• ALGAE
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• v.35 no.3
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• pp.263-275
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• 2020

Water temperature is known to affect the growth and feeding of marine dinoflagellates. Each dinoflagellate species grows well at a certain optimal temperature but dies at very cold and hot temperatures. Thus, changes in water temperatures driven by global warming and extremely high or low temperatures can affect the distribution of dinoflagellates. Yihiella yeosuensis is a mixotrophic dinoflagellate that can feed on only the cryptophyte Teleaulax amphioxeia and the chlorophyte Pyramimonas sp. Furthermore, it grows fast mixotrophically but rarely grows photosynthetically. We explored the direct and indirect effects of water temperature on the growth and ingestion rates of Y. yeosuensis feeding on T. amphioxeia and the growth rates of T. amphioxeia and Pyramimonas sp. under 7 different water temperatures (5-35℃). Both the autotrophic and mixotrophic growth rates of Y. yeosuensis on T. amphioxeia were significantly affected by temperature. Under the mixotrophic and autotrophic conditions, Y. yeosuensis survived at 10-25℃, but died at 5℃ and ≥30℃. The maximum mixotrophic growth rate of Y. yeosuensis on T. amphioxeia (1.16 d^-1) was achieved at 25℃, whereas the maximum autotrophic growth rate (0.16 d^-1) was achieved at 15℃. The maximum ingestion rate of Y. yeosuensis on T. amphioxeia (0.24 ng C predator^-1 d^-1) was achieved at 25℃. The cells of T. amphioxeia survived at 10-25℃, but died at 5 and ≥30℃. The cells of Pyramimonas sp. survived at 5-25℃, but died at 30℃. The maximum growth rate of T. amphioxeia (0.72 d^-1) and Pyramimonas sp. (0.75 d^-1) was achieved at 25℃. The abundance of Y. yeosuensis is expected to be high at 25℃, at which its two prey species have their highest growth rates, whereas Y. yeosuensis is expected to be rare or absent at 5℃ or ≥30℃ at which its two prey species do not survive or grow. Therefore, temperature can directly or indirectly affect the population dynamics and distribution of Y. yeosuensis.

• Journal of Soil and Groundwater Environment
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• v.16 no.2
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• pp.12-29
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• 2011

Risk-based screening levels (RBSLs) of some pollutants for residential adults were derived with risk assessment tools developed by United States Environmental Protection Agency (USEPA), American Society for Testing and Materials (ASTM), and Korea Ministry of Environment (KMOE) and compared each other. To make the comparison simple, ingestion of soil, dermal contact with soil, outdoor inhalation of vapors, indoor inhalation of vapors, and inhalation of soil particulates were chosen as exposure pathways. The results showed that the derived RBSLs varied for every exposure pathway. For direct exposure pathways (i.e., ingestion of soil and dermal contact with soil), the derived RBSLs varied mainly due to the different default values for exposure factors and toxicity data. When identical default values for the parameters were used, the same RBSLs could be derived regardless of the assessment tools used. For inhalation of vapors and inhalation of soil particulates, however, different analysis methods for cross-media transfer rates were used and different assumptions were established for each tool, identical RBSLs could not be obtained even if the same default values for exposure factors were used. Especially for inhalation of soil particulates pathway, screening level derived using KMOE approach (most conservative) was approximately 5000~10000 times lower than the screening level derived using ASTM approach (least conservative). Our results suggest that, when deriving RBSL using a specific tool, it is a prerequisite to technically review the analysis methods for cross-media transfer rates as well as to understand how the assessment tool derives the default values for exposure factors.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.8 no.1
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• pp.44-57
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• 2003

