• The Korean Journal of Ecology
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• v.8 no.1
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• pp.21-29
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• 1985

The physico-chemical properties of sediment, the species composition and biomass of benthic diatoms were investigated in the intertidal zone of Kum river estuary, from July 1983 to May 1984. Sandflat sediment was more oligotrophic than mudflat one. The diatom composition was primarily associated with sediment grain size. The dominant epipelic diatoms belonged to the centric diatoms such as Paralia sulcata and Thalassiosira spp., while the epipsammic diatoms consisted mainly of Achnanthes haukiana and Amphora sabyii. Diatom flora of sandflat was more significantly diverse than that of mudflat. Mean yearly crop of sandflat diatoms was 2.8 times greater than that of mudflat diatoms and peaked at March reflecting the greater availability of ammonia.

• Microbiology and Biotechnology Letters
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• v.41 no.1
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• pp.79-87
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• 2013

An unstable yet efficient phenanthrene-degrading bacterium strain Ph-3 was isolated from a petroleum-contaminated site at the Mathura Oil Refinery, India. The strain was identified as Pseudomonas sp. using a polyphasic approach. An analysis of the intermediates and assays of the degradative enzymes from a crude extract of phenanthrene-grown cells showed a novel and previously unreported pattern of 1, 2-dihydroxy naphthalene and salicylic acid production. While strain Ph-3 lost its phenanthrene- degrading potential during successive transfers on a rich medium, it maintained this trait in oligotrophic soil conditions under the stress of the pollutant and degraded phenanthrene efficiently in soil microcosms. Although the maintenance and in vitro study of unstable phenotypes are difficult and such strains are often missed during isolation, purification, and screening, these bacteria constitute a substantial fraction of the microbial community at contaminated sites and play an important role in pollutant degradation during biostimulation or monitored natural attenuation.

• The Korean Journal of Ecology
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• v.12 no.4
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• pp.237-244
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• 1989

The moor vegetation of Daeryong-po on Mt. Daeam, east-central Korea was investigated in July 26th-29th, 1989, It was classified into I community group, 4 communities and 5 subcommunities; Sanguisorba tenuifolia var. alba community group, Sphagnum palustre community. Typical subcommunity, Eleocharis mamillata var. cyclocarpa subcommunity, Carex canescense subcommunity, Carex dispalata community, Spiraea salicifolia community, Geranium eriiostemon var. megalanthum community, Arundinella hirta-Phragmites communis subcommunity, Angelica purpuraefolia subcommunity. According to this classification, the actual vegetation map was made. The distribution of vegetation in this moor was divided characteristically into two areas. One was a typical oligotrophic area characterized by S. palustre community. The other was an area having mesotrophic or eutrophic conditions where its original state was disturbed by inflow of soil particles and removal of peat. It this disturbed area, C. dispalata, S. sibiricus, G. eriostemon var. megalanthum, were invaded.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.16 no.10
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• pp.6567-6574
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• 2015

