• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.8 no.3
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• pp.251-261
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• 2003

As a part of an on-going project investigating flux of materials in Gomso Tidal Flat, we have monitored temporal and spatial distribution of nitrogen components(TN, PON, DON, DIN) and have sought the relationships with the freshwater input(tidal range, salinity), the biological activities(chlorophyll-${\alpha}$, TP, DIP, silicate) and the resuspended bottom sediment in seawater(SPM) from 1999 to 2000. TN in seawater was 39.05 $\mu\textrm{m}$ol 1$\^$-1/ (31.03∼42.93 $\mu\textrm{m}$ol 1$\^$-1/) without any statistical difference(p<0.05) between the studied periods. Organic nitrogen (DON and PON) occupied 75％, 95％, 73％, and 75％ in April, August, September and November, respectively. DON and PON have been found within the narrow concentration ranges of 11.30∼16.38 $\mu\textrm{m}$ol 1$\^$-1/ and 13.16∼20.04 $\mu\textrm{m}$ol 1$\^$-1/ in spite of severe environmental differences through the studied periods. Dissolved fractions of nitrogen(DON and DIN) occupied 53∼65％ of TN. Only DIN varied with an evident temporal variability: low concentrations(1.325∼1.616 $\mu\textrm{m}$ol 1$\^$-1/) in August and high enrichment(8.377∼14.65 $\mu\textrm{m}$ol 1$\^$-1/) in September. High consumption rate of DIN by phytoplankton and a long-lasted drought probably induced such low concentration of DIN in August. Eventually heavy precipitation probably introduced plenty of new nitrogen sources into Gomso Bay in September. The portion of PON, DON and DIN in the total nitrogen was 40％, 38％ and 22％, respectively. Their contents were in the order of DON>PON>DIN for the year round except PON>DON>DIN only in September. The highest DON portion in August probably due to the active microbial decomposition of organic material in summer. Only in April, some evident negative correlations have been found between chlorophyll-${\alpha}$ and DIN mostly nitrate(-0.64, p<0.01), phosphate(-0.46, p<0.01) and silicate(-0.55, p<0.01). The Si(OH)$_4$/DIN/DIP ratios in the water column suggests the limitation of DIN for the growth of phytoplankton during the dry summer in Gomso Bay, which was the case of August in this work. Even with some difference between the studied periods, the primary factors on the distribution of nitrogen components in seawater overlying the Gomso Tidal Flat have been the tidal range and the freshwater input, but the additional variations were due to the biological activities.

• 한국해양학회지
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• v.23 no.4
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• pp.194-206
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• 1989

Seasonal variations of nutrients (ammonium, nitrite, nitrate, phosphate and silicate), primary productivity and ammonium regeneration rate of macrozooplankton were investigate to understand the relationship between nitrogen recycling and nitrogen requirement by phytoplankton from Feburuary 1986 to November 1987 in the Kyunggi Bay, shallow estuarine water of Yellow Sea. In general, nutrients increased during the winter and depleted during the spring and the early summer except temporally sharp increase after flood in September. Ammonium was prevalently generally found in high concentration throughout the study area and it occasionally raised N/P ratio in the range of 30 to 70 as in the freshwater environment. Daily net primary productivity ranged from 30.3 to 3580.0 mgC/$m^2$/d with an average of 883.9 mgC/$m^2$/d. Annual primary productivity was determined to be 320.0 gC/$m^2$/yr. Carbon assimilation number ranged from 2.9 to 19.4 mgC/mg chl-a/h which increased in the summer and decreased in the winter. Nitrogen requirement by phytoplankton ranged from 0.4 to 45.0 mg at-N/$m^2$/d and turnover time of inorganic nitrogen ranged from 2.4 in the late summer to 122.7 days in the winter. Nitrogen regeneration rate of mixed macrozooplankton determined by bottle incubation method ranged from 0.02 to 1.34 mg at-N $m^2$/d and it could contribute from 2.8 to 38.7% with an annual average of 14.9% of total nitrogen requirement by phytoplankton in this shallow estuarine environment.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.14 no.11
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• pp.6008-6014
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• 2013

