• The Korean Journal of Malacology
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• v.32 no.3
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• pp.203-209
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• 2016

Growth and survival of the hard shelled mussel spat were investigated to confirm the possibe spat culture in seawater pond from September 2014 to April 2015. Also, we measured simultaneously environmental factors including water temperature, salinity, dissolved oxygen, pH, DIN, DIP, chlorophyll a, and abundance and dominant species of phytoplankton in seawater pond every month. Ranges of water temperature and salinity were $4.0-23.4^{\circ}C$ and 18.8-25.2 psu, respectively, which were rather lower than the reported optimal level. Monthly measured survival rates in all the spat cages were over 90%. Concentration of chlorophyll-a and abundance of phytoplankton were very high, and dominant species phytoplankton were cryptomonads and nanoflagellates. These dominant species were considered to be good food organisms for the bivalve spat. The experimental cage stocked 100 individuals per basket ($2,700ind.\;m^{-2}$) hanging in bottom of seawater pond revealed the highest growth in shell height ($7.63{\pm}4.65mm$), but all experimental cages stocked below 200 individuals per basket ($5,400ind.\;m^{-2}$) did not show statistically significant difference. We may expect that seawater pond would be one of the best culture ground for bivalve spats when appropriate measures are available.

• Journal of the Korean Society for Marine Environment & Energy
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• v.7 no.1
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• pp.13-21
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• 2004

Temporal changes of Chl-α, physical and chemical factors were investigated by diurnal observation at 2-hour interval at three fixed stations in the western Chinhae Bay from 12 Aug. to 13 Aug. 1999. Difference of dissolved oxygen between surface and bottom layer was maximum when the thermocline were strong. Organic distribution such as COD was affected by the growth of phytoplankton. Limitting factor was nitrogen, that is, inorganic nitrogen plays a significant role on regulating the algal growth. Surface distribution of dissolved inorganic nitrogen was very low compared to bottom layer by uptake of organisms. Maximum value of Chl-α at station C2 and C11 were observed from subsurface layer, ranges of which exceeded possibility concentration of red tide outbreak, 10 mg/㎥. On the other hand, that of C15 exist at surface layer. In this area, DIN and DIP concentrations increased by input sources such as rainfall and benthic flux before the bloom of phytoplankton. Accumulation of phytoplankton occurred at subsurface layer by the rapid uptake of DIN, especially nitrate ion, when strong thermocline existed as approach to the afternoon, which led to the increase of organics in water column and oxygen deficiency water mass at bottom layer until late at evening. Since then, DIN increases gradually as water temperature decrease to minimum. The quantitative understanding of nitrogen of fluxed to and from the various sources is necessary for environmental management.

• Journal of Aquaculture
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• v.15 no.1
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• pp.61-68
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• 2002

A comparative study on the effect of rearing depths at 2 (surface) and 5 (bottom) m on growth of the scallop was undertaken in Nam-myeon coastal area during June to December, 1997. There were very little difference in the levels of temperature (12.2 ~24.5$^{\circ}C$), salinity (27.3 ~33.1$\textperthousand) and dissolved oxygen (>7.05 mg/l) at a given month. But the chlorophyll level fluctuated between 1.2 and 11.0 $\mu g/l$ at the surface but below 2 $\mu g/l$ at the bosom. Highest phytoplankton density occurred in August and Ceratium dominated it during the period from June to October. Mean growth of the bay scallop at surface and bottom for the six months rearing period was as follows; 0.19 and 0.16 mm/day for shell height, and 0.16 and 0.12 g/day for total weight. Maximum predicted values of shell height calculated by von Bertalanffy growth model were 52.62 mm for the surface and 46.73 mm for the bottom reared scallop. Survival of the scallop was higher (80 %) for the surface group than that at the bottom (60%).

• Korean Journal of Fisheries and Aquatic Sciences
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• v.35 no.4
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• pp.386-394
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• 2002

Carrying capacity model focused on interactions between the filter-feeder growth and their environments is presented, and differences among existing various carrying capacity models are reviewed. For carrying capacity modeling of shellfish system, we constructed a new numerical model coupled oyster growth model with an ecosystem model (EUTRP2). Physical and biological processes such as water transport and mixing, primary production, feeding and growth of the cultivated oyster, Crassostrea gigas and benthic-pelagic exchange were included in the model, Simulated results for validation showed that the more phytoplankton biomass decreased, the more oyster meat weight and nutrients increased, suggesting a powerful tool for reasonable management of shellfish aquaculture. The model was sensitive to parameters controlling the primary production. Among the ecosystem compartments, the oyster growth is highly influenced by small changes in the physiological parameters of phytoplankton and oyster. This sensitivity analysis indicated the importance of experimental data on biological parameters for calibration of the model.

