• Journal of the Korean earth science society
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• v.37 no.6
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• pp.325-331
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• 2016

Three diatom assemblage zones were erected from HMB-103 core sediment of the Heuksan Mud Belt. The paleoenvironmental changes were reconstructed basing on diatom analyses using indicator species, cold and warm water species, and salinity. Seventy-six species belonging to 41 genera were identified in the core sediments. The number of diatom valves per gram of dry sediment ranged from 0.1 to $15.4{\times}10^4g^{-1}$. As a result, diatom assemblage I in about 45,000 yr B.P showed a high abundance in cold species indicating a major influence by the Korea Coastal Current. Diatom assemblage II from 14,000 to 11,646 yr B.P is characterized by rare abundance and indicative of the cold periods at Younger Dryas with the lower sea-level. However, diatom assemblage III from 11,646 yr B.P to Holocene was more affected by the Yellow Sea Warm Current while the progressive sea level rise.

• Ocean and Polar Research
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• v.24 no.4
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• pp.359-365
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• 2002

The qualitative and quantitative composition of the phytoplankton of the coastal waters off Vladivostok during the period 1991-1994 was studied. The following trends in the phytoplankton composition with decreasing distance from the source of eutrophication were revealed: 1) total density and bio-mass increased; 2) the density of the diatom Skeletonema costatum, which reflects a decrease in the Shannon-Weaver species diversity index during the summer microalgal bloom, increased significantly; and 3) the density of the non-diatom component of the phytoplankton increased.

• ALGAE
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• v.26 no.4
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• pp.299-315
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• 2011

The morphology, taxonomy, and distribution of species belonging to the diatom family Rhizosoleniaceae were studied from the marine coastal waters of Korea. Rhizosolenid diatom taxa were collected at 30 sites from September 2008 to February 2010 and were analyzed by light and scanning electron microscopy. We identified 6 rhizosolenid genera, including Rhizosolenia, Proboscia, Pseudosolenia, Neocalyptrella, Guinardia, and Dactyliosolen. We describe 5 genera in this study, except Rhizosolenia. Five genera were compared in detail with congeneric species. Six genera within the family Rhizosoleniaceae were divided into two groups based on morphological diagnostic characters including valve shape, areolae pattern, the shape of external process, and girdle segments in the column. The first group had a conoidal valve and loculate areolae, which comprised Rhizosolenia, Proboscia, Pseudosolenia, and Neocalyptrella, and the second group of Guinardia and Dactyliosolen showed a flat or rounded valve and poroid areolae. Important key diagnostic characters were based on valve shape, areolae pattern on the segment, external process, position of the tube, and the valve margin. D. phuketensis was new to Korean coastal waters.

• ALGAE
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• v.25 no.2
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• pp.57-64
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• 2010

A variety of Cyclotella atomus were discovered among the epiphytic diatoms on eelgrass (Zostera marina L.) in Korean waters. Cyclotella atomus var. marina has a flat and disc-shaped valve, and is clearly differentiated into a striate marginal zone and a smooth central zone. The valves have a very small diameter ranging from 3.1-3.4 ${\mu}m$. This small diatom does not have any central ornamentation. The marginal striate zone has numerous granules toward the mantle. The valves have five or six marginal fultoportulae with two satellite pores and a single marginal rimoportula.

• Bulletin of the Korean Chemical Society
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• v.34 no.2
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• pp.353-354
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• 2013

• ALGAE
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• v.25 no.3
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• pp.133-140
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• 2010

