• The Korean Journal of Malacology
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• v.19 no.2
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• pp.143-152
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• 2003

Water temperature during the culturing period was 10.4-25.5$^{\circ}C$ and there was a little difference between rearing sites. Salinity (25.00-31.17 psu) and DO (over 6.13 mg/l) showed reasonable condition for the growth of bay scallop. Concentrations of chlorophyll-a were ranged 1.69-7.40 $^{\mu}$g/l, and they fluctuated monthly in the every sampling site. During the growing period from June to October, dominant phytoplankton species were Ceratium sp. in Nammeon and Hoejin, Chaetoceros sp. in Dolsan. Density of phytoplankton was high in July, August and October, but it was low in September and November. When young bay scallops were cultured for 185 days in Nammyeon, Hoejin and Dolsan, shell heights were grown for 0.19 mm/day, 0.18 mm/day and 0.16 mm/day, respectively, and total weights were increased 0.16 g/day, 0.16 g/day and 0.13 g/day, respectively. Daily growth rates of shell height were 0.606%, 0.581% and 0.549%, and daily growth rates of total weight were 1.972%, 1.857% and 1.746%, respectively. Maximum predicted values of shell height calculated by von Bertalanffy growth model were 52.62 mm, 51.74 mm and 48.91 mm, respectively. Survival rate was the highest in Nammyeon (87.0%), but the rates in Hoejin and Dolsan sharply decreased after November.

• Korean Journal of Ecology and Environment
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• v.50 no.1
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• pp.46-56
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• 2017

The Youngsan River estuary was physically changed by the construction of a sea embankment at near the mouth of estuary. Weirs were also constructed recently in the freshwater zone and it was reported that algal blooms occur more frequently. The freshwater introduced into saltwater zone from sluice gates of the embankment affects water quality but it has not been addressed that how the freshwater inputs influence the health of marine ecosystem. In this study, we used the data of water properties and phytoplankton communities collected at three stations for 4 days including before the freshwater discharge, during the discharge and after 1 and 2 days of discharge events. WQI(water quality index), TRIX (trophic status index) and P-IBI(phytoplankton index of biotic integrity) were used to evaluate the ecosystem health and long-term data were also utilized to determine the criteria for P-IBI. The results showed that grades of the ecosystem health assessed by the indices were low at the station near the gates and increased as downstream. However, the temporal pattern of grades was different depending on methods. Grades of WQI and TRIX decreased during the discharge and restored after the discharge whereas the grades of P-IBI decreased slightly even after the discharge. This suggests that P-IBI is more applicable to estuarine systems where experience extreme change of water properties than WQI and TRIX since P-IBI includes phytoplankton that can respond quickly to the change.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.13 no.1
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• pp.27-41
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• 2008

Distribution characteristics of phytoplankton community were investigated by HPLC and flow cytometry in Jeju Strait and the Northern East China Sea (NECS) in May 2004, in order to understand the relationship between physical environmental factors and distribution pattern of phytoplankton communities. Based on temperature and salinity data, three distinct water masses were identified; warm and saline Tsushima Warm Current (TWC), which is flowing from northwest of Jeju Island, warm and low saline water at the center of Jeju Strait, which is originated from China Coastal Water (CCW) and relatively cold and high saline water originated from Yellow Sea at the bottom of the Jeju Strait. At Jeju Strait, less saline water (<33 psu) of 15 km width occupied surface layer up to 20 m which located at 20 km offshore and strong thermal front between warm and saline water and cold and less saline water was found in the middle of the Jeju Strait. Vertical transect of temperature and salinity at the NECS also showed that low saline (<33 psu) water occupied the upper 20 m layer and cold and saline water was present at the eastern part. Chl a was measured as $0.06{\sim}3.07\;{\mu}g/L$. Spring bloom of phytoplankton was recognized by the high concentrations of Chl a at the low saline water masses influenced by the CCW and subsurface chlorophyll maximum layer appeared between $20{\sim}30\;m$ depth, which was at thermocline depth or below. Abundances of Synechococcus and picoeukaryote were $0.2{\sim}9.5{\times}10^4\;cells/mL$ and $0.43{\sim}4.3{\times}10^4\;cells/mL$, respectively. Dinoflagellate, diatom and prymnesiophyte were major groups and minor groups were chlorophyte+prasinophyte, chrysophyte, cryptophyte and cyanophyte. Especially high abundance of dinoflagellate was identified by high concentration (>1\;{\mu}g/L$) of peridinin at the bottom of the thermocline, which showed an outbreak of red tide by high density of dinoflagellates. Abundances of picoeukaryote in Jeju Strait were about $5{\sim}10$ times higher than abundance measured in Kuroshio water and showed a good correlation with Chl b (Pras+Viola), which implies the most of population of picoeukaryote was composed of prasinophytes. Prochlorococcus was not detected at all, which suggests that Kuroshio Current did not directly influenced on the study area. Based on the strong negative correlations between biomass of phytoplankton (Chl a) and temperature+salinity, the primary production and biomass of phytoplankton in the study area were controlled by the nutrients supply from CCW.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.13 no.4
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• pp.325-332
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• 2008

