• Korean Journal of Ecology and Environment
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• v.34 no.4 s.96
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• pp.267-276
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• 2001

The downstream reach of the Han River adjoining Seoul in Korea was the upper boundary of an estuary where tidal effect on the flow rate could be exerted. According to the comprehensive river regulation project, the river was channelize dand impounded by two overflow dams, which provided favorable condition for algal growth in this sewage polluted eutrophic reach. In this study primary productivity of phytoplankton was measured in the down reach and the autochthonous and allochthonous organic carbon loadings were estimated. Primary production of phytoplankton measured by C-14 uptake and P-I model method ranged from 140 to $4,890\;mgC\;m^{-2}\;d^{-1}$ (median value $1,865\;mgC\;m^{-2}\;d^{-1}$) showing the level of eutrophic lakes. Phytoplankton density that varied according to water flow rate was highest in spring. Allochthonous organic carbon loading was dominated by sewage input through tributaries in most of days except flood flow period. The average proportion of autochthonous carbon generation by phytoplankton was 40.9%, which is very high proportion for a lotic habitat.

• Journal of Environmental Science International
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• v.18 no.4
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• pp.463-471
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• 2009

A study on vegetation in the Mangyeong River and Dongjin River basins and the surrounding regions of the Saemangeum Reclaimed Land was conducted in a series of efforts to determine the expected ecological changes in the salt marshes, to restore their vegetation, to explore the restoring force of halophyte, to examine the community mechanism and, ultimately, to rehabilitate marshy land vegetation along the lakeside, coastal dune and salt marshes of the Saemangeum Project Area. The findings of the study may be summed up as follows: Five species such as Suaeda japonica, Salicornia herbacea, Atriplex gmelini, Aster tripolium and Suaeda asparagoides that are mostly distributed in the estuary of the Saemangeum Reclaimed Land were analyzed to examine the mechanism of halophyte to maintain their community. To find out the strategies of plants for survival and the cause of forming community structure, a research was made as for appearance ratio of biomass, root lengths and germination. With regard to biomasses of halophyte, the biomass of Suaeda japonica increases rapidly, while Salicornia herbacea adopts a strategy of unstable growth pattern by which the biomass increases slowly in parallel with its slow speed of growth since initial appearance of young sapling. In contrast, Suaeda asparagoides, Atriplex gmelini and Aster tripolium choose to adapt themselves to environment promptly by being transformed into life form of annual or biennial plant, a pattern that is presumed to be favorable and stable for survival in the later stage of growth. In short, there is a sharp distinction among the 5 species: i.e. Suaeda japonica that begins to grow fast in the length of surface and underground section but slows down from the mid-stage on; Salicornia herbacea that grows slowly in the beginning step but starts to step up from the middle onward; Atriplex gmelini and Aster tripolium growing slowly in the initial stage but fast later on; and Suaeda asparagoides that turns from the constant growth in the beginning to rapid growth in the later period. The outcomes of the analysis into status of growth and influencing factors of Suaeda japonica in the sowing field that is most widely prevalent in the Saemangeum Reclaimed Land as a sort of ecological pioneer in the salt marshes showed that the average size of grass lands, density and number of individuals increase in the natural sowing field as well as in the plowing field regardless of their physical as well as physico-chemical features of the soil as the season progresses from June to October of a year.

• Journal of the Korean Geographical Society
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• v.49 no.6
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• pp.812-832
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• 2014

We analyzed physical and chemical properties of sediments from 20 subtidal points and 9 beach points to define sedimentary environment between summer and winter of Shindu Marine Protected Area. Means of particle size in summer were generally finer than winter's. There was distinctively spatial pattern that particle sizes became increasingly fine as west direction and apart from beach in summer, but this pattern was not shown in winter. Coarse sediments were prevailed in winter. To explain these patterns, we propose possible two causes which are spatially different water depth condition related with seasonal wave climate or fine sediment input from an estuary located in south of this area during summer rainy season. Contents of exchangeable cations of sediment in summer were shown $Na^+$>$Ca^{2+}$>$Mg^{2+}$>$K^+$ in order, but those of winter were shown $Na^+$>$Mg^{2+}{\fallingdotseq}Ca^{2+}$>$K^+$. Contents of $Na^+$, $Mg^{2+}$, and $K^+$ were related with contents of fine sediment and showed high correlation in each other. These relations were not shown between $Ca^{2+}$ and others. Our results show that there are spatio-temporal unique sedimentary environments between subtidal zone, beach, and dune near Shindu Marine Protected Area. Therefore, we should consider these spatio-temporal patterns for environmentally sound management of Shindu coastal system.

