• Korean Journal of Fisheries and Aquatic Sciences
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• v.54 no.4
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• pp.445-455
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• 2021

We aimed to study the structure of the zooplankton community in the Southern Sea of the Republic of Korea. Zooplankton samples were collected in February (winter), May (spring), August (summer), and November (autumn) of 2020. The zooplankton collected belonged to a total of 166 taxa and 12 phyla, including some unidentified individuals and those from upper taxa. The number of taxa collected were the highest in winter at 117, and the lowest in May at 93. The dominant taxa were Oikopleura spp. in the winter, Gastropoda larvae in the spring, and Paracalanus parvus s.l. in the summer and autumn. The community structure of the zooplankton was clearly distinguishable between the seasons. The mean density of zooplankton was the highest in autumn and the lowest in summer (576,039 and 313,000 individuals/1,000 m³, respectively). Based on the analysis of relationships between the density of the six major taxa and environmental factors, a significant correlation (P<0.05) between the four taxa and environmental factors was found. Therefore, in order to understand changes in the zooplankton community, quantitative and qualitative investigations of biological factors as well as physical factors should be conducted.

• Ocean and Polar Research
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• v.31 no.4
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• pp.327-338
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• 2009

Zooplankton community structure was investigated in the Saemangeum region in March, May, July and October of 2007 and 2008 in order to understand the potential effect of post construction of Saemangeum dyke on their temporal and spatial distribution. Mean abundance of zooplankton in the inner and outer area of the dyke, except for dinoflagellate Noctiluca scintillans, ranged from 173 to 15,830 ind.m$^{-3}$, showing higher variability in the inner area compared to the outer area. Zooplankton abundance was higher in the outer area than the inner area in 2007, and vice versa in 2008. In the inner area of the dyke, zooplankton abundance was the highest in May 2007 and March 2008. In the outer area of the dyke, abundance was the highest in October 2007 and July 2008. Brackish species such as Tortanus derjugini and Pseudodiaptomus inopinus were dominant prior to construction of the dyke, and appeared less frequently in the inner area. Marine zooplankton taxa such as juvenile hydromedusa, and calanoid copepods Acartiahongi and Paracalanus parvus s.l. dominated both areas of the dyke. In CCA analysis, zooplankton community structure in the inner and outer area was similar in March and May, but different in July and October. Temperature, salinity and COD were important environmental factors affecting zooplankton community structure. These results suggest that zooplankton community structure in the inner and outer area of Saemangeum dyke are significantly affected by whether the sluice gates are closed or open.

• Korean Journal of Ecology and Environment
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• v.45 no.4
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• pp.490-498
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• 2012

This study demonstrates the investigation of zooplankton communities (e.g. rotifers, cladocerans and copepods) and environmentally related driving factors (e.g. elevation, area size, water depth, types of dike construction, and bottom substrates). We hypothesized that zooplankton community structure and composition would be influenced by ambient driving forces in different scales of the irrigation ponds (Dumbeong). A total of 66 zooplankton species/groups (56 rotifers, 9 cladocerans, 1 copepods) were found and identified at 45 Dumbeong of Goseong region (i.e. Goseong-gun) in 2011. The rotifers occupied 84.9% of the total zooplankton abundance. We could categorize a clear separation of zooplankton communities into 4 different patterns based on cluster analysis. Zooplankton diversities in Dumbeongs were lower than those in natural ponds or wetlands. In addition, community structure of zooplankton was also simpler and had a broken stick distribution based on SHE analysis. Species composition in each Dumbeong was not significantly discriminated each other. The result of canonical correspondence analysis (CCA) pinpointed that significant influential variables upon zooplankton community were dissolved oxygen percent saturation, pH, and Dumbeong's material. This study indicated that morphological type of the Dumbeong and its water quality could determine the community structure of zooplankton. Furthermore, the connectivity between ambient habitats and materials could be necessary to be rigorously considered in respect to producing the Dumbeongs to subsidize alternative habitats for wetland ecosystem in freshwater landscape.

