• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.16 no.2
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• pp.106-115
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• 2011

The aim of this study is to assess the importance of ballast water discharge as a vector for the introduction of exotic species into Pusan and Daesan Ports, Korea. We also examined to understand the impacts of environmental factors on the survival success of introduced species by ship's ballast water in laboratory experiments. Seven ship's ballast water originated from the coastal water of China (Taicang, Ningbo and Jinshan), Japan (Tokuyama, Moji and Akita), and Singapore. According to PCA (principal components analysis) analysis, environmental factor in the each ballast and shipside waters were different by bioregion. Based on cluster analysis, the phytoplankton community structures were distinguished for ballast water origin. Most of the major taxonomic groups were diatoms and, the others were dinoflagellate, silcoflagellate and several fresh-waters species. In particular, species number and standing crops of phytoplankton in the ballast tanks decreased with the increasing age ofballast water(r = -0.35 for standing crop; r = -0.63 for species number). In the laboratory study, although phytoplankton in ballast water treatment did not survive even in optimal temperature, the in vivo fluorescence of phytoplankton viability increased under the nutrient typical of shipside water and F/2 medium at $15^{\circ}C$ and $20^{\circ}C$. The diatoms species such as Skeletonema costatum and Thalassiosira pseudonana in ballast water were successfully regrown. On the salinity gradient experiments for Shui Shan (2) vessel, several freshwater species, brackish and marine species were successfully adapted. Of these, S.costatum was able to tolerate a wide range of salinities (10 to 30 psu) and its species-specific viability was suitable for colonization.

• Korean Journal of Environmental Biology
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• v.39 no.4
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• pp.559-572
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• 2021

A survey was conducted to analyze water masses and spatial distributions of phytoplankton communities at 15 stations on the surface and chlorophyll a maximum layers (CML) in the western South Sea of Korea from September 8 to 9, 2021. As a result, water masses were classified into Coastal Waters (CW) with relatively low salinity, the Tsushima Warm Current (TWC) with high water temperature and high salinity, and mixed waters (MW) showing a mixture of these two water masses. Turbidity showed high concentration in both the surface and CML. The chlorophyll a concentration was as low as 0.90±0.43 ㎍ L^-1 in the surface, more than 1.1 ㎍ L^-1 in CW, around 1.0 ㎍ L^-1 in MW, and less than 0.5 ㎍ L^-1 in the TWC. CML was 1.64±0.54 ㎍ L^-1. Regarding species composition of phytoplankton communities, there were 57 species in 31 genera(diatoms, 57.8%; dinoflagellates, 35.1%; and other phytoflagellates, 7.1%). The phytoplankton standing crop had 4.6±7.6 cells mL^-1 in the surface, more than 30 cells mL^-1 in the CW, 2-5 cells mL^-1 in the MW, and less than 2 cells mL^-1 in the TWC. CML was slightly higher than the surface with a variation of 5.7±8.4 cells mL^-1. Dominant species were found to be Rhizosolenia flagilissima f. flagilissima, Skeletonema costatum-ls, and Nitzschia sp./ small size in the surface. For the CML Rh. flagilisima f. flagilissima showed a dominance of 12.0%. For the surface, the diversity variation was 2.36±0.40, which was high for TWC but low for MW. For CML, the diversity variation was 2.29±0.52, which was slightly lower than that of the surface. The dominance in the surface was 0.50±0.15, with a fluctuation range of more than 0.5 in MW and less than 0.5 in the TWC, which was different from the diversity. According to correlation analysis and principal component analysis (PCA), the presence of phytoplankton standing crops was high in CW but low in MW and TWC. That is, phytoplankton communities in early autumn were strongly affected by the expansion and mixing of water masses in western South Sea.

• Journal of The Korean Society of Grassland and Forage Science
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• v.38 no.2
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• pp.84-90
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• 2018

Cultivation of high-quality forage crop by using fallow field during winter is required for national high feed self-sufficiency and establishment of self-supply system of high-quality forage crop. Field experiments for cultivation of high-quality winter forage crop were conducted at the paddy and upland fields in Cheonan and Anseong city with treatments of single Italian ryegrass(IRG) and IRG mixed with forage barley at the paddy field and of single forage barley and forage barley mixed with IRG at the upland field in the Mid-west plain. Several cultivation conditions such as broadcasting IRG seed under standing rice, sowing time, tillage method, drainage condition, mixed sowing with forage barley were compared to know the change of growth, yield and quality of winter forage crop. In particular, over-wintering rate and dry matter yield were decreased significantly in late-sown IRG and moisture-stressed forage barley. Yield and quality of forage crops were increased by sowing after tillage, mixed sowing of IRG with barley at the paddy field with good drainage. High yield as much as dry matter $10MT\;ha^{-1}$ with high feed value could be obtained by early sowing of feed barley mixed with IRG at the upland field. Cultivation conditions such as early sowing, sowing after tillage, drainage management are required for higher dry matter yield, quality and stable cultivation of winter forage crops in the mid-west plain of Korea.

