• Korean Journal of Ecology and Environment
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• v.33 no.3 s.91
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• pp.197-205
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• 2000

Factors most strongly related to zooplankton growth rates were studied along a lake and a river stretch in the middle part of the lowland River Spree. The study was conducted at the lake inflow (S1), the lake outflow (S2), and at the end of a 21 km stretch of the outflow (S3) from March to November of 1999. Total zooplankton biomass increased significantly at S2 and then sharply decreased at S3. The abundance of microzooplankton (rotifers and nauplii) was strongly higher than macrozooplankton (cladocerans and copepodids) at all station. However, macrozooplankton biomass (${\mu}$g dw 1$^{-1}$) was similar or much higher than microzooplankton biomass. Large-bodied cladocerans (Daphnia cucullata) dominated at S2 while small-bodied cladocerans (Bosmina longirostris) dominated at S1 and S3. Patterns in growth rates (r$_{t}$ in d$^{-1}$ of the major zooplankton community were greatly different between S1 and S2 (lake stretch) and between S2 and S3 (river stretch). In the lake, growth rates generally were positive, while values of growth rates were negative in the river stretch. Among the environmental variables considered, partial retention time (PRT, d$^{-1}$) seemed to play the most important role in determining characteristics of the zooplankton community structure in the middle part of River Spree.

• Journal of the korean society of oceanography
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• v.32 no.3
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• pp.145-155
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• 1997

The distribution of microzooplankton and hydrographic variables were measured in the Virginia portion of Chesapeake Bay and its major rivers. Samples were collected at 14 locations at monthly interval from September 1993 through December 1995. Ciliates were numerically dominated (>90%) and copepod nauplii comprised highest proportion of the total microzooplankton biomass (>77%). Copepod nauplii and ciliates were the most abundant at oligohaline water and rotifers at freshwater. Total microzooplankton density and biomass were usually higher at oligohaline stations than fresh water and polyhaline stations. Despite high nutrient concentration and phytoplankton density at eutrophic water, micro- and mesozooplankton biomass were low. Mesozooplankton were relatively abundant at polyhaline stations. The comparison between annual mean biomass of ciliates (12.7 ${\mu$}gC/1) and that of autotrophic picoplankton (13.5 {$\mu$}gC/1) revealed that ciliates were a major consumer of picoplankton production. The secondary production by ciliates was 12.7 ${\mu}$gC/1/day, representing 5% of the annual mean primary production in Chesapeake Bay, Total microzooplankton comprised 84% of the total zooplankton carbon content, representing five times higher than mesozooplankton biomass.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.5 no.2
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• pp.141-145
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• 2000

The daily fluctuations of occurrence rate and standing stock of zooplankton, the relationship between dry and wet weights of gelatinous zooplankton, and the size distributions of body length and body weight of zooplankton were investigated in the sea around Cheju Island from September 1996 to August 1997. Mean ratios of wet to dry weights were 66.46 (raging from 47.05 to 84.64) in the gelatinous zooplankton and 10.89 (raging 9.21 to 14.85) in the non-gelatinous zooplankton which consisted of crustaceans such as copepods, decapods, mysids, and ostracods etc. Rarios of gelatinous zooplankton to non-gelatinous zooplankton (G/NG) in wet weight was 0.99 (0.28-2.30), indicating high occurrence rate of gelatinous in the study area. The seasonal and diel fluctuations of the gelatinous zooplankton were very large, and G/NG ratios greatly varied with seasons and dat/night cycles. The size distributions of body length of zooplankton (250-500 urn: 35.5% in maximum), and wet (0.1-0.2 mg: 34.4%) and dry weights (0.025-0.05 mg: 44.8%) showed much difference depending composition of the zooplankton groups. These results show that quantitative estimations of zooplankton produc- tivity only based on wet weight should be corrected to better understand and evaluate marine resources in Korean waters.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.55 no.2
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• pp.154-170
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• 2022

The zooplankton composition, abundance, community structure, and species diversity in the major commercial fishery species spawning grounds in the southern coast of Korea were investigated in this study. A total of 80 taxa were sampled, with the mean abundance range of 5,612-11,720 ind. m^-3 and the mean biomass range of 41.6-1,086.8 mg m^-3. The dominant species were Paracalanus copepodites, Paracalanus parvus s. l., Oithona copepodites, Paracalanus nauplii, Noctiluca scintillans, Oithona similis, and Ditrichocorycaeus affinis. The species diversity indices were highest in August, suggesting that diversity is influenced by neritic and oceanic warm-water species. A cluster analysis with non-metric multidimensional scaling (nMDS) revealed three groups of zooplankton communities. The April and May samples clustered into Group A, having the highest mean total zooplankton abundance and lowest species diversity, consisting mainly of temperate species located in the middle region of the southern coast of Korea. Cluster Group B was from the early summer season (June) and contained the highest species diversity with some oceanic and neritic zooplankton species. Cluster Group C from the summer season (July and August) mainly comprised P. parvus s. l. and O. similis. The redundancy analysis (RDA) indicated that abundance is positively correlated with salinity, and chlorophyll-a concentrations.