• Journal of Korean Society on Water Environment
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• v.39 no.3
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• pp.215-222
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• 2023

Zooplankton are primary consumers in the food web connecting primary producers and predators such as small fish, playing an important role in energy transfer in aquatic ecosystems. Therefore, it is essential to understand the zooplankton community structure in material cycle and energy flow in aquatic ecosystems. Zooplankton in large rivers with a low flow rate would distribute vertically as in lakes. In this study, we collected zooplankton by surface water filtration and vertical haul method with 64 ㎛-mesh plankton net at three stations (ND-1, ND-2, ND-3) in Nakdong River fortnightly from June 2018 to December 2019. Species composition and individual densities were analyzed. All three stations showed differences in relative abundance of zooplankton groups between surface water and vertical integrated water, with the largest difference shown in the deepest station, ND-2. In vertically integrated water at ND-2, the relative abundance of rotifera was low by a maximum of 25% and that of cladocera was high by a maximum of 22% compared to surface water samples. These results indicate that surface water filtration method is not enough to represent the community structure of zooplankton compared to the vertical haul method in large rivers.

• Korean Journal of Environmental Biology
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• v.30 no.1
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• pp.64-70
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• 2012

This study compares the abundance and community structure of zooplankton organisms from the littoral and pelagic regions, and considers particularly trophic levels vs. zooplankton abundances. Zooplankton samples, collected every 3 months over a year from 2010 to 2011 at 29 temperate lakes and reservoirs, which belong to two different river basins (Youngsan and Seomjin River). The spatial pattern of rotifers was similar to that of total zooplankton abundance. This reflected the fact that rotifers strongly dominated the zooplankton community. There were considerable spatial variations in total zooplankton abundance (ANOVA, p<0.01), while there were no significant differences both in littoral and pelagic regions in abundance of zooplankton (ANOVA, p=0.205). The mean abundance of zooplankton in eutrophic systems was much higher than that of mesotrophic systems, while significant difference in number of species and diversity index were not shown in both trophic systems.

• Journal of Korean Society on Water Environment
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• v.26 no.5
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• pp.850-859
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• 2010

Structure and succession of zooplankton community studied by hydraulic and ecological characteristics targeting the five lakes in the Han river system from March to December 2008. Results separated by river-type lake and lake-type lake depending on the type of hydraulic, Paldang lake and Cheongpyeong lake were river-type lake, while Chungju lake, Hoengseong lake and Doam lake was lake-type lake. The Paldang lake was a eutrophic lake, zooplankton community density and species number were the most among the five lakes. Relative dominance of the rotifera was the largest and the yearly first dominant species was a small cladocera Bosmina longirostris. The Cheongpyeong lake was a mesotrophic-eutrophic lake, hydraulic characteristics and zooplankton community changes were similar the Paldang lake. Relative dominance of the cladocera was the largest and the yearly first dominant species was a small cladocera Bosmina longirostris. The Chungju lake was a oligotrophic-mesotrophic lake, zooplankton community density was the least among the five lakes. Relative dominance of the copepoda was the largest and the yearly first dominant species was a large cladocera Daphnia galeata. The Hoengseong lake was a oligotrophic-mesotrophic lake, relative dominance of the rotifera was the largest and the yearly first dominant species was a small cladocera Bosmina longirostris. The Doam lake was a mesotrophic-eutrophic lake, zooplankton community density showed dramatic difference at the investigation time. Relative dominance of the rotifera was the largest and the yearly first dominant species was the copepoda Nauplius.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.54 no.1
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• pp.64-72
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• 2021

The feeding habits of the Japanese jack mackerel Trachurus japonicus were studied in the Southern Sea of the Republic of Korea. To assess the effects of season, sampling was conducted in February (winter), May (spring), and August (summer), 2020. The total length of each fish was measured in 1 cm intervals. Diet composition showed the highest species diversity during winter. Diet composition changed from copepods to euphausiids as the total length of jack mackerel increased, except during winter. The most important seasonal prey were copepods in winter and summer and euphausiids in spring. Species diversity of the zooplankton community structure was highest in winter. Among the zooplankton communities, copepods were dominant in all seasons. Species with a high electivity index in all seasons were relatively large zooplankton of ≥2 mm. Jack mackerel had ontogenetic diet change, exhibited diet selectivity depending on size, and its feeding habits were affected by the zooplankton community structure.

