• 한국환경과학회지
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• 제19권5호
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• pp.607-615
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• 2010

We investigated the temporal variations of heterotrophic dinoflagellates (hereafter HDNF) and photosynthetic dinoflagellates (hereafter PDNF) from 14 June to 4 September 2003 at a single station in Jangmok Bay. We took water samples 47 times from 2 depths (surface and bottom layers) at hide tide. A total of 63 species were encountered and in general the most abundant genera were Prorocentrum and Protoperidinium. The abundance of PDNF and HDNF was in the range of $0.04{\sim}55.8{\times}10^4$ cells/L and in the range of $0.01{\sim}4.35{\times}10^4$ cells/L, respectively. The mean abundance of PDNF was approximately 7 times higher than that of HDNF, and was higher in the surface layer where has enough irradiance for photosynthesis than in the bottom layer. The total dinoflagellate abundance was higher in the NLP (nitrogen limitation period) than in the SLP (silicate limitation period), and the abundance in the hypoxic conditions was similar to that in the normal conditions. The Shannon-Weaver species diversity index were slightly higher in the bottom layer, the SLP and the hypoxic conditions. The PDNF abundance were correlated with temperature, DO, total inorganic nitrogen and phosphate in the whole water column, and the HDNF abundance was significantly correlated with temperature, salinity and DO. This study shows that the dinoflagellate abundance might be affected by abiotic factors such as irradiance, temperature, salinity, DO and the concentrations of inorganic nutrients, and provides baseline information for further studies on plankton dynamics in Jangmok Bay.

• Ocean and Polar Research
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• 제41권3호
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• pp.135-145
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• 2019

We investigated the mass occurrence of the salp Salpa fusiformis during spring in the southern waters of Korea and the northern East China Sea. Abundance of S. fusiformis and dominant taxonomic groups including copepods, ostracods, euphausiids, and appendicularian was examined along with environmental factors (e.g., temperature, salinity, and chlorophyll-a concentration). The abundance of S. fusiformis at 27 stations ranged from 0 to $183\;inds\;m^{-3}$. Both aggregate and solitary forms of S. fusiformis occurred with a mean abundance of $62\;inds\;m^{-3}$ and $4\;inds\;m^{-3}$, and mean body length of 6.5 mm and 15.4 mm, respectively. Redundancy analysis showed that the abundance of S. fusiformis was negatively correlated with chlorophyll-a concentration, indicating the intensive grazing impact of S. fusiformis on phytoplankton. While the abundance of S. fusiformis increased, the species diversity of zooplankton community decreased. The abundances of total copepods and the dominant copepod species (e.g., adults and/or copepodites of Paracalansus parvus s.l., Calanus sinicus, Oithona similis, and Corycaeus affinis) also decreased with the increase of S. fusiformis abundance. However, the abundance of ostracods, euphausiids, and appendicularians was not affected by the mass occurrence of the salps. These results suggest that the mass occurrence of S. fusiformis in spring could negatively affect ecosystem conditions by changing trophodynamics in the zooplankton community.

• ALGAE
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• 제36권4호
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• pp.263-283
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• 2021

To explore the ecophysiological characteristics of the kleptoplastidic dinoflagellate Shimiella gracilenta, we determined its spatiotemporal distribution in Korean coastal waters and growth and ingestion rates as a function of prey concentration. The abundance of S. gracilenta at 28 stations from 2015 to 2018 was measured using quantitative real-time polymerase chain reaction. Cells of S. gracilenta were detected at least once at all the stations and in each season, when temperature and salinity were 1.7-26.4℃ and 9.9-35.6, respectively. Moreover, among the 28 potential prey species tested, S. gracilenta SGJH1904 fed on diverse prey taxa. However, the highest abundance of S. gracilenta was only 3 cells mL^-1 during the study period. The threshold Teleaulax amphioxeia concentration for S. gracilenta growth was 5,618 cells mL^-1, which was much higher than the highest abundance of T. amphioxeia (667 cells mL^-1). Thus, T. amphioxeia was not likely to support the growth of S. gracilenta in the field during the study period. However, the maximum specific growth and ingestion rates of S. gracilenta on T. amphioxeia, the optimal prey species, were 1.36 d^-1 and 0.04 ng C predator^-1 d^-1, respectively. Thus, if the abundance of T. amphioxeia was much higher than 5,618 cells mL^-1, the abundance of S. gracilenta could be much higher than the highest abundance observed in this study. Eurythermal and euryhaline characteristics of S. gracilenta and its ability to feed on diverse prey species and conduct kleptoplastidy are likely to be responsible for its common spatiotemporal distribution.

