• Korean Journal of Fisheries and Aquatic Sciences
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• v.41 no.1
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• pp.54-60
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• 2008

High- and multi-frequency acoustic systems can measure a zooplankton patch successively and estimate the spatial distribution and abundance of zooplankton according to size using a multi-frequency inversion (MFI) method. This study measured zooplankton distribution to a depth of 150m using a multi-frequency acoustic system (TAPS-6), installed on a CTD system with a fluorometer and analyzed it using the MFI method. Simultaneously, zooplankton samples were collected by north pacific standard (NORPAC) net to confirm the species composition. The results showed that the combined method is valuable for estimating the zooplankton profile in detail and investigating the relationship between the zooplankton and phytoplankton profiles.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.38 no.3
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• pp.205-213
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• 2005

A hydroacoustic and a close-open-close zooplankton net survey were conducted to understand the distribution characteristics of the deep scattering layer (DSL) and to estimate the density of zooplankton in the DSL, in the Uljin coastal area. The survey was carried out during March 13-14 and June 4-5, 2003 at each station for zooplankton. The vertical migration mechanisms of zooplankton are very variable to the taxa. In this study, after we grasp the vertical migration of zooplankton through the results of an echo-sounder survey, we verified the mechanisms of their vertical migration in the Uljin coastal area. Also, to estimate effectively the biomass of zooplankton, we researched the acoustic scattering strength according to the species. On the basis of these results, we devised a method for estimating zooplankton biomass through comparing net and echo-soundings. We obtained the results as a follows; 1) According to the examination of collections from the net sampling, in March, 2003, Euphausia pacifica comprised $38\%$ of zooplanktons inhabiting the sound scattering layer, while copepods, chaetognaths, and amphipods accounted for $29\%,\;23\%\;and\;10\%$, respectively. And in June, 2003, the ratio of E. pacifica was $51\%$, copepods $43\%$, and the others comprised $6\%$. In both March and June E. pacifica showed dominance among the species of zooplankton. 2) The analysis of vertical distribution through acoustic data in the scattering layer was more apparent in June (spring/summer) of 2003, than in March (winter/spring) of that year. The vertical migration of zooplankton peaked around sunrise and sunset in both March and June. 3) As for the sound scattering layer, it distributed in the open sea in March, and in the inland sea in June. Therefore it is suggested that some zooplankton species such as E. pacifica performed ontogenic horizontal migration througth the spring and early summer.

• Korean Journal of Environmental Biology
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• v.24 no.4
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• pp.329-336
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• 2006

Distribution of zooplankton communities was sampled vertically with a NORPAC net investigated in costal area of Wando from 30, August at 7 stations. A total of 37 taxa were sampled with a total abundance of zooplankton ranged from $147{\sim}1,696indiv.\;m^{-3}$. Evadne tergestina, Acartia pacifica, Paracalanus parvus s. 1, Decapod larvae, Sagitta crassa were dominant species in coastal area of Wando and they contributed 90% of mean abundance of total zooplankton. Multivariate analysis revealed significant differences in community structure among the three regions: the site 1 (A), the middle part of the sampling area (B) and other sites (C). The number and abundance of zooplankton varied significantly among the three regions (p < 0.05). Of these, the distribution of zooplankton communities in the coastal area of Wando was controlled by Tsushima Warn Current and bottom cold water of Yellow Sea.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.9 no.1
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• pp.13-19
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• 2004

We compared two different zooplankton data sets simultaneously obtained at the same place with different mesh-sized nets. Smaller mesh-sized net yielded less diverse zooplankton taxa. However, it was difficult to generalize the relationship between the size of the mesh of the net used and the length of the species list observed. It was not only because the sample sizes obtained by smaller mesh net were relatively smaller due to the clogging problem but also because smaller mesh net usually collected more tiny animals that were difficult to identify at lower taxonomic categories. In terms of abundances, on the other hand, the smaller and the larger mesh-sized nets collected smaller and larger-sized animals more effectively, respectively. The abundances of small sized animals were usually greater than those of large-sized animals by about an order of differences. Due to this different catchability of the nets, the community analyses based on Principal Component Analysis led to different results for the same community.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.36 no.6
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• pp.749-756
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• 2003

Hydroacoustic and open-closing zooplankton net survey were conducted to understand the characteristics of the sound scattering layer (SSL) and to estimate the density of an euphausiid (Euphausia pacifica) in the SSL, in the northwestern part of the East China Sea. The survey was carried out during July 6-9 2002 at 8 sampling stations for zooplankton. The virtual echogram technique was used to identify E. pacifica from all acoustic scatters. Mean volume backscattering strength difference $(MVBS_{120kHz-38kHz})$ and target strength equation for E. pacifica were derived from the Distorted-wave Born Approximation (DWBA) model. Although vertical migration of the SSL is similar to the general pattern, dispersion at night shows some differences. Estimated mean density using acoustic data ranged from $20.4-221.4\;mg/m^3$ over the whole depth, and $87.1-553.5\;mg/m^3$ in the SSL. The density using the zooplankton net ranged from $0.2-362.4\;mg/m^3$ and was not related to net deploying method. The results from the acoustic and net survey suggest that E. pacifica might be an important zooplankton community in the northwestern part of the East China Sea.

