• ALGAE
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• 제38권1호
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• pp.1-22
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• 2023

An enormous body of research is focused on finding ways to commercialize carotenoids produced by the unicellular green alga, Haematococcus, often without the benefit of a sound phylogenetic assessment. Evidence of cryptic diversity in the genus means that comparing results of pigment studies may be confounded by the absence of a phylogenetic framework. Moreover, previous work has identified unnamed strains that are likely candidates for species status. We reconstructed the phylogeny of an expanded sampling of Haematococcus isolates utilizing data from nuclear ribosomal markers (18S rRNA gene, 26S rRNA gene, internal transcribed spacer [ITS]-1, 5.8S rRNA gene, and ITS-2) and the rbcL gene. In addition, we gathered morphological, ultrastructural and pigment data from key isolates of Haematococcus. Our expanded data and taxon sampling support the concept of a new species, H. privus, found exclusively in North America. Despite overlap in numerous morphological traits, results indicate that ratios of protoplast length to width and akinete diameter may be useful for discriminating Haematococcus lineages. High growth rate and robust astaxanthin yield indicate that H. rubicundus (SAG 34-1c) is worthy of additional scrutiny as a pigment source. With the description of H. privus, the evidence supports the existence of at least five, species-level lineages in the genus. Our phylogenetic assessment provides the tools to frame future pigment investigations of Haematococcus in an updated evolutionary context. In addition, our investigation highlighted open questions regarding polyploidy and sexuality in Haematococcus which demonstrate that much remains to be discovered about this green flagellate.

• Journal of Ecology and Environment
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• 제47권3호
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• pp.118-133
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• 2023

Background: Free-living amoebae (FLA) are widely distributed in freshwater, seawater, soil, and extreme environments, and play a critical role as feeders on diverse preys in the ecosystem. Also, some FLA can become opportunistic pathogens in animals including humans. The taxa Amoebozoa and Heterolobosea are important amoeboid groups associated with human pathogens. However, the identification and habitat of amoebae belonging to Amoebozoa and Heterolobosea remain poorly reported in the Republic of Korea. This study highlights the first record for identification and source of four amoebae including putative pathogens in the Republic of Korea. Results: In the present study, four previously reported FLA were isolated from freshwaters in Sangju Gonggeomji Reservoir (strain GO001), one of the largest reservoirs during the Joseon Dynasty period, and along the Nakdong River, the largest river in the Republic of Korea (strains NR5-2, NR12-1, and NR14-1) for the first time. Microscopic observations and 18S rDNA phylogenetic trees revealed the four isolated strains to be Acanthamoeba polyphaga (strains NR5-2 and NR12-1), Tetramitus waccamawensis (strain GO001), and Naegleria australiensis (strain NR14-1). Strains NR5-2 and NR12-1 might be the same species and belonged to the morphological Group 2 and the T4 genotype of Acanthamoeba. Strain GO001 formed a clade with T. waccamawensis in 18S rDNA phylogeny, and showed morphological characteristics similar to previously recorded strains, although the species' flagellate form was not observed. Strain NR14-1 had the typical morphology of Naegleria and formed a strongly supported clade with previously recorded strains of N. australiensis in phylogenetic analysis of 18S rDNA sequences. Conclusions: On the bases of morphological and molecular analyses, four strains of FLA were newly observed and classified in the Republic of Korea. Three strains belonging to the two species (A. polyphaga and N. australiensis) isolated from the Nakdong River have the potential to act as opportunistic pathogens that can cause fatal diseases (i.e. granulomatous amoebic encephalitis, Acanthamoeba Keratitis, and meningoencephalitis) in animals including humans. The Nakdong River in the Republic of Korea may provide a habitat for potentially pathogenic amoebae, but additional research is required to confirm the true pathogenicity of these FLA now known in the Republic of Korea.

