• Ocean and Polar Research
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• v.27 no.3
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• pp.341-349
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• 2005

Temporal variation of the natural planktonic community in the Southern Sea of Korea was investigated by using low floating enclosed bags (3.2m deep and 2,500 liter) in order to understand the effect of enriched nitrate on the planktonic community in the spring (March-April) of 2002. Prior to beginning the incubation, the bags were placed in two different concentrations of nitrate, which consisted of control (ambient water) and experimental mesocosms (final concentration of $12{\mu}M$). The nitrate concentration in the experimental mesocosms remained significantly higher than those in control mesocosms throughout the study period (ANOYA, p<0.001). Following the addition of nitrate, abundance and chi-a concentration of phytoplankton peaked on Day 1, when diatoms established the peak in the experimental mesocosms. Diatoms consisted mainly of Thalasxiosira decipiens, Pseudo-nitzschia pungem, Leptocylindrus danicu, Thalassionema nitzschioides, Chaetoceros pseudocrinitus and Actinoptychus senariu. However, the peak did not lead to the difference in abundance and composition of phytoplankton between control and experimental mesocosms during the study period. The dinoflagellates began to increase soon after the diatoms decreased in all mesocosms. Copepods, as a dominant group in the rnosozooplankton community, showed no immediate peak in relation to the nitrate addition, but only their own developmental process from the eggs to adult stage during the study period. The bottom-up control from enriched nitrate via phytoplankton to adult copepods was not distinguished in terms of the abundance of the planktonic community. This might stem from the relatively low nitrate availability of phytoplankton at no N-limited seawater and the weak coupling between rapidly sunken diatoms and copepods through the water column.

• Journal of the Korean Association of Geographic Information Studies
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• v.10 no.3
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• pp.40-48
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• 2007

We analyze relation between phytoplankton and marine environment based on data such as water temperature, phytoplankton, zooplankton, nutrient collected from the southern coast of Korea in the summer, 2004. The water temperature range of the study area was $20.5{\sim}31.5^{\circ}C$ and there was formed a water temperature frontal zone from $20.5^{\circ}C$ to $25.0^{\circ}C$ in Geojedo southern coast and Geomundo island. Especially, high density of nutrients were shown in the southern coast of Geojedo in which water temperature frontal zone was formed strongly, the concentration of chlorophyll-a which is appeared at the highest rate among the phytoplankton pigments was shown more than $0.4{\mu}g/L$ in the inside of frontal zone and zooplankton biomass was than $500mg/m^2$ in that area.

• Korean Journal of Ecology and Environment
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• v.44 no.3
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• pp.280-291
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• 2011

Bottom-up approaches to control of Microcystis aeruginosa blooms were comparatively investigated through an in situ mesocosm experiment using aquatic plants (Iris pseudoacorus). In the mesocosm experiments, floating I. pseudoacorus, seemed to be effective in controlling massive M. aeruginosa blooms in an agricultural reservoir, exhibiting a close coupling with temporal variations in Chl-a and DO concentration. Shading by floating I. pseudoacorus resulted in a reduced phytoplankton abundance inhibiting light energy availability. Moreover, I. pseudoacorus may suppress phytoplankton growth through the excretion of chemical substances, likes a allelopathy, that inhibit phytoplankton photosynthetic activity. The $^{15}N$ atom % of I. pseudoacorus showed higher values than POM, suggesting that I. pseudoacorus assimilates DIN predominantly compared to phytoplankton, which was mostly M. aeruginosa. This result strongly suggests that the M. aeruginosa bloom should be regulated by aquatic plants, like I. pseudoacorus, this approach can affect zooplankton composition. This is the first study that has used stable isotope tracers to evaluate the biomanipulation efficiency through floating I. pseudoacorus.

• 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.33 no.1
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• pp.21-34
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• 2011

We determined potential meso-scale benthic-pelagic ecosystem coupling in the north equatorial Pacific by comparing surface chl-a concentration with sediment bacterial abundance and adenosine triphosphate (ATP) concentration (indication of active biomass). Water and sediment samples were latitudinally collected between 5 and $11^{\circ}N$ along $131.5^{\circ}W$. Physical water properties of this area are characterized with three major currents: North Equatorial Current (NEC), North Equatorial Count Current (NECC), and South Equatorial Current (SEC). The divergence and convergence of the surface water occur at the boundaries where these currents anti-flow. This low latitude area ($5{\sim}7^{\circ}N$) appears to show high pelagic productivity (mean phytoplankton biomass=$1266.0\;mgC\;m^{-2}$) due to the supplement of high nutrients from nutrient-enriched deep-water via vertical mixing. But the high latitude area ($9{\sim}11^{\circ}N$) with the strong stratification exhibits low surface productivity (mean phytoplankton biomass=$603.1\;mgC\;m^{-2}$). Bacterial cell number (BCN) and ATP appeared to be the highest at the superficial layer and reduced with depth of sediment. Latitudinally, sediment BCN from low latitude ($5{\sim}7^{\circ}N$) was $9.8{\times}10^8\;cells\;cm^{-2}$, which appeared to be 3-times higher than that from high latitude ($9{\sim}11^{\circ}N$; $2.9{\times}10^8\;cells\;cm^{-2}$). Furthermore, sedimentary ATP at the low latitude ($56.2\;ng\;cm^{-2}$) appeared to be much higher than that of the high latitude ($3.3\;ng\;cm^{-2}$). According to regression analysis of these data, more than 85% of the spatial variation of benthic microbial biomass was significantly explained by the phytoplankton biomass in surface water. Therefore, the results of this study suggest that benthic productivity in this area is strongly coupled with pelagic productivity.