Seasonal variations of bacterial abundance and production, heterotrophic nanoflagellate (HNF) abundance and HNF ingestion rates on bacteria using FLB together with environmental variables were investigated at intervals of a month in Kyeonggi Bay from December 1991 to November 1998. Bacterial abundance and production ranged from 0.38$\times$10$^{9}$ ~ 3.25$\times$10$^{9}$ cells 1$^{-1}$ (average 1.19$\pm$0.69$\times$10$^{9}$ cells 1$^{-1}$ ) and from 1.51 to 20.4 cells 1$^{-1}$ h$^{-1}$ (average 6.04$\pm$ 1.88$\times$10$^{6}$ cells 1$^{-1}$ h$^{-1}$ ), respectively. Bacterial abundance and production showed no differences at the high tide and low tide, and bacterial abundances were not different with depth, but bacterial production decreased with depth. Seasonal variation of bacterial abundance showed almost similar fluctuation pattern to those of DOC (dissolved organic carbon). HNF abundances ranged from 388 to 4,374 cells ml$^{-1}$ (average 1,344$\pm$130 cells ml$^{-1}$ ), were high in March, April, July and August. HNF abundance showed no difference between the high tide and low tide, and was not different with depth. The ingestion rates of HNF on bacteria were 1.0 to 6.3$\pm$10$^{6}$ bacteria 1$^{-1}$ h$^{-1}$ (average 3.12$\pm$0.55$\times$10$^{6}$ bacteria 1$^{-1}$ h$^{-1}$ ), resulting ingestion rates of HNF removed 19.4 to 141.4 %(average 62.3$\pm$12.0%) of bacterial production. Ingestion rates and grazing pressure of HNF on bacteria showed high correlation with HNF abundance. Although we cannot exactly discussion about seasonal variation of bacteria community in this study area where physical and chemical parameters were very complex, the results indicate that bacterial abundance and production were mainly controlled by resources supply as dissolved organic carbon and chlorophyll-a(bottom-up) except March which bacterial abundance and production uncoupled chlorophyll-a because of low dissolved organic carbon and low temperature, and were controlled by HNF grazing pressure(top-down) in the warm seasons except the winter.

• Nutrition Research and Practice
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• v.7 no.5
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• pp.393-399
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• 2013

Asian populations are thought to receive significant health benefits from traditional diets rich in soybeans due to high isoflavone contents. However, available epidemiologic data only weakly support this hypothesis. The present study was carried out to assess the pharmacokinetics of isoflavones in South Korean women after ingestion of soy-based foods. Twenty-six healthy female volunteers (20-30 y old) consumed three different soy products (i.e., isogen, soymilk, and fermented soybeans) with different aglycone/glucoside ratios. Plasma and urine isoflavone concentrations were measured by high-performance liquid chromatography (HPLC) after ingestion of one of the soy products. Pharmacokinetic parameters were determined using the WinNonlin program. The area under the curve (AUC) for plasma daidzein levels of the soymilk group ($2,101{\pm}352ng{\cdot}h/mL$) was significantly smaller than those of the isogen ($2,628{\pm}573ng{\cdot}h/mL$) and fermented soybean ($2,593{\pm}465ng{\cdot}h/mL$) groups. The maximum plasma concentration ($C_{max}$) of daidzein for the soymilk group ($231{\pm}44$ ng/mL) was significantly higher than those of the isogen ($160{\pm}32$ ng/mL) and fermented soybean ($195{\pm}35$ ng/mL) groups. The half-lives of daidzein and genistein in the soymilk group (5.9 and 5.6 h, respectively) were significantly shorter than those in the individuals given isogen (9.6 and 8.5 h, respectively) or fermented soybean (9.5 and 8.2 h, respectively). The urinary recovery rates of daidzein and genistein were 42% and 17% for the isogen group, 46% and 23% for the fermented soybean group, and 33% and 22% for the soymilk group. In conclusion, our data indicated that soy products containing high levels of isoflavone aglycone are more effective for maintaining plasma isoflavone concentrations. Additional dose-response, durational, and interventional studies are required to evaluate the ability of soy-based foods to increase the bioavailability of isoflavones that positively affect human health.