• Journal of fish pathology
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• 제24권3호
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• pp.197-204
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• 2011

The edible ascidian Halocynthia roretzi is a commercially important fisheries resource in Korea. However, for the last several years, outbreaks of mass mortalities of the species have been occurring along the south and east coasts of Korea, where most ascidians are produced. Although it is known that tunic-softness syndrome is associated with these mortality events, the agent causing the syndrome has not yet been confirmed. To determine the agent causing tunic-softness syndrome, healthy and diseased ascidians were collected in March 2011 from Tongyeong, on the south coast of Korea, and were used for biological and pathological investigations. The results showed that diseased ascidians exhibited remarkably reduced body fluid, fatness index, and tunic index compared with healthy specimens. Interestingly, bi-flagellated protozoans were observed specifically in the tissue imprints and tunic cultures of diseased ascidians at an occurrence rate of 97.5%. Histological observation showed that the thickness of the tunics of diseased ascidians was reduced by half, and irregular structure and breakdown of the tunic fiber bundles were observed. In particular, flagellate-like cells were observed in the diseased ascidians. Our study clearly shows that bi-flagellated protists are present only in the softened ascidians, suggesting that the flagellates are partly or entirely associated with soft-tunic syndrome. Accordingly, further investigations to verify the effects of the flagellates found in the present study on soft-tunic syndrome should be conducted.

• ALGAE
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• 제19권4호
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• pp.293-301
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• 2004

A chain-forming toxic din flagellate, Gymnodinium catenatum (Graham) was known as a paralytic toxin-producer among Gymnodinoid group. In the study, the effects of water temperature, salinity and irradiance on the growth of G. catenatum isolated from Yeosuhae Bay, Korea were investigated. Water temperature range in which G. catenatum showed specific growth rate higher than 0.3 day$^{-1}$ were above about 18${^{\circ}C}$. However, salinity did not have such an effect on growth of G. catenatum. The maximum growth rate (0.5 day$^{-1}$) was obtained at 25${^{\circ}C}$ and 30 psu. The specific growth rate (u) expressed as a polynomial equation as functions of temperature (T; ${^{\circ}C}$) and salinity (S; psu) was $\mu$ = 0.005·T$^2$ - 0.0001164 T$^3$ - 0.063-S + 0.005-S$^2$ - 0.00007608-S$^3$ - 0.003-T-S + 0.00005308-T$^2$-S. Thus, in aspects of water temperature and salinity, the species may be expected to survive in most Korean coastal waters from early summer to autumn. The irradiance-growth curve was described as = 0.16 (I - 10.4)/(1 + 21.8) at 18${^{\circ}C}$ and 30 psu, indicating a half-saturation (Ks) photon flux density (PFD) of 42.6$\mu$mol m$^{-2}s^{-1}$ and compensation PFD (I$_0$) of 10.4$\mu$mol m$^{-2}s^{-1}$. These characteristic responses to irradiance suggest that G. catenatum can reside at the sub-surface.

• Korean Journal of Environmental Biology
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• 제34권2호
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• pp.124-131
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• 2016

The toxic responses of flagellate Euglena agilis Carter to 8 heavy metals (Ag, Cd, Cr (VI), Cu, Hg, Ni, Pb, Zn) were measured using E. agilis system (E-Tox), an automated biomonitoring system. The E-Tox measures cell movement parameters, such as velocity, motility, and forms of the cells, as biological endpoints. $EC_{50}$ values from the E. agilis biomonitoring test were compared with the literature data from the tests with Daphnia magna, Vibrio fischeri and Euglena gracilis. Measurement of the E. agilis movement behavior and D. magna acute toxicity test were also conducted for the wastewater samples. E. agilis is less sensitive than D. magna but is comparable to or more sensitive than V. fischeri and E. gracilis for the heavy metals tested in this study. E. agilis shows prompt changes of these parameters for the toxic metal plating wastewater. Major advantages of the E-tox are automatic, easy to handle and fast ecotoxicity monitoring system compared to other biological test systems. These results imply that E. agilis biomonitoring test using E-Tox can be a putative ecotoxicity test as a good early warning tool for the monitoring of toxic wastewater.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• 제3권4호
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• pp.193-202
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• 1998