To characterize the initiation, propagation and termination of Cochlodinium polykrikoides blooms in the southeast coastal waters of Korea, 2007, we have analyzed the data set of phytoplankton composition, physical and chemical water properties, and meterological data. The development of C. polykrikoides bloom in 2007 can be summarized in three steps. The first stage from middle of July to end of August was characterized by an unusually persistent and strong southerly wind. C. polykrikoides blooms established already by the strong wind in the middle of south coastal waters were advected intermittently into the study area. Accordingly, highly variable cell densities of C. polykrikoides were observed. At the second stage a favorable growing conditions for C. polykrikoides was developed, which was directed by changes in wind direction from south to northeast and thus enhanced transportation of offshore waters into inshore (August 8 to 30). C. polykrikoides bloom occurred through typical mechanism and showed high cell density. The last stage was represented by disappearance of C. polykrikoides. Typoon 'Nari' carrying heavy rain brought an unfavorable habitat to C. polykrikoides. Low saline condition formed in coastal water due to typoon effects continuously drove the dominant species to diatoms and flagellates which were prevailing over C. polykrikoides in this circumstances(from the middle of September). These stepwise processes could be the causative mechanism of the extraordinarily persistent C. polykrikoides bloom observed in southeast coastal water of Korea, 2007.

• Journal of the Korean Society for Marine Environment & Energy
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• v.20 no.1
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• pp.1-11
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• 2017

Nakdong River Estuary is affected by the dam, barrage construction and dredge and reclaim worked artificially. So, we have studied the area input both freshwater and sea water to understand marine environment of Nakdong River estuary related to the effect of artificial work from 2013 to 2015. As a result, The discharge flow to the estuary remarkably decreased before barrage construction and the average of salinity at the estuary increased. So, the brackish water zone reduced under the influence of decreased discharge flow. The major sources of nitrate and silicate were freshwater, phosphate supplied from bottom and the open sea water. The concentration of phosphate and dissolved oxygen (DO) decreased remarkably in spring and summer. we investigated that phosphate in freshwater was removed under the influence of the estuary dam and phosphate in sea water was removed under the influence of phytoplankton. The low concentration of DO was due to decomposition of the organic compound by microorganism after phytoplankton blooms. Generally, the concentrations of chlorophyll-a in summer was higher than spring and fall. Therefore, the change of ecosystem in Nakdong river estuary was due to decrease of freshwater influx, the other change is facing because of the barrage.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.26 no.6
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• pp.405-412
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• 2014

A number of algal bloom models (red-tide models) have been developed and applied to simulate the redtide growth and decline patterns as the interest on the phytoplankton blooms has been continuously increased. The quantitative error analysis of the model is of great importance because the accurate prediction of the red-tide occurrence and transport pattern can be used to setup the effective mitigations and counter-measures on the coastal ecosystem, aquaculture and fisheries damages. The word "red-tide model" is widely used without any clear definitions and references. It makes the comparative evaluation of the ecological models difficult and confusable. It is highly required to do the performance test of the red-tide models based on the suitable classification and appropriate error analysis because model structures are different even though the same/similar words (e.g., red-tide, algal bloom, phytoplankton growth, ecological or ecosystem models) are used. Thus, the references on the model classification are suggested and the advantage and disadvantage of the models are also suggested. The processes and methods on the performance test (quantitative error analysis) are recommend to the practical use of the red-tide model in the coastal seas. It is suggested in each stage of the modeling procedures, such as verification, calibration, validation, and application steps. These suggested references and methods can be attributed to the effective/efficient marine policy decision and the coastal ecosystem management plan setup considering the red-tide and/or ecological models uncertainty.

• Ocean and Polar Research
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• v.30 no.4
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• pp.379-399
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• 2008