• Journal of Korean Society of Forest Science
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• v.68 no.1
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• pp.60-68
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• 1985

To study the comparison of the aboveground biomass of Robinia pseudoacacia L. of 8-, 13- and 20-year-old plantations, the experimental plot of $100m^2$ in size located in Youngin-gun were selected. Seven sample trees at different stand ages selected taking account of DBH distribution were felled and the diagram of oven-dry weight distribution of stem, branch and leaf for each 1m segment was constructed. The dry weight of each part of plots was estimated by the method of basal area ratio. If the estimations are extended to a hectare area stand, it contains 36.72, 69.28 and 118.67 tons of the aboveground standing crops in 8-, 13- and 20- year-old stand respectively. The net production was estimated to be as much as 12.56, 13.23 and 16.78 tons per hectare per year and the net assimilation ratio 3.66, 4.13 and 2.50 kg/kg/yr in 8-, 13- and 20-year-old stand respectively. And the efficiency of leaves to produce stem was 1.69, 2.10 and 0.96 kg/kg/yr in same order.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.15 no.11
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• pp.6958-6965
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• 2014

This study examined the occurring pattern of potential risky species and the related abiotic factors for port-specific environmental management considering the control of ballast water-induced foreign species at Incheon seaport. From a total of 62 species observed during the study, 13 red-tide and 7 toxic phytoplankton, normally occurring species in Korean waters, occurred from the seasonal investigation at the inner and outer sites of the Incheon seaport from 2007 to 2009. The number of potential risky phytoplankton was relatively high at the outer site of the port during summer and winter. Red-tide species, such as Skeletonema spp., Thalassiosira nordenskioldii, and Paralia sulcata, dominated the total standing crops at the inner site (avg. 72.4%) and outer site (avg. 77.6%) in spring and summer, being positively correlated with the concentrations of total suspended solids (TSS) and pH (p<0.05). In summer, the red-tide species (Skeletonema spp.) and toxic species (Alexandrium catenella, A. tamarense, Dinophysis acuminata and Pseudo-nitzschia spp.) co-dominated (avg. 74.2%) at the inner site, while Skeletonema spp. and P. sulcata predominated (avg. 67.2%) at the outer site. During the study periods, the toxic species were significantly and positively correlated with the chemical oxygen demand (COD), dissolved inorganic nitrogen, silicate and phosphate (p < 0.05). The chlorophyll-a (chl-a) concentration of phytoplankton at the outer site ranged from 1.49 to $5.46{\mu}g/L$ on average, which was 3-5 times higher than that at the inner site in spring, summer and autumn, whereas there was no difference in the concentration between inner (avg. $0.94{\mu}g/L$) and outer (avg. $0.95{\mu}g/L$) sites in winter. In summary, diverse red-tide species dominated and a relatively high chl-a concentration existed at the outer site, whereas a relatively high number of toxic species and low chl-a concentration was observed at the inner site in summer. The potential risky species can outbreak in association with the concentration of nutrients, COD and TSS, suggesting that distinctive management of potential risky species is needed considering the environmental characteristics of Incheon seaport.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.16 no.3
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• pp.2287-2300
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• 2015