• The Korean Journal of Ecology
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• v.19 no.6
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• pp.543-562
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• 1996

Zooplankton community structure and the factors correlated with community differences were examined in sandusky Bay (SB) and the open water of Lake Erie (LE, U.S.A.). SB zooplankton communities differed from those in LE by having a greater rotifer density and species richness. Keratella spp., Brachionus spp., and Pompholyx complanata dominated SB rotifers; Brachionus and Pompholyx were rarely seen in LE. Of 19 rotifer species observed, nine species were found only at SB sites. Ordination of zooplankton species abundance by detrended correspondence analysis (DCA) showed an overlap between SB and LE sites, but indicated a portion of the space that was occupied by only SB communities. The seasonal trajectories of zooplankton dynamics in the ordination space at SB sites differed from that of LE. The zooplankton most important in forcing site separation along a DCA Axis I at SB sites were Brachionus angularis, Pompholyx complanata, Keratella valga, Keratella quadrata, Filinia terminalis (rotifers), and Eubosmina coregoni and Daphnia (cladocerans). These species had axis scores which were significantly correlated (p<0.01) with bacterial density and bacterial phosphorus, total phosphorus, and algal density. Very high baterial density and very abundant bacterivorous rotifers in SB suggest that the transport of bacterial carbon through rotifers may be a relatively important link to higher trophic leaels. We believe that this "microbial carbon flow" from the base of the food web may be important in determining the suitability of SB as a spawning site and nursery for larval and juvenile fish.nile fish.

• Korean Journal of Ecology and Environment
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• v.51 no.1
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• pp.29-39
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• 2018

Long-term variation of zooplankton community and species composition was studied from 2003 to 2014 in a deep reservoir, Lake Soyang, in monsoon climate region, Korea. In addition, we examined the correlation with environmental factors. Annual precipitation of watershed showed a large variation in the $705{\sim}1,779mm\;yr^{-1}$ and more than 70% of it was being concentrated from June to September. The water quality of Lake Soyang was shown a clearly seasonal variations and particularly turbid water flowing into the lake during rainy season was the most important environmental factors. Zooplankton community in Lake Soyang showed a significant difference before and after 2006. Zooplankton biomass has shown a large increase and also showed a change in the zooplankton community structure since 2006. The of zooplankton showed positive correlation with temperature and BOD, Chl. a, TP concentration. These results are considered that nutrient and organic matter contained in the turbid water influences the increase in zooplankton biomass and species composition. However, water quality was limited to account for the increase in biomass of zooplankton. For example, increase of small zooplankton density (rotifer; Keratella cochlearis, Polyarthra vulgaris) in spring which is dominated by diatoms (large size; Melosira, Synedra etc.) is considered as a bottom-up effect by the microbial loop. And increased density of crustaceans in autumn was considered a top-down effects by the relationship between predator and prey of microzooplankton and mesozooplankton. In other words the inflow of allochthonous organic matter during rainy season also affected to zooplankton food web in Lake Soyang. In conclusion, biomass, diversity and long-term variations of zooplankton in Lake Soyang were determined by physico-chemical factors but also it is considered that biological interactions is important.

• Ocean and Polar Research
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• v.26 no.2
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• pp.351-360
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• 2004

To investigate latitudinal variations in the zooplankton community along the meridian line ($5^{\circ}N-12^{\circ}N$, $131.5^{\circ}W$), we measured temperature, salinity, nitrate, chlorophyll-a and zooplankton at depths above 200 m from July $10^{th}$ to $25^{th}$, 2003. For comparative analysis, data of the physico-chemical properties and chl-a were matched to the two sampling depths (surface mixed layer and thermocline depth-200 m) of zooplankton. Latitudinal differences in the mesozooplankton distribution were mainly influenced by divergence formed at a boundary line formed by currents of opposing directions, consisting of North Equatorial Current (NEC) and North Equatorial Counter Current (NECC). High concentrations of chl-a south of $9^{\circ}N$, caused by equatorial upwelling related nutrients, is thought to be affected by the role of this divergence barrier, supported by relatively low concentrations in waters north of $9^{\circ}N$. The latitudinal differences of the chl-a were significantly associated with the major groups of zooplankton, namely calanoid and cyclopoid copepods, appendicularians, ostracods, chaetognaths, invertebrate larvae, and others. And temperature significantly affected the latitudinal variation of radiolarians, siphonophores, salps and immature copepods. The latitudinal differences in the two factors, temperature and chl-a, which explained 71.0% of the total zooplankton variation, were characterized by the equatorial upwelling as well as the divergence at $9^{\circ}N$. The physical characteristics also affected the community structure and abundance of zooplankton as well as average ratios of cyclopoid versus calanoid copepods. The abundance of dominant copepods, which were consistent with chl-a, were often associated with the carnivorous zooplankton chaetognaths, implying the relative importance of bottom-up regulation from physical properties to predatory zooplankton during the study period. These results suggested that latitudinal distribution of zooplankton is primarily controlled by current-related divergences, while biological processes are of secondary importance in the northeastern Equatorial Pacific during the study period in question.