• Korean System Dynamics Review
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• v.16 no.1
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• pp.25-51
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• 2015

The purpose of this paper is to analyze nutrients dynamics depending on biomass of Menyanthes trifoliata L., the endangered species, in a small closed-type wetland. In order to understand dynamics between Menyanthes trifoliata L. and eutrophication, causal loops and stock-flow diagram were constructed. The result of the model simulation was matched well with monitoring data (Menyanthes trifoliata L. biomass, TN, TP, DO). The model was simulated with 3 scenarios. In case of scenario 1, the initial value of biomass was 0mg/L, and the eutrophic state period was 77 days. In case of scenario 2, the initial value of biomass was 35.8 mg/L, and the eutrophic state lasted for 13 days. In case of scenario 3, the initial value of biomass was 71.6 mg/L, and the eutrophic state was nonexistent. The scenario 3 was selected as planting plan of Menyanthes trifoliata L. Through this study, planting design with an endangered plant was developed to control eutrophication in small closed-type wetland.

• Journal of Ecology and Environment
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• v.35 no.4
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• pp.291-299
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• 2012

This experiment was conducted to investigate the effects of the addition of wintering waterfowl's feces prior to planting rice on nutrient dynamics, rice growth, and decomposition of rice straws in a controlled mesocosm. Waterfowl's feces and rice straws were placed on paddy soils in a mesocosm and the water level maintained at 5 cm. The amounts of supplied feces were 0 (control), 222, and 444 g/$m^2$. While the addition of feces showed no immediate effects, nutrients in the surface water increased in the month following treatment. Nutrients increased to a greater degree in the treatments with more feces added. Simultaneously, the decomposition of rice straws was promoted, indicating that more nutrients would be made available over time. The rice showed high productivity in the period during which nutrient level was increased, when rice needs more nutrients for the tillering stage. Therefore, the wintering waterfowl's feces could be associated with increased productivity during the growing season of rice through promoting nutrient supply and rapid decomposition of rice residue.

• 한국생태학회:학술대회논문집
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• 2002.08a
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• pp.101-105
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• 2002

Fine root decomposition and nutrient release patterns were examined using in situ buried fine root (< 2mm in diameter) bags inserted vertically into the mineral soil to a depth of the top 15 cm in a sawtooth oak (Quercus acutissima) and a Korean pine (Pinus korainesis) stands in the Jungbu Forest Experiment Station, Kyonggi-do, Korea. The pine roots compared with the oak roots showed rapid mass loss in early stages of decomposition, but decomposed similarly after 12 months of incubation. Decomposition rates of fine roots were about 33%/yr for the oak roots and 37%/yr for the pine roots. Nutrients except for calcium and phosphorus showed similar concentrations between the oak and the pine roots during the study period. However, calcium concentration was significantly higher in the oak than in the pine roots. Nutrient concentrations in both stands except for nitrogen decreased during the study period. In addition, potassium compared with other nutrients was the most mobile ion and about 70% of initial amount was released during the first 3 months of incubation. The results indicate that tree species influence mass loss and nutrient dynamics of fine roots on similar site conditions.

• The Korean Journal of Ecology
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• v.25 no.4
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• pp.235-239
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• 2002

Fine root decomposition and nutrient release patterns were examined using in situ buried fine root (＜ 2mm in diameter) bags inserted vertically into the mineral soil to a depth of the top 15 cm in a sawtooth oak (Quercus acutissima) and a Korean pine (Pinus korainesis) stands in the Jungbu Forest Experiment Station, Kyonggi-do, Korea. The pine roots compared with the oak roots showed rapid mass loss in early stages of decomposition, but decomposed similarly after 12 months of incubation. Decomposition rates of fine roots were about 33%/yr for the oak roots and 37$\%$/yr for the pine roots. Nutrients except for calcium and phosphorus showed similar concentrations between the oak and the pine roots during the study period. However, calcium concentration was significantly higher in the oak than in the pine roots. Nutrient concentrations in both stands except for nitrogen decreased during the study period. In addition, potassium compared with other nutrients was the most mobile ion and about 70$\%$ of initial amount was released during the first 3 months of incubation. The results indicate that tree species influence mass loss and nutrient dynamics of fine roots on similar site conditions.

• Proceedings of the Zoological Society Korea Conference
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• 1996.10a
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• pp.125.1-125
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• 1996

No Abstract, See Full Text

• Korean Journal of Ecology and Environment
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• v.38 no.4 s.114
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• pp.445-453
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• 2005

Relative importance between bottom-up and top-down controls on phytoplankton dynamics was investigated in the Juam Reservoir, Chonnam based on the results from statistical analyses including regression and artificial neural network (ANN) modeling. Effects of nutrients on size-structured phytoplankton dynamics were explored by simple linear regression analysis and relative importance between bottom-up and top-down controls was estimated based on results from the artificial neural network analyses. Although there is a limitation in determining direct grazing effects since chlorophyll a : pheopigments ratios, indirect index for grazing activity rather than grazing rates or herbivores biomass were used, the results from regression analysis showed that nutrients especially orthophosphates were positively correlated with the phytoplankton biomass and chlorophyll a : pheopigments ratios were also positively correlated with the phytoplankton biomass at lower coefficient of determination ($r^2$) compared to orthophosphates. The simulation results from ANN suggested that the bottom-up mechanisms including water temperature and availability of nutrients, especially orthophosphates were more important than top-down mechanisms such as grazing in the phytoplankton dynamics.