• Korean Journal of Environmental Biology
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• v.38 no.1
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• pp.47-60
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• 2020

To assess the characteristics of phytoplankton community structures related to environmental factors, seasonal surveys were conducted in the vicinity of Dokdo. In 2019, phytoplankton of four phyla and 69 species were observed. During winter, unidentified nanoflagellates dominated, with an average of 3.19×10⁴ cells L^-1. In spring, unidentified nanoflagellates occupied about 50% of the composition and a variety of dinoflagellates appeared. The summer phytoplankton population showed very low abundance. In autumn, various species of Chaetoceros appeared, along with diatoms, such as Bacteriastrum spp., Guinardia striata, and Pseudo-nitzschia spp. In addition, tropical species Amphisolenia sp. and Ornithocercus sp. were observed in both 2018 and 2019. The diversity was high in the summer of 2018 and the winter of 2019 and the characteristics of each index varied. Cluster analysis was divided into four groups according to species and population characteristics regardless of the season. The stratification of spring was particularly weak. In the autumn of 2018, the water mass was stabilized in the same way as in the summer, which is considered a suitable condition for phytoplankton growth. However, in 2019, the water masses were mixed, resulting in a low population. In a phytoplankton comparison, the dominant group showed seasonal differences, except for summer when the population was low, and the difference was most pronounced in autumn. Therefore, the waters surrounding Dokdo have different environmental and ecological characteristics from the East Sea, but the seasonal characteristics of each year are considered to be different depending on the topography, various currents, the island effect, and other factors.

• Korean Journal of Environmental Biology
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• v.22
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• pp.54-62
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• 2004

We examined the impacts of anthyopogenic pollutant (benzo〔a〕pyrene) on the growth and photosynthesis of five marine phytoplankton species (Skeletonema costatum, Heterosigma akashiwo, Prorocentrum dentatum, P. minimum, Aknshiwo sanguinea), which are dominant in Korean coastal water. After the 72 h exposure to benzo〔a〕pyrene, the dramatic decrease in cell numbers was observed in the range of 1 to 10 $\mu\textrm{g}$ L$^{-1}$ for S. costatum, P. minimum, P. dentatum, whereas for A. sanguinea and H. akashiwo at the low concentrations 0.1 to 1 $\mu\textrm{g}$ L$^{-1}$ . Among the 5 phytoplankton species, the highest growth inhibition concentration ($IC_{50}$/) was 6.20 $\mu\textrm{g}$ L$^{-1}$ for P. minimum, followed by 2.14 $\mu\textrm{g}$ L$^{-1}$ for P. dentatum, 1.68 $\mu\textrm{g}$ L$^{-1}$ for S. costatum, 0.74 $\mu\textrm{g}$ L$^{-1}$ for H. akashiwo, 0.10 $\mu\textrm{g}$ L$^{-1}$ for A. sanguinea. The five species exposed to the low concentration of 1 $\mu\textrm{g}$ L$^{-1}$ were recovered after transferring to new media, but the species exposed to the high concentrations of 10 and 100 $\mu\textrm{g}$ L$^{-1}$ were not recovered, with the exception of P. minimum. Those results indicate that the thecate dinoflagellate P. minimum is most tolerant to the chemical and the athecate dinoflagellate A. sanguinea is not. Geneyally, the cell-specific photosynthetic capacity of H. akashiwo exposed to the low concentrations of 0.1 and 1 $\mu\textrm{g}$ L$^{-1}$ was higher than that of the cells in the control, whereas the cells exposed to the high concentrations of 5 and 10 $\mu\textrm{g}$ L$^{-1}$ showed the negligible photosynthetic level by the first few days of the experiment. In the case of the cells exposed to the concentration of 5 $\mu\textrm{g}$ L$^{-1}$ , after 12 days of the experiment the photosynthetic capacity was increased toward the end of the experiment. This indicates that H. akashiwo may utilize the benzo〔a〕pyrene as a carton source for its growth when exposed to low concentrations. Results suggest that anthropogenic pollutants such as benzo〔a〕pyrene may have significant influence on the succession of phytoplankton species composition and the primary production in coastal marine environments.

