• Journal of the Korean Society of Marine Environment & Safety
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• v.22 no.6
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• pp.708-722
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• 2016

Land-Ocean Interactions in the Coastal Zone (LOICZ) models for nutrient budgets were used to estimate the seasonal capacity of the Youngsan Estuary and Youngam-Geumho Estuary to sink and/or supply nutrients such as dissolved inorganic phosphorus (DIP) and nitrogen (DIN) to provide an understanding of the behavior of the coupled biogeochemical cycles of phosphorus and nitrogen in the estuaries (Youngsan Estuary, Youngam-Geumho Estuary) near Mokpo Harbor. During non-stratified periods (May, September, and November, 2008), simple three-box models were applied in each sub-region of the system, while a two-layer box model was applied during on-site observation of stratification development (July, 2008). The resulting mass-balance calculation indicated that even after large discharges from artificial lakes (in May and July), DIP influxes due to a mixing exchange ($V_{X-3}$, or $V_{deep}$) were more than terrigenous loads, indicating the backward transportation of nutrients from a marine source. The model results also indicated that for nutrient loads (DIP and DIN fluxes) in September, an extreme congestion of nutrients occurred around the mouths (sub-region III of the model) of the estuaries, possibly due to an imbalance in physical circulations between the estuaries and offshore locations. In November, the Youngam-Geumho Estuary, into which freshwater was discharged from artificial lakes (Youngam and Geumho Lake), showed nutrient enrichment in the water column, but the Youngsan Estuary showed nutrient depletion. In conclusion, to efficiently control water quality in the estuaries near Mokpo Harbor, integrated environmental management programs should be implemented. I.e., the reduction of nutrient loads from land basins as well as the deposit of nutrient loads into adjacent coastal lines.

• Korean Journal of Ecology and Environment
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• v.36 no.4 s.105
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• pp.403-412
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• 2003

Temporal and spatial variations of size-structured phytoplankton (chlorophyll a) were investigated over an annual cycle (February-October, 2003) to elucidate phytoplankton dynamics in the Juam Reservoir, Chonnam. Physical properties were also measured to investigate the relationship between the properties and temporal and spatial variations of size structured phytoplankton using simple linear regression. Phytoplankton (chlorophyll a) were grouped into three size classes: micro-size(> 20 ${\mu}m$), nano-size (3-20 ${\mu}m$) and pico-size (< 3 ${\mu}m$) in this study. Physical properties included water temperature, light attenuation coefficients, PAR (photosynthetically active radiation) and turbidity. Maximum chlorophyll a was observed in April, 2003 in the lower region whereas a peak of chlorophyll a developed in October, 2003 in the upper region. Large cell-sized phytoplankton (micro-size class)were dominant in the events of the chlorophyll a peaks. Potential mechanisms in the physical properties affecting the size-structured phytoplankton dynamics in the Juam Reservoir were discussed.

• 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 Korean Society on Water Environment
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• v.31 no.6
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• pp.665-679
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• 2015

Yearly mean temperature in the 29 lakes surveyed ranges from 12.6 (Suncheon) to 13.9℃ (Mokpo), the lowest in −2.7℃ (January) and the highest in 25.9℃ (July). Monthly mean the amount of rainfall recorded the highest of 336.7 mm in August and the lowest with 4.9 mm in January. A total of 424 species of phytoplankton were identified. They were 157 Chlorophyceae, 161 Bacillariophyceae, 39 Cyanophyceae, and 67 other algal taxa. The phytoplankton diversity were low in stream type reservoirs such as Guemho, Youngsan and Youngam. The population density of phytoplankton ranged from 19 to 53,161 cells/ml. Annual mean of total zooplankton abundance in 45 sites was 369±827 ind./L (n=180). Rotifers were the most common taxa and their relative abundance was high (65~77%). The benthic microinvertebrate fauna of 10 reservoirs of Jeonnam province were 71 species of 61 genera of 44 families of 16 orders of 7 classes of 4 phyla. Aquatic insects of Phylum Arthropoda were 50 species of 44 genera of 28 families of 6 orders. The number of individuals was 6,132. Diptera was highiest (41.3%), and Ephemeroptera (31.0%), Trichoptera (17.5%), Anellida (3.8%), Mollusca (3.3%), Crustacea (0.4%). Large hydrophytes were identified 32 taxa, 2 varieties 30 species 26 genera and 20 families. Especially, Jijung and Juam lakes require management such as physical remove of this ecosystem disturbance field plants. Fishes were identified total 44 taxa, such as 25 Cyprinidae (56.8%), 8 Cobitidae (17.0%), 3 Gobiidae (6.4%), 2 Bagridae (4.3%), 2 Osmeridae (4.3%), 2 Odontobutidae (4.3%), 2 Centrachidae (4.3%), 1 Siluridae (2.1%), and 1 Centropomidae (2.1%). A pale chub was dominant species (18.9%).