• Title, Summary, Keyword: abundance

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Spatial Abundance and Diversity of Bacterioplankton in a Typical Stream-Forming Ecosystem, Huangqian Reservoir, China

  • Wei, Guangshan;Li, Jing;Wang, Ningxin;Gao, Zheng
    • Journal of Microbiology and Biotechnology
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    • v.24 no.10
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    • pp.1308-1318
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    • 2014
  • The specific freshwater environment of reservoirs formed by streams has not been well studied. In this paper, the bacterioplankton community in such a reservoir, the Huangqian Reservoir in eastern China, was described using culture-independent molecular methods. We found that the most dominant bacterioplankton were affiliated with Cyanobacteria, followed by Betaproteobacteria, Bacteroidetes, Gammaproteobacteria, and Actinobacteria. Both bacterial abundance and diversity increased along the direction of water flow, and the 16S rRNA gene copy number in the water outlet was nearly an order of magnitude higher than that in the water inlet. Pearson correlation analyses indicated that nitrate had a significantly negative correlation with the bacterial abundance (p < 0.05) and that ammonium was positively correlated with bacterial abundance (p < 0.05). Interestingly, owing to a remarkably negative correlation (p < 0.01), the ratio of nitrate and ammonium might serve as a good pre dictor of the relative abundance of bacterioplankton. According to redundancy analysis, nitrate and dissolved oxygen were the major factors influencing the bacterial communities. In addition, we attempted to determine the reasons why such a reservoir could maintain good ecological balance for a period of decades, and we found that the environmental factors and bacterial communities both played critical roles. This research will benefit our understanding of bacterial communities and their surrounding environments in freshwater ecosystems.

A New Abundance Estimate for the Finless Porpoise Neophocaena asiaeorientalis on the West Coast of Korea: An Indication of Population Decline

  • Park, Kyum Joon;Sohn, Hawsun;An, Yong Rock;Kim, Hyun Woo;An, Doo Hae
    • Fisheries and aquatic sciences
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    • v.18 no.4
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    • pp.411-416
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    • 2015
  • We estimated abundance of the finless porpoise Neophocaena asiaeorientalis in the west coast of Korea in 2011 and compared it to the abundance data estimated by Park et al. (2007). The two researches used same line transect method operated by a vessel, and the study area were divided into the offshore and the inshore regions to assess variations in their abundance. In offshore regions population density of finless porpoises was $0.122ind./km^2$, which was lower than $0.565ind./km^2$ estimated in 2004. In inshore regions the population density was $0.151ind./km^2$, which was much lower than $0.638ind./km^2$ estimated in 2005. Thus, we estimate that the population densities of the finless porpoises in both the offshore and the inshore regions of the west coast of Korea has decreased by approximately 70% between 2004/2005 and 2011.

Species composition and abundance of larval fishes in the coastal waters off Gori, Korea in 2006 (2006년 고리 주변해역에 출현하는 자치어의 종조성과 출현양상)

  • Baeck, Gun Wook;Park, Joo Myun;Nam, Ki Moon;Huh, Sung-Hoi
    • Journal of the Korean Society of Fisheries and Ocean Technology
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    • v.48 no.3
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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.

THE LATE TYPE SPIRAL GALAXY NGC 7793. I. ABUNDANCES OF HII REGIONS

  • Chun, Mun-Suk
    • Journal of The Korean Astronomical Society
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    • v.16 no.1
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    • pp.1-5
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    • 1983
  • Four HII regions of the Sd galaxy NGC 7793 were observed using AAT/IPCS. From these spectra we determined abundances of the elements using observed emission lines and electron temperatures. The calculated abundances show that this galaxy does not show any significant radial abundance gradient. The mean oxygen abundance is very much like the Orion nebulae and the nitrogen abundance is similar to the late type barred spiral galaxy NGC 1313.

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Studies on the Functioanl Significance of Pollen Surface Characters (화분표면형질의 기능적 의의에 관한 연구)

  • 이상태
    • Journal of Plant Biology
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    • v.22 no.1_2
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    • pp.45-51
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    • 1979
  • From 32 angiosperm species, pollen surface characters such as sculpture pattern, roughness, oil abundance and stickiness were subjectively scored, and compared with size and weight of the grains, and pollination mechanisms. There was a linear relationship between size and weight of the grains. Animal-pollinated grains showed significantly higher roughness, oil abundance and stickiness than wind-pollinated grains. In the former, the grain size was highly correlated with roughness and oil abundance. No such relationship was found in the latter. It was suggested, therefore, that the large the animal-pollinated grains, the greater is the stickiness required, where the stickiness depends on the surface soil abundance and roughness. No functional significance of the sculpture pattern could not be detected in this study.

