• Ocean and Polar Research
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• 제31권3호
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• pp.265-276
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• 2009

Acartia hongi is the most dominant and widespread planktonic copepod in Gyeonggi Bay, Yellow sea. Ingestion rates and selectivity of A. hongi on phytoplankton and planktonic ciliates were determined in the laboratory. Ingestion rates of A. hongi on planktonic ciliates and phytoplankton increased in proportion to prey concentration increase. When A. hongi was fed with various mixture combinations of planktonic ciliates and phytoplankton, their ingestion rate on ciliates tended to increase as the percentage of ciliates in prey biomass increased. Clearance rate of A. hongi on planktonic ciliates was higher than for phytoplankton in all experiments without regard to relative percent of ciliate biomass. This trend suggests that A. hongi was preferentially preying on planktonic ciliates. Under mixed prey availability, it is likely that selective feeding and higher clearance rate of planktonic ciliates by A. hongi is related to the higher nutritional value of ciliates compared to phytoplankton. Therefore, our results suggest that selective ciliate feeding by A. hongi will positively benefit its growth and abundance, and as a result negatively impact the population dynamics of planktonic ciliates in Gyeonggi Bay.

• 대한의생명과학회지
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• 제15권1호
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• pp.73-80
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• 2009

Bloodstream infections (BSI) are caused by planktonic microorganisms, sometimes leading to serious infections such as bacteremia and sepsis. BSI occurs more frequently to the patients wearing the central venous catheter (CVC). The ciprofloxacin-incorporated CVC (CFX-CVC) has been reported previously to possess antimicrobial activity. In this study, the antibacterial activity of CFX-CVC and its mechanism against planktonic BSI cells were explored by using the shake flask test and by examining the release rate of 260 nm-absorbing substances from the bacterial cells indicative of the membrane damage of the bacterial cells. CFX-CVC reduced more than 99.9% of the viable planktonic BSI cells demonstrating its potent antibacterial activity. It provoked bacteriolysis causing leakage of a large amount of 260 nm-absorbing materials from the planktonic bacterial cells like S. aureus and E. coli. These results provide evidence that the antibacterial activity of CFX-CVC came from the inhibition of the stability of the planktonic bacterial cells.

• Ocean and Polar Research
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• 제26권2호
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• pp.287-298
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• 2004

As a part of Korea Deep Ocean Study program, we investigated the distribution of planktonic protists in the upper 200 m of the northeast Pacific from $5^{\circ}N$ to $17^{\circ}N$, along $131^{\circ}30'W$. Area of divergence was formed at $9^{\circ}N$ which is boundaries of the north equatorial counter current (NECC) and the north equatorial current (NEC) during this cruise. Chlorophyll-a concentration was higher in NECC than in NEC area. Pico chl-a(<$2\;{\mu}m$) to total chl-a accounted for average 89% in the study area. The contribution of pico chl-a to total chl-a was relatively high in NEC area than in NECC area. Biomass of planktonic protists, ranging from 635.3 to $1077.3\;mgC\;m^{-2}$(average $810\;mgC\;m^{-2}$), was most enhanced in NECC area and showed distinct latitudinal variation. Biomass of HNF ranged from 88.7 to $208.3\;mgC\;m^{-2}$ and comprised 15% of planktonic protists. Biomass of ciliates ranged from 123.6 to $393.0\;mgC\;m^{-2}$ and comprised 25% of planktonic protists. Biomass of HDF ranged from 407.2 to $607.8\;mgC\;m^{-2}$ and comprised 60% of planktonic protists. HDF was the most dominant component in both NECC and NEC areas. Nano-protist biomass accounted for more than 50% of total protists in the both areas. The contribution of nanoprotist to total protists biomass was relatively higher in NEC area than in NECC. The biomass of planktonic protists was significantly correlated with phytoplankton biomass in this study area. The size structure of phytoplankton biomass coincided with that of planktonic protists. This suggested that the structure of the planktonic protists community and the microbial food web were dependent on the size structure of the phytoplankton biomass. However, biomass and size structure of planktonic protist communities might be significantly influenced by physical characteristics of the water column and food concentration in this study area.