In order to estimate the characteristics of the growth and composition of phytoplankton according to the available nutrients, we added nitrate (0, 1, 5, 10, 20, 50, $100{\mu}M$) and phosphate (0, 0.1, 0.5, 1, 2, 5, $10{\mu}M$) to field samples in a eutrophic site (St. 1) and an oligotrophic site (St. 22) in 2010 as well as a eutrophic site (St. 1, 5), a mesotrophic site (St. 19), and an oligotrophic site (St. 22) in 2011 at Jinhae Bay, Korea. The phytoplankton growth in the areas with additional nitrates and phosphates on St. 1 were significantly different from the control (One-way ANOVA:P<0.01). The dominant species at St. 1 in 2010 were Heterocapsa triquetra and Pseudo-nitzchia spp., to which nitrate and phosphate were added, respectively. The dominant species at St. 22 in 2010 differed between treatment conditions as follows: nitrate treatment Chaetoceros spp. (${\leq}10{\mu}M$), Thalassiosira spp. ($20{\mu}M$), and Pseudo-nitzchia spp.(${\geq}50{\mu}M$) for nitrate treatment; Cylindrotheca spp. ($2{\mu}M$) and Pseudo-nitzchia spp. ($5{\mu}M$) for phosphate treatment. Phytoplankton growth in 2011 according to the added nutrient were significantly different with treatment concentrations (One-way ANOVA: P<0.01). Moreover, the beginning of exponential growth in phytoplanktons was different between the eutro-mesotrophic sites (St. 1, 5, and 19) and the oligotrophic sites (St. 22) on day 2 and day 6 respectively. This implies that phytoplankton growth in the low nutrient condition may be retarded. The dominant species at St. 1 were Eucampia spp. and Chaetoceros spp. in the low nutrient treatment compared to Skeletonema spp., and Thalassiosira spp in the high nutrient treatment. The dominant species at St. 5 and St. 19 were mostly Skeletonema spp. and Chaetoceros spp. However, the dominant species at St. 22 was Thalassiosira spp.. The results of this study showed that phytoplankton growth and composition were different in areas with different nutrient characteristics resulting from the additional nutrients. Therefore, the nutrients additional algal assay could be indirectly explained why the biomass and composition of phytoplankton in Jinhae Bay has shown spatial differences.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.13 no.11
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• pp.5615-5622
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• 2012

Seasonal distributions of the viral abundance and physicochemical parameters were analyzed at three different regions in Gwangyang Bay. Morphological structure of marine virus was observed using transmission electron microscopy. Most of marine virus had bacteriophage-like structure, but some were similar with eukaryotic microalgal virus, Ectocarpus siliculosus virus (EsV). Viral abundance at Group 1 (closed eutrophic region) was higher than viral abundances at Group 2 (closed oligotrophic region) and Group 3 (open oligotrophic region). Seasonal abundances of marine virus at Group 1 were dynamically changed. The viral density was variably changed from maximum $7.33{\times}10^8ml^{-1}$ in August to minimum $0.3{\times}10^8ml^{-1}$ in December and maintained middle value in spring and autumn. The concentration of nitrogen and phosphate sources was correlated with viral abundance. Particularly, seasonal change of dissolved oxygen concentration was opposite to the variation of viral abundance. These results showed that viral abundances were closely related with fluctuation of marine physicochemical environment in Gwangyang bay.

• Microbiology and Biotechnology Letters
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• v.39 no.2
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• pp.119-125
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• 2011

The Egr-1 gene is known to be a transcription factor for activating the expression of many tumor-repressing genes. In this study, three strains activating the promoter of the Egr-1 gene were selected, through the use of Egr-1 luciferase reporter assay and western blotting, from amongst approximately 3,800 oligotrophic bacteria isolated from the cultivated soils of various regions within Korea. These strains were identified as Pseudomonas koreensis on the basis of phylogenetic tree analysis of their 16S ribosomal DNA sequences and biochemical characteristics analyses using a variety of commercial kits (API 20NE, ID 32GN, API ZYM kits). In addition, we discovered that these strains produced anti-bacterial activity against Bacillus subtilis, Staphylococcus aureus and Listeria monocytogenes.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.22 no.3
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• pp.77-87
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• 2017

Picophytoplankton, an important primary producer especially at the oligotrophic region, is known to contribute a significant portion of the total phytoplankton biomass in the East Sea of Korea. During autumn in the southwestern East Sea, frequent upwellings and oligotrophic conditions occur and annual variation of primary productivity is known to be significant. Moreover sea surface temperature (SST) of the East Sea is steeply increasing compared to global average increase, so various changes in marine ecosystem related with increase of SST are reported. Taking such circumstances into consideration, we measured the contribution from picophytoplankton fraction to total phytoplankton composition by size fraction of phytoplankton biomass during the autumn seasons from 2011, 2013 and 2015 and examined the variation of the phytoplankton composition. As a result of size fraction analyses, we found that the variation of contribution from picophytoplankton(<$3{\mu}m$) to total community of phytoplankton was high and the average fractions of picophytoplankton were measured as 38% (2011), 59% (2013), 7% (2015), respectively. The difference between measured SST and annual mean SST (${\Delta}T$) was highest ($+1.6^{\circ}C$) in autumn of 2013 and lowest ($-0.9^{\circ}C$) in autumn of 2015. The close positive correlation between ${\Delta}SST$ and fraction of picophytoplankton was confirmed($R^2$ > 0.9). The increase in SST at the southern East Sea was confirmed as one of the main environmental factors in the increase in the increase of the contribution from picophytoplankton. Monitoring of changes in the community structure of primary producers and the influences of the environmental factors including SST in the East Sea is necessary to understand the interactions of ecosystem of the East Sea and the climate change in the near future.