This study examined the spatio-temporal distributions of the phytoplankton community in the coastal waters of Gogunsan Islands (CoWGIs), West Sea of Korea, from January to September 2011. A total of 104 species of phytoplankton belonging to 56 genera were identified. This was low compared to the surrounding seas of the West Sea. In particular, diatoms and dinoflagellates comprised 60.5% and 34.6%, respectively, and it was most diverse in autumn. The standing crops fluctuated from $9.6{\times}10^4cells/L$ to $1.0{\times}10^7cells/L$. This was high in winter and summer and low in spring and autumn. The seasonal dominant species were Skeletonema costatum-like species, Thalassiosira nordenskioeldii, Dactyliosolen fragillisimus, and Chaetoceros debilis in winter, Guinardia delicatula in spring, Eucampia zodiacus, Cylindrotheca closterium, Ch. debilis, and Ch. curvisetus in summer, and S. costatum-like species, Ch. debilis, Ch. curvisetus, G. delicatula, and Leptocylindrus danicus in autumn. The total number of autochthonous and tychopelagic species was 39 species. This showed a 1/3 (33.3%) decrease compared to the 1980's. The chlorophyll a concentration fluctuated from $3.82{\mu}g/L$ in autumn to $13.36{\mu}g/L$ in summer. The bio-oceanographic characteristics of the CoWGIs based on principle component analysis (PCA) showed that it was dominated by the Saemangeum water mass in the high temperature season and by the Geum River water mass in the low temperature season. In other words, there has been a conversion to a closed inner bay followed by the dramatic progress of eutrophication, even in the CoWGIs after completion of the Saemangeum embankment.

• Korean Journal of Ecology and Environment
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• v.46 no.4
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• pp.524-540
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• 2013

After the construction of the Geum River estuary dam, we investigated the ecological property of phytoplankton community with physicochemical property in 9 stations of Geum River estuary 4 times seasonally in 2010 about the environmental changes through the change of phytoplankton. Physicochemical property seems to show eutrophication which developed from the tendency of accruing of the nutrients (those involved in intermittency of freshwater which flows from the dike and the surrounding cities), caused by the changing of tidal flow, the decreasing of the inflow of seawater after the construction of the Geum River estuary dam (dike). A total of 233 species of species composition of phytoplankton emerged, showing a highly increased result compared to that of the former research. The reason for the increase in number is considered as a phenomenon resulting from the mix of blackish and freshwater marine species in the flow of intermittency of freshwater discharge. Also, the standing crops of phytoplankton considerably increased compared to when the dike had not yet been built. Highly affected by the discharge of occasional freshwater, the diatoms of blackish water zone dominated in spring and winter, while freshwater species appeared to dominate in summer and autumn. The species diversity showed over 2.0 except in winter season. After a cluster analysis, the result showed that the Geum River estuary was influenced by runoff from cities like Gunsan, the sewage which flows from Gyeongpo River, and the intermittency of freshwater discharge from the Geum River estuary dam.

• Korean Journal of Environmental Biology
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• v.25 no.1
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• pp.16-26
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• 2007

To study the succession of epilithic diatoms on the artificial substrate, we investigated environmental factors and the diatom assemblages biweekly from Mar. 2004 to Feb. 2005 at 2 stations in the lower part of the Han River. A total of 60 taxa, representing 2 orders, 3 suborders, 8 families, 17 genera, 51 species, 7 varieties and 2 forms were identified, and mean number of species were 19 species in spring, 20 in summer, 22 in autumn and 22 in winter. Standing crops of epilithic diatoms varied extensively by months and stations; mean values of those were $3.2{\times}10^4$ cells $cm^{-2}$ in spring, $1.9{\times}10^4$ in summer, $1.7{\times}10^4$ in autumn and $1.8{\times}10^5$ in winter. Chlorophyll a concentrations were also similarly showed as variations of the diatom assemblages. Succession of the diatoms in St. 1 was as follows; Melosira varians, Fragilaria capucina, Cyclotella comta, Nitzschia palea in spring, Fragilaria capucina in summer, Aulacoseira granulata var. angustissima in autumn, Aulacoseira granulata var. angustissima and Melosira varians, Cymbella minuta in winter. In station 2, Aulacoseira granulata and Nitzschia palea dominated in spring as a pioneer in early stage of succession, Fragilaria capucina in summer, and Nitzschia palea in winter. According to Canonical Correspondence Analysis (CCA), there showed similar to that of succession of epilithic diatoms within St. 1 and St. 2, and they were not changed by stations but seasons. Nitzschia palea belonged to saprophilous taxa correlated with nitrogen sources and suspended solids. Meanwhile, Fragilaria capucina and Cymbella minuta included in xenosaprobic taxa show correlation with DO and pH. Eurysaprobic taxa correlated with all environmental factors.