• Fisheries and Aquatic Sciences
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• 제12권3호
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• pp.240-248
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• 2009

Distribution and abundance of planktonic shrimps were studied in the southern sea of Korea from 1987 to 1991. Nine species of five genera belonging to three families were identified. Of these, Leptochela sydniensis and Lucifer intermedius were predominant species and Lucifer penicilifer and Lucifer typus were common species. Remaining five species, Acetes chinensis, Leptochela gracilis, Lucifer chacei, Process wheeleri and Sergestes similis occurred sporadically and rarely. The distribution pattern of planktonic shrimps varied with species and sampling periods. L. intermedius occurred abundantly along inshore waters. L. penicilifer and L. typus appeared in both inshore and offshore waters, but more abundantly in offshore waters under influence of the Tsushima Current. In conclusion, the distribution patterns of planktonic shrimps may be related with hydrographic characteristics and seasonality in the southern sea of Korea.

• 생태와환경
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• 제41권4호
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• pp.554-562
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• 2008

To evaluate the limitation for epiphytic and planktonic algal growth, acid extractable inorganic phosphorus (AP), implying the luxury uptake phosphorus, was measured in five reed zones of Lake Biwa. The AP in epiphytic substances was 0.7 to 1.4 mg P surface stem $m^{-2}$ in summer and 1.2 to 2.8 mg P $m^{-2}$ in winter. On the other hand, the amount in planktonic substances was 1.4 to 5.7 mg P m -3 and 0.8 to 5.4 mg P $m^{-3}$ in both seasons. Contribution of AP in the epiphytic and planktonic phosphorus was 23 to 31% and 8 to 27% in summer, and 17 to 22% and 9 to 17% in winter. It suggests that in summer both epiphytic and planktonic algae had been luxuriously taken up phosphate into cells. The weight ratios of C : N : P were averaged 79 : 20 : 1 for the epiphytic substances and 81 : 12 : 1 for the particulate substances. On the other hand, the ratios without the luxurious phosphorus were 93 : 24 : 1 and 103 : 15 : 1, showing much higher values than the Redfield ratio. High ratio in the epiphytic substances indicates that the phosphorus is the limiting parameter, rather than nitrogen, regulating the growth of epiphytic algal populations.

• Ocean and Polar Research
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• 제35권2호
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• pp.181-191
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• 2013

To investigate the occurrence of modern living planktonic foraminiferal species and their seasonal variations around Jeju Island, we conducted planktonic foraminiferal sampling at KIOST's regular sampling sites during 16 months. In total seven genus and 16 modern planktonic foraminiferal species were identified with six dominant species. Dominant species were Gloigerinoides sacculifer, Globigerinoides ruber, Globigerina bulloides, Noegloboquadrina dutertrei, Pulleniatina obliquiloculata, and Globorotalia inflata. Most of the species were characterized as being typical subtropical species and showed seasonal variations and/or intermittent occurrence from season to season. The occurrence of living foraminifera revealed a strong relationship with water temperature, but not with salinity. Species succession seems to occur along with water temperature changes. Some patch distribution and water temperature dependences appear to be significant since there is a high degree of variation in the occurrence patterns of species and standing stock. More detailed quantitative study is necessary to confirm the species diversity and seasonal variations of planktonic foraminifera and related ocean environmental changes.

• Journal of the korean society of oceanography
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• 제33권1-2호
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• pp.8-17
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• 1998

Paleoceanographic history of the East Sea is reconstructed based on several environmental parameters (coarse fraction content, planktonic foraminifera/benthic foraminifera ratio, fragmentation and assemblages of planktonic foraminifera, and coiling ratio of Neogloboquadrina pa-chyderma, etc,) of the late Quaternary sediments obtained from the Ulleung Basin. N. pa-chydeyma and Globigerina bulloides are dominant species (greater than 90% in abundance)among the total planktonic foraminifera assemblages in the late Quaternary sediments. The benthic foraminifera rarely occurred throughout the cores. Sinistrally-coiled specimens of N. pa-chyderma representing cold water temperature are observed more abundantly than dextrally-coil-ed ones. In addition, the sinistrally-coiled N, pachydeyma showed more the amount at the lower part of the cores than at the upper part suggesting the restriction of the Tsushima Warm Current into the East Sea during glacial period. G. bulloides, a species representative of upwelling condition, shows more abundant occurrence in the sediments of Core 941013 than those of Core 941006. This implies that Core 941013 is more influenced by upwelling than Core 941006. The upper part of the two cores contain more fragmentation of planktonic foraminifera suggesting significant dissolution by corrosive bottom wafer. Ascending CCD also played an important role for the absence of planktonic foraminifera at the upper part of the cores.

