• Journal of Environmental Science International
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• v.21 no.3
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• pp.313-326
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• 2012

Three embankments, namely Changpo, Bokkil and Guil, in Chunggye Bay were investigated to assess the influence of environmental changes to phytoplankton size structure, distribution of species and standing crops. Three stations was sampled near at each embankment in Nov. 2006, Feb. 2007, May 2007 and Aug. Phytoplankton were classified into net-size (>20${\mu}m$) and nano-size (<20${\mu}m$). In summer, the freshwater discharge seemed to have influence in the decrease of salinity and in the increase of turbidity, ammonium and phosphorus concentrations. Chl a concentration and phytoplankton abundance in Feb. 2007 were observed to be generally higher in all stations compared to other periods. Net-size phytoplankton was observed to be higher in Feb. 2007 and May 2007 compared to nano-sized phytoplankton. However, there was shift in phytoplankton composition in Nov. 2006 and Aug. 2007. Phytoplankton under seven class (Bacillariophyceae, Chlorophyceae, Chrysophyceae, Cryptophyceae, Cyanophyceae, Dinophyceae, Euglenophyceae) was identified during the study period. It was found out that the major phytoplankton class was Bacillariophyceae. Phytoplankton was more diverse in autumn compared to any other season. Cyanophyceae was increased in summer. In rainy season, change in physical factors (salinity, transparency) seemed to have more influence on phytoplankton growth compared to inorganic nutrients.

• Korean Journal of Ecology and Environment
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• v.41 no.4
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• pp.530-540
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• 2008

The temporal and spatial variations of size-structured phytoplankton dynamics in Youngsan Lake were investigated to explore potential mechanims controlling the dynamics in the Youngsan Lake. Field data were collected monthly from February to October, 2003 at 6 stations along the axis of Youngsan Lake. In this study, phytoplankton (chlorophyll $\alpha$) were categorized into three size classes: micro-size ($>20{\mu}m$), nano-size ($2{\sim}20{\mu}m$) and pico-size ($<20{\mu}m$). Water temperature, light attenuation coefficients, PAR (photosynthetically active radiation) and suspended solids were measured to analyze relationship between physical-chemical properties and size structure of phytoplankton. Phytoplankton blooms developed during March, July and October in the upper region of the main stem whereas small-scaled spring bloom was observed in the lower region. The scales of phytoplankton blooms were higher in the upper regions than the lower region and blooms were predominated by micro-size class in upper region but predominated by nano-size class in lower region. Growth of size-structured phytoplankton appeared to be controlled by rather light availability than temperature-dependant metabolisms in the system. Phytoplankton growth may be also supported by ambient nutrients available in the water column from analyses of chlorophyll $\alpha$ vs. nutrient concentrations including nitrite+nitrate and orthophosphate. Growth of nano-sized phytoplankton alone appeared to be supported by orthophosphate as well as nitrite+nitrate indicating that response of phytoplankton to nutrient inputs may be size-dependent.

• Fisheries and Aquatic Sciences
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• v.25 no.1
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• pp.20-30
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• 2022

The present study was carried out to investigate the food and feeding habits of Oreochromis niloticus in Lake Shala to manage this species in this high Soda Lake. Stomachs of 226 fish (65.9%) had different food items, while those of 117 fish (34.1%) were empty. Phytoplankton was the dominant food categories occurring in 90.3% of the stomachs estimated and contributed 75.5% of the total volume. Bacillariophyceae (Nitzschia, Anomoeoneis, Navicula and Melosira) were identified as the most desired phytoplankton item. The prey items of O. niloticus differed among size classes (ANOVA, p < 0.05). The main prey items were zooplankton by the smaller-size class, and phytoplankton in fish of the larger-size class. Seasonal variation in the diet composition was evident (t-test, p < 0.05) and zooplankton, chironomids, nematodes, fish scales and detritus were important during the wet season, while phytoplankton predominates during the dry season. This study concludes that O. niloticus had a phytoplanktivores feeding mainly on phytoplankton and their feeding habits influenced by season and fish size in Lake Shala.

