• Korean Journal of Ecology and Environment
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• v.41 no.spc
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• pp.11-20
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• 2008

In this study, we applied a Particle Swarm Optimization (PSO) algorithm to predict the changes of chlorophyll-${\alpha}$ related to environmental factors in agricultural reservoirs in Korean national scale. Data were obtained from water quality monitoring networks of reservoirs operated by the Ministry of Agriculture and Forestry and the Ministry of Environment of Korea. From the database of the monitoring networks, 290 reservoirs were chosen with variables such as chlorophyll-${\alpha}$ and 13 environmental factors (COD, TN, TP, Altitude, Bank height, etc.) measured in 2002. Based on Carlson's trophic status index, reservoirs were divided into five groups, and most agricultural reservoirs $(TSI_{CHL}\;64.1%,\;TSI_{TP}\;75.5%)$ were in the eutrophic states. The groups were discriminated with environmental variables, showing that COD, DO, and TP were important factors to determine the trophic states. MLP-PSO (Multilayer perceptron (MLP) with PSO for the optimization) was applied for the prediction of chlorophyll-${\alpha}$ with environment factors, and showed high predictability (r=0.83, p<0.001). Additionally, the sensitivity analysis of the MLP-PSO model showed that COD had the strongest positive effects on the concentration of chlorophyll-${\alpha}$, and followed by TP, TN, DO, whereas altitude and bank height had negative effects on the concentration of chlorophyll-${\alpha}$.

• Journal of Fisheries and Marine Sciences Education
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• v.28 no.5
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• pp.1444-1458
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• 2016

The expansion of high-density aquaculture in the limited waters has caused a wide variety of problems. The problems include environmental problems nearby aquaculture sites, growth rate of aquatic organisms, quality decline of farmed fish and price fall in the market. The phenomenon of aquaculture industry happens in not only inshore but also offshore. Therefore, the fisheries authorities have been changing their policy paradigms from mass production to sustainable production based on ecosystem. Other countries, however, focusing on relieving poverty and providing protein from fish production have not recognized the degree of seriousness. When it comes to enhancing the problems, National Institute of Fisheries Science has been developing the technology of Integrated Multi-Trophic Aquaculture (IMTA) to reduce and to prevent contaminants from fish and aquaculture sites, remained feed from fish farming process. In long-terms of view, the system is one of the most sustainable fishery production methods based on ecosystem. As integration of nutrient feed system from aquatic organisms is firmly established, the earlier mentioned problems will be diminished gradually. In term of the substantiality, this study was conducted. The research on management system for IMTA also has been incorporated. This study also investigated the features and current status of IMTA and demonstrated the developed management system and direction for the future advancement.

• Journal of Ginseng Research
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• v.31 no.1
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• pp.51-53
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• 2007

Ginseng shows protective and trophic effects in neurodegenerative diseases in experimental models, and showed cognitive improvement in normal population. To investigate the efficacy of ginseng in patients with Alzheimer's disease, patients, who met NINDS-ADRDA criteria for AD were studied Subjects were randomly assigned to ginseng group and control group, and ginseng group was treated with Korean white ginseng powder (4.5 g/day) for 12 weeks. Efficacy variables included changes in mini-mental status exam (MMSE) and cognitive subscales of Alzheimer's disease assessment scale (ADAS-cog) at 4 weeks and 12 weeks. Baseline MMSE and ADAS scores showed no difference between the two groups. Results showed that ginseng improved ADAS-cog compared to the control group at 12 weeks (p<0.05). MMSE was also increased by ginseng treatment compared to the control at 12 weeks (p<0.01). This study suggests the symptomatic efficacy of ginseng in patients with Alzheimer's disease.

• The Korean Journal of Ecology
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• v.16 no.1
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• pp.115-131
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• 1993

Six nutrient cycles involving terrestrial plants are identified and characterized. Plants affect biotic and abiotic cycles through their effects on soil properties. They determine their internal nutritional status and nutrient concentrations in their environment via internal and external cycles. Contributions of organic matter to mycorrhizal, trophic, and detrital mediated external cycles and alterations of nutrient concentrations by plants can promote positive feedbacks leading to increased availability and retention of soil nutrients in open systems. Recognizing alternative cycles through plants leads to a definition of nutrient use efficiency for ecosystems: the ratio of system production to nutrient content of organic matter. A simple graph model to predict changes of nutrient use efficiency during primary succession is then presented.

• Korean Journal of Ecology and Environment
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• v.45 no.3
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• pp.329-339
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• 2012

In the spring (March to June) in 2010, one diatom Skeletonema costatum occurred outbreaks in Lake Hwajinpo, one of the typical lagoons on the east coast of South Korea. We compared the characteristics of the phytoplankton community during the bloom and extinction period of S. costatum, and evaluated the water quality based on nutritional indices. Results indicate that 1) this bloom showed the highest cell density ($>10^5$ cells $mL^{-1}$) among outbreaks of S. costatum occurred Korea, 2) occurred in below or over $20^{\circ}C$ water temperature, and 3) was destroyed in the early summer with higher temperature than the bloom period. Water quality or trophic status of the lake was eutrophic to hypertrophic with high salinity, BOD, COD and phosphate, and low N/P ratios and transparency. Phytoplankton community in the spring bloom had a high dominance and low diversity, but rightly recovered to low dominance and high diversity in the summer season. Therefore, we temporarily conclude that the bloom of S. costatum in Hwajinpo was triggered by the extended spring drought and the reduced influx of river water, and appeal that the bloom can happen repeatedly every year.