Spatial-temporal variations in physiochemical water qualities (temperature, salinity, DO, SPM, POC and nutrients) of surface and bottom waters were investigated along the mid-western coastal area (Taean Peninsula to Gomso Bay) of Korea. Spatial distribution patterns of temperature and salinity were mostly controlled by the physical mixing process of freshwater from Geum River and/or Gyunggi Bay with nearby coastal water. A strong tidal front is formed off Taean Peninsula during spring and summer. Seasonal variations in nutrient concentrations, lower in spring and summer and higher in fall and winter, are primarily regulated by magnitude of phytoplankton occurrence rather than freshwater loadings into the bay. Based on seasonal and spatial variability of physicochemical parameters, water quality of the study area can be divided into four water masses; Gyunggi Bay-influenced Water Mass (GBWM), Geum River-influenced Water Mass (GRWM), Yellow Sea Bottom Cold Water Mass (YSBCWM) and Cheonsu Bay Water Mass (CBWM). Water quality of the GBWM (Taean Peninsula coastal area), which has relatively low salinity and high concentrations of nutrients, is strongly controlled by the Gyunggi Bay coastal water, which is under influence of the Han River freshwater. In this water mass, the mixed layer is always developed by strong tidal mixing. As a result, a tidal front is formed along the offshore boundary of the mixed layer. Such tidal fronts probably play an important role in the distribution of phytoplankton communities, SPM and nutrients. The GRWM, with low salinity and high nutrients, especially during the flood summer season, is closely related to physiochemical properties of the Geum River. During the flood season, nutrient-enriched Geum River water mass extends up to 60 km away from the river mouth, potentially causing serious environmental problems such as eutrophication and unusual and/or noxious algal blooms. Offshore (<$30{\sim}40m$ in water depth) of the study area, YSBCWM coupled with a strong thermocline can be identified in spring-summer periods, exhibiting abundant nutrients in association with low temperature and limited biological activity. During spring and summer, a tidal front is formed in a transition zone between the coastal water mass and bottom cold water mass in the Yellow Sea, resulting in intensified upwelling and thereby supplying abundant nutrients to the GBWM and GRWM. Such cold bottom water mass and tidal front formation seems to play an important role in controlling water quality and further regulating physical ecosystem processes along mid-western Korean coastal area.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.9 no.4
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• pp.164-172
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• 2004

Water temperature, salinity, the phytoplankton community and population of a marine photosynthetic ciliate, Mesodinium rubrum (=Myrionecta rubra), were monitored every 0.5-2 weeks in Gomso Bay and the Geum River Estuary from September 1999 to December 2000. Patterns of temporal variation of the M. rubrum population and phytoplankton community were compared with each other in relation to the differences in temporal fluctuation patterns of the water temperature and salinity in the two study areas. Higher population densities and more frequent blooms of M. rub rum in the Geum River Estuary than those in Gomso Bay could be due to the relatively higher nutrient input by freshwater influx in the Geum River Estuary. In the Geum River Estuary which experience more abrupt and irregular fluctuations of salinity, M. rubrum with its greater tolerance to salinity change exhibited increased dominance while neritic diatoms such as Skeletonema costatum, Asterionellopsis glacialis, A. kariana, Chaetoceros debilis, Eucampia zodiacus, Paralia sulcata, Thalassiosira pacifica, T. nordenskioeldii showed decreased dominance compared with those in Gomso Bay. Thus, it is possible that M. rubrum replaces the dominant diatom species in coastal waters where artificial modification of coast lines as in the case of Saemankeum Reclamation Project should increase the frequency as well as the absolute scale of freshwater discharges.

• Journal of Wetlands Research
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• v.22 no.2
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• pp.161-170
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• 2020

Constructed wetlands (CWs) are widely used to solve water quality problems caused by diffuse pollution from agricultural areas; however, phytoplankton blooms in CW systems can occur due to long hydraulic retention time (HRT), high nutrient loading, and exposure to sunlight. This study was conducted to evaluate the efficiency of a CW designed to treat agricultural diffuse pollution and develop a design concept to improve the nature-based capabilities of the system. Monitoring was conducted to assess contribution of individual wetland components (i.e. water, sediments, and plants) in the treatment performance of the system. During dry days, the turbidity and particulates concentration in the CW increased by 80 to 197% and 10 to 87%, respectively, due to the excessive growth of phytoplankton. On storm events, the concentration of particulates, organics, and nutrients were reduced by 43% to 70%, 22% to 49%, and 15% to 69% due to adequate water circulation and constant flushing of pollutants in the system. Based on the results, adequate water circulation is necessary to improve the performance of the CW. Free water surface CWs are usually designed to have a constant water level; however, the climate in South Korea is characterized by distinct dry and rainy seasons, which may not be suitable for this conventional design. This study presented a concept of multifunctional design in order to solve current CW design problems and improve the flood control, water quality management, and environmental functions of the facility.

• Korean Journal of Ecology and Environment
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• v.41 no.1
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• pp.54-65
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• 2008

The seasonal dynamics of phytoplankton and water quality were evaluated bimonthly at 7 park ponds in the capital region from October 2004 to August 2005. With out the change of water temperature $(0.4\sim26.0^{\circ}C)$, cyanobacteria dominated in park ponds such as Gyungbokgung Gyunghyaeru and Seokchon reservoir. The standing crops of phytoplankton was significant related with cell densities of cyanobacteria (r=0.993), while they did not significant correlation with environmental factors. Almost of all park ponds in the capital region were classified as eutrophic state with high TP concentrations and TN/TP ratios less than 10. Major dominant cyanobacteria were as followed; Anabaena sp., Aphanocapsa elachista, Lyngbya contorta, Merismopedia elegans, Microcystis aeruginosa, M. wesenbergii, Microcystis sp., Oscillatoria sp., Phormidium tenue, and Plectonema sp. To date, although the concentration of chlorophyll-${\alpha}$ and cyanobacterial densities in the capital region was below the 'danger' level of WHO guidelines value, the monitoring of cyanobacterial densities and its toxin (microcystin) in recreational/bath water should be continued.