coastal sea water, we developed sea water Rn-222 distribution model within whole Yatsushiro Sea, based on apreviously constructed ocean currency simulation model. The net SGD-originated Rn-222 concentrations were estimated bysubtracting simulated river-originated Rn-222 concentrations from the observed towing Rn-222 monitoring data.
A total SGD flux within the Yatsushiro Bay was evaluated following traditional box model concept, by multiplying advection
rate deduced from continuous Rn-222 monitoring results at mooring survey sites, and SGD patch area estimated by Rn-222
towing survey results. Consequently, it was concluded that 15% of the total water transported toward the Yatsushiro Sea fromthe land is SGD origin. Furthermore, we tried to understand the possible components contributing to Yatsushiro coastal water,
FSGD, RSGD, river water, and sea water, with their contribution degree quantitatively. Our analysis also suggested interesting
aspect that wind velocity on the coastal sea surface would be an important triggering factor of SGD.
As a result of our study, it was suggested within the Yatsushiro Sea that Rn-222 concentration could not play as a direct tracer
of groundwater because the Rn-222 in the coastal sea water can be partially derived from rivers flowing into the bay. Althoughprevious studies have not taken this effect into account in interpreting sea water Rn-222 observation results, our findings, and oursolution idea, would be essential to be incorporated in a future study in an area of similar climate and topographical condition likeYatsushiro area. With this topic, we will propose distribution property, estimated flux, and discharging mechanism of submarine
groundwater comprehended by a recent Rn-222 study in the Yatsushiro Sea.

Keywords: SGD, Rn-222, simulation, tidal flat, discharge rate, distribution

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ACG33-03

Room:202

Time:May 26 09:36-09:51

Analyses of submarine groundwater discharge based on Radon-222 concentrations of thecoastal water in JapanTANIGUCHI, Makoto1∗ ; HONDA, Hisami1 ; ONO, Masahiko2 ; HOSONO, Takahiro3 ; UMEZAWA, Yu4 ;SUGIMOTO, Ryo5 ; YAMADA, Makoto1
1

Research Institute for Humanity and Nature, 2 National Institute of Advanced Industrial Science and Technology, 3 Kumamoto
University, 4 Nagasaki University, 5 Fukui Prefectural University
Radon-222 is one of the useful tracers for evaluating submarine groundwater discharge (SGD), because the groundwater has
extremely high concentration in 222Rn compared with surface water. In this study, we attempted to compile and compare radon
data observed in ten study areas in Japan, with SGD observed by seepage meters as well as local environmental parameterssuch as precipitation, gradient, permeability, basin area, tidal range, and others. We used geographical information system (GIS)
and digital elevation model (DEM) to evaluate the characteristics of the basin. The highest 222Rn concentrations was recorded
in Yuza (Northwestern Tohoku area) in Japan, where the highest SGD by seepage meter was observed. 222Rn concentrations
increases with precipitation within the study areas of four bays in Yuza and four bays in Otsuchi. Multivariable analyses ofdriving factors of submarine groundwater discharge were performed in the ten study areas.

Keywords: submarine groundwater discharge, Radon, coastal groundwater

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ACG33-04

Room:202

Time:May 26 09:51-10:06

The origin of submarine groundwater discharge in the coastal zone of Hiji, Oita prefecture
YAMADA, Makoto1∗ ; OHSAWA, Shinji2 ; MISHIMA, Taketoshi2 ; SHOJI, Jun3 ; TANIGUCHI, Makoto1
1

