• Journal of Species Research
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• v.11 no.3
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• pp.162-168
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• 2022

Compared to marine dinoflagellates, freshwater species are rarely recorded in Korea. In the present study, we isolated a freshwater dinoflagellate, Palatinus, from the Paldang Reservoir, Korea, in December 2021. The overall cell shape was ovoid, and the cell size was 34.3 ㎛ in length (25.8-39.5 ㎛) and 28.4 ㎛ in width (21.5-34 ㎛). An eyespot was usually observed near the sulcal region. The Kofoidian plate formula of the species was determined to be 4', 2a, 7", 6c, 5s, 5''', and 2''''. Apical pore complex was not observed. However, variations in the cingular plate caused by the fusion of 3C and 4C were observed. Analyses of 28S rDNA sequences revealed that the unidentified species is 100% similar to Palatinus apiculatus, and clustered together in the same lineage in the phylogenetic tree (100% bootstrap value). Our findings confirmed that the isolated dinoflagellate is Palatinus apiculatus, which was discovered for the first time in Korean freshwaters.

• Ocean and Polar Research
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• v.40 no.4
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• pp.191-202
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• 2018

In this study we conducted a weekly monitoring exercise at a fixed station in the saltwater zone during the dry season (Jan-Mar, 2013) and wet season (Jun-Aug, 2013) to understand the fluctuations in phytoplankton communities and environmental factors in the Youngsan River estuary altered by a dike constructed in the coastal area. Phytoplankton communities displayed seasonality; diatoms were dominant during the dry season whereas dinoflagellates were dominant during the wet season. T-test analysis showed that water temperature was significantly different between the seasons whereas freshwater discharge from the dike was not significantly different. This suggests that seasonal variations of phytoplankton are more likely affected by water temperature than freshwater discharge. However, a short-term fluctuation was also observed in response to freshwater discharge; freshwater species appeared during or after the discharge in the dry and wet seasons and blooms of harmful species developed after the discharge. Phytoplankton communities may be affected by changes in physical factors such as turbidity and salinity and nutrient supply resulting from freshwater discharge. Especially, the nutrient supply may directly contribute to the harmful algal blooms (HABs) composed of dinoflagellates which can adapt to low salinity after freshwater discharge.

• Journal of Ecology and Environment
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• v.37 no.4
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• pp.271-284
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• 2014

The morphology of 26 species of the genus Tripos was studied among a total of 51 species of this genus, which were taken using $20{\mu}m$ net samples from June 2006 to January 2011 at 14 stations around Jeju Island. Of these, 23 species were first described as new records in Korean waters and 3 species were redescribed. Short descriptions and synonyms are given for each species in the present study. The dinoflagellates of family Ceratiaceae include marine and freshwater species, belonged to originally the genus Ceratium. Recently, this genus were divided into a new combination with the genus Tripos, which contains the marine species, and the original genus Ceratium, including the freshwater species. We used the Tripos genus for the marine species in this study as a valid name.

• Journal of the Korean Society of Marine Environment & Safety
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• v.22 no.6
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• pp.738-749
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• 2016

To understand the characteristics of the spatio-temporal distribution of phytoplankton after barrage construction in the Nakdong River Estuary, this study investigated relevant environmental parameters and phytoplankton status based on bi-monthly samples collected from the Nakdong River Estuary itself from February 2013 to December 2015. Environmental parameters did not differ significantly across these years but did vary between zones and seasons. The results suggested that the upper zone was dominated by fresh-water diatoms, green algae, and blue-green algae, whereas the lower zone was mostly dominated by dinoflagellates. The presence of Stephanodiscus spp., Asterionellopsis formosa, and Microcystis spp. in the upper zone was related to the inflow of freshwater discharge by artificial control of dyke gates. The dominant phytoplankton species in this zone were dependent on temperature, wind speed, DIP, and DIN, while those in the lower zone were mostly dependent on nutrients and wind speed. In addition, at the lower zone, there were negative correlations between Prorocentrum donghaiense, DIN, and wind speed, with its abundance being higher during the summer than other seasons. Analysis of temporal variations did not indicate any significant differences in the upper zone but did reveal variations among seasons at the lower zone. Except in 2014, the lower zone could be divided into periods dominated by diatoms (October-April) and dinoflagellates (June-August). These results suggest that the characteristics of the phytoplankton community were influenced by changes in the inflow of freshwater species and nutrients given the difference in the range affected by freshwater discharge.

• ALGAE
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• v.31 no.3
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• pp.205-217
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• 2016

Freshwater red tides due to dinoflagellates have caused spectacular and regular “summer reddening” in recent years in Baishihai Lake, a temperate, meromictic, meso- or oligotrophic, high-altitude, landslide-dammed, deep lake located at the eastern edge of Tibetan Plateau in China. Based on morphological and molecular analyses, the causative organism has been identified as a new woloszynskioid dinoflagellate, Tovellia diexiensis Q. Zhang et G. X. Liu sp. nov. The vegetative cells are 20-32 μm long and 16-24 μm wide. They have a hemispherical episome and a broadly rounded hyposome with a short characteristic antapical spine. Usually cells are bright red due to the presence of numerous red-pigmented bodies, which often masked the yellowish green discoid chloroplasts. The amphiesma of motile cells comprise mainly quadrilateral, pentagonal or hexagonal thin plates, arranged in 4-5 latitudinal series on the episome, 1 in the cingulum and 4 on the hyposome. Molecular phylogenies based on small subunit ribosomal DNA and large subunit ribosomal DNA (LSU) indicate T. diexiensis from Baishihai Lake to belong to the family Tovelliaceae, which was monophyletic in our LSU phylogenies. During the bloom-forming period in 2005, cell density of T. diexiensis reached 9.15 × 10⁵ cells L⁻¹. Astaxanthin and its diester were found to be the major pigments in T. diexiensis, resulting in a characteristic blood-red color of the water in Baishihai Lake.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.6 no.2
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• pp.93-102
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• 2001