This study aimed to understand seasonal variation of physico-chemical factors and biomass of size-fractionated phytoplankton at Ulsan seaport during the period from February 2007 to November 2009. Water temperature, salinity, dissolved oxygen (DO), pH, chemical oxygen demand (COD) and total suspended solid (TSS) varied in the range of 8.94-$24.26^{\circ}C$, 25.06-34.54 psu, 4.30-10.73 mg/L, 7.97-8.53, 0.66-40.70 mg/L and 57.4-103.3 mg/L, respectively. These factors showed no clear spatial variation unlike spatial pattern of inorganic nutrients and total chlorophyll-a (chl-a) concentration as biomass. Concentration of phosphate, nitrate and silicate ranged from 0.01 to 3.03 ${\mu}M$, 0.05 to 21.62 ${\mu}M$, and 0.01 to 27.82 ${\mu}M$, respectively, with 2 times higher concentration at inner stations than that at outer stations during the study period. Within the range of total chl-a concentration (0.36-7.11 ${\mu}gL^{-1}$), higher concentration (avg. 1.88 ${\mu}gL^{-1}$) of total chl-a were observed at inner stations compared to that (avg. 0.90 ${\mu}gL^{-1}$) at outer stations. Micro-sized phytoplankton dominated total biomass of phytoplankton in spring (34.0-81.2%), summer (35.1-65.6%) and winter (3.9-62.0%). Nano- and pico-sized phytoplankton contributed 58.2-74.5% and 22.4-38.2% to total biomass of phytoplankton in autumn, respectively. However, contribution in biomass of size-fractionated phytoplankton to total phytoplankton biomass showed no clear difference between inner and outer stations. Consequently, these results indicated that spatio-temporal distribution of phytoplankton biomass at Ulsan seaport was dominated by micro-phytoplankton (avg. 52.3%) during the study period except autumn, which was closely dependent on the concentration of inorganic nutrients (p<0.05).

• Korean Journal of Fisheries and Aquatic Sciences
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• v.34 no.5
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• pp.457-464
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• 2001

Algal growth potential (AGP) assay using Cochlodinium polykrikoides was conducted in Saryang Island coast where C. polykrikoides red tide occurred annually from July to October 1998. The effects of macro- and micro-nutrients on the growth of C. polykrikoides were specifically evaluated by the algal assay method. Two different types of growth response of C. polykikoides for the addition of nutrients were clearly obseued. For both before and after C. polykrikoides occurrence, the growth of C. polykikoides was significantly stimulated by the addition of either nitrate or ammonium of $50{\mu]M$ with phosphate of $5{\mu}M$. The addition of a single nutrient had no clear effect on the growth of C. polyhikoides and the addition of trace metals, vitamins, and EDTA etc. did not stimulate the algal growth, also. This result indicates that both N and P potentially limited the growth of C. polyhikoides in this period. However, during a bloom of C. polyhikoides, the growth was unlikely to be stimulated by the addition of both macro- and micro-nutrients. At that time the nutrient concentration of Saryang Island coast was $24.33{\mu}M$ for ammonium, $1.61{\mu}M$ for phosphate, and $0.58{\mu}M$ for nitrate, respectively. The concentrations of nutrients increased, on average, 8.2-fold for ammonium and 4.8-fold for phosphate, decreased 3.3-fold for nitrate compared to both before and after the red tide. This result shows that the growth of C. polykikoides was not limited by the nutrients during the bloom in September. Therefore, our results suggest that the C. polykrikoides red tide may outbreak especially when the water is fertilized due to the increased N and P.

• Korean Journal of Soil Science and Fertilizer
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• v.27 no.1
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• pp.33-39
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• 1994

This survey was conducted to investigate the factors affecting on salt accumulation and chemical components of soils cultivated with horticulture crops in plastic film houses. The soil samples were taken from 40 sites in the northern central areas of Korea and were analyzed for the chemical properties and soil separates. The data were evaluated with soil texture and years of cultivation as major factors. The results are summarized as follows : 1. The chemical properties of surface soils in plastic film house were pH 5.80, EC $3.59mScm^{-1}$, O.M. 4.20%, Av. $P_2O_5$ 1,178ppm, $NO_3-N$ 180ppm, Av. $SO_4{^{2-}}$ 353ppm, $Cl^-$ 240ppm, Ex. Na 0.40me/100g. 2. Compared to the outside soil of plastic film house, the inside soil had 2.5~3 times higher contents of $NO_3-N$, Av. $SO_4{^{2-}}$ and $Cl^-$, 1.2~1.8 times higher exchangeable base elements, and 2.8 times higher electrical conductivity. But pH value of the inside soil was lower than the outside soil by 0.3 pH unit. 3. Soil texture classification showed that sandy loam, loam and silt loam were 32.5 %, 37.5 %, and 30.0 %, respectively. The contents of $NO_3-N$, Av. $SO_4{^{2-}}$, $NH_4-N$ and EC value were very high in silt loam soils. Av. $P_2O_5$ content and pH value of sandy loam soils were higher than those of silt loam and loam soils. 4. The contents of O.M. and Av. $P_2O_5$ were higher in long term cultivation, but the contents of $NO_3-N$, Av. $SO_4{^{2-}}$, $Cl^-$, Ex. Mg and Ex. Na including EC of the soil with 2~4 years cultivation were higher than those of the soil with above 5 years cultivation. 5. Multiple linear regression analysis showed that contribution degree of soil chemical properties to the EC was high in the order of $NO_3-N$ > Av. $SO_4{^{2-}}$ > Ex. Na > $Cl^-$ > Av. $P_2O_5$ > $NH_4-N$ > Ex. Mg>Ex. Ca. Among the soil chemical properties the contribution of anions was remarkably high. 6. EC value correlated with ${\sum}A$(total content of anions)as $r=0.932^{**}$ and with ${\sum}C$(total content of cations) as $r=0.452^{**}$.

