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Featured researches published by Yongsik Sin.


Northwest Science | 2007

Nutrient Fluxes in the Microalgal-dominated Intertidal Regions of the Lower Yaquina Estuary, Oregon (USA).

Yongsik Sin; Anne C. Sigleo; Eunsook Song

The effects of benthic microalgae on sediment nutrient fluxes were investigated at three sites across the intertidal zone of lower Yaquina Bay. Study sites were selected where microalage were present but where seagrass and mud shrimp were absent. Sediment columns were collected seasonally from one to three stations from September 1999 through August 2000 to determine the seasonal and spatial range in benthic fluxes. Collected sediments were carried to the nearby laboratory for light and dark incubation experiments. Nitrate fluxes ranged from −122 to −4 μmol N m−2 hr−1, whereas ammonia fluxes ranged from −52 to 101 μmol N m−2 hr−1. The ranges for orthophosphate and silicate were −7.4 to 12 μmol P m−2 hr−1 and −93 to 283 μmol Si m−2 hr−1. The sediments were always a net sink for nitrate. Nitrate uptake rates were highest during the warmest month (August) and lowest during the coldest months (November and January). Nitrate fluxes were not statistically different for light and dark conditions. Ammonium was generally released from sediments into the water column in the dark, whereas it was taken up in the light. The sediments were a net sink for all tested nutrients under light conditions, whereas all nutrients except nitrate were released into the water column in the dark, indicating that ammonia, orthophosphate and silicate were utilized by benthic microalgae at the sediment-water interface in the light.


Algae | 2009

Characteristics of Benthic Chlorophyll a and Sediment Properties in the Tidal Flats of Kwangyang Bay, Korea

Yongsik Sin; Sang Ock Ryu; Eunsook Song

Characteristics of benthic microalgae and sediment properties were investigated for the intertidal flats of Kwangyang Bay, Korea. Sampling stations were selected every 100 m in the intertidal flats from land-side to open ocean at two different sampling sites. Samples were collected in June 2004, July, September, November, February and May 2005. Sediments properties were measured including temperature, water contents, sediment bulk density, nutrient concentrations in porewater. Chlorophyll a concentrations in surface sediment (0.5 cm) were measured and relationships between the chlorophyll a and various sediment properties were analyzed to identify major mechanisms regulating biomass of benthic microalgae in the intertidal flats using simple linear regression analysis. Sediment chlorophyll a concentrations were maximum during winter and minimum during warm seasons ranging from 4.4 mg m –2 to 81.2 mg m –2 . No clear spatial variations were observed for the sediment chlorophyll a in the study sites. Results from regression analysis suggested that benthic microalgae biomass was affected by sediment temperature and nutrients especially ammonium and silicate. Grazing effect was estimated using chlorophyll: pheopigments ratio, indirect indicator of grazing activity, and the positive correlation of the ratio and chlorophyll a implied that microalgae biomass is affected by grazing of zoobenthos although direct measurement of grazing activity is required to determine the importance of top-down controls in the benthic microalgae dynamics.


Microbes and Environments | 2018

Host-Specific Bacteroides Markers-Based Microbial Source Tracking in Aquaculture Areas

Hye Young Ko; Kyuseon Cho; SungJun Park; Jin Hwi Kim; Joo-Hyon Kang; Yong Seok Jeong; Jong Duck Choi; Yongsik Sin; Cheonghoon Lee; GwangPyo Ko

Various waterborne pathogens originate from human or animal feces and may cause severe gastroenteric outbreaks. Bacteroides spp. that exhibit strong host- or group-specificities are promising markers for identifying fecal sources and their origins. In the present study, 240 water samples were collected from two major aquaculture areas in Republic of Korea over a period of approximately 1 year, and the concentrations and occurrences of four host-specific Bacteroides markers (human, poultry, pig, and ruminant) were evaluated in the study areas. Host-specific Bacteroides markers were detected widely in the study areas, among which the poultry-specific Bacteroides marker was detected at the highest concentration (1.0–1.2 log10 copies L−1). During the sampling period, high concentrations of host-specific Bacteroides markers were detected between September and December 2015. The host-specific Bacteroides marker-combined geospatial map revealed the up-to-downstream gradient of fecal contamination, as well as the effects of land-use patterns on host-specific Bacteroides marker concentrations. In contrast to traditional bacterial indicators, the human-specific Bacteroides marker correlated with human specific pathogens, such as noroviruses (r=0.337; P<0.001). The present results indicate that host-specific Bacteroides genetic markers with an advanced geospatial analysis are useful for tracking fecal sources and associated pathogens in aquaculture areas.