Research Institute for Humanity and Nature, 2 BGRL, Institute for Geothermal Sciences, Kyoto University, 3 Hiroshima University
It is believed that groundwater discharges from the seabed of the coastal zone of Hiji, Oita prefecture. The marbled sole which
lives around this submarine groundwater discharge (SGD) is called the ”Shirosita Karei”, and is held in high regard by the local
community. From ancient times, local people have believed that this Shirosita Karei grows because of SGD. However, the ecological link between marbled sole and SGD has not been well established. Moreover, although it is clear that there is SGD in thearea, there is almost no information about the origin and dissolved components of the SGD. In this study, we directly collected
SGD and analyzed its chemical composition and water stable isotopes. Additionally, we analyzed the chemical composition andwater stable isotopes of the inland cold spring water. We considered the origin of the SGD by comparing the result of the SGD
analysis and the inland cold spring analysis. Since we expected that the temperature of SGD would be different than seawater,
we used a thermometer for the identification of the discharge location. We inserted a stainless steel pipe in the identified locationand collected SGD water. The sodium concentration from the collected SGD water was 12.1 mg/l, indicating fresh water. The
isotopic composition of the SGD water resembled that of the inland cold spring water. The recharge area of the inland cold springwater is at an elevation of 200 m or more. These results suggest that the SGD water comes from an elevation of 200 m or more.
It indicates that the origin of SGD is water recharged in the forest area of the mountain slope, and that the water moves under theplain and is discharged at the seabed.
Keywords: Submarine groundwater discharge, Stable isotope, recharge area, Hiji

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ACG33-05

Room:202

Time:May 26 10:06-10:21

Submarine groundwater discharge and nutrients state of around coastal seawater
HONDA, Hisami1∗ ; OHSAWA, Shinji2 ; SUGIMOTO, Ryo3 ; HEN, Teki2 ; MISHIMA, Taketoshi2 ;YAMADA, Makoto1 ; SHOJI, Jun4 ; TANIGUCHI, Makoto1
1

Research Institute for Humanity and Nature, 2 Kyoto University, 3 Fukui Prefectural University, 4 Hiroshima University

In recent years, the importance of nutrient input to the coastal seawater through submarine groundwater discharge (SGD)
has been pointed out in several studies. The coastal area of Hiji town in Oita Prefecture, it is known that there is a submarine
groundwater discharge. However, the effects of SGD-derived nutrients has not yet been clarified in this area. Therefore, weinvestigated the spatial distribution of SGD using radon-222 isotope as a groundwater tracer and assessed the impact on the
nutrient (DIN and DIP) concentrations of surrounding seawater. In May 26-30, 2014, we monitored 222 Rn and nutrients along
the coast of Hiji. In addition, we collected the spring water on the land and the spring water of a salt water mixture discharged on
the coast. As a results, 222 Rn concentrations was clearly highest on SGD point. Nutrients concentrations around the SGD point
were higher DIP concentrations than elsewhere and the N/P ratios lower than the Redfield ratio. These results imply that SGD ismain source of DIP in coastal area of Hiji.
Keywords: Submarine groundwater discharge, 222Rn, Nutrients, Primary production

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ACG33-06

Room:202

Time:May 26 10:21-10:36

The influence of groundwater discharge on primary production in a shallow coastal sea,
Obama bay,Japan
KOBAYASHI, Shiho1∗ ; SUGIMOTO, Ryo2 ; MIYATA, Youji1 ; HONDA, Hisami3 ; YAMADA, Makoto3 ;TOMINAGA, Osamu2 ; TAHARA, Daisuke2 ; SHOJI, Jun4 ; TANIGUCHI, Makoto3
1

Kyoto University, 2 Fukui Prefectural University, 3 Research Institute for Humanity and Nature, 4 Hiroshima University

Submarine groundwater discharge (SGD) often influences on biogeochemical properties in coastal seas. We observed spatial
and temporal variations in SGD using 222 Rn and seepage meter along the shoreline of Obama bay, Japan. The results showed
SGD exists even in the shallow sea adjacent to the small water catchment area (˜1 km2 ), where the range of the tide is relatively
small (10 ˜30 cm). The spatial and temporal variations in chlorophyll observed at the same time suggest that the SGD influenceson primary production.
Keywords: land-ocean interaction, submarine groundwater discharge, costal ecosystem, primary production