Biomass and species composition of phytoplankton and zooplankton along the salinity gradients in the Seomjin River estuary were investigated in March, July, September and November, 1999. The locations of sampling sites were set based on the surface salinity during each cruise rather than geographic locations. A total of 96 phytoplankton species were identified with 60 diatom species in the study area. The species number of green algae was relatively high in low salinity region while the number of dinoflagellates increased in high salinity areas. Monthly mean of phytoplankton biomass ranged from 183 cells/ml to 833 cells/ml. There was a diatom bloom of Skeletonema costatum in November at the 5-15 psu salinity region and sharp decrease of biomass in very low salinity region occurred in March. During the rainy season in July with the salinity less than 8.1 psu, the green algae dominated in most of the study areas. Chroomonas spp. were highly dominant in March and September and the biomass increased towards the high salinity regions. A total of 83 zooplankton taxa were identified with 72 marine and 11 freshwater taxa. Major group of marine form was copepods with34 taxonomic groups. Most freshwater taxa were aquatic insects. Threshold salinities of freshwater zooplankton appearance were 8.1 psu in July, 4.7 psu in September, and 0.2 psu in November. The number of taxa appeared and abundances of zooplanktons were minimal in the middle of salinity gradients in this estuary.

• Economic and Environmental Geology
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• v.45 no.4
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• pp.407-429
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• 2012

There has been much debates on the geologic age of the sediments of the Domi Basin, since age results varied after research methods and fossil groups. This study carried out palynological analysis and seismic interpretation to establish a stratigraphy and environmental reconstruction mainly based on fossil dinoflagellates and Seismic data from the Domi-1 and Sora-1 wells. The dinocyst assemblages found enabled zonation of the well sediment sequence resulting in 4 ecozones. Index fossils among dinocysts and palynomorphic substances indicate geologic age of the well ranges from Eocene to Pleistocene, and paleoenvironment varies from freshwater to inner-neritic marine. The fossil association also suggests strong relationship to Japanese Tertiary basins in Kyushu area in terms of stratigraphy and basin developmental history.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.12 no.3
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• pp.200-210
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• 2007

Phytoplankton community was investigated in Asan Bay, South Korea. Samples were collected at 5 stations along Asan Bay axis during wet season from June to August, 2006. In June and July, salinity decreased especially at inside stations. Nutrients were high in June and July, however, decreased in August. We observed the community of phytoplankton including diatoms(62.8%), dinoflagellates(17.3%), cryptophytes(14.8%), euglenophytes(1.0%), cyanophytes (0.9%), chlorophytes(0.4%), and some of unidentified taxa(2.8%) during summer 2006 in Asan Bay. In June, dinoflagellates (mainly Prorocentrum sp.(29.6%)) were dominated, accounting for about 43.5% of total cell number, whereas in July and August diatoms (mainly Leptocylindrus sp.(21.4%), Chaetoceros sp.(27.6%)) were dominated occupying 69.1% and 89.9%, respectively. The results suggest that freshwater inputs affected phytoplankton community in the Asan Bay ecosystem.

• Korean Journal of Environmental Biology
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• v.29 no.3
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• pp.212-224
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• 2011

The Yeongsan River estuary, located in the south west coast, was a typical estuary before a dike was constructed in December 1981. After the construction, the water quality and plankton communities are expected to change. We investigated the change of phytoplankton community and environmental properties in the Yeongsan River estuary by comparing the data collected recently with the results reported before and/or shortly after the construction. Concentrations of $NH_4$-N were significantly increased in the freshwater zone. Concentrations of DO at the surface, $NO_2+NO_3$ and $NH_4$-N were increased while the concentrations of $PO_4$ at the surface were decreased in the seawater zone. The number of green algae species was decreased in the freshwater zone. The number of diatom species was decreased while the numbers of green algae and dinoflagellates were increased in the seawater zone. This study can provide information for better management of the Yeongsan River estuary since no comparison study has been documented between the phytoplankton community before and after the construction of the dike in the estuary.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.17 no.2
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• pp.95-111
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• 2012

Relationship between plankton assemblage and environmental factors in a semi-closed Chunsu Bay was examined. Temporal changes in phytoplankton assemblage was rather drastic than those found in most Korean coastal area in the Yellow Sea primarily due to the seawater temperature (T) and nutrient input from the dikes nearby. Freshwater discharge seemed to cause winter time increase of Diatoms (February) and summer time increase of Dinoflagellates at surface (July to August). Structural change in cell size with time was also found in Diatom. Zooplankton community structure was also changed with season probably due to the food concentration, seawater temperature and salinity (S). From principal component analysis (PCA) of zooplankton distribution, it was postulated that seasonal environmental changes such as T and S could explain about 32% of variability in zooplankton distribution along with phytoplankton cell numbers, while freshwater discharge could explain about 17%. Comparing with past data of 1985-1986, 1991-1992, the distributional patterns and percent composition of major species, Acartia hongi, Paracalanus parvus sensu lato and Centropages abdominalis, were similar. However, the abundances have been increased more than three times. The composition of other taxa than copepods showed significant changes.