• Korean Journal of Ecology and Environment
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• v.37 no.1 s.106
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• pp.130-136
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• 2004

In the present study, prey preference of juvenile fishes was examined using an experimental approach. Zooplankton composition, as a prey of the fish, was evaluated by taking into account the species as well as body size of juveniles in the aquarium. The predation of juvenile fishes is known to be an important factor in changes of zooplankton communities. In some previous studies at the regulated Nakdong River, the collapse of large cladcoerans and an increase in the rotifer population by selective predation during spring and summer were observed. This study focused on the predation of juvenile fishes such as Hyporhamphus sajori, Rhinogobius brunneus, and Opsariichtys uncirostris amurensis on zooplankton community structure in mesocosm scale experiments. These fishes selected the cladoceran Moina micrura with highest individual preference value (Manly/Chesson index)among zooplankton prey in the experimental aquarium. When the size-selective prey preferences of the juvenile fish were compared, both small (body size <2 cm) and large (body size >2cm) juveniles of O. uncirostris positively selected M. micrura. In the outdoor experimental tanks, juvenile fishes consumed the cladoceran M. micrura, resulting in an high abundance of the rotifer, Polyarthra spp. The results suggest that juvenile fish predation may play an important role in regulating the zooplankton community structure by reducing the cladoceran density and increase of rotifers in the Nakdong River during spring and summer.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.30 no.5
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• pp.201-206
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• 2018

This study investigated the changes in pore water quality of polluted sediment by mixing ratio of granulated coal ash. The mesocosm experiments were carried out with 0%, 10%, 30% and 50%, respectively, of the material mixture ratio relative to the sediments. According to the results of the experiments, pH increased depending on the mixing ratio. Phosphate and ammonia concentrations were significantly decreased in the mixing ratio of 30% and 50% compared to the control (p < 0.05). The concentration of hydrogen sulfide was reduced by 72% at the mixing ratio of 10%, and it was not detected at the mixing ratio of 30% and 50%. This study was confirmed that granulated coal ash can change the pore water quality of polluted sediments in proportion to the amount of material. However, the effect of the mixing ratio between 30% and 50% was not significantly different, thus it is concluded that mixing of 30% of the volume of the sediment is economically feasible.

• Korean Journal of Ecology and Environment
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• v.45 no.1
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• pp.123-128
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• 2012

We aimed to estimate the accumulated degree days required for the development of $Cloeon$ $dipterum$ (Ephemeroptera: Baetidae) in an experimental tub under field conditions from August 7 to October 10 in 2011. After 4 days in a tub setting, a dead female adult was found on the water surface at which oviposition had presumably occurred. Adults emerged from 39 days to 61 days after the oviposition date. The total number of emerged adults was 229, and the sex ratio (number of females : total population) was 0.45, although not statistically significant ($p$ >0.05). The males generally emerged earlier than females. Assuming that the basal temperature ($T_b$) value is $0^{\circ}C$, we estimated the number of accumulated degree days required for the development of $C.$ $dipterum$ to be $1,221.8{\pm}116.0$ DD (mean${\pm}$SD). Since the annual number of accumulated degree days in the reference wetland was measured to be 5,650.0 DD, we estimated that $C.$ $dipterum$ is multivoltine, with a maximum of 4 cohorts in 1 year in natural habitats.

• Korean Journal of Environmental Biology
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• v.38 no.1
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• pp.71-81
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• 2020

In Korea, more than 70% of the ammonia(NH₃) released into the atmosphere is known to originate from livestock manure. The total emission (kg year^-1) is calculated by multiplying the emission factor (kg head^-1 yr^-1) and the activity data (head). To improve the accuracy and reliability of the NH₃ emission estimation process, an accurate account of livestock manure production, calculation of NH₃ conversion and generation during the composting and liquefaction of manure, estimation of NH₃ generation in the storage and transportation of manure and compost, and a comparative study of NH₃ emission during the soil spreading process must be performed. Compared to the US and EU-28, in particular, the domestic emission factor is relatively even and the spatial/temporal scale is not broken down sufficiently to reflect the domestic situation. As a way to improve the accuracy and expertise of estimating NH₃ emission factors, a 'dynamic chamber-capture system' can be utilized, which allows complex considerations of compost, liquid manure, soil, and climate characteristics. By reviewing and comparing the data related to domestic and foreign NH₃ emission, we identified shortcomings in the current domestic system and the directions to be taken and suggested a chamber system that could estimate NH₃ emission flux. It is also necessary to establish a methodology for mesocosm systems in the field, in addition to indoor chamber systems, to be linked with practical policies, such as the calculation of new emission factors for missing sources.

• Korean Journal of Ecology and Environment
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• v.44 no.4
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• pp.347-357
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• 2011

We examined two reservoirs (Inkyung res. and Joongang res.) and two streams (Kyungan str. and Jecheon str.), all of which were eutrophic, during the 2010 warm season, to evaluate the water quality improvement activity (WQIA) of plant-mineral composite (PMC), which was previously developed to control suspended solids, including cyanobacterial bloom (Kim et al., 2010). We simultaneously measured both solid (S-MCLR) and dissolved microcystin-LR (D-MCLR), before and after PMC treatment, in the Joongang reservoir. Taking water body size and volume into account, we conducted the whole-scale experiment in the Inkyung reservoir, and mesocosm-scale experiments in the other three systems. The WQIAs of PMC were found to be comparatively high in SS (70~81%), TP (75~91%), BOD (65~91%), Chl-a (88~98%), phytoplankton (84~92%) and zooplankton (68~88%), except for the Kyungan stream, which was below 45% in all parameters. After PMC treatment, the concentrations of both SMCLR (47%) and D-MCLR (96%) decreased within two days, suggesting a mitigation possibility of hazardous chemicals such as agrochemicals and endocrine disrupters in the aquatic ecosystem. Our results collectively indicate that PMC is a useful agent to control suspended solids, including nuisance cyanobacterial bloom and their exudates, in an undisturbed water system with a long residence time.

