• Korean Journal of Ecology and Environment
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• v.38 no.4 s.114
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• pp.435-438
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• 2005

We observed the physical, chemical, and biological characteristics of an acidic lake, Lake Katanuma, from 1998 to 2002 at weekly or biweekly intervals, except during the winter. This volcanic lake has a dimictic thermal pattern. In summer, the volcanic heat supply at the lake bottom results in weak thermal stratification. In 1998, 1999, and 2002, short-term holomixis was observed during the stratification period, when the anoxic, hydrogen sulfide-rich water from the hypolimnion spread across the entire lake. In contrast, distinct short-term holomixis did not occur during the stratificatlon period in 2000 and 2001. However, the early onset of the autumn turnover in August 2000 and 2001 caused anoxic conditions to persist throughout the entire water column for more than 2 weeks. The anoxic and hydrogen sulfide-rich conditions affected population densities of chironomid larvae (Chironomus acerbiphilus) and planktonic algae (Chlamydomonas acidophila), both dominant species in Lake Katanuma. Thus, the interannual variations of limnological characteristics influenced the seasonal population changes of these species.

• Korean Journal of Ecology and Environment
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• v.34 no.4 s.96
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• pp.349-356
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• 2001

This paper briefly describes the classification of GIS- based model, and introduces some practical grid- based models such as TOPMODEL (Beven of al., 1979, 1984), AGNPS (Young of al., 1989), KIMSTORM (Kim, 1998; Kim of al,, 1998), and GRISMORM (Kim of al.,20110). Current status of GIS data construction promoted by Ministry of Construction and Transportation (MOCT) and system development of water resources information by Korea Water Resources Corporation (KOWACO) is briefly described. Further research needs for GIS-based modeling will be emphasized with some recommendations on GIS data preparation and proper field observation data collection.

• Korean Journal of Ecology and Environment
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• v.41 no.3
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• pp.320-330
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• 2008

For twenty-nine aquatic insect taxa common to mountain headwater streams in central Korean peninsula, body length-dry mass and -ash free dry mass relationships were developed by using a natural log transformed power function. Most of the predicted mass at length of this study was rather similar to those of other studies. Taxa with higher predicted mass at length than predicted by others tend to have soft exoskeleton and move by stretching and contracting their body. Ash rate in average was 10% of dry mass and was not significantly different among functional feeding groups.

• Korean Journal of Ecology and Environment
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• v.53 no.2
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• pp.156-164
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• 2020

The accurate estimation of fish assemblages is highly dependent on the sampling gear used for sampling. We used data from 15 sampling sites along the Nakdong River, which is a large river in South Korea, to identify differences in assemblages and sizes of freshwater fishes collected with either cast nets or gill nets, the two most commonly used sampling gear in South Korea. The two gears differed in the fish assemblages they captured, with more species caught by gill nets. Further, due to its tighter mesh size, the cast net caught significantly smaller fishes than the gill nets(independent t-test, p<0.05). We found the cast net to be appropriate for species that inhabit shallow (less than 2 m) and open water, but inappropriate for deep water, habitats with plant beds, and nocturnal species. Thus, cast net sampling is not efficient in a large river environment, and a combination of sampling methods is more suitable for understanding fish assemblages in such habitats. In general, appropriate selection of fishing methods to specific habitats is necessary to improve data quality and minimize the misrepresentation of environmental conditions.

• Korean Journal of Ecology and Environment
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• v.53 no.2
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• pp.138-147
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• 2020

The Singil Stream, flowing into an artificial lake, Lake Shihwa (South Korea), experiences a strong anthropogenic pressure with continuous organic matter (OM) inputs from rural, urban, and industrial areas. In this study, we investigated suspended particulate matter (SPM) and streambed sediments collected along the Singil Stream in 2014 and 2016, by applying a dual element approach (δ¹³C and δ¹⁵N) to identify OM sources. The SPM and streambed sediment samples from the indusrial area showed higher organic carbon and nitrogen concentrations (or contents) than those from the other areas, with distinctively lower δ¹⁵N values. Accordingly, our dual element approach indicates that the industrial area was the predominant OM source influencing OM quality and thus water quality of the Singil Stream flowing into Lake Shihwa during the study periods. However, further studies are necessary to better constrain OM sources in the Singil Stream since OM sources from the industrial area appear to be complex.

• Korean Journal of Ecology and Environment
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• v.38 no.spc
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• pp.39-43
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• 2005

The dynamics of water quality with the storm events were analyzed in a small reservoir for irrigation, Lake Wangkung. Water quality of the inflowing stream fluctuated seasonally with the variation of flow rate. Thermal stratification was consistent from April to October below 2 m depths and anoxic layer was developed below 2 m depth in summer. The unique feature of temperature showed that thermal stratification was disrupted by a heavy rain event during monsoon, but hypolimnetic hypoxia were reestablished after a few days. Phosphorus and nitrogen increased immediately following storm events. The marked increase may be due to the input of P-rich storm runoff from the watershed. Internal phosphorus loading can be one of the explanations for TP increases in summer. When there was a storm, total populations of phytoplankton and zooplankton was reduced immediately following the storm, indicating possible flushing of algae and zooplankton. After a lag period of low-density the plankton population bloomed to a peak again within five days after the storm. Turbid water in lake became clear again which coincided with the time of the phytoplankton buildup. The results demonstrate that water quality is regulated greatly by rainfall intensity in Lake Wangkung.

