• Korean Journal of Ecology and Environment
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• v.37 no.4 s.109
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• pp.455-461
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• 2004

Effects of the different strengths and intervals of the periodic outer water intrusions (kyuchos and bottom intrusions) on the dynamics of phytoplankton biomass in a small embayment were examined with a simple numerical model. Environmental conditions of Kitanada Bay in the Bungo Channel were applied to the model. As the interval of the intrusion became longer and the amplitude became smaller, phytoplankton biomass In the bay became higher. On the other hand, as the interval became shorter and the amplitude became larger, the growth rate of the phytoplankton became higher. It suggested that when the intrusion was weaker, water exchange of the bay decreased and the phytoplankton in the bay accumulated at a high density, When water exchange was improved by active intrusions, availability of light would become more efficient and the growth rate of the phytoplankton was enhanced.

• Korean Journal of Ecology and Environment
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• v.37 no.4 s.109
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• pp.448-454
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• 2004

In order to evaluate the water quality (N, P and C) and the biological mass balance of semi-enclosed brackish Lake Obuchi, Japan, an ecosystem model was developed and applied to the lake, using the flow field calculated by a hydrodynamic model. The time series data of the observed tide level, river discharge and meteorological parameters from January 2001 to December 2002 were incorporated as the parameters of the hydrodynamic model. Water quality and biomass balance were estimated by the ecosystem model, and simulated fluctuations In water quality agreed with our observations. The carbon contents of POC, phytoplankton and zooplankton in the lake were calculated by the model at an average 7200, 1500 and 22 kg, respectively, which somewhat agreed with our observations of POC (5900 kg), phytoplankton (3800kg), and zooplankton (150kg).

• Korean Journal of Ecology and Environment
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• v.37 no.4 s.109
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• pp.406-410
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• 2004

The alkaline phosphatase activity (APA) of two dam reservoirs and inflowing streams were measured monthly in 2000. During summer months in 2001, the vertical profiles of APA and related parameters were also examined in one of the reservoirs. The APA was relatively high during the summer season in the epilimnion while it was almost invariable in the hypolimnion. A small increase in APA was observed at just above the bottom. The APA fluctuation was independent of the concentration of soluble reactive phosphorus. It was assumed that APA is not indicative of the phosphorus availability status. An examination of size-fractionated samples suggested that APA in reservoirs was attached to particles larger than $0.4{\mu}m$, whereas in streams it existed in a dissolved form. There was a positive significant correlation between chlorophyll a concentration and APA in the photic zone. In the aphotic zone, APA correlated positively with the colony count of heterotrophic bacteria, but not with microscopic total bacterial counts.

• Korean Journal of Ecology and Environment
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• v.37 no.4 s.109
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• pp.400-405
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• 2004

Since a large bank-protection works project was undertaken during winter in the middle reaches of the Chikuma, the riverbed structure was drastically altered. In order to assess the short-term impact of bank-protection works on the abundance Pattern of Stenopsyche marmorata (Trichoptera) from spring to early summer, we conducted an investigation on the capture of adults using light traps before and after construction work. The patterns of the daily capture of S. marmorata and the Namely, after construction, the daily catch of adult numbers increased only slightly during the investigation periods. This suggested that the age structure of the S. marmorata larval population had changed in the construction area. Our data suggest that bank-protection projects impact the abundance pattern of adult caddisflies in the river ecosystem.

• Korean Journal of Ecology and Environment
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• v.36 no.1 s.102
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• pp.9-20
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• 2003

Response-species of zooplankton on precipitation and temperature were investigat-ed in the tributaries of Han River from May to November, 2002. Total 42 species(Rotifer twenty three species, Cladocera ten species, Copepoda eight species and Protozoa one species) were collected in the target location. The highest abundance and the number of species were observed in May. Due to the summer precipitation the abundance of Rotifer and Cladocera were largely decreased in August. Dominant species of Rotifer appeared Brachionus urceolaris, Euclanis dilatata, Lecane Inua, Brachionus quadridentatus and Brachionus calyciflorus in May, Monostyla bulla and Conochilus unicornis in August and Brachionus quadridentatus, Euclanis dilatata and Lecane Iuna in November. Also, the dominant species of Cladocera were Moina weismanni, Simocephalus vetulus, Scapholebris aucrgnafa, Chydorus sphaericus in May, Chydorus sphaericus, Scapholebris mucronata in August, Chydorus sphaericus and Alona rectangular in November. Nearest neighbour clustering was implemented for classification of zooplankton abundance indifferent month of survey locations. The patterning of May and November appeared similar but August was different.

• Korean Journal of Ecology and Environment
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• v.38 no.3 s.113
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• pp.334-340
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• 2005

The chemical forms of Cd, Cu, Pb, and Zn were analysed by sequential extraction technique to evaluate the effects of drying and heating of dredged sediments from Lake Chungcho. The most abundant fraction of Cd, Cu, and Zn in the wet and untreated sediment was organic/sulfidic fraction that is state in reducing environment such as the bottom condition of Lake Chungcho, while Pb dominated in residual fraction. This means that the source of Cd, Cu, and Zn in the Chungcho lake sediment is related to the organic degradation and Pb to the erosion from surrounding rocks. With drying and oxidation by dredging, heating treatment, and disposal of the lake sediment, the chemical forms of studied metals changed greatly from organic/sulfidic fraction to adsorbed and reducible fractions which are more labile in oxygenated environment. Organic/sulfidic fraction of Cd, Cu and Pb in the wet sediment was transformed with drying and heating treatments to the labile ones like adsorbed and reducible fraction, but Zn to carbonate and reducible fraction. Heating of the sediment at $320^{\circ}C$ greatly increased the labile fraction of Cd and Cu, while that at $105^{\circ}C$ for Pb and Zn. It is believed that the increase in labile forms of heavy metals in the sediments by drying and heating is caused by the contact with oxygen during drying and heating and by the increase of pH of the pore water at the expense of organic/sulfidic fraction. It is concluded that the drying and oxidation currently used in the treatment of dredged sediment can increase labile forms of heavy metals in the sediment, and the potential of the metal availability from the sediment.