• Journal of Environmental Policy
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• v.1 no.1
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• pp.1-24
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• 2002

Due to the recent increase in greenhouse gases in atmosphere, world climate is rapidly changing and in turn, the earth ecosystem responds upon the climate changes. Comparing the ecosystem in the past, the present shapes of ecosystem is the result of the serious modification. Fishery resources in marine ecosystem, which usually occupy the upper trophic level, are also inevitable from such changes, because they always react to the natural environmental conditions. The northwestern Pacific is the most productive ocean in the world producing about 30% of world catch. From time to time, however, it has been notified that abundance, distribution and species composition of major fish species were altered by climate events. Furthermore, primary productivity of the ocean is not stable under the changing environments, so that carrying capacity of the ocean varies from one climate regime to another. Major climate events such as global warming, atmospheric circulation pattern, climate regime shift in the North Pacific, and El Nino event in the Pacific tropical waters were introduced in relation to fisheries aspects. The current status and future projection of fishery production was investigated, especially in the North Pacific including Korean waters. This new paradigm, ecosystem response to environmental variability, has become the main theme in marine ecology and fishery science, and the GLOBEC-type researches might provide a solution far cause-effect mechanism as well as prediction capability. Ecosystem management principles for multi-species should be adopted for better understanding and management of ecosystem.

• Journal of the korean society of oceanography
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• v.39 no.1
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• pp.20-25
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• 2004

The Yellow Sea is known to be a very productive region in terms of fisheries. However, its trophic status seems to be highly variable, ranging from oligotrophic to eutrophic, based on new production (NP) values. The NP and regenerated production (RP) values estimated from $^{15}N$-labelled nitrate and ammonium uptake in spring (April 1996) and winter (February 1997) during this study ranged from 0.05 to 19.8 mg $N m^{-2} d^{-1}$ and from 0.1 to 22.8 mg $N m^{-2}d^{-1}$, respectively. Our measurements and earlier observations suggested that NP in the Yellow Sea varied over the four orders of magnitude (range 0.05-180.9 mg $N m^{-2} d^{-1}$) temporally and spatially, and that RP (range 0.1-507.5 mg $N m^{-2}d^{-l}$) based on ammonium predominated during most period of the year, except in winter when both productions were low. The significant nitrogen uptake by phytoplankton below the euphotic zone and episodic entrainment of phytoplankton from below the euphotic zone into the euphotic zone, and nitrite excretion and dissolved organic nitrogen release during nitrate uptake might explain the apparent dominance of RP in the Yellow Sea.

• 한국해양학회지
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• v.25 no.3
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• pp.145-150
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• 1990

An analysis of collected data on components of dissolved organic phosphorus (DOP) and DOP is made to search for important components of DOP pool and their implications in phosphorus (P) cycling. The significance of dissolved nucleic acids (D-NA) apparently tends to increase with increasing trophic status of oceanic waters. Interestingly the sum of all 5-nucleotide and D-NA seems to dominate the DOP pool. Thus, materialization of D-NA could be a significant pathway of P cycling in surface oceanic waters and it might be of great importance in lakes where P limits primary production. Processes related to death of Microbes are responsible for D-NA and DOP production in surface waters, and incomplete digestion of preys by grazers seems to be an important mechanism in D-NA production.

• ALGAE
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• v.21 no.4
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• pp.433-443
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• 2006

This study was performed to understand the morphological and ecological characteristics of Peridinium bipes var. occultatum Lindem., which is the organism responsible for freshwater red tides in Sangsa dam and Miryang dam reservoirs. The samples were collected from April to July 2004 when the freshwater red tides occurred. In the study, we were able to differentiate P. bipes var. occultatum from P. bipes, a closely related species, by its smaller antapical horn size. In Miryang dam reservoir the red tide occurred only within the area of the upstream, but it was well developed in all of the water area in Sangsa dam reservoir. In 2004 average LTSI (Lake Trophic Status Index; Yang and Dickman, 1993) of Miryang dam reservoir was 3.53 of mesotrophic state and Sangsa dam reservoir was 8.59 of eutrophic state. It was determined, through culture experiments under various conditions that vitamins, trace elements, phosphorus and nitrogen were important contributing factors to the growth of P. bipes var. occultatum. A rapid toxic effect of P. bipes var. occultatum on aquatic organisms such of Daphnia magna and Oryzias latipes was not identified in this study.

• Ocean Science Journal
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• v.42 no.3
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• pp.179-192
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• 2007

Understanding in climate effects on marine ecosystem is essential to utilize, predict, and conserve marine living resources in the 21st century. In this review paper, we summarized the past history and current status of Korean fisheries as well as the changes in climate and oceanographic phenomena since the 1960s. Ocean ecosystems in Korean waters can be divided into three, based on the marine commercial fish catches; the demersal ecosystem in the Yellow Sea and the East China Sea, the pelagic ecosystem in the Tsushima Warm Current from the East China Sea to the East/Japan Sea, and the demersal ecosystem in the northern part of the East/Japan Sea. Through the interdisciplinary retrospective analysis using available fisheries, oceanographic, and meteorological information in three important fish communities, the trend patterns in major commercial catches and the relationship between climate/environmental variability and responses of fish populations were identified. Much evidence revealed that marine ecosystems, including the fish community in Korean waters, has been seriously affected by oceanographic changes, and each species has responded differently. In general, species diversity is lessening, and mean trophic level of each ecosystem has decreased during the last $3\sim4$ decades. Future changes in fisheries due to global warming are also considered for major fisheries and aquaculture in Korean waters.