• Journal of Wetlands Research
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• v.13 no.2
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• pp.355-362
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• 2011

Bog bean (Menyanthes trifoliata L.) is an endangered species in Korea and a perennial macrophyte with long rhizome, inhabiting in oligotrophic fen or edges of montane lakes. To decide appropriate substrate type for restoration of this plant, we investigated the effect of substrates (e.g. water, Sphagnum mat, paddy soil) on growth of bog bean. There were two water conditions on paddy soils: saturated and flooded. We planted 10cm rhizome in mesocosms and measured coverage, leaf area, leaf number and rhizome biomass. Bog bean growed until August in water and Sphagnum mat and until October in paddy soil. Rhizome biomass at the end of November were 49, 77, 239, and 312g in water, Sphagnum mat, paddy soil with water saturated, and paddy soil with water flooded conditions, respectively. The results indicate that bog bean can grow better in paddy soil which have higher nutrient than water or Sphagnum mat which represents natural habitat condition of bog bean. This reveals that actual ecological niche of bog bean is different from fundamental ecological niche in substrate. For successful restoration of bog bean in nutrient rich area, it is necessary to know the competitiveness of bog bean in various substrate conditions.

• Journal of the Korean Society for Marine Environment & Energy
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• v.15 no.3
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• pp.238-246
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• 2012

Once oil is spilled into marine environment, it experiences various weathering processes among which evaporation is the most dominant process in the initial stage of weathering. This study aimed to elucidate the effects of evaporation on the physicochemical properties of spilled oil using standardized laboratory experiments. Laboratory evaporation process was successfully reproduced using controlled rotary evaporation method. In case of Iranian Heavy crude (IHC), evaporation rate after 48 hours was $29.3{\pm}0.4%$ (n=40, p<0.001). Evaporation was simulated using ADIOS2 weathering model and the result was in agreement with laboratory experiment. Chemical composition changes of petroleum hydrocarbons including alkanes, polycyclic aromatic hydrocarbons (PAHs) and biomarkers by evaporation rate were also analyzed. As oil evaporated, low molecular weight alkanes and PAHs decreased, while biomakers showed conservative characteristics. Among biomarkers, $17{\alpha}(H)$, $21{\beta}(H)$-hopane was used for calculation of weathering rates, which matched with evaporative mass losses. Weathering rate calculation using hopane showed that stranded oils of weathering stage I (28.9%) and mesocosm oil weathering experiment till 5 days (26.5%) were mainly affected by evaporation process.

• Journal of Wetlands Research
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• v.11 no.1
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• pp.39-48
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• 2009

Wetland plants are an important component for wetland design and construction because they determine functions of wetlands through interactions with the abiotic environment such as wetland soil and hydrology as well as with other wetland organisms. In this study, germination experiments with soils from a natural wetland that contain seeds of wetland plants were conducted in wetland mesocosms to investigate the applicability of natural wetland soils for introducing and establishing wetland plants into constructed wetlands. Seven species were germinated in the experiment, with two new species that were not found in the field survey of wetland plants in the West Nakdong River area, Korea. The number of plant individuals germinated in submerged conditions (15 individuals) was much greater than that in waterlogged conditions (2 individuals). In experiments in which soils from a natural wetland and a wetland construction site were mixed at different ratios, the largest number of plant individuals was observed in the condition with 100% natural wetland soil. The highest growth was observed at 50% natural wetland soil for Hydrilla verticillata and 100% for Ceratophyllum demersum. These results suggest that 1:1 mixture of soils from natural wetland wetlands and wetland construction sites would provide an appropriate condition for secure establishment of submerged plants in constructed wetlands.

• Journal of Wetlands Research
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• v.15 no.3
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• pp.289-300
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• 2013

In this study, two types of wetland plants, Eichhornia crassipes (a floating plant) and Ceratophyllum demersum (a submerged plant) were introduced to wetland mesocosms to understand how the water properties of wetlands such as pH, dissolved oxygen content, water temperature, oxidation reduction potential, and nutrient concentrations are affected by different types of wetland plant. The floating plant lives on the water surface and can block light penetration; it exhibited the lowest water temperature and temperature difference between lower and upper layers. After the addition of contaminants, the dissolved oxygen (DO) concentration decreased abruptly but recovered continuously in all mesocosms; especially the submerged plants, which photosynthesize in water, showed the largest increases in DO and diel periodicity DO, as well as in pH value. The oxidation-reduction potential in both water and sediment were affected by the presence of wetland plants and plant type and the results suggest that various aspects of wetland biogeochemistry are affected by the presence and type of wetland plants. The total nitrogen and phosphorous concentrations in water decreased in the following order: Water only < Water + Soil < Floating Plants < Submerged Plants. Although both floating and submerged plants can control algal concentrations, the effect was more prominent for floating plants.

• Journal of the Korean Society of Marine Environment & Safety
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• v.25 no.1
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• pp.74-80
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• 2019

In this study, pyrolyzed oyster shells at a low temperature ($350^{\circ}C$) were applied for a mesocosm experiment to confirm resulting changes in the properties of sediment. After creating a covering of oyster shells, an increase in ORP and decrease in ammonia in the overlying water was observed in an experimental case. The decrease of TOC in this experiment was due to the dilution of organic matter due to the addition of inorganic matter (pyrolyzed oyster shells). The decrease in the concentration of AVS was observed due to the adsorption of AVS by the surface of the oyster shells. From the results obtained in this experiment, it has been concluded that pyrolyzed oyster shells at a low temperature can be used for remediation of polluted sediment.