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ACG33-07

Room:202

Time:May 26 11:00-11:15

Location estimation of submarine groundwater discharge from Mt. Fuji in Suruga Bay(II)
MURANAKA, Yasuhide1∗ ; KAMITANI, Takafumi1 ; ITO, Akira1 ; OHYAMA, Koichi1 ; WATANABE, Masayuki2 ;ONO, Masahiko3 ; MARUI, Atsunao3
1

Shizuoka Institute of Environment and Hygiene, 2 Industrial Research Institute of Shizuoka Prefecture, 3 National Institute ofAdvanced Industrial Science and Technology
Around the foot of Mt. Fuji, the main flow passages of groundwater are thought to be in the Younger Fuji volcano, which
consists of the pervious basaltic lavas in new volcanic stage. Especially, the Fujikawa-kako fault zone, which stretches south
to north in the southwestern side of Mt. Fuji, has a potentially effect on the local groundwater flow system into Suruga Bay.
Therefore, precipitation at Mt. Fuji have been considered to be discharging partly from seabed in Suruga Bay and making a great
impact on the biological production at the coastal sea area.
For the purpose of contribution to make sense of the rich coastal ecosystem in Suruga Bay, we conducted a survey for submarine
groundwater discharge (SGD) in Oku-Suruga Bay: from the mouth of the Fuji River, at which the fault is found, to Tagonoura,
where the lavas of the Younger Fuji volcano are distributed from 100 to 200 m below sea level. We are trying to estimate somelocations of SGD from bottom topography, condition of seabed and geological structure by using multibeam sonar, side scansonar and sub-bottom profiler, respectively. We also use a remotely operated vehicle (ROV) for photographing for the image ofthe extrapolated spring points. In this presentation, we introduce our works noted above.

Keywords: submarine groundwater discharge (SGD), Mt. Fuji, multibeam sonar, side scan sonar, sub-bottom profiler, remotely
operated vehicle (ROV)

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ACG33-08

Room:202

Time:May 26 11:15-11:30

Effects of submarine groundwater discharge on coastal fishery production: emphasizing
on fish community
SHOJI, Jun1∗ ; SUGIMOTO, Ryo2 ; HONDA, Hisami3 ; TOMINAGA, Osamu2 ; KOBAYASHI, Shiho4 ;YAMADA, Makoto3 ; TANIGUCHI, Makoto3
1

Hiroshima University, 2 Fukui Prefectural University, 3 RIHN, 4 Kyoto University

Biotic and abiotic surveys were conducted at four sites in Japan, where submarine groundwater discharge has been confirmed.
In order to evaluate the contribution of nutritional input from the terrestrial ecosystems to production of fishery resources incoastal areas, sampling for fish and their prey organisms were conducted. Number of fish species, fish abundance and biomass
were compared between areas of different levels of Radon concentration at each site.

Keywords: coast, water-food NEXUS, Fishery resources, biodiversity, submarine ground water, biological production

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ACG33-09

Room:202

Time:May 26 11:30-11:45

The evaluation of the effectiveness of the d13C signature in bivalve shells as proxy forenvironment of SGD
TOMINAGA, Osamu1∗ ; HORIBE, Nanami1 ; NISHI, Saori1 ; SUGIMOTO, Ryo1 ; YAMADA, Makoto2 ; SHOJI, Jun3 ;HONDA, Hisami2 ; KOBAYASHI, Shiho4 ; TANIGUCHI, Makoto2
1

Fukui Prefectural University, 2 Research Institute for Humanity and Nature, 3 Hiroshima University, 4 Kyoto University