• ALGAE
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• v.22 no.3
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• pp.185-192
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• 2007

A study was carried out in nine fertilized fish ponds under three treatments (T-I, T-II and T-III) at Bangladesh Agricultural University, Mymensingh to see the bloom of euglenophytes with the intention of observing its impact on the growth of fish in culture condition. Some water quality parameters viz., temperature, dissolved oxygen, pH, PO4-P and NO3-N concentration and some biological parameters viz., phytoplankton population and growth of fish were monitored at fixed intervals. Euglenophytes showed a heavy bloom in late August in the ponds of T-II. The bloom was occurred by the genera, Euglena, Phacus and Trachelomonas of which Euglena was the most dominant genus. In relation of water quality parameters with euglenophytes bloom, it was hypothesized that euglenophytes prefers higher temperature and acidic environment with higher nutrient concentrations. Acidic environment and nutrient enrichment enhanced the bloom of euglenophytes which hampered the growth of other beneficial algal groups (chlorophytes and bacillariophytes) and fish. Due to heavy bloom, the fishes breathed with difficulty at the surface. The fishes in the heavy bloom ponds presented the weight values were lower than verified for those in the ponds where the bloom did not occur. Total production (calculated) of fish in different treatments ranged from 1355.89 to1760.63 kg ha–1 with significantly (p < 0.05) lowest in the ponds of T-II.

• Korean Journal of Ecology and Environment
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• v.37 no.1 s.106
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• pp.47-56
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• 2004

To understand the effect of nutrient deficiency on the plankton community in three stations with different water qualities in Pal'tang Reservoir, Korea, phytoplanktons(> 10 ${\mu}m$) were cultured in nutrient enrichment Allen's media (AM) and nutrient-deficient Allen's media. A distinct shift in the species composition and biomass of phytoplankton (as chlorophyll- a) showed in all treatments. In particular, it was very interesting that the new development of cyanobacterium Microcystis aeruginosa occurred by the Fe-deficient AM. Except for Si, a community growth (as chlorophyll- a) was inhibited in all nutrient deficient treatments. Species diversity after nutrient deficiency was changed to below 2.0; slightly increased in N and P-deficiency, while decreased in Si and Fe, respectively. As suggested, dominance was entirely opposite to diversity. Therefore, the nutrient deficient effectively induced the succession of species and biomass, phytoplankton community, suggesting a possibility as a reliable tool to control the algal bloom in eutrophic lakes and reservoirs.

• Korean Journal of Ecology and Environment
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• v.44 no.3
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• pp.280-291
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• 2011

Bottom-up approaches to control of Microcystis aeruginosa blooms were comparatively investigated through an in situ mesocosm experiment using aquatic plants (Iris pseudoacorus). In the mesocosm experiments, floating I. pseudoacorus, seemed to be effective in controlling massive M. aeruginosa blooms in an agricultural reservoir, exhibiting a close coupling with temporal variations in Chl-a and DO concentration. Shading by floating I. pseudoacorus resulted in a reduced phytoplankton abundance inhibiting light energy availability. Moreover, I. pseudoacorus may suppress phytoplankton growth through the excretion of chemical substances, likes a allelopathy, that inhibit phytoplankton photosynthetic activity. The $^{15}N$ atom % of I. pseudoacorus showed higher values than POM, suggesting that I. pseudoacorus assimilates DIN predominantly compared to phytoplankton, which was mostly M. aeruginosa. This result strongly suggests that the M. aeruginosa bloom should be regulated by aquatic plants, like I. pseudoacorus, this approach can affect zooplankton composition. This is the first study that has used stable isotope tracers to evaluate the biomanipulation efficiency through floating I. pseudoacorus.

• Journal of environmental and Sanitary engineering
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• v.5 no.2
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• pp.117-122
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• 1990

The Jido Pond system was investigated from April, 1979 through March, 1980, in respect of seasonal changes in physico-chemical factors: i.e., temperature, pH, DO, BOD, COD, $Cl^-, \; Mg^{++}$, alkalinity, detergent, $SiO_2, PO_4\;^{3-}, NH_4\;^+, NO_2\;^-, NO_3\;^-$, total N, OM and OC; phytoplankton community growth; and the ecosystem metabolism. The phytoplankton community was represented by 23 species belonging to Chlorophyta, Bacillariophyta and Cyanophyta; each sharing 11, 9 3 respectively. The Chlorophyceans dominated the phytoplankton community contributing 75% of the total ？미 counts. The ranges of biotic diversity indices were, d, 0.85~2.80; H, 1.10~2.40; c, 0.13~0/40; and 3, 0.56~0.90. The chlorophyll standing crop varied in between 0.043 and 0.385g/$\textrm{cm}^2$ surface area. The ranges of photosynthetic and respiratory rates were 0.36~4.50; and 0.10~1.40 $O_2$ mg/1/hr, respectively. The monthly areal net primary production varied from 23.9 to 305.1C g/$\textrm{m}^2$/month. The Eu of the net production seasonally varied in between 0.31 and 7.80%, and the annual mean was 2.44%. The annual turnover times of phosphorus and nitrogen were 20 and 3 days, respectively.