• Korean Journal of Remote Sensing
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• v.36 no.6_1
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• pp.1339-1348
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• 2020

Phytoplankton controls marine ecosystems in terms of nutrients, photosynthetic rate, carbon cycle, etc. and the degree of its influence on the marine environment depends on their physical size. Many studies have been attempted to identify marine phytoplankton size classes using the remote sensing techniques. One of successful approach was the three-component model which estimates the chlorophyll concentrations of three phytoplankton size classes (micro-phytoplankton; >20 ㎛, nano-; 2-20 ㎛ and pico-; <2 ㎛) as a function of total chlorophyll. Here, we examined the applicability of Geostationary Ocean Colour Imager (GOCI) to the mapping of the phytoplankton size class distribution in the East Sea. A fit of the three-component model to a biomarker pigment dataset collected in the study area for some years including a large harmful algal bloom period has been carried out to derive size-fractioned chlorophyll concentration (CHL). The tuned three-component model was applied to the hourly GOCI images to identify the fractions of each phytoplankton size class for the entire CHL. Then, we investigated the distribution of phytoplankton community in terms of the size structure in the East Sea during the harmful Cochlodinium polykrikoides blooms in the summer of 2013.

• Korean Journal of Ecology and Environment
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• v.36 no.4 s.105
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• pp.403-412
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• 2003

Temporal and spatial variations of size-structured phytoplankton (chlorophyll a) were investigated over an annual cycle (February-October, 2003) to elucidate phytoplankton dynamics in the Juam Reservoir, Chonnam. Physical properties were also measured to investigate the relationship between the properties and temporal and spatial variations of size structured phytoplankton using simple linear regression. Phytoplankton (chlorophyll a) were grouped into three size classes: micro-size(> 20 ${\mu}m$), nano-size (3-20 ${\mu}m$) and pico-size (< 3 ${\mu}m$) in this study. Physical properties included water temperature, light attenuation coefficients, PAR (photosynthetically active radiation) and turbidity. Maximum chlorophyll a was observed in April, 2003 in the lower region whereas a peak of chlorophyll a developed in October, 2003 in the upper region. Large cell-sized phytoplankton (micro-size class)were dominant in the events of the chlorophyll a peaks. Potential mechanisms in the physical properties affecting the size-structured phytoplankton dynamics in the Juam Reservoir were discussed.

• Korean Journal of Environmental Biology
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• v.24 no.1 s.61
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• pp.7-18
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• 2006

Samples were collected from five stations monthly from October 2003 to September 2004 to investigate seasonal variation of size structure of phytoplankton and relationship between size-fractionated phytoplankton and environmental factors in the Asan Bay. The contribution of large cells (microphytoplankton, $>20\;{\mu}m$) to total concentrations of chlorophyll $\alpha$ was higher than small cells (nanophytoplankton, $3\sim20\;{\mu}m$; picophytoplankton, $<3\;{\mu}m$) during the sampling period. Especially, large cells contributed 80% to the total chlorophyll a from February, 2004 to April 2004 when chlorophyll $\alpha$ concentrations were high. The size structure of phytoplankton shifted from micro-size class to nano-size class and picophytoplankton rapidly increased when phytoplankton biomass decreased in May 2004. Microphytoplankton exhibited a high biomass in the upper region during winter-spring season whereas nano- and picophytoplankton showed two peaks in the middle-lower regions (Station 3,5) during spring and summer. Microphytoplankton are most likely controlled by water temperature and nutrient supply during the cold season whereas nano- and picophytoplankton may be affected by stratification, light exposure during the warm season.

• Journal of Microbiology
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• v.34 no.4
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• pp.300-304
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• 1996

To define the effects of zooplankton and phytoplankton to bacteria, bacterial numbers, frequency of dividing cells (FDC) and size distribution were performed with image analysis in the surface layer of Lake Soyang. In August 1992, when Anabaena was blooming, the bacterial number increased at daytime. Bacterial numbers and FDC value had a negative correlation (r = 0.83, P < 0.01). Bacterial size spectrums were dynamically changed during the day and night, especially the small bacteria less than $0.5\;{\mu}m^3$. Meanwhile, in October, after the bloom, the bacterial number was only one third of that in August, even though the FDC was higher than that in August. The bacterial numbers of small size class dropped at 13:00. But the size spectrums were relatively constant during the night time. These results suggest that the bacterial growth was tightly coupled with phytoplankton during Anabaena bloom. And after the bloom, the bacterial number was controlled grazing activity of zooplankton at daytime.