• 한국해양학회지
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• 제19권2호
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• pp.217-227
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• 1984

1981年에서 1982年 사이 淺水灣 入口에서 小型定置網으로 蒐集한 魚類 群集 의 種組成과 量的 變動을 季節別로 分析하였다. 總 64種의 魚類가 採集되었으며, 小數種이 魚類群集을 優占하였다. 이른 봄에는 漁獲量이 적었으며, 베로라치 (Enedias fangi)와 까나리(Ammodytes personatus)가 優占하였다. 魚類의 種數, 個體數 및 漁獲量은 늦봄에 年中最大값을 보였으며, 이는 魚類들이 産卵 혹은 攝餌를 위하여 灣으로 回族하여 들어오기 때문인 것으로 보인다. 이 시기에는 3種 의 乳泳生魚類, 밴댕이 (Harengula zunasi), 멸치(Engraulis japonica) 및 전어 (Konosirus punctatus)가 優占하였으며, 種類, 個體數 및 어획량이 낮에 비하여 밤에 훨씬 많았다. 여름에는 種數 및 漁獲量이 크게 감소하였으며, 이는 産卵후 成漁가 죽거나, 널리 퍼져 있기 때문인 것으로 보인다. 가을에는 그 해에 태어난 魚類가 再介入하여 어획량이 증가하였다. 이 시기에는 봄, 여름에 産卵한 밴댕이, 멸치 및 전어의 幼漁가 우점하였다. 또, 낮과 밤의 種組成도 큰 차를 보이지 않았다.

• Ocean and Polar Research
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• 제43권4호
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• pp.279-293
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• 2021

To investigate the effect of seasonal marine environment conditions on the cyanobacteria abundance and diversity in the South Sea, four-seasonal surveys were conducted along the 127.5°E survey transect line in the central South Sea using flow cytometry and 16S-23S ITS on the Miseq platform from August 2016 to May 2017. The average abundance of Synechococcus varied from 3.3 × 10³ to 7.4 × 10⁴ cells ml^-1. The abundance was the highest in the summer and the lowest in the winter, and the abundance fluctuated according to water temperature. The abundance was high in the outer sea affected by TWC. However, in summer, the Coastal areas affected by the Yangtze River were more populated than the outer sea. Prochlorococcus was rare and could not penetrate into coastal areas due to the fronts, but showed its dominance in the waters influenced by the TWC. Synechococcus clades II, VII, IX, CRD1, and CRD2 were predominant in the outer sea area affected by the TWC. In the coastal area, clades I and IV showed higher dominance whereas clades V, VI, WPC1, and 5.3-MS3 with euryhaline characteristics, showed a high dominance rate in the water masses affected by the low-salinity water of the Yangtze River in the summer. Clade XVI, XVII, CB1, CB5, and 5.3-I/II showed high dominance in nutrient-rich waters in the summer with increased water temperature. The abundance and community composition of cyanobacteria changed in the South Sea due to the influence of the TWC and stratification. In the summer, the abundance and the community composition differed, and were mainly affected by the general influence of the TWC in addition to the influence of the Yangtze River low-salinity water.

• 환경생물
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• 제30권1호
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• pp.64-70
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• 2012

This study compares the abundance and community structure of zooplankton organisms from the littoral and pelagic regions, and considers particularly trophic levels vs. zooplankton abundances. Zooplankton samples, collected every 3 months over a year from 2010 to 2011 at 29 temperate lakes and reservoirs, which belong to two different river basins (Youngsan and Seomjin River). The spatial pattern of rotifers was similar to that of total zooplankton abundance. This reflected the fact that rotifers strongly dominated the zooplankton community. There were considerable spatial variations in total zooplankton abundance (ANOVA, p<0.01), while there were no significant differences both in littoral and pelagic regions in abundance of zooplankton (ANOVA, p=0.205). The mean abundance of zooplankton in eutrophic systems was much higher than that of mesotrophic systems, while significant difference in number of species and diversity index were not shown in both trophic systems.

