• Journal of the Korean earth science society
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• v.21 no.2
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• pp.128-136
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• 2000

To understand the variation and transport pattern of suspended matters, salinity, tidal current and suspended matters in semiclosed Muan Bay have been monitored during winter and summer. The suspended matters show considerably seasonal variations with low concentration and homogeneity in the water column during winter season, but with high concentration and layering during summer season. Particularly, during summer season, the freshwater and the suspended matters influxed by the gate operation of the Youngsan River sea-dike are transported northward in accordance with the would flow into the inner-bay by relaxed flood currents after the construction of sea-dike and sea-walls in the Mokpo coastal zone. But, in the south bay-mouth, those matters outflow through the bay-mouth, resulting from tidal ebb dominance and asymmetry in the west bay-mouth. The residual suspended matter flux is much higher in the south bay-mouth(-0.0955kg/m ${\cdot}$ sec) than that of west bay-mouth(0.0078kg1m ${\cdot}$ sec). Accordingly, The Muan Bay is interpreted as erosion-dominated environments, and the erosion somewhat progresses in the intertidal flat of the bay.

• Korean Journal of Ecology and Environment
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• v.37 no.4 s.109
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• pp.462-468
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• 2004

Most of the surveys of periphyton carried out for environmental and ecosystem health assessment of streams have considered the impact made on their fixative substrates (stones, rocks, sand, silt, clay and other abiotic matters), but there has been virtually no research that considered moving substrates. This study attempted to make an analysis and assessment of the habitat environments of the microalgae attached to the skin surfaces of fish living in small streams, with a focus on their species composition and community structure. The dominant fish in the this survey were Zacco temmincki and Zacco platypus, which are usually found in the streams, and rivers, and they accounted for 62% and 19%, respectively, in relative abundance. Substrates of fish, a representative organism with the trait of moving a long distance, show a marked contrast with those of organisms fixed at a certain place. Characteristics of both the upstream and the downstream reach well reflected in the microalgae attached to the skin surface of fishes, of which diatoms took the major composition. The result of this observation is considered to be useful to provide basic data in assessment of stream health. Also it may be suggested as a biological tool for the assessment of aquatic environment in the future.

• Korean Journal of Ecology and Environment
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• v.53 no.2
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• pp.148-155
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• 2020

In this study, we analyzed the effects of the presence or absence of weirs on fish assemblages in wadeable streams (Stream order 1^st~4^th). More specifically, we investigated these effects by evaluating the differences in stream size. The results showed differences in the fish assemblages in third or higher order streams (PERMANOVA, P<0.005). The presence or absence of weirs mainly affected variables such as the number of species the individuals, and species richness index, whereas no difference was observed in the populations of exotic, endemic, and endangered species. A SIMPER analysis showed that the common species Zacco platypus, Zacco koreanus, and Pungtungia herzi are dominant in their corresponding streams (contribution>5%), and that these are the main contributors to differences among the fish assemblages. All these species showed high relative abundances at the sites with weirs. Altered environments by the presence of weirs provided these species with concentrated habitats. In summary, this study analyzed the effects of weirs on fish assemblages on a broad, nationwide, scale, and these results can effectively aid future studies on the specific effects of weirs.

• Ecology and Resilient Infrastructure
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• v.3 no.2
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• pp.134-142
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• 2016

Temperature increase and precipitation changes caused by change alter aquatic environments including water quantity and quality that eventually affects the habitat of aquatic organisms. Such changes in habitat lead to changes in habitat suitability of the organisms, which eventually determines species distribution. Therefore, conventional habitat suitability models were investigated to evaluate habitat suitability changes of freshwater fish cause by change. Habitat suitability models can be divided into habitat-hydraulic (PHABSIM, CCHE2D, CASiMiR, RHABSIM, RHYHABSIM, and River2D) and habitat-physiologic (CLIMEX) models. Habitat-hydraulic models use hydraulic variables (velocity, depth, substrate) to assess habitat suitability, but lack the ability to evaluate the effect of water quality, including temperature. On the contrary, CLIMEX evaluates the physiological response against climatic variables, but lacks the ability to interpret the effects of physical habitat (hydraulic variables). A new concept of ecological habitat suitability modeling (EHSM) is proposed to overcome such limitations by combining the habitat-hydraulic model (PHABSIM) and the habitat-physiologic model (CLIMEX), which is able to evaluate the effect of more environmental variables than each conventional model. This model is expected to predict fish habitat suitability according to climate change more accurately.

