• 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.

• Korean Journal of Ecology and Environment
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• v.56 no.3
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• pp.268-279
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• 2023

Nowadays, artificial intelligence model approaches such as machine and deep learning have been widely used to predict variations of water quality in various freshwater bodies. In particular, many researchers have tried to predict the occurrence of cyanobacterial blooms in inland water, which pose a threat to human health and aquatic ecosystems. Therefore, the objective of this study were to: 1) review studies on the application of machine learning models for predicting the occurrence of cyanobacterial blooms and its metabolites and 2) prospect for future study on the prediction of cyanobacteria by machine learning models including deep learning. In this study, a systematic literature search and review were conducted using SCOPUS, which is Elsevier's abstract and citation database. The key results showed that deep learning models were usually used to predict cyanobacterial cells, while machine learning models focused on predicting cyanobacterial metabolites such as concentrations of microcystin, geosmin, and 2-methylisoborneol (2-MIB) in reservoirs. There was a distinct difference in the use of input variables to predict cyanobacterial cells and metabolites. The application of deep learning models through the construction of big data may be encouraged to build accurate models to predict cyanobacterial metabolites.

• Journal of Korea Water Resources Association
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• v.46 no.4
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• pp.401-412
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• 2013

Water footprint of a product and service is the volume of freshwater used to produce the product, measured in the life cycle or over the full supply chain. Since water footprint assessment helps us to understand how human activities and products relate to water scarcity and pollution, it can contribute to seek a sustainable way of water use in the consumption perspective. For the introduction of WFP scheme, it is indispensable to construct water inventory/accounting for the assessment, but there is no database in Korea to cover all industry sectors. Therefore, the aim of the study is to develop water footprint inventory within a nation at 403 industrial sectors using Input-Output Analysis. Water uses in the agricultural sector account for 79% of total water, and industrial sector have higher indirect water at most sectors, which is accounting for 82%. Most of the crop water is consumptive and direct water except rice. The greatest water use in the agricultural sectors is in rice paddy followed by aquaculture and fruit production, but the greatest water use intensity was not in the rice. The greatest water use intensity was 103,263 $m^3$/million KRW for other inedible crop production, which was attributed to the low economic value of the product with great water consumption in the cultivation. The next was timber tract followed by iron ores, raw timber, aquaculture, water supply and miscellaneous cereals like corn and other edible crops in terms of total water use intensity. In holistic view, water management considering indirect water in the industrial sector, i.e. supply chain management in the whole life cycle, is important to increase water use efficiency, since more than 56% of total water was indirect water by humanity. It is expected that the water use intensity data can be used for a water inventory to estimate water footprint of a product for the introduction of water footprint scheme in Korea.

• Korean Journal of Ecology and Environment
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• v.42 no.3
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• pp.350-363
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• 2009

Inter- and intra-specific differences in removal activities, filtering rates (FR) and production of feces-and pseudo-feces (PF) between a native freshwater bivalve in Korea, Anodonta woodiana Lea and Unio douglasiae Griffith et Pidgeon, were compared using a continuous removal of organic matters (CROM) system. The CROM system comprised five steps; input of polluted water, control of water flow, mussel treatment, analysis of water quality and discharge of clean water. The study was designed to compare the removal activity of organic matters between A. woodiana and U. douglasiae, and the intra-specific differences between density and length in A. woordiana. Results clearly indicate that two kinds of mussels had obvious removal activities of seston in the eutrophic reservoir. First, if both are similar in shell length, there were no significant inter-specific differences in removal activity between A. woordiana and U. douglasiae (P>0.5), but FRs of U. douglasiae was relatively high due to low ash-fee dry weight. Second, if both are same in animal density, the smaller mussels (1$\sim$2 years old) showed a higher filtering rate and production of feces- and pseudo-feces and less release of ammonium than the larger mussels. Third, if both are same in biomass, FRs and PF of mussels were higher in the low-density tank than the high-density tank, While the Concentration of $NH_4$-N and $PO_4$-P released WRS similar to each other (P>0.5). Therefore, these results suggest that CROM system using a young bivalve A. woordiana can be applied to control the nuisance seston in eutrophic lake system, if a relevant species and density were selected. Additional pilot tests to optimize the age and density of domestic bivalves were needed for the generalization of CROM operation.