• Proceedings of the Korea Society of Environmental Biology Conference
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• 2004.05a
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• pp.63-63
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• 2004

• Journal of the Korean Society of Marine Environment & Safety
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• v.18 no.6
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• pp.520-529
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• 2012

Geographic distribution and species composition of phytoplankton were investigated in Jinhae Bay for 12 months. Total 158 species were found including 95 bacillariophyceae, 58 dinophyceae, 1 euglenoids, and 4 dictyochaceae. The total cell numbers of phytoplakton ranged from $4.0{\times}10^3{\sim}9.0{\times}10^7\;cells{\cdot}L^{-1}$. Highest and lowest amounts of cells were found in July (Chl.a 13.19 $mg{\cdot}m^{-3}$) and March(Chl.a 3.44 $mg{\cdot}m^{-3}$), respectively. Leptocylindrus danicus and Pseudo-nitzschia spp. were dominant in spring, and Dactliosolen fragilissimus and Pseudo-nitzschia spp. were dominant in summer. Chaetoceros spp. and Skeletonema spp. were domonant in autumn and winter. The amounts of nitrogen and phosphorus were also measured during the survey. Higher ratio of nitrogen (DIN : DIP = 28 : 1) was found in the east Jinhae Bay compared to the ratio of the west Jnhae Bay that showed 14 : 1 of N : P ratio. The total amounts of nitrogen, phosphorus and Chl.a were also higher in the east Jinhae Bay compared to the west area. The geographic differences between the east and west of Jinhae Bay were also discussed along with phytoplankton compostion.

• Journal of the Korean Society for Marine Environment & Energy
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• v.15 no.3
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• pp.198-207
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• 2012

In this study, we investigated the effect of ocean fertilization by deep sea water, using an ecosystem model which contains not only phytoplankton but also zooplankton. The model is based on NEMURO which consists of eleven compartments - two species of phytoplankton, three species of zooplankton, $NO_3$, $NH_4$, $Si(OH)_4$, particulate organic nitrogen, dissolved organic nitrogen and particulate silicon. We introduced nitrogen cell quota in the both species of phytoplankton, and silicon cell quota in the large phytoplankton in addition to the eleven compartments of NEMURO. We made the experiment at Izu Oshima Island in order to investigate the effect of ocean fertilization. In this experiment, we could not find clear differences between the cases with and without deep sea water. We investigated the causes of the experiment results by the model simulations. One of the causes was high concentrations of nutrients in surface seawater used in the experiment. Another was that the increase of total concentration of inorganic nitrogen does not necessarily accelerate the photosynthetic rate because inorganic nitrogen uptake rate is related to the ratio of $NO_3$ to $NH_4$. Because the model can represent the results of the experiment, we investigated the effect of ocean fertilization by deep sea water using this model. We found that the effect of ocean fertilization hardly appeared when the interval of the addition of deep sea water was too short, or the amount of deep sea water was too much. It is supposed that if the addition of deep sea water is too frequent or too much, the dilution of plankton's concentrations will exceed the effect of promoting phytoplankton's photosynthesis.

• Journal of the Korean Society of Marine Environment & Safety
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• v.12 no.3 s.26
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• pp.165-170
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• 2006

In this study, organic matters production was calculated with long term data in Wando costal area where was selected for non influent of fresh water. The objective of this study was to evaluate relationship between nutrients and phytoplankton and, between phytoplankton and organic matter. The result of DIN was the highest with 0.138 mg/L in winter season and the lowest with 0.052 mg/L in summer season. Similarly, DIP was shown to be 0. 017 mg/L in winter and 0.011 mg/L in summer. Limiting nutrient was revealed with nitrogen in Wando costal area. Specially in summer season, nitrogen limitation was the greatest with 10.5 of N/P ratio. Chl. -a was increased 80%, 108% in spring and summer compare with winter. COD was the lowest with 0.84 mg/L in winter and the highest with 1.10 mg/L in summer. The interrelation between nutrients and Chl. -a was high. Relationship $coefficient(r^2)$ were 0.93(P<0.05), 0.89(P <0.05) between DIN and Chi. -a, DIP and Chl. -a. This results suggest dissolved nutrients might be utilized at the production of phytoplankton. Also Relationship $coefficient(r^2)$ was 0.77(P<0.05) between Chl. -a and COD. COD production rate was calculated with regression equation. The COD production rate was 17% in winter and 36% in summer. It was revealed nutrients were decreased according to temperature increasing and then Phytoplankton and organic matter were increased. The Relationship of Nutrients, Chl. -a and COD was very high.

• Journal of Environmental Science International
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• v.12 no.7
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• pp.725-733
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• 2003

This survey was carried out to assess important species of phytoplankton in the ocean and bay in Korea from 32 references. The number of important species assessed from 50 genera 116 species. Of them, Bacillariophycea(diatoms) 34 genera 89 speceis(76.6%), Dinophyceae(dinoflagellates) 11 genera 22 species(18.9%), Chrysophyceae 2 genera 2 species(1.7%), Cyanophycea(blue-green algae), Raphidophyceae, Euglenophyceae(euglenoids) 1 genera 1 species(0.9%) respectively. By ecological characters, the number of dominant species were 79 species including Actinoptychus seranius, 50 species including Coscinodiscus centralis were recorded as frequently apperaing species and 36 species including Cochlodinium polykrikoides were recorded as red-tide causative organism. Also, 11 species including Prorocentrum micans were surveyed as the indicator including all ecological characters.