• Korean Journal of Ecology and Environment
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• v.43 no.1
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• pp.117-128
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• 2010

The water qualities of Namdae-stream, Yeongok-stream and Sacheon-stream were examined, by using physicochemical factors, trophic status and epilithic diatoms from May 2008 to February 2009. The physicochemical water qualities of three streams were, except for some construction areas and sites of downstream, generally good, having less concentration than BOD of $2\;mg\;L^{-1}$. As for the sites of downstream, there were ongoing pollution such as graduation of nutrients in Namdae-stream and Sacheon-stream, due to salinity of seawater and topographical feature of the closed estuary. The examination of trophic status of Namdae-stream showed mesotrophic status in all the sites. Also, eutrophication was in progress as from the upstream to the downstream of Yeongok-stream, and Sacheon-stream showed eutrophic status in all its sites. As a result of the biological water quality assessment, Namdae-stream, excluding the downstream site, came out to be $\beta\sim\alpha$-oligosaprobic, and biological water quality was good, having TDI less than 50. Some construction sites and downstream site of Namdae-stream are $\beta$-mesosaprobic, and with the TDI over 70, the biological water quality assessment came out to be polluted. Yeongok-stream is $\beta\sim\alpha$-oligosaprobic, and its biological water quality is good, having TDI less than 40. Sacheon-stream, excluding the upstream site on May 2008 and February 2009, is $\beta\sim\alpha$-mesosaprobic, and its TDI over 70 shows that it has been polluted. The correlation analysis showed a high correlation in both DAlpo and TDI. Also, biological assessment of water quality (DAIpo, TDI) showed higher correlation with TSI rather than BOD.

• ALGAE
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• v.32 no.1
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• pp.47-55
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• 2017

We explored feeding by the mixotrophic ciliate Mesodinium rubrum, heterotrophic nanoflagellates (HNFs), and small ciliates (<$30{\mu}m$ in cell length) on natural populations of heterotrophic bacteria in Masan Bay, Keum River Estuary, and in the coastal waters of the Saemankeum area, Korea when M. rubrum red tides occurred. We also measured ingestion rates of M. rubrum on cultured heterotrophic bacteria as a function of bacterial concentration in the laboratory. The ingestion rates of M. rubrum on natural populations of heterotrophic bacteria (2.3-16.8 bacteria $grazer^{-1}h^{-1}$) were comparable to or lower than those of co-occurring HNFs (10.7-41.7 bacteria $grazer^{-1}h^{-1}$), but much lower than those of co-occurring small ciliates (76.0-462.2 bacteria $grazer^{-1}h^{-1}$). However, the maximum grazing coefficient of M. rubrum ($0.245d^{-1}$) on natural populations of heterotrophic bacteria was much higher than that of small ciliates ($0.089d^{-1}}$), and slightly higher than that of HNFs ($0.204d^{-1}$). With increasing bacterial concentrations, ingestion rates of M. rubrum on cultured heterotrophic bacteria continuously increased, but became saturated at higher prey concentrations over $1-5{\times}10^6cells\;mL^{-1}$. The maximum ingestion rate of M. rubrum on cultured heterotrophic bacteria was 34.4 bacteria $grazer^{-1}h^{-1}$. Based on the present study, it is suggested that M. rubrum may be an important grazer of heterotrophic bacteria and sometimes have considerable grazing impact on natural populations of heterotrophic bacteria.

• Journal of the Mineralogical Society of Korea
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• v.31 no.4
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• pp.257-266
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• 2018

East China Sea (ECS) is known to be supplied with large amounts of sediments form Huanghe, Changjiang and various rivers in Korea. Many studies have been conducted to identify the effects of rivers and deposition process of ECS, but no consensus has been reached. In this study, clay minerals, rare earth elements (REEs) and grain size were analyzed to study the provenance and sedimentation environment of core 99MAP-P63 in ECS. Clay mineral contents of 99MAP-P63 are abundant in order of illite, chlorite, kaolinite, and smectite. The provenance of 99MAP-P63 sediments using clay minerals is interpreted as the Changjiang regardless of depth. As a result of REEs analysis, 99MAP-P63 sediments are very similar to Chinese rivers sediments. Therefore, the provenance of 99MAP-P63 is Changjiang, and the influence of Korean river seems to be insignificant. 99MAP-P63 sediments are generally classified as sandy silt, but the top of the core is divided into sand with a sand contents of 85 %. Compared with surrounding cores, sandy silt sediments arecorresponded to the low stand stage when sea-level was low, and the sediments were thought to have been supplied directly through the paleo-Changjiang. Sandy sediments in uppermost of core are corresponded to transgressive stage. Although distance from estuary was increased due to sea-level rise, it was possible to supply coarse sediments due to high bottom stress, and the paleo-Changjiang sediments deposited in study area were re-deposited.

