• Korean Journal of Ecology and Environment
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• v.36 no.2 s.103
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• pp.97-107
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• 2003

Fish vitellogenin produces in female liver during oogensesis through estradiol cycle, and produces even in male liver by endocrine-disrupting chemicals (EDCs) such as alkylphenols. The resulting effects of EDCs lead to the low fecundity of female and the feminization (eg. shrinkage of testis) in male. Especially, the production of vitellogenin in male indicates the environmental contamination of EDCs, resulting in the modulation of gene expression profiles and the monitoring of environmental contamination at specific area. In this paper, we suggest that fish vitellogenin is useful for biomonitoring for environmental contamination and would be substantially useful as a biomarker for a detection of EDCs in aquatic environment.

• Korean Journal of Ecology and Environment
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• v.37 no.3 s.108
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• pp.263-271
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• 2004

To collect the basic ecological information about the microbial food webs in eutrophic water system with different residence time, the monthly variation of bacterioplankon (bacteria and small-sized cyanobacteria) and nanoplankton (phytoplankton and protists) were examined from December 2000 to September 2001. Kyungan stream is shorter in resident time (ca.5.4 d) than Seokchon reservoir (ca.72 d), even though they showed the same pattern in precipitation. With the basic environments, we examined the biomass (standing crops and its carbon content) of each plankton collected from the surface water. Large-sized planktons flourished in the time of low temperature, while small planktons were in the time of the high temperature period. Especially, in the Kyungan stream with much disturbance by rainfall and outflow, high diversity showed in term of species and cell morphology, compared to that of Seokchon lake. The time-lag relationship remarkably showed between phytoplankton and bacteria in Seokchon reservoir, and between protists and bacteria in Kyungan stream, respectively.

• Korean Journal of Ecology and Environment
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• v.37 no.3 s.108
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• pp.313-318
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• 2004

Di-2-ethylhexyl phthalate (DEHP) is a widely used plasticizer known to be a suspected xenoestrogen and a causative agent of oxidative damage to the RBC cell membrane ir vitro. We evaluated the toxic effects of a scarcely documented aquatic environmental pollutant, DEHP, on selected haematological endpoints in the bagrid catfish, Pseudobagrus fulvidraco. Bagrid catfish were exposed to DEHP (300, 1,000 mg DEHP kg body weight$^{-1}$) through thrice intraperitoneal injection and effects were assessed in blood of the exposed organisms. Haematological property, serum organic and inorganic chemistry were monitored in blood of Bagrid catfish. DEHP exposed-fish showed erythropenia; low hematocrit (Ht) and hemoglobin (Hb) content and red blood cell count showed a significantly higher than in that of the control group. The treatment group showed a significantly lower concentration of serum total protein, cholesterol and triglyceride compared with those in the control group. The value of calcium and osmolality were significantly decreased in the DEHP treatment group, compared with the control group.

• Korean Journal of Ecology and Environment
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• v.37 no.3 s.108
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• pp.304-312
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• 2004

The transient dynamics of three-trophic populations (prey, predator, and super predator) using ratio-dependent models responding to environmental impacts is analyzed. Environmental factors were divided into two parts: periodic factor (e.g., temperature) and general noise. Periodic factor was addressed as a frequency and bias, while general noise was expressed as a Gaussian distribution. Temperature bias ${\varepsilon}$, temperature frequency ${\Omega}$, and Gaussian noise amplitude ${\`{O}}$ accordingly revealed diverse status of population dynamics in three-trophic food chain, including extinction of species. The model showed stable limit cycles and strange attractors in the long-time behavior depending upon various values of the parameters. The dynamic behavior of the system appeared to be sensitive to changes in environmental input. The parameters of environmental input play an important role in determining extinction time of super predator and predator populations.

• Korean Journal of Ecology and Environment
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• v.48 no.3
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• pp.188-194
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• 2015

River channel dredging and riparian development have been influenced morphology and quantity of natural river habitat. We compared distribution of riverside land and alluvial island in the Nakdong River with field survey and remote sensing analysis after the 4 Large River Project in South Korea. We digitized geomorphological elements, includes main channel, riverside land, and alluvial island by using georeferenced aerial photos taken in pre-dredging (2008) and post-dredging (2012) periods. Field survey was followed in 2012 for a ground truth of digitized boundaries and identification of newly constructed wetland types such as pond, channel, branch, and riverine type. We found that during the dredging period, riverside land and alluvial island were lost by 20.2% and 72.7%, respectively. Modification rate of riverside land was higher in the section of river kilometer 50~90, 140~180, and 210~270. Alluvial island had higher change rate in the section of river kilometer 50~70, 190~210, and 270~310. Average change rate for the riverside land and alluvial island was $-1.02{\pm}0.14km^2{\cdot}10km^{-1}$ and $-0.05{\pm}0.05km^2{\cdot}10km^{-1}$, respectively. Channel shaped wetlands (72.5%) constituted large portion of newly constructed wetlands.