• Korean Journal of Ecology and Environment
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• v.51 no.1
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• pp.86-95
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• 2018

The objective of this study was to describe the development and testing of an initial ecological health assessment model, based on the index of biological integrity (IBI) using fish assemblages, before establishing the final and currently used model for ecological health assessment, conservation and management of freshwater fish in Korea. The initial fish IBI model was developed during 2004~2006 and included 10 metrics, and in 2007 the final IBI 8-metric model was established for application to streams and rivers in four major Korean watersheds. In this paper, we describe how we developed fish sampling methods, determined metric attributes and categorized tolerance guilds and trophic guilds during the development of the multi-metric model. Two of the initial metrics were removed and the initial evaluation categories were reduced from six to four (excellent, good, fair, poor) before establishing the final national fish model. In the development phase, IBI values were compared with chemical parameters (BOD and COD as indicators of organic matter pollution) and physical habitat parameters to identify differences in IBI model values between chemical and physical habitat conditions. These processes undertaken during the development of the IBI model may be helpful in understanding the modifications made and contribute to creating efficient conservation and management strategies for stream environments to be used by limnologists and fish ecologists as well as stream/watershed managers.

• Korean Journal of Microbiology
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• v.39 no.3
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• pp.175-180
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• 2003

Microbial Fe(III) reduction is an important factor for biogeochemical cycle in anaerobic environments, especially sediment of freshwater such as lakes, ponds and rivers. In addition, the Fe(III) reduction serves as a model for potential mechanisms for the oxidation of organic compounds and the reduction of toxic heavy metals, such as chrome or uranium. Shewanella putrefaciens DK-1 was a gram-negative, facultative anaerobic Fe(III) reducer and used ferric ion as a terminal electron acceptor for the oxidation of organic compounds to $CO_{2}$ or other oxidized metabolites. The ability of reducing activity and utilization of various electron acceptors and donors for S. putrefaciens DK-1 were investigated. S. putrefaciens DK-1 was capable of using a wide variety of electron acceptor, including $NO_{3}^{-}$, Fe(III), AQDS, and Mn(IV). However, its ability to utilize electron donors was limited. Lactate and formate were used as electron donors but acetate and toluene were not used. Fe(III) reduction of S. putrefaciens DK-l was inhibited by the presence of either $NO_{3}^{-}$ or $NO_{2}^{-}$. Further S. putrefaciens DK-1 used humic acid as an electron acceptor and humic acid was re-oxidized by nitrate. Environmental samples showing the Fe(III)-reducing activity were used to investigate effects of the limiting factors such as carbon, nitrogen and phosphorus on the Fe(III) reducing bacteria. The highest Fe (III) reducing activity was measured, when lactate as a carbon source and S. putrefaciens DK-1 as an Fe(III) reducer added in untreated sediment samples of Cheon-ho and Dae-ho reservoirs.

• Korean Journal of Ichthyology
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• v.25 no.2
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• pp.135-140
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• 2013

Microphysogobio koreensis, an endemic Korean freshwater fishes belonging to Cyprinidae, is protected as a 2nd grade of endangered fishes by the ministry of the Environment. For this species, the study on the spawning microhabitat including structure of streambed and spawning grounds was carried out. The streambed that this species mainly lives consists of boulders, cobbles, and pebbles, the so-called Bb type, with a depth of 0.3 to 1.0 m and a rapid velocity of $0.5{\pm}0.2$ m/sec. But the main spawning grounds where the spawning is actually occurring, is relatively shallower, $0.4{\pm}0.1$ (0.4~0.6) m depth, and faster, $0.8{\pm}0.1$ (0.6~0.9) m/sec velocity, whereas the region that the fertilized eggs are attached are rather slowest to 0.4m/sec. The spawning starts at a water temperature of $20^{\circ}C$ in earlier May, laying their eggs on the cobbles' or boulders' surface or in between them. In particular, with a wide range of streambed structures, natural spawning grounds' environments may let the fertilized eggs not be swept from rapid current and secure efficient dissolved oxygen. The individuals, however, do not appear at the grounds any more after the spawning season, and it is expected that they may move into deeper water such as Lakes or lower streams.