• 한국해양학회지:바다
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• 제19권4호
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• pp.265-271
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• 2014

시화호에서 식물플랑크톤 및 섬모충류의 포식자인 중형동물플랑크톤 개체수가 크게 증가하는 하계에 섬모충류의 초식압에 미치는 중형동물플랑크톤의 영향을 파악하기 위해 희석실험과 요각류 첨가 배양 실험을 병행하였다. 희석실험에서 섬모충류는 식물플랑크톤 생산량의 104%를 하루에 소비하였으나, 요각류 Acartia sinjiensis를 첨가한 실험구에서 섬모충류의 초식압은 19%로 크게 감소하였다. 이는 미소형식물플랑크톤의 주요 초식자인 $&gt;20{\mu}m$ 빈섬모충류에 대한 중형동물플랑크톤의 선택적 섭이에 기인하는 것으로, 중형동물플랑크톤에 의해 섬모충류의 개체수가 강하게 지배되는 시기에는 섬모충류의 실제 초식압은 과대평가될 수 있음을 의미한다. 따라서 시화호에서 요각류 개체수가 크게 증가하는 춘계와 하계에는 식물플랑크톤의 초식자로서 섬모충류의 역할은 크게 감소될 것으로 판단되며, 초식자로서 섬모충류의 역할을 더 정확하게 평가하기 위해서는 섬모충류에 대한 중형동물플랑크톤의 포식압을 반드시 고려해야 할 것으로 보인다.

• Asian-Australasian Journal of Animal Sciences
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• 제16권2호
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• pp.172-175
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• 2003

The regression equations of dry weight of planktonic biomass upon physico-chemical characteristics of fifteen ponds in three replicates under the influence of artificial feed, broiler manure, buffalo manure, N:P:K (25:25:0) and a control pond was obtained after one year of experimental period by using stepwise regression method. Water samples from each of the ponds were analyzed daily. However, the average values were calculated on the basis of 15 day intervals designated as fortnight. In artificial feed supplemented pond the regression of average nitrates on dry weight of planktonic biomass accounted for 71.7% of the variation in biomass. In broiler manure fertilization pond the regression of total nitrogen on dry weight of planktonic biomass held it responsible for more than 74.6% of variation in biomass. In buffalo's manure fertilized pond more than 82% of the variations in biomass were due to total nitrogen. In case of N:P:K (25:25:0) treated pond 66% of the variation in the dry weight of planktonic biomass was due to average nitrates. The control pond showed the dependence of biomass on light penetration. This equation explained more than 62 percent of variation in biomass. Other variables also showed some contribution towards variation in biomass under all the treatments in these regression studies.

• 상하수도학회지
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• 제20권5호
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• pp.685-690
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• 2006

The differences in microbial community structures between planktonic microorganism and biofilm in rivers were investigated using respiratory quinone profiles. The compositions of microbial quinone for 4 tributaries of the Kyongan Stream located in/flowing through Yongin City, Gyeonggi-Do were analyzed. Ubiquinone(UQ)-8, UQ-9, menaquinone(MK)-6 and Plastoquinone(PQ)-9 were observed in all samples of planktonic microorganism and biofilm for the sites investigated, Most planktonic microorganism and biofilm had UQ-8(15 to 30%) and PQ-9(over 30%) as the dominant quinone type. These results indicated that oxygenic phototrophic microbes(cyanobacteria and/or eukaryotic phytoplankton) and UQ-8 containing proteobacteria constituted major microbial populations in the river. The quinone concentration in the river waters tested, which reflects the concentration of planktonic microorganisms, increases with increasing DOC. Further research into this is required. The microbial diversities of planktonic microorganism and biofilm calculated based on the composition of all quinones were in the range from 4.2 to 7.5, which was lower than those for activated sludge(ranging from 11 to 14.8) and soils(ranging from 13.4 to 16.8). The use of quinone profile appears to be a useful tool for the analysis of microbial community structure in river.