• Journal of Environmental Science International
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• v.10 no.1
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• pp.65-71
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• 2001

HRP(high rate pond) which had kept the manufactured clay of 3cm-thickness as benthic clay in reactor and the 6 flat-blade turbine as impeller for agitation was named HRASP(high rate algae stabilization pond). And the experiment for treatment of artificial synthesis wastewater containing COD :300mg/$\ell$, NH$_3$-N : 300mg/$\ell$, T-P : 9mg/$\ell$ as nutrients was been performed successfully. This reactor was been operated under conditions : 24hrs.-irradiation and water temperature, $25^{\circ}C$ and pH 7 and agitation velocity, 15, 30, 45rpm and the effect of agitation velocity on algal bioaccumulation of nutrients was been studied with view point of fluid dynamics. The next followings could be obtained as results. 1. The agitation with a turbine impeller blade in HRASP makes clay particle indicate superior suspension effect by means of forming of excellent curl/shear flow in reactor. 2. The excessive suspension of clay particle which is created at 45rpm as rotation velocity of impeller blade of turbine disturbs the light penetration and algal photosynthesis reaction. 3. Efficiencies for removal of nutrients come out as COD : 93.9%~94.3%, ($NH_3-N + NO_3-N$) : 81.9%~99.0%, T-P : 46.8%~53.6%. 4. Kuo values of $K_1$for algal growth come out seperately as 15rpm : $1.876{\times}10^{-2}, 30rpm : 4.618{\times}10^{-3}$. 5. Kuo values of $K_2$for removal of N, P come out seperately as 15rpm : $8.403{\times}10^{-1}$ and $1.397{\times}10^{-1}$, 30rpm : $4.823{\times}10^{-1} and 2.052{\times}10^{-1}$. 6. It can be guessed easily that the excessive agitation can inhibit the algal and bacterial symbiotic reaction if it is considered that micro organism\` sense to preservation of life is relied on natural function of metabolism. Therefore the studies for this matter should be followed continuously.

• Proceedings of the Zoological Society Korea Conference
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• 1997.10b
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• pp.160.2-160
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• 1997

No Abstract, See Full Text

• Korean Journal of Ecology and Environment
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• v.41 no.4
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• pp.457-465
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• 2008

The purpose of the study was to evaluate spatial and temporal dynamics of nutrients (TN, TP), organic pollution (BOD, COD), and ionic dynamics (electrical conductivity, EC) in the North Han-River, South Han-River, and merged downriver using the dataset of $1998{\sim}2007$, obtained from the MEK (Ministry of Environment, Korea). Accord. ing to interannual nutrient analysis, TN varied slightly in the North Han-River and South Han-River, but decreased in the merged downriver along with BOD. Longitudinal analysis in the water quality showed that BOD, COD, and nutrients had linear decreasing trend along the main axis of headwater-to-downriver. Concentrations of TP and TN in the North Han-River averaged $26.97{\mu}g\;L^{-1}$, $1.696mg\;L^{-1}$, respectively, which were minimum in the three watersheds, followed by South Han-River and then the merged downriver in order. Ratios of TN:TP in the watersheds were >40 in all the sites, indicating that nitrogen may be enough for periphyton or phytoplankton growth and phosphorus may be limited partially. After the North Han-River water is merged with South Han-River, the concentrations of BOD, COD, TN, and TP were similar to the values of $S6{\sim}S7$, respectively or a little bit higher, but increased abruptly in Site M4 (Fig. 3). Thus, mean values of all the water quality parameters in the reach of $M4{\sim}M7$ sites were greater than any other sites. Seasonal data analysis indicated that BOD and EC in the downstream ($S3{\sim}S7$) was greater in the premonsoon than two seasons of the monsoon and postmonsoon, and no significant differences in BOD between the three seasons were found in the upstream ($S1{\sim}S2$). Empirical models of COD in the merged downriver was predicted ($R^2=0.87$, p>0.01, slope = 0.84, intercept = -1.28) well by EC. These results suggest that EC to be measured easily in the field may be used for estimations of nutrients and organic matter pollutions in the merged downriver and these linear models are cost-effective for the monitoring of the parameters.

• Fisheries and Aquatic Sciences
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• v.26 no.7
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• pp.423-436
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• 2023

The objectives of this review were to synthesize the community structure of phytoplankton and the role of atelomix in the phytoplankton dynamics in Ethiopian highland lakes. Changes in a lake's physical structure, light dynamics, and availability of nutrients are closely associated with phytoplankton ecology, and phytoplankton assemblages provide insight into phytoplank- ton responses to these environmental changes. Based on the available information, a total of 173 species of phytoplankton are grouped under seven classes, Chlorophyceae (80 taxa), Bacillariophyceae (55 taxa), Cyanophyceae (24 taxa), Dinophyceae (6 taxa), Eugleonophyceae (6 taxa), Xanthophyceae (1 taxon), and Cryptophyceae (1 taxon) were recorded in five different tropical Ethiopian highland lakes. Chlorophyceae and Bacillariophyceae dominated in terms of species composition. Partial atelomixis, seasonality, and low nutrient concentrations seem to be the main drivers in structuring phytoplankton composition and abun-dances in Ethiopian highland lakes, characterized by a high diversity of atelomix-dependent benthic diatoms and desmids. Thus, this review will help understand the role of atelomix and nutrient availability in the phytoplankton composition and biomass of tropical highland lakes of Ethiopia.