• Journal of the Korean Society of Marine Environment & Safety
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• v.27 no.7
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• pp.924-942
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• 2021

The expansion of the Changjiang Diluted Water (CDW) plume during summer is known to be a major factor influencing phytoplankton diversity, community structure, and the regional marine environment of the northern East China Sea (ECS). The discharge of the CDW plume was very high in the summer of 2020, and cruise surveys and stationary monitoring were conducted to understand the dynamics of changes in environmental characteristics and the impact on phytoplankton diversity and community structure. A cruise survey was conducted from August 16 to 17, 2020, using R/V Eardo, and a stay survey at the Ieodo Ocean Research Station (IORS) from August 15 to 21, 2020, to analyze phytoplankton diversity and community structure. The southwestern part of the survey area exhibited low salinity and high chlorophyll a fluorescence under the influence of the CDW plume, whereas the southeastern part of the survey area presented high salinity and low chlorophyll a fluorescence under the influence of the Tsushima Warm Current (TWC). The total chlorophyll a concentrations of surface water samples from 12 sampling stations indicated that nano-phytoplankton (20-3 ㎛) and micro-phytoplankton (> 20 ㎛) were the dominant groups during the survey period. Only stations strongly influenced by the TWC presented approximately 50% of the biomass contributed by pico-phytoplankton (< 3 ㎛). The size distribution of phytoplankton in the surface water samples is related to nutrient supplies, and areas where high nutrient (nitrate) supplies were provided by the CDW plume displayed higher biomass contribution by micro-phytoplankton groups. A total of 45 genera of nano- and micro-phytoplankton groups were classified using morphological analysis. Among them, the dominant taxa were the diatoms Guinardia flaccida and Nitzschia spp. and the dinoflagellates Gonyaulax monacantha, Noctiluca scintillans, Gymnodinium spirale, Heterocapsa spp., Prorocentrum micans, and Tripos furca. The sampling stations affected by the TWC and low in nitrate concentrations presented high concentrations of photosynthetic pico-eukaryotes (PPE) and photosynthetic pico-prokaryotes (PPP). Most sampling stations had phosphate-limited conditions. Higher Synechococcus concentrations were enumerated for the sampling stations influenced by low-nutrient water of the TWC using flow cytometry. The NGS analysis revealed 29 clades of Synechococcus among PPP, and 11 clades displayed a dominance rate of 1% or more at least once in one sample. Clade II was the dominant group in the surface water, whereas various clades (Clades I, IV, etc.) were found to be the next dominant groups in the SCM layers. The Prochlorococcus group, belonging to the PPP, observed in the warm water region, presented a high-light-adapted ecotype and did not appear in the northern part of the survey region. PPE analysis resulted in 163 operational taxonomic units (OTUs), indicating very high diversity. Among them, 11 major taxa showed dominant OTUs with more than 5% in at least one sample, while Amphidinium testudo was the dominant taxon in the surface water in the low-salinity region affected by the CDW plume, and the chlorophyta was dominant in the SCM layer. In the warm water region affected by the TWC, various groups of haptophytes were dominant. Observations from the IORS also presented similar results to the cruise survey results for biomass, size distribution, and diversity of phytoplankton. The results revealed the various dynamic responses of phytoplankton influenced by the CDW plume. By comparing the results from the IORS and research cruise studies, the study confirmed that the IORS is an important observational station to monitor the dynamic impact of the CDW plume. In future research, it is necessary to establish an effective use of IORS in preparation for changes in the ECS summer environment and ecosystem due to climate change.