International Journal of Environmental Research and Public Health | 2016

Physiological and Molecular Response of Prorocentrum minimum to Tannic Acid: An Experimental Study to Evaluate the Feasibility of Using Tannic Acid in Controling the Red Tide in a Eutrophic Coastal Water

Byungkwan Jeong; Eui-Suk Jeong; Jacqueline Malazarte; Yongsik Sin

Bioassay and gene expression experiments were conducted in order to evaluate the growth and physiology of Prorocentrum minimum isolated from a eutrophic coastal water in response to tannic acid. In the bioassay experiments, variations in abundance, chlorophyll (chl) a concentration, maximum fluorescence (in vivo Fm), and photosynthetic efficiency (Fv/Fm) were measured over the course of a seven-day incubation. Moreover, stress-related gene expression in both the control and an experimental (2.5 ppm TA treatment) group was observed for 24 h and 48 h. The molecular markers used in this study were the heat shock proteins (Hsp70 and Hsp90) and cyclophilin (CYP). The findings show that P. minimum can thrive and grow at low concentrations (<2.5 ppm) of tannic acid, and, above this concentration, cells begin to slow down development. In addition, TA concentration of 10 ppm halted photosynthetic activity. At the molecular level, treatment with tannic acid increased the expression of Hsp70, Hsp90, and CYP, and heat shock proteins are more upregulated than the cyclophilin gene. Exposure to tannic acid increased the expression of stress factors over time (48 h) by 10- to 27-fold the expression level of the control group. These results suggest that tannic acid can be used to control harmful algal blooms such as those containing P. minimum in eutrophic coastal waters.


Marine Environmental Research | 2013

Impacts of eutrophic freshwater inputs on water quality and phytoplankton size structure in a temperate estuary altered by a sea dike

Yongsik Sin; Bongkil Hyun; Byungkwan Jeong; Ho Young Soh


Estuaries and Coasts | 2012

Phytoplankton Size and Taxonomic Composition in a Temperate Estuary Influenced by Monsoon

Yongsik Sin; Bonggil Hyun; Quang-Dung Bach; Sung-Ryull Yang; Chul Park


Aquaculture | 2004

2-D HYDRODYNAMIC MODEL SIMULATING PADDLEWHEEL-DRIVEN CIRCULATION IN RECTANGULAR SHRIMP CULTURE PONDS

Yun Ho Kang; Moon Ock Lee; Sang Duk Choi; Yongsik Sin


Estuarine Coastal and Shelf Science | 2015

Short-term variations of phytoplankton communities in response to anthropogenic stressors in a highly altered temperate estuary

Yongsik Sin; Byungkwan Jeong


symposium on experimental and efficient algorithms | 2006

Spatio-temporal Variation of Mesozooplankton in Asan Bay

Cw Lee; Chul Park; Yongsik Sin; Yang Sung Ryull


Estuarine Coastal and Shelf Science | 2015

The river–estuarine continuum of nutrients and phytoplankton communities in an estuary physically divided by a sea dike

Yongsik Sin; Eojin Lee; Yeonjung Lee; Kyung-Hoon Shin

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Byungkwan Jeong

Mokpo National Maritime University

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Chul Park

Chungnam National University

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Bongkil Hyun

Mokpo National Maritime University

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Yun Ho Kang

Yosu National University

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Bonggil Hyun

Mokpo National Maritime University

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Byeong-Gweon Lee

Chonnam National University

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Eojin Lee

Mokpo National Maritime University

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GwangPyo Ko

Seoul National University

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Ho Young Soh

Chonnam National University

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