• Journal of the Korean Society of Marine Environment & Safety
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• v.18 no.2
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• pp.101-114
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• 2012

The physico-chemical characteristics including water temperature, salinity, dissolved oxygen(DO), chemical oxygen demand (COD), chlorophyll-a(Chl. a), suspended particulate matter(SPM) and dissolved inorganic nutrients were investigated in the Garolim Bay, Yellow Sea, Korea in 2010 carried out six times per year at 11 fixed stations by Korea Fisheries Research & Development Institute. The water temperature, salinity, COD, dissolved inorganic nutrients, Chl. a and SPM showed significant difference between surface and bottom water but the other parameters didn't. There were not significant difference between stations. The water temperature showed typical change patterns of the temperate seawater. The annual average of salinity showed more than 31 so that there could not have occurred low saline water. The average of DO from June to August showed over than 3mg/L which showed higher than the below standard value of the hypoxic (oxygen-deficient) water. The average of Chl. a varied $1.68{\mu}g/L$ at surface, $2.38{\mu}g/L$ at bottom layer in June and $1.68{\mu}g/L$ at surface, $1.57{\mu}g/L$ at bottom layer at August. The dissolved inorganic nutrients showed high concentration in February and low concentration in August due to the limitation of the freshwater input in summer and phytoplankton used to the dissolved inorganic nutrients. The ratio of DIN/DIP showed 30.52 at surface and 37.89 at bottom layer in June which was higher than other month. The SPM was 44.15mg/L at bottom layer in February which was the highest value in this study due to the northwest monsoon. Because of the actively water change in the open sea without inflow of freshwater from land in Garolom Bay, there were not occurred low saline water and hypoxic water. thus, this Bay showed good water quality and required to be conserved continuously as important costal area for fisheries.

• Journal of the Korean earth science society
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• v.43 no.1
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• pp.91-109
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• 2022

The ocean is a significant sink for atmospheric anthropogenic CO₂, absorbing one-third of the total CO₂ emitted by human activities. In return, oceans have experienced significant declines in seawater pH and the aragonite saturation state also called ocean acidification. This study evaluates the distribution of aragonite saturation state, an indicator to assess the potential threat from ocean acidification, by combining newly obtained data from the west coast of South Korea with previous datasets covering the Yellow Sea, East Sea, northern South China Sea, and southeast coast of South Korea. In general, offshore waters absorb atmospheric CO₂; however, most of the collected water samples show aragonite oversaturation. On the southeast coast, the aragonite saturation state was significantly affected by river discharge and associated variables, such as freshwater input with nutrients, seasonal stratification, biological carbon fixation, and bacterial remineralization. In summer, hypoxia and mixing with relatively acidic freshwater made the Jinhae and Gwangyang Bays undersaturated with respect to aragonite, possibly threatening marine organisms with CaCO₃ shells. However, widespread aragonite undersaturation was not observed on the west coast, which receives considerable river water discharge. In addition, occasional upwelling events may have worsened the ocean acidification in the southwestern part of the East Sea. These results highlight the importance of investigating site-specific ocean acidification processes in coastal waters. Along with the above-mentioned seasonal factors, the dissolution of atmospheric CO₂ and the deposition of atmospheric acidic substances will continue to reduce the aragonite saturation state in Korean waters. To protect marine ecosystems and resources, an ocean acidification monitoring program should be established for Korean waters.

• 한국해양학회지
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• v.27 no.4
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• pp.303-310
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• 1992

Studies on the distribution of nitrogenous compounds, and respiratory oxygen consumption rate were carried out in Masan Bay, Korea where large amount of industrial and domestic wastewaters are discharged. In August 1986 the surface layer was significantly influenced by freshwater input. Below the seasonal pycnocline, an oxygen-deficient condition developed in a large area of Masan Bay. Concentrations of DIN, DON and PN were 735.6, 1261.8 and 48.5 umol/l at the head, and 79.1, 73.0 and 39.5 umol/l at the mouth of the inner Masan Bay, respectively. Phytoplankton carbon production was 2,695 mgC/m$^2$/day at the mouth of inner Masan Bay. Dissolved oxygen contents were lower than 1 ml/l from 3 m depth in inner Masan Bay and from 10 m depth in the outer Masan Bay. The high concentration of ammonium and phosphate in the lower layer suggests the active degradation of organic materials in the bottom waters and leaching from sediments. The ERS activity was 232.1 ul O$_2$/l/h in the surface waters of the innermost part of Masan Bay and respiratory oxygen consumption is likely to proceed at a rate of 442 ml O$_2$/m$^2$/day in the bottom waters of this bay. Nitrate removal rate was estimated to be 0.25 umol/l/day via denitrification in the bottom waters of the Masan Waterway. It is estimated from the ETS activity that, at the mouth of inner Masan Bay, 9.3-10.5% of carbon fixed in the upper layer was decomposed below the themocline.