• Ocean and Polar Research
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• v.34 no.2
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• pp.201-218
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• 2012

The purpose of this study is to investigate climatological variations from the sea surface temperature (SST), chlorophyll-a concentration (Chl-a), and phytoplankton size class (PSC), using NOAA AVHRR, SeaWiFS, and MODIS data in the South Sea of Korea (SSK) and East China Sea (ECS). 26-year monthly SST and 13-year monthly Chl-a and PSC data, separated by whole and nine-different areas, were used to understand seasonal and inter-annual variations. SST and Chl-a clearly showed seasonal variations: higher SST and Chl-a were observed during the summer and spring, and lower values occurred during the winter and summer. The annual and monthly SST over 26 years increased by $0.2{\sim}1.0^{\circ}C$. The annual and monthly Chl-a concentration over 13 years decreased by $0.2{\sim}1.1mg/m^3$. To determine more detailed spatial and temporal variations, we used the combined data with monthly SST, Chl-a, and PSC. Between 1998 and 2010, the inter-annual trend of Chl-a decreased, with decreasing micro- and nano-size plankton, and increasing pico-size plankton. In regional analysis, the west region of the study area was spatially and temporally correlated with the area dominated by decreasing micro-size plankton; while the east region was less sensitive to coastal and land effects, and was dominated by increasing pico-size plankton. This phenomenon is better related to one or more forcing factors: the increased stratification of ocean driven by changes occurring in spatial variations of the SST caused limited contributions of nutrients and changed marine ecosystems in the study area.

• 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.

• Korean Journal of Environmental Biology
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• v.34 no.1
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• pp.18-29
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• 2016

The effects of water temperature, salinity, water column nutrient contents, and phytoplankton primary productivity on pigment composition and concentration, as well as primary productivity of Pyropia yezoensis Ueda purple lavers were studied at the primary cultivation areas in the Manho (Jindo-Haenam) region on the southwestern coast of Korea in March 2014. The water temperature was $9.1{\sim}9.6^{\circ}C$, salinity was 32.5~33.1, and transparency was 0.7~1.5 m. The shallow euphotic depth resulted from the high turbidity. Water column dissolved inorganic nitrogen (DIN), dissolved inorganic phosphorus (DIP), and silicate concentrations were $3.59{\sim}5.73{\mu}M$, $0.16{\sim}0.41{\mu}M$, and $12.41{\sim}13.94{\mu}M$, respectively. Chlorophyll a (Chl a) concentration was $0.51{\sim}1.25{\mu}g\;L^{-1}$. Nanoplankton ($0.7{\sim}20{\mu}m$ size class) accounted for 58% of the total Chl a concentration. Fucoxanthin was the dominant photosynthetic pigment at all sites. Microplankton ($20{\sim}200{\mu}m$ size class) accounted for 64% of the total fucoxanthin concentration. The primary productivity of phytoplankton was $57.72{\pm}4.67(51.05{\sim}66.71)mg\;C\;m^{-2}d^{-1}$. The nanoplankton ($0.7{\sim}20{\mu}m$ size class) accounted for 77% of the total phytoplankton primary productivity. The calculated phytoplankton primary productivity was $11,337kg\;C\;d^{-1}$. The primary productivity of Pyropia blades was $1,926{\pm}192(1,102{\sim}2,597)mg\;C\:m^{-2}d^{-1}$, i.e., calculated as $39,295kg\;C\;d^{-1}$. The total primary productivity of phytoplankton and Pyropia blades was $50,632kg\;C\;d^{-1}$. The primary productivity of Pyropia blades was 3.5 times greater than that of phytoplankton in the Manho region on the southwestern coast of Korea.