• Korean Journal of Environmental Biology
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• v.41 no.1
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• pp.89-100
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• 2023

We investigated the spatial distribution of heterotrophic bacteria associated with different water masses in the northern East China Sea(ECS) in summer. The surface water masses were divided into the Changjiang Diluted Water (CDW) and high salinity water (HSW). In the CDW region, the concentrations of dissolved inorganic nitrogen (DIN) and chlorophyll-a (Chl-a), and micro Chl-a contribution were high; and bacterial abundance (BA) and ciliate abundance (CA) were also high. In the HSW region with relatively low DIN concentrations, Chl-a concentration and micro Chl-a contribution were low, but pico Chl-a contribution was increased compared to those in the CDW region. BA did not show any significant difference from the CDW region, but CA was decreased. BA showed a positive correlation with Chl-a concentration in the CDW region; however, it did not show a significant correlation with Chl-a concentration in the HSW region. The ratio of bacterial carbon biomass/phytoplankton carbon biomass was exponentially increased with a decrease in the Chl-a concentration. Compared to the past (1990-2000s), the surface phosphate concentrations and the size of dominant phytoplankton have recently decreased in the ECS. Considering this trend of nutrient decrease and miniaturization of the phytoplankton, our results indicate that changes in the strength of the oligotrophic water mass could alter the function of the microbial food web.

• Journal of the korean society of oceanography
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• v.39 no.1
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• pp.20-25
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• 2004

The Yellow Sea is known to be a very productive region in terms of fisheries. However, its trophic status seems to be highly variable, ranging from oligotrophic to eutrophic, based on new production (NP) values. The NP and regenerated production (RP) values estimated from $^{15}N$-labelled nitrate and ammonium uptake in spring (April 1996) and winter (February 1997) during this study ranged from 0.05 to 19.8 mg $N m^{-2} d^{-1}$ and from 0.1 to 22.8 mg $N m^{-2}d^{-1}$, respectively. Our measurements and earlier observations suggested that NP in the Yellow Sea varied over the four orders of magnitude (range 0.05-180.9 mg $N m^{-2} d^{-1}$) temporally and spatially, and that RP (range 0.1-507.5 mg $N m^{-2}d^{-l}$) based on ammonium predominated during most period of the year, except in winter when both productions were low. The significant nitrogen uptake by phytoplankton below the euphotic zone and episodic entrainment of phytoplankton from below the euphotic zone into the euphotic zone, and nitrite excretion and dissolved organic nitrogen release during nitrate uptake might explain the apparent dominance of RP in the Yellow Sea.

• Journal of Microbiology and Biotechnology
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• v.15 no.1
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• pp.192-196
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• 2005

Abstract Oligotrophic microbial fuel cells (MFCs) were tested for the continuous monitoring of low biochemical oxygen demand (BOD) by using artificial wastewater, containing glucose and glutamate, as check solution. Ten times diluted trace mineral solution was used to minimize the background current level, which is generated from the oxidation of nitrilotriacetate used as a chelating agent. The feeding rate of 0.53 ml/min could increase the sensitivity from 0.16 to 0.43 ${\mu}$A/(mg BOD/l) at 0.15 ml/min. The dynamic linear range of the calibration curve was between 2.0 and 10.0 mg BOD/l, and the response time to the change of 2 mg BOD/l was about 60 min. The current signal from an oligotroph-type MFCs increased with the increase in salts concentration, and the salt effect could be eliminated by 50 mM phosphate buffer.