• Korean Journal of Environmental Biology
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• v.33 no.1
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• pp.19-26
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• 2015

Pre-monsoon dynamics of zooplankton community were investigated in the estuary of the Tamjin River flowing into the Doam Bay of the southern coast of Korea. Monthly sampling was carried out to collect zooplankters at five sites in the estuary and the river during the period between March and June 2014. Dissolved oxygen contents were low between $5.0{\sim}7.0mgL^{-1}$ in the estuary and high, 7.0~11.0, in the river. Water temperature increased gradually from 12.0 to $28.0^{\circ}C$ and pH fluctuated between the range 7.4~8.8, respectively. A total of 85 taxa consisted of 25 species of rotifer, 30 kinds of copepod, 8 species of cladoceran, six kinds of aquatic insect larvae, four kinds of decapod and two kinds of Cirripedia larvae and Polychaeta larvae and one kind of Amphipoda, Ispopoda, Appenidicularia, Nematoda and Cnidaria, and Nocticluca scintillans was occurred. Brackish copepods distributed at almost all studied sites with freshwater zooplankters being restricted to upper waters of the river. Monthly succession of Acartia spp. was observed in the estuary with the occurrence of A. hudsonica in March and April then A. omori in May and June. Zooplankton abundance showed to vary from 450 to $87,818ind\;m^{-3}$ due to the explosion of copepodite and copepod nauplius in the estuary. Species diversity indices varied between 0.6~2.3 and generally low in the estuary and high in the river. Sea water input into the river seems to affect the river biota for more than some kilometers of the upper waters of the Tamjin River.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.35 no.1
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• pp.86-96
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• 2002

The distributions of suspended particulate matter (SPM), chlorophyll a, particulate organic carbon (POC) and nitrogen (PON) and particulate biogenic silica (PBSi) along the salinity gradient were investigated in the Seomjin River estuary from March 1999 to April 2001. Sampling sites were set based on the surface salinity during each cruise rather than geographic locations. Concentrations of SPM were less than 20 mg/L, suggesting relatively low input of terrestrial SPM despite large freshwater discharge through Seomiin River, Chlorophyll a peaks occurred at 5$\~$ 15 psu salinity zone (10$\~$20 km from Nan Cho Island) in November 1999, at 15$\~$25 psu (10$\~$20 km) salinity zone in April 2000 and at 1$\~$15 psu salinity zone (15$\~$20 km) in October 2000 (ca. 8$\~$58%\mu$g/L). Concentrations of POC, PON and PBSi were also high at the same zone. Relatively low ratios of POC to chlorophyll a in mid-salinity zone where POM peak occurred suggests high contribution of living phytoplankton to the total POC. On the other hand, relatively high ratios of POC to chlorophyll $\alpha$ in very low salinity zone and the mouth of estuary indicated relatively high portions of detrital POC. Consequently, the low concentrations of SPM in this estuary and the high concentrations of chlorophyll $\alpha$ and the low ratios of POC to chlorophyll $\alpha$ in the mid-salinity zone suggest that production of living phytoplankton is primary factor in controlling distribution of POM along the salinity gradients in the Seomjin River estuary.

• Korean Journal of Ichthyology
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• v.7 no.1
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• pp.56-63
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• 1995

Ecological study of the Cynoglossus joyneri was conducted based on the specimens from the western coast of Korea from 1992 to 1994. Ecological characteristics of this species such as gonadal development, occurrence of larvae, stomach contents, and environmental conditions were investigated. Few larvae of Cynoglossus joyneri occurred in Kunsan coast. This coast is influenced by the freshwater input of the Mangyong and Kum River, especially during the summer. Therefore, the larvae of C. joyneri were considered to be spawned and grown during their early life stage in the high saline water in outer bay. Spawning occur from June to September, having the peak spawning period from July to August. Biological minimum size of matured fishes containing mature oocytes is about 143.5mm in total length, which requires about 20 months after hatching. The ranges of total length by age are as follows : 0-ring group(floating stage), 30~70mm ; 1-ring group, 49.0~133.0mm 2-ring group, 128.6~167.0mm ; 3-ring group, 169.0~202.0mm ; 4-ring group, 200.7~240.0mm. The major food items of young fish under 8cm were copepods and invertebrate larvae, and those of adult fishes were annelids(polychaets) in winter, and bivalves and shrimps in summer and autumn. Therefore, it can be assumed that the population of C. joyneri could be reduced due to the decrease of food organisms caused by the continuous reclamation activities in the inner bays of the west coast of Korea.