• Journal of Wetlands Research
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• v.8 no.3
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• pp.67-77
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• 2006

Sedimentological investigations on surface and suspended sediments were performed in Masan Bay of the South Sea in order to reveal recent changes in depositional environments concerning anthropogenic influence. Surface sediments had been classified as 3 sediment facies: mud, slightly gravelly mud, and gravelly mud. In general, mud facies with more than 60% of silt is predominant and slightly gravelly mud facies occurs at the watercourse of bay's central area. The silt-dominant mud faices appears to be predominant before and after dredging. Temperature and salinity changes during one tidal cycle for each season suggest that water columns were stratified without vertical mixing regardless of the season due to weak intensity of tide from the effect of geographical features. The effect of freshwater discharge from the land seems to be insignificant. The strongest current was observed during ebb tide in spring and autumn while observed during flood tide in summer and winter. Net sediment flux (fs) and net suspended sediment transport (Qs) for suspended sediment were determined by remaining drift developed here. Net suspended sediment transport loads were seaward with $62.02{\times}10^3kgm^{-1}$, $31.84{\times}10^3kgm^{-1}$ in spring and fall, respectively, and landward with $18.23{\times}10^3kgm^{-1}$, $3.22{\times}10^3kgm^{-1}$ in summer and winter, respectively.

• Journal of the Korean Applied Science and Technology
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• v.39 no.5
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• pp.605-613
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• 2022

The genus Flavobacterium, type genus of the family Flavobacteriaceae and a member of the phylum Bacteriodetes includes gram-negative and yellow-pigmented rods. Those bacteria have been isolated from various environments of the earth. A yellow-pigmented, gram-negative rod was isolated from a pond in the campus of the Changwon University, Changwon, Kyeongnam and designated as strain B1. Strain B1 was further analyzed physiologically, biochemically and phylogenetically, and concluded to be a member of genus Flavobacterium. BLAST search of the 16S rRNA gene sequence of strain B1 shows homology no higher than 99.0% with those sequences of other bacteria. The major fatty acids of strain B1 are iso-C_15:0 (19.6%), summed feature 3(C_16:1 ω7c and/or C_16:1 ω6c, 16.1%), iso-C_17:0 3OH(10.2%), iso-C_15:0 3OH(8.4%) and iso-C_15:1 G(6.6%) showing significant differences in fatty acid compositions between strain B1 and the other known Flavobacterium species. DNA sequence of 16S rRNA gene of strain B1 was deposited in genbank under accession number OP060681.

• Korean Journal of Ecology and Environment
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• v.55 no.3
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• pp.212-220
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• 2022

An estuary is a water ecosystem with a high abundance of the species diversity, due to a variety of complex physicochemical factors of the area where freshwater and ocean mixed. The identification of Corbicula species in the estuary environments is difficult because of various morphological characteristics. In this study, we provide taxonomic information on Corbicula species with taxonomic difficulties using morphological and genetic analysis. This study was conducted on clams from the Seomjin River-Gwangyang Bay, one of the major production area of marsh clam in Korea. As a result, we characterized Cytocrome C Oxidase subunit I (COI) sequences of the Corbicula. The 636 bp nucleotide sequences of COI have 98% homology among Corbicula species collected from 2 sites of Seomjin River-Gwangyang Bay. The phylogenetic analysis with 17 species of Corbicula indicated that most of the species collected from Seomjin River-Gwangyang Bay were brackish water clam (Corbicula japonica), and only one Asian clam (Corbicula fluminea). The evolutionary distance between C. japonica and C. fluminea was less than 0.003. Therefore, it was confirmed that C. japonica is phylogenetically closely related to C. fluminea. In 9 species of Cyrenidae, phylogenetic tree was classified into three lineages. These results will be used as an important data for an identification of clam species by providing genetic information for Corbicula species with a morphological diversity.