• Journal of the Korean Society of Marine Environment & Safety
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• v.25 no.4
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• pp.457-467
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• 2019

To investigate the long-term variation characteristics of nutrients in the east coast of Korea, water temperature, salinity, dissolved oxygen, and nutrients were measured at three stations of Sokcho, Jukbyeon and Gampo coasts for five years from 2013 to 2017. For five years, the water temperature of the East Sea coast was in the range of $1.2{\sim}28.8^{\circ}C$, the salinity was in the range of 30.63~34.79 and the dissolved oxygen (DO) was in the range of 3.53~7.64 mL/L. Distribution and variation of the water environment factors in the study area were determined by the vertical stratification of water column and distribution of water temperature. The high DO concentration in Sokcho coast From 2015 to August 2016 is presumed to be the result of the southward inflow of North Korean Cold Water (NKCW). Concentrations of dissolved inorganic nitrogen (DIN, $NH_4-N+NO_2-N+NO_3-N$) ranged $0.11{\sim}24.19{\mu}M$, phosphate concentration ranged $0.01{\sim}1.75{\mu}M$, and silicate ranged $0.17{\sim}32.80{\mu}M$. The N:P ratio was in the range of 0.7~54.3 (mean 15.2) and the N:P slope was in the range of 11.67~13.75. The N:P ratios in this study were lower than the Redfield ratio (16), indicating that nitrate did act as a limiting factor in phytoplankton growth. The correlation ($R^2$) of total N:P ratio was as high as 0.95, indicating that the effect of the surrounding land or non-point sources was not significant. In conclusion, the spatial and temporal variation of nutrients in the east coast of Korea was determined by the vertical mixing of water mass with thermocline and mainly affected by physical factors such as influx of external water masses and coastal upwelling, and the influences from inflows from the land were minimal.

• Journal of the Korean Society for Marine Environment & Energy
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• v.18 no.3
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• pp.166-178
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• 2015

We investigated marine environmental characteristics of Goheung coastal areas in August where is known to be the first outbreak site of Cochlodinium polykrikoides (hereafter C. polykrikoides) blooms, based on the oceanographic data observed from 1993 to 2013 around the Korean southern coastal waters including Eastern China Sea by National Fisheries Research and Development Institute (NFRDI). The data of NOAA/NGSST satellite images as well as numerical simulation results by Seo et al. [2013] were also used for analysis. Water temperatures at the surface and bottom layers in Goheung coast, i.e. Narodo, were $25.0^{\circ}C$ and $23.7^{\circ}C$ so that they were higher than $23.8^{\circ}C$ and $19.4^{\circ}C$ in Geoje coast where is a reference site, respectively. In addition, salinities at the surface and bottom layers in Goheung coast were 31.78 psu and 31.98 psu so that they were a little higher than 31.54 psu at the surface but a little lower than 32.79 psu at the bottom in Geoje coast, respectively. That is, the differences in water temperature or salinity between the surface and bottom layers in Goheung coast in August were not large compared to Geoje coast. This suggests that stratification in Goheung coast in August is fairly weak or may not be established. In addition, the concentrations of DIN and DIP at the surface layer were 0.068 mg/L ($4.86{\mu}M$) and 0.015 mg/L ($5.14{\mu}M$) in Goheung coast while 0.072 mg/L ($5.14{\mu}M$) and 0.01 mg/L ($0.32{\mu}M$) in Geoje coast, so they did not indicate a meaningful difference. On the other hand, when C. polykrikoides blooms, water temperature and salinity in August at the station 317-22 ($31.5^{\circ}N$, $124^{\circ}E$) of the East China Sea, where is near the mouth of Yangtze River, were $27.8^{\circ}C$ and 31.61 psu, respectively. Thus, water temperature was much higher whereas salinity was almost similar compared to Goheung coast. Furthermore, concentrations of $NO_3-N$ and $PO_4-P$ in the East China Sea in August were remarkably high compared to Goheung coast. When C. polykrikoides blooms, according to not only the image data of satellites NOAA/NGSST but also numerical experiment results by Seo et al.[2013], the freshwater out of Yangtze River was judged to clearly affect the Korean southern coastal waters. Therefore, the supply of nutrients in terms of Yangtze River may greatly contribute to the outbreak of C. polykrikoides blooms in Goheung coast in summer.