• 수산해양기술연구
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• 제48권3호
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• pp.284-292
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• 2012

Species composition and abundance of larval fishes in the coastal waters off Gori in the southeastern Korea were investigated from January to December in 2006. During the study period, 32 larvae species belonging to 20 families were collected. The dominant species were Engraulis japonicius, Hexagrammos agrammus, Sillago japonicus, Acropoma japonicum, Apogon lineatus, and Konosirus punctatus. These six species accounted for 87.0% of the total number of individuals collected. The number of species, number of individuals, and species diversity indices fluctuated by season. The peak numbers of species and individuals occurred in July and May, respectively. Correlation analysis showed that monthly variations in water temperature and salinity could act as an indicators of seasonal variations in the larval fish community structure and abundance of the dominant species; in particular, the abundance of S. japonicus, A. japonicum, and A. lineatus were significantly corrected with the water temperature.

• 천문학논총
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• 제15권spc1호
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• pp.15-30
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• 2000

A large scatter of the chemical abundances among globular cluster red giants has been observed. Especially the chemical elements C, N, O, Na, Mg, and Al vary form star to star within globular clusters. Except for $\omega$ Cen and M22, most globular clusters could be considered to be monometallic of their iron peak elements within error ranges. The variations in light elements among globuar cluster giants appear much more pronounced than in field halo giants of comparable Fe-peak metallicity. It has been found that in general the nitrogen abundance is anticorrelated with both carbon and oxygen, while it is correlated with Na and AI. These intracluster abundance inhomogeneities can be interpreted either by mixing of nucleosythesized material from the deep stellar interior during the red giant branch phase of evolution or by inhomogeneities of primordially processed material, from which the stars were formed. The simple way of distingushing between two senarios is to obtain the element abundances of main-sequence stars in globular clusters, which are too faint for high resolution spectroscopic studies until now. Both 'evolutionary' and 'primodial' origins are accepted for explanations of abundance variations among red giants and CN-CH anticorrelations among main-sequence stars in globular clusters. This paper reviews chemical abundances of light elements among globular cluster giants, with brief reviews of cannonical stellar evolution of low mass stars after main-sequence and deep mixing for abundance variations of cluster giants, and a possible connection between deep mixing and second parameter.

• 천문학회보
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• 제41권2호
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• pp.43.4-44
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• 2016

The presence of multiple stellar populations is now well established in most globular clusters (GCs) in the Milky Way. The origin of this phenomenon, however, is yet to be understood. In this respect, the study of NGC 2808, an intriguing GC which hosts subpopulations with extreme helium abundances, would help to resolve this problem. In order to investigate chemical abundance patterns among different subpopulations in this GC, we have performed low-resolution spectroscopy for the red-giant-branch (RGB) stars and measured CN & CH bands, and Ca line strength. We have identified at least three subpopulations from the CN abundance distribution. This GC shows CN-CH anti-correlation following the general trend among "normal" GCs. In addition, we have cross-matched our results with the high-resolution data in literature, and found a tight correlation between CN strength and sodium abundance. However, CN is anticorrelated with oxygen abundance, as expected from the well known N(&Na)-O anticorrelation. In this talk, we will discuss the implication of these results.

• 한국토양비료학회지
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• 제48권2호
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• pp.132-137
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• 2015

Effects of chitin and chitosan treatments on soil microorganisms and the mesofauna were investigated in a microcosm and a fumigated field experiment. Responses of microorganisms were determined using microbial phospholipid fatty acid (PLFA) analysis, whereas responses of the mesofauna were measured in terms of the abundances of nematodes and microarthropods. Soil nitrate concentration increased on the application of chitin. Overall, chitin promoted bacterial and fungal abundance, leading to an increase in abundance of free-living soil nematodes that feed on decomposers. The ratio of saturated to unsaturated fatty acids was highest in the chitin-treated soil. Chitosan had a minimal effect on the abundance of microorganisms; however, it reduced the abundance of collembolans in the microcosm experiment. These results indicate that the application of chitin has beneficial effects on the supply of nutrients and promotion of the abundance of soil organisms.