• Ocean and Polar Research
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• v.27 no.2
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• pp.149-159
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• 2005

Samples were collected from five stations in February, May, July, and September 2004 to investigate seasonal variations in the phytoplankton community and the relationship between dominant genera and environmental factors in Asan Bay. In February, microphytoplankton contributed 80% to the total chlorophyll a. Diatom dominated the phytoplankton community, accounting for 85.9% of the total cell number, followed by dinoflagellates (6%). Dominant species were Skeletonema costatum and Thalassiosira spp. Abundant diatom, including S. costatum and Thalassiosira spp., may be affected by water temperature and silicate at Station 1 and 2 in February 2004. In May, the nanophytoplankton contribution to total phytoplankton was higher than in other seasons. However, abundance of S. costatum and Thalassiosira spp. decreased, since the growth of S. costatum and Thalassiosira spp. might be limited by phosphates (P) resulting from low P concentration and a high DIN:DIP ratio in the outer region. In July, dominant phytoplankton groups were diatom (39%), cryptophyceae (28%), and cyanophyceae (20%). Dominant genera were Oscillatoria spp. and phytoflagellate of a monad type in the inner region (Station 1 and 2), whereas S. costatum was dominant in the outer region (Station 4 and 5). In September, dominant phytoplankton were diatom (69%) and cryptophyceae (28%). Dominant genera were phytoflagellate of the monad type, S. costatum in the inner region, while Chaetoceros spp. was dominant in the outer region.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.12 no.4
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• pp.370-379
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• 2007

Short-term variations of phytoplankton community structure in the southeast coastal waters of Korea from July to September in 2006 were investigated with data set of phytoplankton, chemical and physical water properties, and meterological data. A total of 11 sampling sites of 4 different depths (surface, 5 m, 10 m, and bottom) were visited on July 11-14, July 24-26, August 7-10, August 21-24 and September 5-8. We identified 151 species in 63 genera of phytoplankton in which diatoms were the most diverse group composed of 92 species in 37 genera. Dinoflagellates were the second diverse group of 52 species in 22 genera. The other groups include 7 species in 4 genera including Raphidophytes, and Euglenophyta. After rainy season, excessive nutrients from adjacent streams to the stratified water column proliferates Chaetoceros group in July. But biomass of phytoplankton and nutrient concentrations were decreased during the period of a drought in August. However, Chaetoceros was the most dominant genera in all depths of the first, second, third and fifth cruises, except the 4th cruise on August 21-24 when dominant group were dinoflagellates including Gymnodinium spp. and Cochlodinium polykrikoides. The characteristic of phytoplankton community and environment condition during summer 2006 can be summarized as: 1) low concentration of nutrients caused by a long lasting drought in August 2) no summer outbreak of C. polykrikoides because the strength of offshore waters was weak than other years, and 3) Chaetoceros spp. was the dominant species despite short period appearance of dinoflagellates.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.21 no.8
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• pp.579-592
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• 2020

This study was designed to assess the water quality and phytoplankton community including chlorophyll a in blood cockle (Tegillarca granosa) farms in May, August and November of 2017 in the northwestern Yeoja Bay, Korea. As a result, the seasonal characteristics of water types by water temperature and salinity were clear. Nutrients were abundant in silicate throughout the season, but phosphate was scarce in spring and summer, and nitrogen sources were scarce in autumn. The species composition of phytoplankton community was a very simple distribution, and the standing crop was also very low. The annual dominant species is dominated by the diatoms, with Skeletonema costatum-ls, Nitzschia longissima in spring, Pleurrosigma normanii, Coscinodiscus gigas in summer, and N. longissima, Pseudonitschia pungens, Chaetoceros curvisetus, Eucampia zodiacus in autumn. In summer the results were different from other coastal waters of Korea. The principal component analysis(PCA) and correlation analysis showed that the characteristics of water quality and biological environments differed according to the season. Furthermore, it was determined by the supply of materials through fresh water on land, seawater congestion caused by the refueling of surface sediments with lower depth, and the balance of biological production and mineralization of organic matters in blood cockle farms.