• Ocean and Polar Research
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• v.43 no.3
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• pp.127-140
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• 2021

At the estuaries of Bonggang and Miryong streams in the Korean southern coast, the spatiotemporal distribution and habitat environment of a nerite snail, Clithon retropictum (Gastropoda: Neritidae), which has been assigned as a legally protected species of Korea, were explored. Physicochemical environmental factors such as water temperature, salinity, tidal level distribution as well as biotic environments (chlorophyll-a concentration and epilithic microalgae composition) were monitored every month. The relationships between the environmental factors and spatiotemporal distribution of the nerite snail population were analyzed. Water temperature, salinity, and water level varied by season and lunar tidal rhythm. The spatiotemporal distribution of the nerite snail was mostly related to water salinity. Among epilithic algae which were the priority prey of snails, blue-green algae and green algae dominated in summer and autumn, while diatoms predominated during winter and spring. Chlorophyll-a concentration was highly and positively correlated with the population density of the nerite snail. The correlation coefficients were different depending on the taxon (Family) of epilithic algae. The mean population density was 302.2 inds m^-2 and 271.8 inds m^-2 in Bonggang Stream and Miryong Stream, respectively. The egg capsules of the nerite snail in the two habitats were observed from March (in Bonggang Stream) or April (in Miryong Stream) to August, and newly hatched juveniles recruited in the habitats from August were assessed with regard to frequency distributions of shell width. The occurrence of large-sized snails in upper stream reaches of both Bonggang and Miryong indicated the movement of spats from the mouth to the upper reaches during the whole life cycle.

• Korean Journal of Ecology and Environment
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• v.54 no.1
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• pp.1-11
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• 2021

Fish community characteristics was investigated in Namyang Lake and tributaries in Han River basin, Korea from April to October 2015. During the period, there were 5,672 individuals of 20 species appeared from tributaries (St. 1~St. 6) and dominant species were Pseudorasbora parva (33.5%). Also 5,672 individuals of 20 species appeared in Namyang Lake (St. 7~St. 9) and dominant species were Carassius auratus (32.2%). There were 5 species of endemic species with Rhodeus uyekii, Acanthorhodeus gracilis, Squalidus japonicus coreanus, Abbottina springeri and Odontobutis interrupta from Namyang Lake watershed. The frequency of endemic species were higher tributaries (18.5%) than Namyang Lake (15%). Exotic species were 3 species with Carassius cuvieri, Lepomis macrochirus, and Micropterus salmoides. there were appeared more frequently Namyang Lake (15.0%) than tributaries(7.4%).

• The Journal of Engineering Geology
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• v.30 no.4
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• pp.589-602
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• 2020

As can be seen in many earthquakes, liquefaction causes differential settlement, which sometimes produces serious damages such as building destruction and ground subsidence. There are many possible active faults near the Busan city and the Yangsan, Dongrae, and Ilgwang faults among them pass through the city. The Busan city is also located within the influence of recent earthquakes, which occurred in the Gyeongju, Pohang, and Kumamoto (Japan). Along the wide fault valleys in the city, the Quaternary unconsolidated alluvial sediments are thickly accumulated, and the reclaimed lands with beach sediments are widely distributed in the coastal area. A large earthquake near or in the Busan city is thus expected to cause major damage due to liquefaction in urban areas. This study conducted an assessment of the liquefaction hazard according to seismic recurrence intervals across the Busan city. As a result, although there are slight differences in degree depending on seismic recurrence intervals, it is predicted that the liquefaction potential is very high in the areas of the Nakdonggang Estuary, Busan Bay, Suyeong Bay, and Songjeong Station. In addition, it is shown that the shorter the seismic recurrence interval, the greater difference the liquefaction potential depending on site periods.

• Journal of Environmental Impact Assessment
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• v.31 no.2
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• pp.95-105
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• 2022

Busan, where the coastal ecosystem health is deteriorating due to high development pressure and intensity of use, needs ecosystem management that considers humans and the natural environment together for sustainable use and ecosystem preservation of the coastal areas. In this study, the InVEST model was applied to assess the habitat status of the coastal land and coastal sea to manage the ecosystem based on habitats. As a result of the assessment of the coastal land, the habitat quality of Gadeok-do, Igidae, and Sinseondae, Gijang-gun are high, and Seo-gu, Jung-gu, Dong-gu, and Suyeong-gu are low. In the case of the coastal sea, the habitat risk of the Nakdong river estuary is low, and some areas of Yeongdo-gu, Saha-gu, Gangseo-gu are high. Therefore, for the sustainable use and preservation of coastal ecosystems, it is necessary to prepare ecosystem-based management measures to improve damaged habitats and reduce threats. In addition, the impact on coastal seas should be fully considered when planning coastal land development. The results of the InVEST habitat quality model in coastal land show similar tendencies to the biotope and environmental conservation value assessment map. The results of the habitat risk assessment in the coastal sea are expected to be utilized to identify habitats in the coastal sea and management of threat factors.