Submarine groundwater discharge (SGD) is often characterized by high concentration of nutrients and documented as an important pathway between land and sea contributing to the biological productivity in coastal waters. However, to our knowledge,
no scientific information about the relationship between environmental conditions of SGD and the extent of biological productivity of the primary consumers is available. The carbon stable isotope composition of dissolved inorganic carbon (δ 13 C{DIC})
is generally different between SGD (low δ 13 CDIC ) and sea water (high δ 13 CDIC ). Bivalves record chemical and biologicalenvironment-signal in their shell. In this study, to examine whether the δ 13 C of bivalve shell (δ 13 CSHELL ) reflect the δ 13 CDICof the ambient water or not, we conducted the rearing experiments of Manila clam Ruditapes philippinarum under laboratory
and field conditions. Manila clam was reared at three different salinity in the laboratory; 100% sea water (100 % SW), 80%
sea water + 20% underground water (80 % SW) and 60 % sea water + 40% underground water (60 % SW). Water temperatureof three salinity groups was maintained at 25 ℃ and the same amount of diet (Chaetoceros gracillis ) was fed every day duringexperiments (3 months). There was a high positive correlation between δ 13 CDIC and salinity (r2 = 0.997, n = 32, p <0.001). Although the significant difference among 100 % SW, 80 % SW and 60% SW was not found (ANOVA, p >0.05), the δ 13 CSHELLof 80 % SW and 60 % SW was tend to be lower than that of 100 % SW. The field experiment was carried out at 6 sites under
different SGD condition in Obama Bay, Japan from July to August 2013. Manila clam was reared in the small containers withbottom sand, which were kept at the depth of 2 m under natural condition. There was a high negative linear relation between
δ 13 CSHELL and Radon 222 (222 Rn) concentration at surface layer of each rearing site ,which is a useful tracer of SGD (r2 =0.920, n = 6, p<0.01). Thus, it seems that the δ 13 CSHELL shows some possibility of being proxy for environmental reconstitutions of submarine groundwater discharge. However, the value of the δ 13 CSHELL was lower by about 5 ‰ than that of theδ 13 CDIC of ambient water in the laboratory experiment. It was the possible reason that isotopically light metabolic carbon,
derived from food, is incorporated into shell carbonated.
Keywords: Dissolved inorganic carbon, metabolic carbon, bivalve shell, carbon stable isotope ratio, submarine groundwater
discharge

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ACG33-10

Room:202

Time:May 26 11:45-12:00

The application of regional groundwater flow model to the underground dam in the ryukyu
limestone aquifer
ABE, Masami1∗ ; HATA, Kyoko1 ; YASUMOTO, Jun2 ; NAKANO, Takuzi2
1

IDEA Consultants, Inc., 2 Ryukyu University

The underground dam was construction in the Ryukyu limestone aquifer and groundwater is used to agricultural water. Water
quality change of groundwater and that affect to sea water quality through submarine groundwater discharge to be expected due
to agricultural use.
Groundwater model for understanding and predicting hydraulics and contaminant transport in aquifer make assumptions about
the distribution and hydraulic properties of geologic features that may not always apply to karst aquifers. In this study, afinite difference groundwater model (MODFLOW-NWT) was applied to construct an equivalent single layer two-dimensional
mathematical model of the Ryukyu limestone aquifer, which is located a southern part of Okinawa main islands. In orderto handle problems at regional scale groundwater model in the aquifer, automated parameter estimation method (PEST) andcoupling the conduit flow process was used in this model. Groundwater level measurements collected in 1994 were used tocalibrate a steady state model of the study area. This study shows the ability of MODFLOW-NWT and PEST to simulate
regional groundwater flow in highly karstified aquifer such as Ryukyu limestone aquifer, which is important for water resource
and groundwater management in the area.
Keywords: Underground dam, groundwater flow, conduit flow, PEST, submarine water discharge

1/1ACG33-11

Room:202

Time:May 26 12:00-12:15

Analysis about the condition of sea water intrusion to Yodo River estuary by the fluid
model
NAKAMURA, Ippei1∗ ; KOYAMA, Yuto1 ; NAKADA, Satoshi1 ; HAYASHI, Mitsuru1
1

Kobe University

Red tide of Alexandrium tamarense occurred in Yodo River estuary in recent years. A. tamarense is marine phytoplankton
and causes shellfish poisoning. Sea water intrusion to Yodo River is one of the reasons of marine phytoplankton survive. We
investigated the distribution of the sea water intrusion by in-situ observation, then reproduced it by the fluid model. Fluid
structure of Yodo River estuary consists by the runoff of fresh water, the esturey circulation, the tidal current and the wind driven
circulation. These had contributed at almost same rate to sea water ascension.