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Bacterial Abundance and Production in July 1997 in the vicinity of Tokdo, East Sea

  • Cho, Byung-Cheol;Shim, Jae-Hyung;Hong, Gi-Hoon
    • Journal of the korean society of oceanography
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    • v.33 no.4
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    • pp.205-211
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    • 1998
  • Participating in a multi-disciplinary oceanography program in July 1997 in the vicinity of Tokdo, we studied the distributions of bacterial abundance and production along with those of phytoplankton and heterotrophic nanoflagellates. In the euphotic zone, chlorophyll a (chl a) concentrations ranged from 0.14 to 0.52 ${\mu}$g 1$^{-1}$. Bacterial abundance in the euphotic zone (0.12-0.21 ${\times}$ 10$^9$ cells 1$^{-1}$) in the study area was quite lower than that expected from the observed chi a concentration in the marine environment. The low bacterial abundance seemed to be due to active grazing pressure on bacteria. The fraction of primary production utilized by bacteria was also low(8-12%). Interestingly, surface water temperatures were love. at stations near islands compared to an offshore station located between Ulleungdo and Tokdo and the highest values of bacterial production and chi a were found at stations near islands, strongly indicating island mass effects.

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Reproductive Phenology of Gracilaria verrucosa (Rhodophyta) in Cheongsapo near Pusan, Korea

  • Kim Young Sik;Choi Han Gil;Kim Hyung Geun;Nam Ki Wan;Sohn Chul Hyun
    • Fisheries and aquatic sciences
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    • v.1 no.1
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    • pp.147-151
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    • 1998
  • The reproductive phenology of Gracilaria verrucosa was studied in Cheongsapo near Pusan, Korea. Among the life history phases, tetrasporic plants occurred dominantly in varying degrees of abundance throughout the year except from July to September. Cystocarpic plants increased rapidly during summer, and then recorded maximum abundance in July. Whereas, seasonal peaks of spermatangial plants were observed in April and September. However, they were less than cystocarpic plants in abundance. Vegetative plants dominated from December to May for long period, with a occurrence peak in February. Even though fertile plants in both gametophytes and tetrasporophytes occurred throughout the year, their seasonal abundance suggests that the positive correlation between reproduction and water temperature is basically found in the reproductive pattern of Gracilaria verrucosa. The distributional aspect of life history phases appears to be related with differences of their longevity, fecundity or survivorship.

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Chemical composition of Am stars: RR Lyn and $\rho$ Pup

  • Yushchenko, A.V.;Lee, J.J.;Kang, Y.W.;Doikov, D.N.
    • Bulletin of the Korean Space Science Society
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    • pp.22.3-22.3
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    • 2008
  • We present the results of the investigations of high dispersion spectra of two stars. These are the eclipsing binary RR Lyn, and $\rho$ Pup - the prototype of the group of pulsating variables. The spectra were obtained at 1.8 m Bohyuunsan observatory telescope, and 8.2 m VLT. We found the chemical composition. The both components of RR Lyn are Am stars (metallic line stars), but the abundance patterns of the components are not similar - the iron abundance and the abundances of other elements are surely different. For few elements the differences exceeds 1 dex. We found the abundances of 56 chemical elements in the atmosphere of $\rho$ Pup. This is one of the best stellar abundance patterns. It permits to investigate the role of the charge-exchange reactions in stellar atmospheres. These reactions can produce the abundance anomalies in the atmospheres of B-F type stars. These reactions can be one of the sources of galactic cosmic rays, and the reason of the braked rotation of A-F type chemically peculiar stars.

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Impact of Interstellar Na on the Estimation of Na Abundance from Low-resolution Stellar Spectra.

  • Park, Hyejin;Lee, Young Sun
    • The Bulletin of The Korean Astronomical Society
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    • v.44 no.1
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    • pp.68.4-68.4
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    • 2019
  • It is inferred that many stars in the Galactic halo or bulge were once members of globular clusters (GCs), which are now dissolved. To distinguish the GC-originated stars, which can provide valuable information on the origin of the bulge and halo, from the in situ field stars, the Na abundance plays an important role. However, the interstellar Na in certain directions can unnecessarily enhance the estimate of the Na abundance from stellar spectra due to blended Na D lines unless the spectral resolution is very high, which allows to resolve the lines from the interstellar Na. In this study, we present a means of correcting the Na abundance affected by the interstellar Na in the low-resolution of the Sloan Digital Sky Survey stellar spectra.

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