• ALGAE
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• v.29 no.2
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• pp.153-163
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• 2014

Mesodinium rubrum is a cosmopolitan ciliate that often causes red tides. Predation by heterotrophic protists is a critical factor that affects the population dynamics of red tide species. However, there have been few studies on protistan predators feeding on M. rubrum. To investigate heterotrophic protists grazing on M. rubrum, we tested whether the heterotrophic dinoflagellates Gyrodiniellum shiwhaense, Gyrodinium dominans, Gyrodinium spirale, Luciella masanensis, Oblea rotunda, Oxyrrhis marina, Pfiesteria piscicida, Polykrikos kofoidii, Protoperidinium bipes, and Stoeckeria algicida, and the ciliate Strombidium sp. preyed on M. rubrum. G. dominans, L. masanensis, O. rotunda, P. kofoidii, and Strombidium sp. preyed on M. rubrum. However, only G. dominans had a positive growth feeding on M. rubrum. The growth and ingestion rates of G. dominans on M. rubrum increased rapidly with increasing mean prey concentration < $321ngCmL^{-1}$, but became saturated or slowly at higher concentrations. The maximum growth rate of G. dominans on M. rubrum was $0.48d^{-1}$, while the maximum ingestion rate was 0.55 ng C $predator^{-1}d^{-1}$. The grazing coefficients by G. dominans on populations of M. rubrum were up to $0.236h^{-1}$. Thus, G. dominans may sometimes have a considerable grazing impact on populations of M. rubrum.

• ALGAE
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• v.29 no.2
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• pp.137-152
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• 2014

Mixotrophic protists play diverse roles in marine food webs as predators and prey. Thus, exploring mixotrophy in phototrophic protists has emerged as a critical step in understanding marine food webs and cycling of materials in marine ecosystem. To investigate the feeding of newly described mixotrophic dinoflagellate Ansanella granifera, we explored the feeding mechanism and the different types of species that A. granifera was able to feed on. In addition, we measured the growth and ingestion rates of A. granifera feeding on the prasinophyte Pyramimonas sp., the only algal prey, as a function of prey concentration. A. granifera was able to feed on heterotrophic bacteria and the cyanobacterium Synechococcus sp. However, among the 12 species of algal prey offered, A. granifera ingested only Pyramimonas sp. A. granifera ingested the algal prey cell by engulfment. With increasing mean prey concentration, the growth rate of A. granifera feeding on Pyramimonas sp. increased rapidly, but became saturated at a concentration of $434ngCmL^{-1}$ (10,845 cells $mL^{-1}$). The maximum specific growth rate (i.e., mixotrophic growth) of A. granifera feeding on Pyramimonas sp. was $1.426d^{-1}$, at $20^{\circ}C$ under a 14 : 10 h light-dark cycle of $20{\mu}Em^{-2}s^{-1}$, while the growth rate (i.e., phototrophic growth) under similar light conditions without added prey was $0.391d^{-1}$. With increasing mean prey concentration, the ingestion rate of A. granifera feeding on Pyramimonas sp. increased rapidly, but slightly at the concentrations ${\geq}306ngCmL^{-1}$ (7,649 cells $mL^{-1}$). The maximum ingestion rate of A. granifera feeding on Pyramimonas sp. was 0.97 ng C $predator^{-1}d^{-1}$ (24.3 cells $grazer^{-1}d^{-1}$). The calculated grazing coefficients for A. granifera feeding on co-occurring Pyramimonas sp. were up to $2.78d^{-1}$. The results of the present study suggest that A. granifera can sometimes have a considerable grazing impact on the population of Pyramimonas spp.

• Journal of Radiation Protection and Research
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• v.32 no.2
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• pp.45-50
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• 2007

In this study, uptake rates of internal organs and daily urinary excretion rates were measured to get more reliable estimation results for Korean. Radioactive iodine($^{131}I$) of $100{\mu}Ci$ was administered by ingestion to 28 adult males for the experiment and then the radioactivity in thyroid gland, liver, stomach, small intestine, kidneys, and urine was measured after time intervals of 2, 4, 6 and 24 hours. Uptake rates of each organ and daily urinary excretion rates were calculated on the basis of these experimental results. As a result, uptake rates of 19.70% for thyroid and daily urinary excretion rates of 71.12%, on the average, were indicated. The maximum of uptake rates and daily urinary excretion rates were recorded after 2 hours of administration of $^{131}I$, but those rates were decreased gradually later. It was also found that uptake rates were the highest in stomach, followed by the left kidney, liver, small intestine and right kidney except for thyroid gland. In this experiment, the calculated uptake change rate in thyroid gland after 24 hours of administration of $^{131}I$ was different from that of ICRP-54/67(30%) and ICRP-78(25%). Thus, it is necessary to apply more reliable approach, reflecting the characteristic of Korean physiology and to obtain the basic data of results using this approach for calculation of the internal adsorbed dose. In the future, this approach can be helpful for the internal dose assessment of radiation workers in a nuclear power plant or in a hospital.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.10 no.1
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• pp.19-30
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• 2005