• Korean Journal of Ecology and Environment
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• v.38 no.spc
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• pp.12-16
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• 2005

Seasonal change in cell number and biomass expressed as chlorophyll a of picophytoplankton community in surface waters was investigated in the north basin of Lake Biwa from September 2001 to November 2002. Two main peaks, in May and summer (from July to October), were observed by change of the cell density of picophytoplankton. It is considered that peak in May was due to water temperature rise and summer peak was attributed to mass-specific nutrient uptake by picophytoplankton. Horizontal distribution in cell number and biomass of picophytoplankton community in surface water of Lake Biwa was investigated at 56 stations on June 6 ${\sim}$ 7 2002. DIN and DIP concentrations were lower in the north basin than in the south basin. The cell density and chlorophyll a of picophytoplankton were distributed almost uniformly in all area. The contribution of picophytoplankton to total phytoplankton chlorophyll a was higher in the north basin than in the south basin. These results suggest that picophytoplankton is important as a primary producer in low nutrient periods and areas of Lake Biwa.

• Korean Journal of Ecology and Environment
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• v.38 no.spc
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• pp.8-11
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• 2005

Carbon stable isotope ratios of producers varied in lake ecosystems. In tile present study, we tried to estimate the seasonal variations of carbon isotope ratios of phytoplankton and benthic diatoms in a strongly acidic lake ecosystem. Lake Katanuma is a volcanic, strongly acidic lake (average pH of 2.2), located in Miyagi, Japan. Only two algal species dominate in Lake Katanuma; Pinnularia acidojaponica as a benthic diatom, and Chlamydomonas acidophila as a green alga. Carbon isotope values of P. acidojaponica varied seasonally, while those of particulate organic matter, which were mainly composed of C. acidophila remained fairly stable. The differences suggested that $CO_2$ gas was more frequently limited for P. acidojaponica than C. acidophila, since high density patches of benthic diatoms were sometimes observed on the lake sediment. Generally, carbon concentration mechanisms (CCMs)of microalgae can fix bicarbonate in lakes, and affect the carbon isotope values of microalgae. While, in Lake Katanuma, CCMs of the microalgae may scarcely function because of high $CO_2$ gas concentration and low pH. This is the reason for low seasonal amplitude of carbon isotope values of phytoplankton relative to those in other lakes.

• Korean Journal of Ecology and Environment
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• v.38 no.spc
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• pp.67-75
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• 2005

The objectives of this study were to understand the runoff characteristics of the non-point sources originating from impervious surfaces and to assess their effect on the aquatic environment in the urban areas. The concentration of pollutants (SS, BOD, COD and T-P) except for T-N showed the highest value in runoff from road, and event mean concentration (EMC) also showed high value from road. The pollutants discharged from road showed a higher concentration in the beginning stage (0 ${\sim}$ 30%) of progressive percentage of rainfall. The contribution percentages of non-point sources by load were 44.9% for SS, 11.2% for BOD, 21.4% for COD, 11.4% for T-N and 8.1% for T-P in the total load of pollutant discharged through sewer. From our results, the road was a significant potential source that deteriorated water quality of the streams and lakes in the vicinity of the urban area during the rain period. Therefore, counter plan is required to reduce pollutant concentration on the road from non-point sources in the urban area. Also, since pollutant concentration in the beginning stage of rainfall was quite high, road cleaning seems to be one of the very useful methods to prevent inflowing of pollutants to the aquatic environment.

• Korean Journal of Ecology and Environment
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• v.38 no.spc
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• pp.1-7
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• 2005

To resolve some of the most pressing uncertainties of Peridinium identity, morphological characteristics of Korean Peridinium were examined using light and scanning electron microscopy. The Peridinium samples were collected from three different regions of Juam, Sang-sa and Togyo Reservoirs, when seasonal blooms occurred. Formula of the epithecal plate was recorded with 7 precingular, 3 intercalary, and 4 apical plates (4', 3a, 7"). An apical pore, 3 ${\sim}$ 5 ${\mu}m$ in size, was apparently present. The cingulum was easily observed under light microscope, and was considerably offset by about 15 ${\mu}m$ (2 ${\sim}$ 3 times per cingulum width). The sulcus was straight longitudinally and widened apparently towards the antapex. None of spine was found on the surface of the thecal plates on scanning electron micrographs. The average body length was 50.4 ${\mu}m$ with a range of 29 ${\sim}$ 63 ${\mu}m$. The geometric dimension, as designated to the body length:width ratio, was found from calculation to be 1.12 with a range of 1.00 ${\sim}$ 1.35, therefore, the cell was shown slightly elongated. Based on their morphology, the causative organisms of red tides in three different Korean waters were identified as P. bipes f. occultatum, which was reported for the first time in Korea.