• Korean Journal of Ecology and Environment
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• v.48 no.3
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• pp.168-175
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• 2015

This study was conducted in autumn to determine phosphorus (P) fraction in sediments of Daechung Lake, to elucidate controlling factors for sedimentary P, and to compare with the other areas. For this study, sediment samples were collected at 6 sites only once on November 2014 using ponar grab and analyzed for solid-phase P (Loosely adsorbed, Fe-bound, Al-bound, detrital apatite, and refractory organic P) by sequential extraction. Total phosphorus (TP) was relatively high in front of Daechung Dam and Hoinam where fish farm was run until 1997. The dominant sedimentary P form was Al-bound P, followed by Fe-bound P, which could be released from sediment to water column during suboxic state. Based on principal component analysis, Al-bound P, Fe-bound, and TP were controlled by grain size of sediments. Loosely adsorbed, detrital apatite, and refractory organic P were relatively highly accumulated at the mouth of major tributaries where suspended sediments were delivered. Sedimentary P concentrations in Daechung Lake sediments were not higher than in other lake sediments. Therefore, based on these results, major controlling factors were grain size and input of suspended sediments from tributaries.

• Korean Journal of Ecology and Environment
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• v.48 no.2
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• pp.86-94
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• 2015

Chironomous is aquatic insect belonging to order Diptera, family Chironomidae. Their larval stage can be found mainly in aquatic benthic environment, hence good model organism to study environmental toxicology assessments and consider as useful bio indicators of contamination of the aquatic environment. In this study, Chironomus Heat Shock Proteins, Cytochrome 450, Glutathione S-transferase, Serine-type endopeptidase gene expressions were compared between polluted field areas (Chironomus plumosus) and under laboratory conditions (Chironomus riparious) to investigate molecular indicators for environmental contaminant stress assessment. Heavy metal (Al, Fe, Mn, Cu, Cr, Zn, Se, Pb, As, Cd) concentrations in sediments collected from three study areas exceeded the reference values. Moreover, HSPs, CYP450 and GST gene expression except SP for C. plumosus showed higher expression than C. riparious gene expression. Similar gene expression pattern was observed in C. riparious that exposed environment waters up to 96 h when compared to C. plumosus exposed to waters that grown in lab conditions. In summary, this comparative gene expression analysis in Chironomous between field and laboratory condition gave useful information to select candidate molecular indicators in heavy metal contaminations in the environment.

• Korean Journal of Ecology and Environment
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• v.42 no.2
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• pp.253-259
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• 2009

We investigated annual and seasonal changes of Keratella spp. among rotifer community in the lower part of the Nakdong River (Mulgum) for four years (1995, 1997, 2005, 2007). As well, the annual and seasonal variations of lorica morphologies including sizes, posterior and anterior spines lengths in K. cochlearis were analyzed. The density of Keratella spp. showed distinct seasonality such as spring peak and winter scarcity. K. cochlearis was the most dominant species within Keratella spp. and the relative abundances of 2005 and 2007 were higher than 1995 and 1997. The lorica length and width of K. cochlearis did not show the annual changes between four years however, there was an obvious width decrease in summer and increase in winter. The proportion of individuals that has the posterior spine was relatively low throughout four years, especially at summer and autumn. K. cochlearis displayed short posterior spine in summer and long posterior spine in winter contrary to the anterior median and intermediate spines.

• Korean Journal of Ecology and Environment
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• v.42 no.1
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• pp.67-74
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• 2009

To study the influence of the rotifer Brachionus calyciflorus on harmful algal bloom suppression, we focused on assessing the rotifer's abilities using several prey species : Microcystis aeruginosa, Synechocystis sp., Chlorella vulgaris and Coelastrum sp. of the warm-weather species and the cold-weather centric diatom Stephanodiscus hantzchii. Grazing effects and growth rates of rotifers B. calyciflorus were 94.5% and $1.29d^{-1}$, respectively, for Synechocystis sp., 87.4% and $0.60d^{-1}$, respectively, for M. aeruginosa, 95.2% and $0.65d^{-1}$, respectively, for C. $vulgaris^{TM}$, 78.6% and $0.45d^{-1}$, respectively, for C. vulgaris UTEX., 86.5% and $0.99d^{-1}$, respectively, for Coelastrum sp., and 82.6% and $0.40d^{-1}$, respectively, for S. hantzchii. Of these, although the growth of Synechocystis and Coelastrum was effectively suppressed by rotifer grazing, efficient suppression effects on Stephanodiscus blooms were unexpected. The present study revealed that reproduction of B. calyciflorus was greatly influenced by its food types in the initial stages and the efficiencies of bio-agents as sole food sources vary depending on the target algae and the agent.

• Korean Journal of Ecology and Environment
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• v.42 no.1
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• pp.26-31
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• 2009

Ecological characteristics of Cobitis pacifica inhabited in the Yeongok Stream, Gangwon-do, Korea was investigated from May 2006 to August 2007. The major habitat was composed of sand bottom with current velocities of $0.23{\sim}0.56m\;sec^{-1}$ and depths of $20{\sim}50cm$. The sex ratio of female to male was 1 : 0.93. It was presumed that the spawning season was the period of water temperatures of $25{\sim}27^{\circ}C$. Sexually matured individuals appeared over the two years of age. Frequency analysis of body length indicated that the group with $40{\sim}59mm$ in body length was one-year-old, the group of $60{\sim}89mm$ was two-years-old, the group of $90{\sim}109mm$ was three-years-old, and the group of over 110 mm was four-years-old. The average number of eggs in the ovaries was estimated as 809 per matured female. Main prey items were Ephemeroptera and Diptera.