Keywords: Yodo River, sea water intrusion, Red tide, shellfish poison, fluid model

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ACG33-12

Room:202

Time:May 26 12:15-12:30

Diurnal variation of pH in Oshoro Bay, Hokkaido: A monitoring study assessing andprojecting impacts of ocean acidific
TAKAO, Shintaro1 ; FUJII, Masahiko1∗
1

Faculty of Environmental Earth Science, Hokkaido University

Coastal marine species have already been experiencing a low pH environment (<7.9) that is not predicted until 2100 in open
oceans in a high CO2 world. To properly assess impacts of ocean acidification on them inhabiting wide ranges of diurnal variationof pH, we need to conduct long-term and high-frequency monitoring measurements of environmental parameters. In this study,
to investigate the diurnal variation of pH in subarctic region, which is less known than tropical and subtropical regions, we
conducted monitoring measurements of pH, seawater temperature, and salinity in Oshoro Bay, Hokkaido from 2013 to 2014.
Mean, maximum, and minimum pH values obtained by a pH meter were 8.02, 8.47, and 7.33, respectively. Although ranges ofdiurnal variation of pH were different with season, increases in pH during the day and decreases during the night were foundin all periods. There are no statistically significant relationships between the variation of pH and that of seawater temperatureor salinity except in some cases. These results suggest that observed diurnal variations of pH may be driven by photosynthesis
and/or respiration in resident organisms in Oshoro Bay.
Keywords: subarctic region, ocean acidification, coastal ecosystem, diurnal variation

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ACG33-13

Room:202

Time:May 26 12:30-12:45

Ongoing stress of transboundary pollution: Assessment of atmospheric N deposition influence by means of nitrate isotopes
SUGIMOTO, Ryo1∗ ; NEGISHI, Kouki1 ; ASAI, Kazuyoshi2 ; MIYASHITA, Yuji3 ; TAHARA, Daisuke1
1

Fukui Prefectural University, 2 Geo Science Laboratory, 3 Hot Springs Research Institute of Kanagawa Prefecture

Anthropogenic emissions of reactive nitrogen (N) due to fossil fuel combustion and modern agriculture practices have dramatically increased in global scale. In the Japanese watershed along the Sea of Japan, large amounts of reactive N emitted
from northeastern Asia have deposited onto forest ecosystems, and thus N concentrations in rivers and groundwaters have been
increased year to year. Remotely modified N concentrations of terrestrial waters in local watersheds would affect coastal ecosystems. However, quantitative influence of N deposition on the watershed along the Sea of Japan is still unclear. In this study, we
assessed the influence of atmospheric reactive N deposition on the watershed in Wakasa Bay by means of the 17 O anomaly (⊿17O) in nitrate, which is an alternative tracer for atmospheric nitrate (NO3 − atm ). As a result, fractions of NO3 − atm in stream
waters of the Kita River observed in 2014 changed from >10% in winter to 6% in summer. This seasonal variation corresponded
to monthly changes in reactive N (= NO3 − , NH4 + and others) deposition rates onto the watershed. However, most of NO3 − instream water was derived from remineralized NO3 − by nitrification (NO3 − re ) within the watershed. Apparent nitrification rates
estimated by ⊿ 17 O were significantly higher than total N deposition rates. Although fractions of NO3 − atm in groundwater andspring water (mean±SD = 4.3±0.3%), which was dated from 2001 to 2009 by SF6 , were significantly lower than that in stream
water, yearly variation in NO3 − atm fractions showed exponential increasing trend in the recent decade. These results imply that
atmospheric reactive N deposition would affect severe influence on not only the forest ecosystem but also the coastal ecosystems.
Keywords: transboundary pollution, atmospheric nitrogen deposition, triple oxygen isotope, nitrogen saturation, retrospective
analysis, Sea of Japan

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