• Journal of the Korean Society of Marine Environment & Safety
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• v.16 no.3
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• pp.259-268
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• 2010

Data on squid catches by the Korean jig fishery in sea blocks ($30'{\times}30'$), water temperatures at depth(30m, 50m and 100m) and zooplankton biomass in the East Sea from 1980 to 1999 were analyzed to examine the mechanism of formation of the high density stock area. Japanese common squid (Todarodes pacificus) catch in the East Sea was low in 1980s, while the catch was high in 1990s. The five sea blocks (No. 76, 82, 83, 87, 88) of the southern part in the eastern coastal waters of Korea showed high levels of percentage of total catch (35.1%), whereas the four sea blocks (No. 65, 71, 72, 78) of the coastal waters of Uleung Island showed high levels of percentage of CPUE (61.2%) for 20 years. Squid catches showed monthly fluctuations according to the vertical distribution of optimum water temperature for fishing ($14^{\circ}C{\sim}19^{\circ}C$). High total catch and high CPUE area matched well with $10^{\circ}C$ isothermal lines at 100m depth indicating northern limiting of Tsushima Warm Current, and temporal and spatial change in $10^{\circ}C$ isothermal line caused the change in total catch and CPUE. Horizontal distribution of zooplankton biomass by sea block was not matched well with those of total catch and CPUE, however pattern of time-series change in total zooplankton biomass was similar to that in total squid catch.

• Korean Journal of Ecology and Environment
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• v.36 no.3 s.104
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• pp.286-294
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• 2003

This study was attempted to understand seasonal dynamics of phyto- and zooplankton communities in shallow, eutrophic Lake llgam and to compare them with the PEG (Plankton Ecology Group) model. Seasonal succession pattern of phytoplankton community was similar to PEG model as Chlorophyceae and Baciliphyceae increase during spring and autumn fellowed by increase of Cyanophyceae. However, based on the cell density and biomass, a dominant phytoplankton community differed with PEG model: Cyanophyceae had been a dominant community throughout a year, except for ice-cover period during which Chlorophyceae was a dominant group. In spring, when ice melted and dissolved nutrients in water column increased, the increase of Chlorophyceae occurred: when nutrients (DIN and DIP) rapidly decreased, Cyanophyceae increase occurred. Microcystis, Oscillatoria, Lyngbya, Merismopedia were maior dominant species of Cyanophyceae and their cell density and/or biomass was the highest in October 2000 (12.9${\pm}$5.8${\times}10^5$ cells/ml, 3.5${\pm}$0.9${\times}10^3{\mu}gC/l$). Cyanophyceae biomass showed positive relationship with chlorophyll a ($r^2$ = 0.71,P< 0.001) and TP concentration ($r^2$ = 0.62, P< 0.001). Small-sized rotifers such as Keratella cochlearis, increased between March and May when Chlorophyceae increased. Both high standing crop of copepods and cladocerans, such as Diaphanosoma brachyrum and Bosmina longirostris occurred between June and September accompanied with the increase of Dinophyceae and Bacillariophyceae. There was no evidence that clear-water phase was caused by zooplankton grazing. The diversity and evenness index of phyto- and/or zooplankton increased with chlorophyll a concentration. These results suggest zooplankton grazing and limiting nutrient deficiency could lead to change of phytoplankton biomass, but not the phytoplankton community in Lake llgam.

• Journal of Ecology and Environment
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• v.40 no.1
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• pp.66-74
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• 2016

