• Korean Journal of Ecology and Environment
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• v.55 no.4
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• pp.368-375
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• 2022

Gut contents analysis is essential to predict the impact of organisms on food source changes due to variations of the habitat environment. Previous studies of gut content analysis have been conducted using traditional methods, such as visual observation. However, these studies are limited in analyzing food sources because of the digestive process in gut organ. DNA metabarcoding analysis is a useful method to analyze food sources by supplementing these limitations. We sampled marine fish of Pennahia argentata, Larimichthys polyactis, Crangon affinis, Loligo beka and Sepia officinalis from Gwangyang Bay and Yeosu fisheries market for analyzing gut contents by applying DNA metabarcoding analysis. 18S rRNA v9 primer was used for analyzing food source by DNA metabarcoding. Network and two-way clustering analyses characterized the relationship between organisms and food sources. As a result of comparing metabarcoding of gut contents for P. argentata between sampled from Gwangyang Bay and the fisheries market, fish and Copepoda were analyzed as common food sources. In addition, Decapoda and Copepoda were analyzed as common food sources for L. polyactis and C. affinis, respectively. Copepoda was analyzed as the primary food source for L. beka and S. officinalis. These study results demonstrated that gut contents analysis using DNA metabarcoding reflects diverse and detailed information of biological food sources in the aquatic environment. In addition, it will be possible to provide biological information in the gut to identify key food sources by applying it to the research on the food web in the ecosystem.

• International Journal of Human Ecology
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• v.12 no.2
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• pp.13-24
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• 2011

This study compared actual weight with perceived weight, described the prevalence of unhealthy weight control behavior, determined the differences in psychological and personal variables between participants that reported unhealthy weight control behavior and those who did not, and examined the relationship of eating habits to unhealthy weight control behavior for Korean adolescents. The study population consisted of a nationally representative sample of middle and high school students who completed the Fifth Korea Youth Risk Behavior Web-based Survey (KYRBWS): Fifth in 2009. Among the 75,066 participants of KYRBWS, 35,473 (n = 18,851 girls and 16,622 boys) were eligible for a research focused on unhealthy weight control behavior. The results of this research were as follows: First, there were considerable discrepancies (45.1% of girls and 32.8% of boys) between the perceived weight and the actual weight. Second, overall, unhealthy weight control behavior was more prevalent in girls and fasting was the most commonly reported behavior. Third, participants that reported unhealthy weight control behavior scored significantly lower on scaled measures of happiness, health, academic achievement, and economic status; in addition, they scored higher on stress measures. Fourth, girls and boys shared common protective factors of having breakfast and vegetables more often, perceiving their weight as underweight rather than overweight, and having a correct weight conception. Protective factors unique to girls were having lunch and dinner more often. Girls and boys shared common risk factors of the consumption of soda, fast food, instant noodles, and snacks more often, while consumption of fruit more often was a risk factor only for girls. The improvement of protective factors and minimization of risk factors through Home Economics classes (and other classes relevant to health) may mitigate unhealthy weight control behavior of adolescents.

• Journal of Ecology and Environment
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• v.37 no.3
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• pp.147-153
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• 2014

Structural heterogeneity results in different spatial distributions of microcrustaceans. Thus, in ecosystems with excessive macrophyte development, it may be difficult to determine the microcrustacean species composition. Given the importance of microcrustaceans in the food web, the elucidation of microcrustacean diversity is essential. In vegetated habitats, bluegill sunfish can prey on microcrustaceans, and therefore have a potential role as microcrustacean monitoring agents. In the present study, we compared microcrustacean species compositions in the field with those in the guts of bluegill, in Jangcheok Lake, South Korea. Our results showed that the number of microcrustacean species was higher in bluegill guts than in the field. Further, microcrustacean species, such as Daphnia galeata, Graptoleveris testudinaria, Leydigia leydigii, Rhynchotalona sp., and Simocephalus exponisus, were found only in bluegill guts. Our findings verify the validity of the fish gut analysis to monitor microcrustacean species compositions and to clarify spatial distributions of microcrustacean species in structurally heterogeneous ecosystems with excessive macrophyte development.