Water quality of Masan-Jinhae Bay was monitored from January 1996 to August 1997. The monitoring focused on the spatial and vertical gradients and seasonal changes of eutrophication parameters such as nutrients, DO and water transparency. Flagellate phytoplanktons persistently bloomed from April to October with monospecific or mixed algal blooms and dynamic algal successions were observed in this area. Algal blooms were highly correlated with salinity drops and made the water less transparent. Stratification of oxygen content was persistent through summer and oligo-oxygenation was developed in the bottom waters. Nutrient gradients were consistently maintained through the depth in summer and through spatial distribution from inner Masan Bay to outer Jinhae Bay in winter. Except the rainfall seasons, water quality was under the influence of the waste waters discharged from watershed around the Masan Bay. The waste waters would act as the primary factor for the water quality deterioration of the bay. Literature data for eutrophication were gathered and analyzed to review the water quality trends of the Masan and Jinhae bays since 1970. Annual mean COD and phosphate concentration consistently increased from 1975 to 1990 and decreased or dropped after 1991. The sediment of inner part of Masan Bay was dredged from 1991 to 1994 as a decontamination process and it is assumed that the dredging has weakened more or less the deterioration trend of the water quality of the bay.

• Journal of Life Science
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• 제25권5호
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• pp.568-576
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• 2015

The marine microalga Pavlova viridis can grow fast and has the ability to accumulate essential nutrients for culturing marine animals, such as EPA and DHA, and it has been used as food for raring larval fish and prawn. The symbiotic relationship between the flagellate microalga Pavlova viridis and its associated bacteria was investigated. An axenic culture of P. viridis was obtained by repeated treatment of the microalga with an antibiotic cocktail. The axenic status was confirmed after sub-culturing three times in a sterile f/2 medium without an antibiotic. The axenic alga was then co-inoculated with five bacteria, arbitrarily designated as I1–I5, isolated from the alga to test the growth promotion of the algae. All bacterial strains promoted the growth of P. viridis, and bacterial isolate I3 was the most effective among the five bacteria tested. The cell number of P. viridis in the co-culture with I3 was significantly higher than that of the control culture. A sequence analysis of the 16S rRNA gene isolated from I3 revealed a 97% nucleotide sequence similarity to that of Citrobacter sp. The growth of strain I3 was also significantly enhanced by co-culturing with P. viridis, indicating a symbiotic relationship between the microalga and its associated bacterium. The association between the microalga and bacterium was confirmed by scanning electron microscopy.

• Korean Journal of Environmental Biology
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• 제37권1호
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• pp.19-30
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• 2019

To investigate the characteristics of seasonal environment and phytoplankton community structure in the coastal area of Dokdo, a survey of Dokdo around waters was conducted during the four seasons. Phytoplankton of 4 phylum 72 species in four seasons were collected in Dokdo around water. The seasonal mean abundance of phytoplankton were $3.32{\times}10^4cells\;L^{-1}$ in winter, $1.04{\times}10^4cells\;L^{-1}$ in spring, $0.28{\times}10^4cells\;L^{-1}$ in summer, and $4.86{\times}10^4cells\;L^{-1}$ in autumn in Dokdo around water. During winter, the diatoms Chaetoceros spp. had dominated. During spring, when the nutrients in the euphotic layer were depleted, the nano-flagellates and Cryptomonas appeared at surface layer. In summer, the abundance of phytoplankton was relatively low, which lead to occurrence of diatoms such as genus of Chaetoceros, Rhizosolenia, and Skeletonema. In autumn, Pseudo-nitzschia spp. was the most dominant species and tropical species such as Amphisolenia sp. and Ornithocercus magnificus were observed, implying that they may have introduced within warm water current such as Kurosiwo Current. Therefore, although natural phytoplankton communities in the vicinity water of Dokdo are mainly influenced by Tsushima Warm Current branched Kurosiwo Current, their population dynamics was affected on the spatio-temporal change of physicochemical factors by short-term wind events, namely "island effect". Long-term survey research is needed to facilitate food-web response in marine ecosystem associated with phytoplankton biomass and physicochemical factors including the warm water current in oligotrophic offshore water of Dokdo, which may have significant role for sustainable use of Dokdo.