• Korean Journal of Environmental Biology
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• v.31 no.1
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• pp.37-44
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• 2013

This study was to investigate water quality and biotic community characteristics in Juam Lake. In water quality, water temperatures was $3.8{\sim}21.2^{\circ}C$, 6.7~8.6 in pH, $64{\sim}76{\mu}s\;cm^{-1}$ in Conductivity, $5.3{\sim}13.2mg\;L^{-1}$ in DO, $2.5{\sim}3.3mg\;L^{-1}$ in COD, $1.0{\sim}5.1mg\;L^{-1}$ in SS, $0.622{\sim}0.841mg\;L^{-1}$ in T-N, $0.007{\sim}0.019mg\;L^{-1}$ in T-P and $2.8{\sim}8.8mg\;m^{-3}$ in Chl-a. Revised Carlson's Index (TSIm) assessment using total phosphorus (TP) and chlorophyll-a domonstrated that the trophic states of Juam Lake were rated as mesotrophic. A total of 53 species of phytoplankton were identified. They were 28 Bacillariophyceae, 13 Chlorophyceae, 3 Cyanophyceae, and 9 Other algal taxa. The standing crops of phytoplankton was ranged from $113cells\;mL^{-1}$ to $2,909cells\;mL^{-1}$. A total of 16 species of zooplankton were identified (10 rotifers, 4 cladocerans and 2 copepods). Total zooplankton abundance was $309ind.\;L^{-1}$ to $435ind.\;L^{-1}$. The collected benthic macroinvertebrates from the surveyed sites in Juam Lake were 1,038 individuals, 33 species, 21 families and 12 orders. A dominant species was Uracanthella rufa and a subdominant species was Ecdyonurus kibunensis. Hydrophytes recorded from Juam Lake were identified 9 taxa. Emerged plants, floating plants among the hydrophytes was classified 8, 1 taxa, respectively. Ecosystem disturbance wildplant by Environment Ministry found were Paspalum distichum var. distichum and Ambrosia artemisiaefolia. A total of 30 species (6 families) were collected fishs from Juam Lake. There were 10 Korean endemic species (33.3% of collected species number) and 3 exotic species (10.0%).

• 한국해양학회지
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• v.30 no.5
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• pp.458-466
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• 1995

To clarify the role of protozooplankton in the microbial food web of Inchon coastal ecosystem, the grazing capacities and growth rates of heterotrophic flagellated (HFL) and ciliates were investigated. We measured the growth rates of bacteria, HFL, autotrophic flagellated (AFL) and ciliates using reverse flow (RF) filter set and obtained the clearance rates and ingestion rates of HFL and dilates by fluorescent labelled bacteria (FLB) method and isolation culture method from natural seawater of Inchon coastal area. The standing crops of bacteria, HFL, AFL and ciliates in this study area were 0.7∼1.5${\times}$10/SUP 6/ cells$.$ml/SUP -1/ 1,680∼2,180 cells$.$ml/SUP -1/, 1,090∼2,180 cells$.$ml, and 3,600∼5,700 cells$.$l/SUP -1/, respectively. The mean growth rates of bacteria, HFL, AFL and ciliates were 0.039 h/SUP -1/, 0.032∼0.033h/SUP -1/, 0.015∼ 0.025h/SUP -1/and 0.021h/SUP -1/, respectively. The growth rates of protozooplankton of Inchon coastal waters were relatively low. Mean grazing rate of HFL, AFL and ciliates were0.039 h/SUP -1/, 0.032∼0.033h/SUP -1/,0.015∼ 0.025h/SUP -1/and 0.021h/SUP -1/, respectively. The growth rates of protozooplankton of Inchon coastal waters were relatively low. Mean grazing rate of HFL on bacteria was 0.055h/SUP -1/. Mean grazing rates of ciliates on HFL was relatively high of 0.057 h/SUP -1/, while the grazing rate of ciliates on AFL was low of 0.019h/SUP -1/. The clearance rates and ingestion rates of HFL on bacteria were 3.6∼61.8nl$.$HFL$.$h/SUP -1/ and 6∼52 BAC. HFL$.$h/SUP -1/ respectively. FLB grazing experiment showed low values, while natural bacteria experiment showed high value meaning high grazing pressure on total bacteria. The clearance rates and ingestion rates of Tintinnopsis sp., dominant ciliates in Inchon coastal waters, were 3.2∼4.6 ul$.$CIL/SUP -1/$.$h/SUP -1/ and 5∼6 cells$.$CIL/SUP -1/$.$h/SUP -1/ respectively, showing higher values in the high tide than low tide. The ingestion rates of ciliates implies that ciliate took up 17∼20% of total nanoflagellates of Inchon coastal waters.