• Korean Journal of Environmental Biology
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• v.38 no.3
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• pp.355-370
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• 2020

We conducted a field survey to analyze the ecological structure and spatial distribution of microplankton (phytoplankton and ciliates) in relation to water masses at 21 stations on the surface and chlorophyll-a maximum layers (CML) in the Northern East China Sea (nECS; 32°-33°N; 124°00'-127°30'E) from August 3 to August 6, 2019. The results showed that the water masses were divided into Chinese Coastal Waters (CCW) and the Tsushima Warm Current (TWC). The CCW showed the environmental characteristics of high temperature and low salinity, and the TWC showed high temperature and high salinity. The characteristics of the phytoplankton community in the CCW showed various community structures related to the nutrients supplied from the large rivers of the Chinese continent. However, the TWC had simple community structures because it originated near the equator and moved northward. The standing crops of phytoplankton and ciliates were very high in the CCW but showed low at the TWC. In particular, from the higher standing crops of protozoa than plant plankton at the TWC, the energy flow at the lower tropic levels caused by the microbial loop that fed on heterotrophic bacteria played an important role in the production of resource organisms. In other words, the marine ecological structure of the nECS in summer could be estimated as a bottom-up system at the CCW and a top-down system at the TWC.

• Ocean and Polar Research
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• v.26 no.2
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• pp.113-120
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• 2004

The abundance, biomass and distribution of phytoplankton, bacterioplankton and heterotrophic protists in the Bering Sea were investigated from July to August 1999. Chlorophyll a concentrations in the surface waters ranged from 0.16 to $3.79{\mu}g\;l^{-1}$ Nano-phytoplankton were found to constitute from 63 to 98% of the total phytoplankton biomass, and were clearly the dominant primary producers. The biomass of bacterioplankton in the surface layers varied from 1.46 to $20.2{\mu}g\;C\;l^{-1}$ and accounted for 30% of the total phytoplankton biomass. The biomass of bacterioplankton integrated over a depth of 0 to 100m averaged 65.4% of the total phytoplankton biomass. The surface biomass of heterotrophic protists ranged from 1.2 to $27.4{\mu}g\;C\;l^{-1}$, and was within the same order of magnitude as that of bacterioplankton. Of the total biomass of heterotrophic protists in the upper 100m of the water column, 65% was attributed to protists in the nano-size class. The results of this study suggest that bacteria and nano-protists are important components of the planktonic community in the Bering Sea during the summer season. The abundance of bacterioplankton and planktonic protists decreased from the western to northeastern and eastern regions of the Bering Sea. The abundance of these organisms also decreased with depth. The available evidence suggests that variation in the abundance and distribution of these organisms may be affected by water currents and vertical temperature variation in the Bering Sea.

• Journal of Environmental Science International
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• v.23 no.12
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• pp.2015-2028
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• 2014

We analyzed with HPLC (High Performance Liquid Chromatography) analysis photosynthetic pigments and environmental factors, microscopic observations of the phytoplankton and zooplankton in the seawater every month from February 2009 to November 2010 in Haengam Bay. The level of dissolved inorganic nutrients was the highest between July and September, when freshwater influx was at its peak, whereas chlorophyll a levels were the highest in April and August. Also, phytoplankton pigment concentration increased when dissolved inorganic nutrients are carried into nearshore waters by rainfall runoff. Based on identification of phytoplankton and photosynthetic pigments results, diatoms were mainly dominant while dinoflagellate populations increased at July and August 2009, May 2010. The zooplankton communities are dominated in terms of Noctiluca scintillans. The contribution of Noctiluca scintillans in 2010 accounts for approximately 77.3% of the total zooplankton. Distribution patterns over time of zooplankton in the seasonal distribution of phytoplankton showed a different pattern.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.24 no.4
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• pp.237-247
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• 1991

To characterize the community structure and spatial distribution of phytoplankton, observations on seawater temperature, salinity, nutrients, primary productivity and abundance and species composition of phytoplankton were made in the polar front region and its neighborhood off the east coast of Korea in summer 1990. Among the 96 taxa identified, Rhizosolenia setigera and Thalassionema nitzschioides were the most dominant species. The assemblage at the surface and 50 m depth was quite different in the northern inshore part of the study area but similar in the southern and offshore part. Principal component analysis by the species abundance showed that the phytoplankton consisted of the communities representing the surface of the northern inshore part with the neritic-warm dinoflagellates, the Northern Korean Cold Water with the cold water diatoms and the southern and offshore part, which seems to represent the Eastern Korean Warm Water, with the warm water diatoms. At the frontal region, diatoms were mixed with warm and cold water species. Primary productivity and phytoplankton standing crops were higher at the front than the neighboring waters. Nutrients were markedly high at the Northern Korean Cold Water. Horizontal advection of the Northern Korean Cold Water accompanied by nutrient supply seems to contribute to the high phytoplankton biomass at the front.