To investigate the seasonal distribution and grazing impacts of benthic protozoa in mud flat, their abundance, biomass and grazing rates of benthic protozoa were evaluated at interval of two or three month in Gangwha Island from April, 2002 to April, 2004. Heterotrophic flagellates and ciliates accounted for an average 98% of benthic protozoa biomass. Abundance and carbon biomass of heterotrophic flagellates ranged from $0.2{\times}10^5$ to $5.9{\times}10^5\;cells\;cm{-3}$ and from 0.02 to $9.2\;{\mu}gC\;cm^{-3}$, respectively. Biomass of heterotrophic flagellates was high in spring and fall, and showed no differences among stations. Abundance and biomass of heterotrophic flagellates decreased with the depth and were high within the surface 2.5 m sediment layer. The majority of heterotrophic flagellates were less than $10\;{\mu}m$ in length, and few euglenoid flagellates were larger than $20\;{\mu}m$. Abundance and carbon biomass of ciliates ranged from $0.1{\times}10^3$ to $17.8{\times}10^3\;cells\;cm^{-3}$ and from 0.02 to $9.1\;{\mu}gC\;cm^{-3}$, respectively, and those of ciliates were high in spring and fall. Biomass of ciliates was high within the surface 2.5 mm sediment layer and was higher at st. J2 and st. J3 than st. J1. Among the revealed benthic ciliates, the hypotrichs were the most important group in terms of abundance and biomass. During the sampling periods, an average 66% of benthic protozoa biomass was covered by ciliates. The seasonal distribution of benthic protozoa showed an almost similar fluctuation pattern to that of chlorophyll-a. The results suggest that the biomass of benthic protozoa were mainly controlled by prey abundance, for example, diatoms. Based on ingestion rates, benthic protozoa removed from 13.4 to 40.7% of bacterial production and from 20.1 to 36.4% of primary production. Ingestion rates of benthic protozoa on bacteria and microphytobenthos were high in April. Benthic protozoa in this study area may play a pivotal role in the carbon flow of the benthic microbial food web during spring.

• Korean Journal of Veterinary Research
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• v.51 no.1
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• pp.55-58
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• 2011

Two 4-day-old Thoroughbred foals with acute clinical signs of depression, elevated pulse and respiratory rates, anemia, and jaundice were referred to the equine hospital of Korea Racing Authority. The foals were seemingly normal at birth, but showed clinical signs such as abnormal behavior, jaundice and anemia suddenly after ingestion of the mare's colostrum, followed by death at 4 days after birth. According to the results of the hematology, serum chemistry analysis, jaundice foal agglutination test, and blood groups test, the foals were diagnosed as neonatal isoerythrolysis (NI) caused by the mare's antibodies. These results suggested that the pregnant mares have a potential for NI.

• Journal of the korean society of oceanography
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• v.31 no.3
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• pp.144-149
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• 1996

I investigated the predation impact by the heterotrophic dinoflagellate Protoperidinium cf. divergens on copepod eggs in the presence of co-occurring phytoplankton prey (a preferred red-tide dinoflagellate Gonyaulax polyedra) and the selective feeding on mixtures of both prey. The ingestion rates of P. cf. divergens on Egg N (unidentified round copepod eggs with a smooth surface, about 80 in diameter) decreased by only 1.7-2 times when mean G. polyedra concentration increased by 57-115 times. In mixed prey experiments, P. cf. divergens preferred Egg N over G. polyedra even at 1.1 ${\mu}g$C $ml^{-1}$ or 470 cells $ml^{-1}$ of the latter. A strong preference of P. cf. divergens for Egg N over G. polyedra can be responsible for this relatively small effect. Protoperidinium may sometimes have a considerable predation impact on the populations of Egg N even during phytoplankton blooms or red-tide periods.