• Journal of Ecology and Environment
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• v.36 no.2
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• pp.141-150
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• 2013

Natural zooplankton communities are composed of many different species at different trophic levels in the aquatic food web. Several researchers have reported that in mesocosm/enclosure experiments, larger cladocerans tend to be more sensitive to carbamate insecticides than smaller ones (Daphnia > Moina, Diaphanosoma > Bosmina). In contrast, results from individual-level laboratory tests have suggested that large cladoceran species are more tolerant than small species. To clarify this inconsistency, we conducted a microcosm experiment using model zooplankton communities with different species compositions, where animals were exposed to lethal (near to the 24 h LC50, concentration estimated to kill 50% of individuals within 24-h for the small cladoceran Bosmina) and lower, sublethal concentrations of carbaryl. In the experiment, population densities of the small cladocerans (Bosmina and Bosminopsis) decreased subsequent to the applications of chemical, but no impacts were observed on the large cladoceran Daphnia. Our results supported the reports of previous individual level toxicity tests, and indicated that the sensitivity of zooplankton to the insecticide was unchanged by biological interactions but the response of population can be modified by compensation of population through hatching from resting eggs and/or the persistence of insecticide in the systems.

• Korean Journal of Ecology and Environment
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• v.39 no.1 s.115
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• pp.131-137
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• 2006

Most South Korean lakes are middle/small size artificial reservoirs, which are almost agricultural reservoirs (17,956). A total of 67 species (21 families) were recorded and collected from 65 agricultural reservoirs though field samplings and literature surveys. Dominant species was Pseudorasbora parva (relative abundance 24.5%), and Carassius auratur (41 sites) was the highest frequency. Feeding group of fish communities in the reservoirs was as follows: carnivorous (16.2%), omnivorous (79.5%) and herbivorous fish (4.3%). The number of individuals (P=0.024), species number (P=0.047) and carnivores number (P=0.024) were significantly correlated with reservoir ages. Reservoirs were classified into 3 groups according to feeding patterns of carnivore, omnivore and herbivore groups. The omnivores were dominant group in agricultural reservoirs. Detailed studies on fish community will be a base for the understanding of food web structure and biomanipulation in reservoir systems.

• Korean Journal of Community Nutrition
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• v.17 no.4
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• pp.494-503
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• 2012

The purpose of this study was to examine the effect of sustainability management (SM) at coffee houses on customers' store image and behavioral intention. In addition, customers' willingness to pay a premium for sustainable coffee houses was studied. During October 2011, a web survey was conducted via an on-line research company with customers aged 20 to 39 visiting one of the top five coffee houses in Korea at least once a month. A total of 300 targeted customers responded and all the data were analyzed. An exploratory factor analysis derived two dimensions of SM: SM in Social and Environmental Perspective and SM in Economic Perspective. The result of structural equation modeling indicated that SM in Economic Perspective at coffee houses had a significant positive effect on customers' behavioral intention with mediating effect by store image, but SM in Social and Environmental Perspective did not have such effect. Approximately one-third (31%) of the respondents were willing to pay a premium for a sustainable coffee house in a scenario. approximately 84% of the respondents unwilling to pay a premium for the sustainable coffee house chose the cost-related reasons including "Coffee price at the coffee house that they most often visit is already expensive (62.3%)" for such unwillingness. The results of this study showed that SM of coffee houses, especially that in Economic Perspective, could contribute to store image, and therefore increase customers' favorable behavioral intention, although the additional cost resulted from such SM practices might not be easily accommodated by customers.

• 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 Environment and Ecology
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• v.37 no.2
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• pp.140-150
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• 2023