Background: When developing water quality improvement strategies for eutrophic lakes, questions may arise about the relative importance of point sources and nonpoint sources of phosphorus. For example, there is some skepticism regarding the effectiveness of partial reductions in phosphorus loading; because phosphorus concentrations are too high in hypertrophic lakes, in-lake phosphorus concentrations might still remain within typical range for eutrophic lakes even after the reduction of phosphorus loading. For this study, water quality and the phytoplankton and zooplankton communities were monitored in a hypertrophic reservoir (Lake Wangsong) before and after the reduction of phosphorus loading from a point source (a sewage treatment plant) by the installation of a chemical phosphorus-removal process. Results: Before phosphorus removal, Lake Wangsong was classified as hypertrophic with a median phosphorus concentration of $0.232mg\;L^{-1}$ and a median chlorophyll-a concentration of $112mg\;L^{-1}$. The dominant phytoplankton were filamentous cyanobacteria for the most of the ice-free season. Following the installation of the advanced treatment process, phosphorus concentrations were reduced to $81mg\;L^{-1}$, and the N/P atomic ratio increased from 42 to 102. Chlorophyll-a concentrations decreased to $42{\mu}g\;L^{-1}$, and the duration of cyanobacterial dominance was confined to the summer season. Cyanobacteria in spring and autumn were replaced by diatoms and cryptomonads. Filamentous cyanobacteria in summer were replaced by colony-forming unicellular Microcystis spp. It was remarkable that zooplankton biomass increased despite the decrease in phytoplankton biomass, and especially cladoceran zooplankton which increased drastically. These responses to the reduction of point source P loading to Lake Wangsong imply that reducing the point source P loading can have a big impact even when nonpoint sources account for a large fraction of the total annual phosphorus loading. Conclusions: Our results also show that the phytoplankton community can shift to decreased cyanobacterial dominance and the zooplankton community can shift to higher cladoceran dominance, even when phosphorus concentrations remain within the typical range for eutrophic lakes following the reduction of phosphorus loading.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.29 no.3
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• pp.271-278
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• 1996

Daytime surface zooplankton were collected bimonthly from April 1993 to March 1994 at six stations around upwelling and adjacent areas of Cosan, western part of Cheju Island. This paper deals with the occurrence, biomass and some other characteristics of zooplankton in these areas. Copepods had two peaks in the abundance in June $(235\;ind./m^3)$ and November $(301\;ind./m^3)$, but were not especially abundant in upwelling area. While gelatinous organisms seldom occurred in the upwelling, and the outer area with high density of $75\;ind./m^3$ (in June) and $458\;ind./m^3$ (in November) at the intermediate area, seasonal values of biomass with mean of $35.8\;mg/m^3$ were the highest in November and the lowest in January. Abundance of chaetognaths (mainly Sagitta spp.) ranged $15\~37\;inds./m^3$ and carcasses of Sagitta occurred very highly in the upwelling area in June ($54\%$ of total Sagitta organisms) and November $(70.5\%)$. Especially $48\~77\%$ of Sagitta individuals in upwelling area in November was attached by Oncaea mediterranea, O. venusta and Candacia bipinata. Pteropods with shells were sampled only in the upwelling area during strong upwelling season (November, $27\~64\;ind./m^3$), indicating the characteristics of ascending behavioral adaptation from the bottom water by upwelling.

• 한국해양학회지
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• v.27 no.4
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• pp.268-276
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• 1992

Multitrophic interactions among gelatinous planktivores, zooplankton, and phytoplankton were in vestigated in Reeves Bay. New York from mid-March to July in 1989 to evaluate the top-down effect by gelatinous macrozooplankton on the Gyrodinium aureolum bloom through cascading tropic interactions. Zooplankton abundances reached maximal density following a decrease in gelatinous macrozooplankton (hydromedusae and scyphomedusae) abundances, and phytoplankton biomass was low at this time. Subsequently, as ctenophore populations increased zooplankton abundances decreased sharply, and the cell concnetration of G. aureolum began to increase. This field observation supports that the top-down control by gelatinous macrozooplankton on grazers, resulting in low grazing pressure on phytoplankton, can cause an algal bloom. The minimal zooplankton grazing measured using /SUP 14/C tracer technique during the bloom period indicated that zooplankton did not prefer G. aureolum as a good source.

• Journal of the Korean Society of Marine Environment & Safety
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• v.15 no.4
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• pp.339-344
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• 2009

The joint cruises of six times between Korea and China were carried out for a better understanding of the environmental and oceanographical characteristics of the Yellow Sea for 6 years from 1998 to 2003. Zooplankton samples were collected one time per year at 24 stations on 3 lines of the Yellow Sea. The aim of this study is to understand the seasonal fluctuation of zooplankton community in the Yellow Sea. There is no trend on the spatio-temporal distribution of zooplankton. Copepoda, the major taxon of the Yellow Sea, was high in distribution in the eastern part and Chaetognatha in the western part of the Yellow Sea. In this results, the dominant copepods were Calanus sinicus, Paracalanus parvus s.l., Oithona atlantica, and Corycaeus affinis during the study periods. The density fluctuation of these dominant species may be an important factor in determining the fisheries resource of the Yellow Sea.