9） Effect of submarine groundwater discharge on Nutrient characteristics in the sediment
Guangzhe Jin (1*), Shin-ichi Onodera (1), Mitsuyo Saito (2), Yuta Shimizu (1),Atsuko Amano (3), Xingyu Guo (2), Takaharu Sato (1), Mayumi Jige (4)1)

Graduate School of Integrated Arts and Sciences, Hiroshima University,
2)

3)
4)

Center for Marine Environmental Studies, Ehime University

Marine Geology research Group Institute of geology and Geoinformation Geological Survey of Japan , AIST

Faculty of Risk and Crisis Management Department of Environmental Security System, Chiba Institute of Sciencein this area, we compared the vertical variance of

1. Introduction
Submarine groundwater discharge (SGD) is

Nutrient in the sediment and sediment porean important source of new nutrients, tracewater from a costal bay area (Kojima Bay) and aelements, and contaminants discharge to thesemi-enclosed bay (Hiuchi-Nada) in Seto-Inland

coastal ocean in many parts of the world. Several

Sea, Japan.

studies showing that SGD makes a significant

2. Method

contribution to the nutrient budget of coastal

Sediment Core samples were taken by pistonwaters. As the importance of SGD, it has led tosampler and by diving in the field trip in 2009

growing research interest in this phenomenon.

and 2010 (Fig.1). The sediment samples were

While the nutrient interaction process and theanalyzed for the pore water nutrient andsignals of sediment in this discharge process as

sediment phosphorus nitrogen, carbon content.

well as the long term effect of nutrient discharge

The dating data of the sediment core was also

through SGD is unknown.

determined byThe

Seto

InlandSeaisthelargest

sediment

pore137Csandwater210Pb

analysis. Thewasextractedbysemi-enclosed coastal sea area in Japan. The

centrifugation for 30 min at 3500 rpm. The

eutrophication incidents occurred in this area

nutrient content in pore water samples werewith most serious scale from the 1960s to 1970s.

measured by spectrophotometry. The sediment

The contribution of nutrient discharge throughphosphorus

SGD in some part of Seto Inland Sea area isdetermined by using the methods of Aspila et al.

focused(1976). Sediment carbon and sediment nitrogen

byotherresearchers.

Inorderto

determine the sediment nutrient characteristics

contentinthesedimentcontent were analyzed by CHN analyzer.

Fig.1 the research location, Kojima Bay (left) and Hiuchi-Nada (right)was3. Results and Discussion

sediment

accumulation

process.

The1) SGD effect on sediment pore watersemi-enclosed bay sediment nutrient structure

The pore water shows significant difference

may have connection with submarine groundtrend between the two locations. The results show

water discharge process reported by Saito et al.

that both the PO4-P and total phosphorus(2011) that provides a nutrient supply and water

concentrations in sediment pore water (Fig.2) are

discharge affection.

comparable higher in Hiuchi-Nada sediment
samples than the pore water samples in Kojima
Bay area. As the SGD is an important way ofdischarging the nutrient into the coastal area.
Also in Seto-Inland sea area, Onodera et al. (2007)
reported that the coastal groundwater around theSeto

InlandSeaischaracterized

byhighphosphorus concentration. The pore water TNshows that the Hiuchi-Nada area has lower TN
concentrations compare to the Kojima bay coresamples. The relationship between N and P in theFig.3 relationship between pore water
nitrogen and phosphorus

pore water (Fig 3) shows significant difference2) Sediment phosphorus and nitrogen content

trend between the two locations. Kojima bay area

The results show that Kojima Lake (anhas high N:P ratios (average 322:1) and theartificial lake by enclosed inner part of thevalues has been in increasing trend down core

Kojima bay) has captured higher phosphorus inwhile Hiuchi-Nada area has a decreasing trend

sediment (0.37-1.19 μg/g) than nearby Bay area

down core with relatively lower value (average(0.42-0.62 μg/g) and Hiuchi-Nada area (0.45-0.6326:1). This may indicate nutrient of the poreμg/g)in Seto Inland Sea. On the other handwater affected by different terrestrial resources

phosphorus

between two locations rather than the different

variations with depth in the sediments in Kojima

didnotshow

thesignificant

bay and Hiuchi-Nada area. Sediment nitrogencontent shows higher level in Kojima bay rather
than the lake and Hiuchi-Nada area, Highcorrelative relationship between the carbon andnitrogen content in sediment(R2=0.64, n=89 ) may
indicates nitrogen deposition was affected by theorganic matter transportation by river discharge
Different

fromtheaffectionbyriverdischarge, SGD did not result in big variations insediment N and P properties. Nutrient discharge
through SGD may more obviously affect the poreFig.2 the pore water phosphorus and nitrogenconcentrations in sediment pore water samples

water nutrient content which is considered an
important pathway of SGD nutrient discharge.