• Korean Journal of Ecology and Environment
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• v.37 no.4 s.109
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• pp.394-399
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• 2004

The species composition and abundance of aquatic insects were investigated by light trap in summer, 2002 at three stations in the Chikuma River, Japan's longest river. A total of 3278 adults/day were collected, the great majority (57.5%) of which were Diptera, followed by Trichoptera (35.4%) and then Ephemeroptera (7.1%). The number of collected aquatic insects and their biomass gradually increased towards downstream, whereas the number of species and species diversity index (H') decreased. 36 species (H'= 4.30) of aquatic insects were collected at St. 1, versus 31 species (H'= 2.81) at St. 3. Moreover, the relative abundance of functional feeding groups changed from St. 1 to St. 3, i.e., 'collectors' increased and 'shredders' decreased.

• Korean Journal of Ecology and Environment
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• v.47 no.4
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• pp.337-341
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• 2014

The changes in the area and standing crop of forests and the understory vegetation structure of various plantations were investigated by literature survey to predict the changes in the structure of forest ecosystems of the Korean Peninsula in the future. The greater part of forest was severely destroyed in 1950's in the Korean Peninsula. The forest standing crop has been dramatically increasing since the nationwide plantation was actively performed in 1970's and 1980's in the Republic of Korea. The area of forest was incessantly decreased at the rate of $5,500ha\;yr^{-1}$. The results of regression analysis on the changes in forest standing crop of the Republic of Korea showed that the forest might approach to the maturity stage in around 2150. It was predicted that the potential natural vegetation of Quercus mongorica, Fraxinus rhynchophyllus, Prunus sargentii, etc. would establish in the plantations of Larix leptolepsis, Pinus koraiensis and Robinia pseudoacacia in the future.

• Korean Journal of Ecology and Environment
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• v.47 no.4
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• pp.292-301
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• 2014

Akinete germination may be a starting point of some akinete-producing cyanobacterial blooms in eutrophic freshwater systems. This study examined germinability of akinete of a cyanobacterium Anabaena circinalis isolated from the sediment of the North Han River (Cheongpyung Dam), Korea, under several environmental factors such as temperature ($5{\sim}25^{\circ}C$), light ($0{\sim}100{\mu}mol\;photons\;m^{-2}\;s^{-1}$), nutrients (nitrogen and phosphorus) and pH (5~12). The high germination rate appeared at high temperature: >55% at $25^{\circ}C$, followed by 15% at $15^{\circ}C$, $10^{\circ}C$ and 10% at $5^{\circ}C$. Low light intensity was favorable for akinete germination. Over 45% of germination occurred at low light intensities (5, 15 and $30{\mu}mol\;photons\;m^{-2}\;s^{-1}$), while less than 10% of germination occurred at both 50 and $100{\mu}mol\;photons\;m^{-2}\;s^{-1}$. No germination occurred in the dark condition. Akinete germination rate increased with nutrient (phosphorus and nitrogen) enrichment, and nitrogen addition showed greater effect on the germination compared to phosphorus addition. Akinetes germinated well at neutral or slightly alkaline pH condition (pH 7 and pH 8: >55%), but no germination was observed at pH 11~12. The present study demonstrates some favorable ambient conditions of Anabaena circinalis germination, which could provide useful information to study the germination conditions of other Anabaena species or akinete-forming algae and predict its bloom in eutrophic freshwaters.

• Korean Journal of Ecology and Environment
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• v.49 no.2
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• pp.130-141
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• 2016

This study was conducted to elucidate the structure of river ecosystem in the watershed of the Seom River and Hoengseong Reservoir located in Hoengseong of Kangwon Province from February to October 2007. Topics of the survey were mainly rainfall, discharge, water quality in abiotic factors and attached algae, benthic macroinvertebrates, fish, birds and mammals of flora and fauna in a biotic factors, respectively. Specifically, the Seom River could be seen as a typical flow rate of the stream is controlled to the effect of the dam. Basic water qualities were great to seasonal effects, it was relatively clean. Diatom Achnanthes, Cymbella, Gomphonema, and Navicula were distributed predominantly in the periphytic algae. Benthic macroinvertebrates were mostly aquatic insects and freshwater shellfish, the aquatic insects were abundant Ephemeroptera and Trichoptera. Freshwater fish was the dominant Zacco platypus, fish species varied toward the downstream. Birds were mainly observed in four species, and species Egretta garzetta, which was distributed in a wide area of the Seom River. In mammals, Lutra lutra of Mustelidae was identified that the number of inhabit widely. In aspects of the ecological trophic level, the Seom River was maintained at a relatively stable state in the producer and the consumer relationship. The results of this study will expected to be utilized as a useful data for understanding the structure and function of the lotic and lentic ecosystems.