• Journal of the Korean Society of Marine Environment & Safety
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• 제22권5호
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• pp.483-489
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• 2016

The type approval test for USCG Phase II must be satisfied such that living natural biota occupy more than 75 % of whole biota in a test tank. Thus, we harvested a community of natural organisms using a net at Masan Bay (eutrophic) and Jangmok Bay (mesotrophic) during winter season to meet this guideline. Furthermore, cell viability was measured to determine the mortality rate. Based on the organism concentration volume (1 ton) at Masan and Jangmok Bay, abundance of ${\geq}10$ and $<50{\mu}m$ sized organisms was observed to be $4.7{\times}10^4cells\;mL^{-1}$and $0.8{\times}10^4cells\;mL^{-1}$, and their survival rates were 90.4 % and 88.0 %, respectively. In particular, chain-forming small diatoms such as Skeletonema costatum-like species were abundant at Jangmok Bay, while small flagellate ($<10{\mu}m$) and non chain-forming large dinoflagellates, such as Akashiwo sanguinea and Heterocapsa triquetra, were abundant at Masan Bay. Due to the size-difference of the dominant species, concentration efficiency was higher at Jangmok Bay than at Masan Bay. The mortality rate in samples treated by Ballast Water Treatment System (BWMS) (Day 0) was a little lower for samples from Jangmok Bay than from Masan Bay, with values of 90.4% and 93%, respectively. After 5 days, the mortality rates in control and treatment group were found to be 6.7% and >99%, respectively. Consequently, the phytoplankton concentration method alone did not easily satisfy the type approval standards of USCG Phase II ($>1.0{\times}10^3cells\;mL^{-1}$ in 500-ton tank) during winter season, and alternative options such as mass culture and/or harvesting system using natural phytoplankton communities may be helpful in meeting USCG Phase II biological criteria.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• 제12권3호
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• pp.147-158
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• 2007

To clarify the bloom pattern and species succession in phytoplankton community, the population dynamics with the determination of physico-chemical factors have been studies in Masan Bay, the south sea of Korea, for the periods November 2003-October 2004. Concentration of $NH_4-N$ was always higher than that of $NO_3-N$, which was similar level as compared to other costal areas. $PO_4-P$ concentration was lower than those in other coastal areas but similar to oligotrophic environments. Thus, phosphate seems the limiting nutrient rather than nitrogen. $SiO_2-Si$ concentration was also low as compared to other costal areas. Si:P ratio was low from autumn to winter, suggesting silicate and/or phosphate limitation during this period. The cell density of phytoplankton was high in winter 2003 and early autumn 2004. The carbon biomass was high in winter 2003 and summer 2004. And chlorophyll-a concentration was high in late autumn 2003 and summer 2004. Among 78 species of phytoplankton found in the bay during the investigated period, dominant species were two diatoms of Cylindrotheca closterium, Skeletonema costatum, and three dinoflagellates of Heterocapsa triquetra, Prorocentrum minimum, P. triestinum, and one raphidophyte of Heterosigma akashiwo. P. minimum dominated from late autumn to winter, but it was replaced by H. triquetra in late winter. P. triestinum dominated from late spring to early summer. Simultaneously, H. akashiwo cell density steadily increased, and it became dominant with C. closterium in late summer. With decreasing of H. akashiwo and C. closterium, S. costatum became the most dominant species in autumn. The canonical analyses showed that total phytoplankton cell density related to diatom cell density and it was affected by temperature, and concentrations of $NO_3-N\;and\;PO_4-P$. The carbon bio-mass and $chlorophyll-{\alpha}$ concentration related to diatom- and dinoflagellate cell densities and these were affected by flagellate cell density, salinity, and concentrations of $SiO_2-Si\;and\;PO_4-P$. Last six years monitoring data in Masan city obtained from Korean Meteorological Agency indicates gradual increase in air temperature. And the precipitation decreased especially in spring season. The winter bloom found in 2003 may be caused by the increase in the temperature and this bloom subsequently induced the nutrients depletion, which continued until next spring probably due to no precipitation. Therefore, the spring bloom, which had been usually observed in the bay, might disappear in 2004.