• Journal of Environmental Science International
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• v.14 no.2
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• pp.177-184
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• 2005

This study was to determine the fluctuation in phytoplankton assemblages with regarding to environmental conditions and nutrients, which were surveyed around Mokpo waters in the southwestern waters, Korea. Sampling was carried out on the Mokpo, Sinan, and Wando coasts from March to November 2003. The maximum sea surface temperature was recorded in August, and it ranged around $25^{\circ}C$ regardless of sampling sites. However, salinity in Mokpo waters showed a great variation, which ranged from 5-30 psu and recoded the minimum of 5 psu in July and the maximum of 30 psu in November. Moreover, in Mokpo waters, the chlorophyll a and SS concentration of the surface layer were also the highest values of $20\;{\mu}g\;l^{-1}\;and\;40\;{\mu}g\;l^{-1}$, respectively than those of Sinan and Wando waters. The concentrations of $NH_4-N,\;NO_2-N,\;NO_3-N,\;and\;PO_4-P$ were also he highest values of $0.018\;{\mu}mol\;^l{-1},\;0.062\;{\mu}mol\;l^{-1},\;1.2\;{\mu}mol\;l^{-1}\;and\;0.078\;{\mu}mol\;l^{-1}$, respectively in Morpo waters than those of Sinan and Wando waters. During the period of this study, the majority of the taxa were diatoms; Thalassiosira rotula, Rhizosolenia setigera, Prorocentrum minimum, Chaetoceros curvisetus, Leptocylindrus danicus, Pseudonitzschia pungens, and Chaetoceros spp. were detected in the dominant species of phytoplankton. The dinoflagellates were relatively abundant during the summer season in Wando waters, which attained an abundance of $10-20\%$. In Mokpo waters, DIN/DIP was the highest value of 700 in March, whereas the lowest was shown in Wando waters. However, DIN/DIP value in summer at Wando waters was extremely reversed, which appeared to be associated with the development of dinoflagellates. On the bais of factor analysis using SYSAT 6.0, nutrient showed somewhat correlation with chlorophyll a. Consequently, the process of discharge of fresh water in Mokpo waters plays an important role in extremely fluctuation in nutrients and conditions. Although Wando waters maintains a lack of nutrients, it should be influenced by different water current and may be associated with a concentration of nutrients.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.5 no.3
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• pp.195-207
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• 2000

Organic and inorganic characteristics including bacterial cell number, enzyme activity, nutrients, and heavy metals have been monitored in twelve acrylic experimental tanks for two weeks to estimate and compare self-purification capacities in two Korean wet-land environments, tidal flat and rice field, which are possibly different with the environments in other countries because of their own climatic conditions. FW tanks, filled with rice field soils and fresh water, consist of FW1&2 (with paddy), FW3&4 (without paddy), and FW5&6 (newly reclaimed, without paddy). SW tanks, filled with tidal flat sediments and salt water, are SW1&2 (with anoxic silty mud), SW3&4 (anoxic mud), and SW5&6 (suboxic mud). Contaminated solution, which is formulated with the salts of Cu, Cd, As, Cr, Pb, Hg, and glucose+glutamic acid, was spiked into the supernatent waters in the tanks. Nitrate concentrations in supernatent waters as well as bacterial cell numbers and enzyme activities of soils in the FW tanks (except FW5&6) are clearly higher than those in the SW tanks. Phosphate concentrations in the SW1 tank increase highly with time compared to those in the other SW tanks. Removal rates of Cu, Cd, and As in supematent waters of the FW5&6 tanks are most slow in the FW tanks, while the rates in SW1&2 are most fast in the SW tanks. The rate for Pb in the SW1&2 tanks is most fast in the SW tanks, and the rate for Hg in the FW5&6 tanks is most slow in the FW tanks. Cr concentrations decrease generally with time in the FW tanks. In the SW tanks, however, the Cr concentrations decrease rapidly at first, then increase, and then remain nearly constant. These results imply that labile organic materials are depleted in the FW5&6 tanks compared to the FW1&2 and FW3&4 tanks. Removal of Cu, Cd, As from the supernatent waters as well as slow removal rates of the elements (including Hg) are likely due to the combining of the elements with organic ligands on the suspended particles and subsequent removal to the bottom sediments. Fast removal rates of the metal ions (Cu, Cd, As) and rapid increase of phosphate concentrations in the SW1&2 tanks are possibly due to the relatively porous anoxic sediments in the SW1&2 tanks compared to those in the SW3&4 tanks, efficient supply of phosphate and hydrogen sulfide ions in pore wates to the upper water body, complexing of the metal ions with the sulfide ions, and subsequent removal to the bottom sediments. Organic materials on the particles and sulfide ions from the pore waters are the major factors constraining the behaviors of organic/inorganic elements in the supernatent waters of the experimental tanks. This study needs more consideration on more diverse organic and inorganic elements and experimental conditions such as tidal action, temperature variation, activities of benthic animals, etc.