Using chlorophyll fluorescence, the vertical migration of benthic diatoms responding to light intensity and affected by sediment grain size was studied. Minimal fluorescence ($F_o$) of surface sediment was measured by imaging pulse amplitude modulated (Imaging-PAM) fluorometer, and used to monitor diatom biomass variation in surface sediments. The test diatoms, Amphora coffeaeformis (C. Agardh) K$\ddot{u}$tzing and Cylindrotheca closterium (Ehrenberg) Reimann & Lewin, migrated to the sediment surface under irradiance from 50 to 500 ${\mu}mol$ photons $m^{-2}s^{-1}$. However, the diatoms exhibited no evident increase of surface biomass under dark conditions, and even showed slightly decrease of surface biomass under irradiances over 1,000 ${\mu}mol$ photons $m^{-2}s^{-1}$. The light intensity inducing the maximum surface migration of A. coffeaeformis was 100 ${\mu}mol$ photons $m^{-2}s^{-1}$, while the light intensity producing the same effect for C. closterium was 250 ${\mu}mol$ photons $m^{-2}s^{-1}$. C. closterium showed higher motility than A. coffeaeformis. Faster diatom surfacing was observed in larger grain size sediments (125-335 ${\mu}m$) than smaller ones (63-125 ${\mu}m$). This study confirmed the significant influence of light as a main triggering factor behind migration, indicated the distinct effect of different sediment grain size, and highlighted the species-specific migratory ability.

• Korean Journal of Microbiology
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• v.52 no.3
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• pp.306-312
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• 2016

Microalgae are the potential bioindicators of environmental changes, for the environmental risk assessment as well as to set limits for toxic chemical release in the aquatic environment. Here, we evaluated the effects of two endocrine disrupting chemicals (EDCs), namely bisphenol A (BPA) and Aroclor 1016, on the green algae Tetraselmis suecica, diatom Ditylum brightwellii, and dinoflagellate Prorocentrum minimum. Each species showed wide different sensitivity ranges when exposed to these two EDCs; the 72 h effective concentration ($EC_{50}$) for these test species showed that Aroclor 1016 was more toxic than BPA. $EC_{50}$ values for the diatom D. birghtwellii were calculated at 0.037 mg/L for BPA and 0.002 mg/L for Aroclor 1016, representing it was the most sensitive when compared to the other species. In addition, these results suggest that these EDC discharge beyond these concentrations into the aquatic environments may cause harmful effect to these marine species.

• Journal of Ecology and Environment
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• v.38 no.4
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• pp.545-562
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• 2015

A study on indigenous diatoms was carried out at 71 sites during the period from April 1999 to August 2014 in marine and fresh water in Korea. Forty species of diatoms are new to Korea and they are divided into three classes, six subclasses, 13 orders, 19 families, and 28 genera. The nomenclatures, references, dimensions, specimens examined, local habitat, distribution in Korea, and photograph are reported here. The 40 species found in marine and fresh water showed speciesspecific habitats.

• ALGAE
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• v.30 no.2
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• pp.103-119
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• 2015

Photosynthetic rates of the large centric diatom Coscinodiscus granii were measured by means of multicolor variable chlorophyll fluorescence imaging, single cell $^{14}C$ assimilation, and optical $O_2$ sensor measurements during light acclimatization of cultures grown at five different irradiances: 50, 150, 235, 332, and $450{\mu}mol$ photons $m^{-2}\;s^{-1}$. Photo-acclimatization was evident from changes of cellular chlorophyll a content, growth rates, and light response curves. Each of the applied methods evaluates different parts and reactions in the photosynthetic apparatus, which makes a direct quantitative comparison of rates difficult, although a different degree of correlation were found between all three methods. However, when used in combination, they provide information about the internal relationship of photosynthetic pathways as well as the variation in photosynthetic capacity between individual cells within a single algal culture.

• ALGAE
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• v.25 no.2
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• pp.65-70
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• 2010

The genus Chaetoceros provides highly diversified diatoms in marine systems. Morphological descriptions of the genus are well-documented, yet the DNA taxonomy of Chaetoceros has not been satisfactorily established. Here, the molecular divergences of the 18S-28S rDNA of Chaetoceros were assessed. DNA similarities were relatively low in both 18S (93.1 $\pm$ 3.9%) and 28S rDNA (81.0 $\pm$ 4.6%). Phylogenies of the 18S, 28S rDNAs showed that Chaetoceros was divided according to individual species, clustering the same species into single clades. Statistical analysis with corrected genetic (p-) distance scores showed that nucleotide divergence of Chaetoceros 28S rDNA significantly differed from that of 18S rDNA (Student's t-test, p < 0.05). This finding suggests that the 28S rDNA may be treated as a more suitable marker for species-level taxonomic distinctions of Chaetoceros.