The Eurasian otter (Lutra lutra) is an apex predator of the riparian ecosystem. It is a keystone and an indicator species; consequently, its presence suggests a sustainable water environment. Otter is a keystone species as a predator at the top of the food web in the aquatic environment and an indicator species representing the health of the aquatic environment. Although Eurasian otters disappeared from the Han River urban water system because of anthropogenic activities like habitat destruction, poaching, and environmental pollution in the 1980s, the species were sighted in the Cheonggye Stream, Jungrang Stream, and Seongnae Stream, which are urban sections of the Han River, in 2016 and 2021. Therefore, it is pertinent to assess the habitat potential in the area for conservation and management measures to ensure its permanent presence. However, existing studies on otter habitats focused on natural rivers and reservoirs, and there is a limit to applying them to habitats artificially confined habitats in narrow spaces such as tributaries in urban areas of the Han River. This study selected the Cheonggye Stream, an artificially restored urban stream, to evaluate its potential as a habitat for Eurasian otters in urban water environments using the habitat suitability index (HSI). The HSI was calculated with selected environment attributes, such as the cover, food, and threat, that best describe the L. lutra habitat. According to the results, the confluence area of Seongbuk Stream and Cheonggye Stream and the confluence area of Cheonggye Stream and Jungnang Stream were suitable otter habitats, requiring appropriate conservation efforts. The HSI model suggests a valuable method to assess the habitat quality of Eurasian otters in urban water environments. The study is crucial as it can help rehabilitate the species' populations by identifying and managing potential Eurasian otter habitats in highly urbanized areas of the Han River basin and its tributaries.

• Korean Journal of Ecology and Environment
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• v.46 no.3
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• pp.332-342
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• 2013

We collected zooplankton from May to October, 2011, with the aim of understanding the zooplankton community distribution and food web interaction between the open water and littoral (aquatic plants) zones in two small reservoirs with different land covers (Sobudang, Myeongdong). Small-sized reservoirs are more abundant in South Korea, and a total of 51 and 65 species of zooplankton were identified at the two small reservoir (Sobudang and Myeongdong), where zooplankton densities were more abundant in the littoral zone than in the open water zone. Cladocerans and copepods densities were also higher in the littoral zone, in contrast, rotifers showed higher densities in the open water zone (t-test, P/0.05). Epiphytic zooplankton dominated at the littoral zone (Lecane, Monostyla, Alona and Chydorus) because aquatic plants provided refuge spaces for attachment. Some rotifers (e.g. Brachionus, Keratella and Polyarthra) were more abundant in the open water zone because of their small size, which might help them to go unnoticed by predators. In two-way ANOVA, rotifers related to two reservoirs or habitat space (littoral zone and open water zone), but cladocerans and copepods showed a statistically significant relationship on only two reservoirs. The results of stable isotope analysis showed that zooplankton in the littoral zone tended to depend on organic matter attached to aquatic plants as a food source, which indicates the avoidance of competition of zooplankton with other macro-invertebrates (e.g. Damselfly larva, Cybister brevis and Neocardina denticulate). As a result, zooplankton community distribution is determined by not only habitat space (aquatic plant zone and open water zone) but also by food source (phytoplankton).

• Korean Journal of Ecology and Environment
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• v.39 no.1 s.115
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• pp.52-61
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• 2006

The aim of this study was to analyze the seasonal patterns of zooplankton community dynamics in the lower Nakdong River (Mulgum, RK; river kilometer; 27 km from the estuarine barrage), with a Self-Organizing Map (SOM) based on weekly sampled data collected over ten years(1994 ${\sim}$ 2003). It is well known that zooplankton groups had important role in the food web of freshwater ecosystems, however, less attention has been paid to this group compared with other community constituents. A non-linear patterning algorithm of the SOM was applied to discover the relationship among river environments and zooplankton community dynamics. Limnological variables (water temperature, dissolved oxygen, pH , Secchi transparency, turbidity, chlorophyll a, discharge, etc.) were taken into account to implement patterning seasonal changes of zooplankton community structures (consisting of rotifers, cladocerans and copepods). The trained SOM model allocated zooplankton on the map plane with limnological parameters. Three zooplankton groups had high similarities to one another in their changing seasonal patterns, Among the limnological variables, water temporature was highly related to the zooplankton community dynamics (especially for cladocerans). The SOM model illustrated the suppression of zooplankton due to the increased river discharge, particularly in summer. Chlorophyll a concentrations were separated from zooplankton data set on the map plane, which would intimate the herbivorous activity of dominant grazers. This study introduces the zooplankton dynamics associated with limnological parameters using a nonlinear method, and the information will be useful for managing the river ecosystem, with respect to the food web interactions.