• Journal of Fisheries and Marine Sciences Education
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• v.29 no.3
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• pp.869-877
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• 2017

The monthly variations of zooplankton community were investigated at 12 stations near Tongyeong and Namhaedo in the South Sea of Korea from April to July, 2012. Zooplankton samples were collected by a plankton net (RN80) from near the bottom to the surface. Zooplankton community consisted of 97 taxa, and the mean abundance ranged from $213inds.m^{-3}$ in July to $426inds.m^{-3}$ in April. Copepods constituted 38.98% of zooplankton abundance, and included 39 species. Calanus sinicus, Corycaeus affinis, Paracalanus parvus s.l., copepodids, Evadne nordmonni, Podon leuckarti, cirriped nauplii, Muggiacea sp., Diphyes sp., and Zonosagitta bedoti were dominant species. Of these, Calanus sinicus was the most abundant throughout the study period, being constituted 18.6% of total zooplankton abundance. The density variations of dominant species between stations and months were correlated with the environmental factors. Zooplankton community varied with by sampling months, being influenced by monthly oceanographic variations.

• 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.

• Ocean and Polar Research
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• v.33 no.2
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• pp.135-147
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• 2011

Zooplankton is an important constituent in assessing ecosystem responses to global warming. The northern East China Sea is an important ecosystem for carbon cycling with a net sink of carbon dioxide. Despite their importance as a major component in carbon cycling, relatively little is known about zooplankton biomass structure and its regulating factors in the northern East China Sea. This study examined zooplankton biomass distribution pattern in the region from multiple cruises encompassing various seasons between 2004 and 2009. Results showed that zooplankton biomass exhibits less cross-shelf gradient in general with declining biomass to the eastern shelf towards the Tsushima Current Water. Size-fractionated biomass showed that the 1.0~2.0 mm size group, mostly copepods, dominated zooplankton biomass, comprising 38 to 48% of total biomass. Smaller zooplankton (0.2~1.0 mm) biomass, consisting mainly of Paracalanus spp, a particle eating herbivorous copepod, was positively related to chlorophyll-a concentration, but no relationship was established for larger zooplankton (1.0~5.0 mm). Spatially-averaged mean total zooplankton biomass was also highly related to chlorophyll-a concentration. These result suggest that the long-term trend of zooplankton biomass increase in this region is partly accounted for by the increases of phytoplankton biomass and productivity underway in the region. However, the underlying mechanisms of how sea surface warming in the study area leads to increased phytoplankton biomass and productivity remains unclear.

• Ocean and Polar Research
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• v.26 no.4
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• pp.607-618
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• 2004

Zooplankton community was surveyed during the Seventh Korea Antarctic Research Program, from 28 December 1993 to 11 January 1994. Zooplankton samples were collected at 40 stations from the waters around the South Shetland Islands with a Bongo net and a MOCNESS. A total of 14 taxa of zooplankton were identified. Zooplankton abundances varied at each station as well as with the sampling gears. Zooplankton abundances were higher in the Western Weddell Sea than those in the Bransfield strait. Zooplankton collected with MOCNESS showed a different vertical distribution depending on its depths at selected stations. Copepods were the major components of zooplankton contributing 72.84% (mesh size $333{\mu}m$) and 68.36% (mesh size $505{\mu}m$) of total zooplankton abundance from the Bongo samples. Salps were the second most abundant group comprising 7.92% $(333{\mu}m)$ and 11.99% $(505{\mu}m)$ of total zooplankton abundance. Euphausiids, chaetognaths, polychaetes, pteropods and ostracods occurred more than 1% of total zooplankton. Copepods were not abundant at stations salps and euphausiids were dominant. Salpa thompsoni, Euphausia superba, Calanoides acutus, Metridia gerlachei and Calanus propinquus were dominant depending on the stations. The hierarchical UPGMA cluster analysis of dissimilarities between sampling stations is displayed with clusters identified similar habitats. Copepods rarely appeared in the clusters 4 and 5, and they appeared a ffw in the cluster 3 (or salps were numerous), while copepods were abundant in the clusters 1 and 2. As in the results of cluster analysis, the distributions of dominant taxa have a well identified correspondence to the geological positions included physical factors.

• Ocean and Polar Research
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• v.24 no.4
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• pp.407-417
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• 2002

Species composition and abundance of zooplankton were investigated around Dokdo in the East/Japan Sea in autumn 1999 and spring 2000. Vertical and horizontal hauls of a bongo net ($300{\mu}m$ mesh size, 60cm diameter) were made to collect zooplankton sample. Surface temperature and salinity ranged from $24.2^{\circ}C\;to\;25.1^{\circ}C$, and from 32.9psu to 33.2psu in September 1999, respectively. In May 2000, surface temperatures were $13.9^{\circ}C\;and\;14.2^{\circ}C$ at stations of A1 and A8, and salinity was 34.5psu at both stations. Zooplankton community was dominated by copepods which comprised 61% (September) and 60% (May) of total numerical abundance, respectively. The next dominant groups were appendicularians (11%) and chaetognaths (9%) in September 1999, and other crustaceans (27%) and appendicularians (4%) in May 2000. The 15.7% (September) and 23.2% (May) of copepods were in the juvenile stage of copepodites. The most dominant copepods were Oncaea media (10.4%) and Clausocalanus sp. (8.2%) which preferred warm water in September. In contrast, cold-water copepods such as Pseudocalanus minutus (9.4%) and Metridia pacifica (8.0%) were dominant in May. The results of cluster analysis based on Bray-Curtis index showed that zooplankton community were classified into two groups which represented different water mass. The average abundance of zooplankton in September was 2.1 times higher than that in May, and species number of them in September outnumbered that in May by 29 species. Zooplankton community varied in associated with a characteristic of warm waters which affected marine ecosystem differently in the study area depending on seasons.