Sok-Jin Hong

Variation in Residence Time and Water Exchange Rate by Release Time of Pollutants Over a Tidal Cycle in Masan Bay

Lagrangian particle transport model coupled with the EFDC have been performed to estimate the residence time and water exchange rate by release time of pollutants over a tidal cycle in Masan Bay. The modelled residence time for the whole bay was about 40 days, ranging from less than 20 days in the southern parts of Budo, to over 100 days in the upper parts of Somodo. The spatial difference of residence time was controlled by tidal residual currents and the distance to the bay channel. The area mean residence time during spring and neap tides was estimated to be about 36 days and 42 days, respectively. The time required for 30% exchange of water was calculated as ranging from 65 to 105 days by release time of pollutants.

Ecological Modeling for Estimation of Autochthonous COD in Jinhae Bay

The three-dimensional eco-hydrodynamic model was applied to estimate the autochthonous COD caused by production of phytoplankton in Jinhae Bay. A residual current was simulated, using a hydrodynamic model, to have a sightly complicated pattern in the inner part of the bay, ranging from 0.001 to 5 cm/s. In the outer part of the bay, the simulated current flowed out to the south sea with a southward flow at a maximum of 25 cm/s. The results of the ecological model simulation of COD levels showed high concentrations, exceeding 4 mg/L, in the inner bay of Masan, an area of wastewater discharge, and lower levels, approaching less than 1 mg/L, closer to the outer part of the bay. The simulation results of Autochthonous COD by two methods using ecological modeling, showed high ratio over 70% of total COD. Therefore, it is more important to consider nutrients than organic matters in the region for control COD standard.

Estimation of a Transport and Distribution of COD using Eco-hydrodynamic Model in Jinhae Bay

To find proper water quality management strategy for oxygen consumption organic matters in Jinhae bay, the physical process and net supply/decomposition in terms of COD was estimated by three-dimensional eco-hydrodynamic modeling. The estimation results of physical process in terms of COD showed that transportation of COD was dominant in loading area from land to sea, while accumulation of COD was dominant in level. In case of surface level, the net supply rate of COD was . The net decomposition rate of COD was ( m, in depth) to 2 level, and to bottom level. These results indicate that the biological decomposition and physical accumulation of COD are occurred for the most part of Jinhae Bay bottom. The variation of net supply or net decomposition rate of COD as reducing land based input loading is also remarkable. Therefore, it is important to consider both allochthonous and autochthonous oxygen demanding organic matters to improve the water quality of Jinhae Bay.

Marine Ecosystem Response to Nutrient Input Reduction in Jinhae Bay, South Korea

We study on the dynamic interaction with a simulated physical-biological coupled model response to nutrient reduction scenario in Jinhae Bay. According to the low relative errors, high regression coefficients of COD and DIN, and realistic distribution in comparison to the observation, our coupled model could be applicable for assessing the marine ecosystem response to nutrient input reduction in Jinhae Bay. Due to the new construction and expansion of sewage treatment plant from our government, we reduce 50% nutrient inputs near Masan Bay and sewage treatment plant. COD achieves Level II in Korea standard of the water quality from the middle of the Masan Bay to all around Jinhae Bay except the inner Masan Bay remaining at Level III. When our experiment reduces 50% nutrient inputs near Masan Bay and Dukdong sewage treatment plant simultaneously, COD decreases to about 0.1-1.2 mg/L . The COD from the middle of the Masan Bay to Jinhae Bay achieves Level II.

Decoupling of Macromolecular Compositions of Particulate Organic Matters between the Water Columns and the Sediment in Geoje-Hansan Bay, South Korea

The biochemical composition of particulate organic matter (POM) is very important to understand in relation to the trophic conditions of marine ecosystems since it forms the primary trophic base. The present study investigated the biochemical compositions (i.e., carbohydrates, proteins, and lipids) of POM monthly from January to December 2015 in Geoje-Hansan Bay to determine if the macromolecular composition of POM is coupled between the water columns and sediment. A spatial difference in the macromolecular compositions was observed in the water columns between the inner and outer bays, which may be caused by the different physiological conditions of phytoplankton growth that are due to the water circulation pattern in the bay. In contrast, no distinctive spatial difference in the macromolecular compositions was found in the sedimentary organic matter. Overall, while carbohydrates were the dominant (45.7%) macromolecules of the POM in the water columns, proteins were dominant (47.9%) in the sedimentary organic matter during our observation period. Decoupling of the macromolecular compositions between the water columns and underneath the sediment in Geoje-Hansan Bay appears to be a result of the various effects of selective filter feeding by oysters and protein-dominant benthic microalgae and fouling organisms.

Plankton Community Composition Related to Marine Environmental Factors in Haengam Bay

We analyzed with HPLC (High Performance Liquid Chromatography) analysis photosynthetic pigments and environmental factors, microscopic observations of the phytoplankton and zooplankton in the seawater every month from February 2009 to November 2010 in Haengam Bay. The level of dissolved inorganic nutrients was the highest between July and September, when freshwater influx was at its peak, whereas chlorophyll a levels were the highest in April and August. Also, phytoplankton pigment concentration increased when dissolved inorganic nutrients are carried into nearshore waters by rainfall runoff. Based on identification of phytoplankton and photosynthetic pigments results, diatoms were mainly dominant while dinoflagellate populations increased at July and August 2009, May 2010. The zooplankton communities are dominated in terms of Noctiluca scintillans. The contribution of Noctiluca scintillans in 2010 accounts for approximately 77.3% of the total zooplankton. Distribution patterns over time of zooplankton in the seasonal distribution of phytoplankton showed a different pattern.