• Korean Journal of Ecology and Environment
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• v.45 no.1
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• pp.21-33
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• 2012

Survey on the phytoplankton community structure and distribution in the upstream watershed of the East River was carried out during the period from May, 2008 to April, 2009. A total composition of phytoplankton included 159 taxa, consisting of 7 orders, 56 genera, 139 species, and 40 unidenfied species. Among those, the diatoms and green algae were more frequently found during the investigation than the other taxa. Cocconeis placentula, Cymbella minuta, Diatoma vulgare, Melosira varians, Navicula cryptocephala, Scenedesmus acuminatus v. acuminatus, were among the most common. The standing crops of the phytoplankton ranged from 86 cells $mL^{-1}$ to 1,467 cells $mL^{-1}$. The dominant species were Achnanthes minutissima, Asterionella formosa, Aulacoseira ambigua, Cocconeis placentula, Coelastrum microporum, Cyclotella sp., Cymbella affinis, C. minuta, C. tumida, Diatoma vulgare, Fragilaria capucina, F. construens, F. crotonensis, Gomphonema affine, G. clevei, Melosira varians, Merismopedia elegans, Navicula cryptocephala, N. pupula, Nitzschia tryblionella, Oscillatoria anna, O. limosa, O. tenuis v. tenuis, Pediastrum duplex v. reticulatum, Phormidium tenue, Scenedesmus acuminatus v. acuminatus, S. acutus v. acutus, S. ecornis v. ecornis, S. quadricauda v. quadricauda, Spirogyra sp., Stigeoclonium sp., Synedra acus, S. ulna, and Ulothrix sp. The most dominant species was Cymbella minuta. The diversity index, evenness index, and dominance index ranged from 1.58 to 3.10, 051 to 0.95, and 0.22 to 0.74, respectively. The phytoplankton community structure of upstream stations of the survey area was influenced by the effluent of the Doam Lake.

• Korean Journal of Environmental Biology
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• v.28 no.2
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• pp.56-63
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• 2010

In order to clarify the ecological properties of phytoplankton community, the distribution of phytoplankton and the relation of water temperature and size-fractionation measurements were studied from November 2004 to August 2005 in Youngsan River, Korea. A total of 265 phytoplankton species was identified. It consists of 48 genera and 123 species (46%) of Chlorophyceae, 27 genera and 89 species (34%) of Bacillariophyceae, 12 genera and 25 species (9%) of Cyanophyceae, respectively. From size fractionation analysis, nanophytoplankton (2~20 ${\mu}m$) dominated from early spring to early summer, and microphytoplankton (20~200 ${\mu}m$) from summer to winter. The relationship between chl-a and nanophytoplankton showed high correlation coefficient value ($r^2$=0.93) from Najudaegyo site. The correlation coefficient values between water temperature and nanophytoplankton were low except Dongkangdaegyo site which showed high value ($r^2$=0.73).

• Korean Journal of Environmental Biology
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• v.32 no.1
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• pp.35-48
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• 2014

In order to estimate the effect of additional nutrients on phytoplankton growth and horizontal phytoplankton community distribution during the autumn season in 2010 and 2011, we investigated the abiotic and biotic factors of surface and bottom waters at 20 stations of inner and offshore areas in Gwangyang Bay, Korea. Also, nutrient additional experiments were conducted to assess additional nutrient effects on phytoplankton assemblage using the surface water. In both years, the total nutrients were high at the enclosed inner bay and the mouth of Seomjin River, whereas it was low at the St.15~20 where in influenced by the surface warm water current from offshore of the bay. On the other hand, nano- and pico-sized Chl. a were gradually increased towards the outer bay and their trends were significant in 2011 than in 2010. The cryptophyta species occupied more than 85% of total phytoplankton assembleges in 2010, whereas their abundance in 2011 remainds to be 1/10 levels of 2010. Following the cryptophata species, the diatom Chaetoceros spp. and Skeletonema-like spp. were found to be dominant species. Further the biosaasy experimental results shows that the phytoplankton biomass in the +N and +NP treatments was higher compared to control and +P treatments and its trend was significant at St.8 and St.20 where nutrient concentration were low. Based on the bioassay and field survey, providing the high nutrients may have stimulated to phytoplankton growth such as S. costatum-like spp.. In particular, opportunistic micro-algae such as Cryptomonas spp. were able to achieve the high biomass under the relatively mid nutrient condition from bottom after break down of seasonal stratification in the Gwangyang Bay.