• Ocean and Polar Research
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• v.26 no.4
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• pp.543-550
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• 2004

Dense macroalgal assemblages are a common feature of the rocky subtidal habitats along the coast of Geumo Archipelago in the central South Sea of Korea, but are highly variable in space. This study addresses two questions concerning the algal assemblages: (1) how variable the distribution, abundance and species composition of the assemblages are in space, and (2) how closely the distribution, abundance and species composition of the assemblages are correlated to the spatial variation in abiotic factors. To answer these questions, we investigated 30 sites along the coast in autumn of 2003. The nonmetric multidimensional scaling analysis showed that there were strong differences in the composition and abundance of species in the assemblages among the sites. The similarity among the sites based on presence/absence data was approximately 51%, whereas the similarity based on abundance data was less than 37%, suggesting that the abundance of species contributed much to these differences. There were also strong differences in the number of species, abundance and vertical distribution of the assemblages along the coast. Multiple regression analyses revealed that the number of species, abundance and vertical distribution of the assemblages had a positive relationship with water depth, but less than 58% of total variation in these variables was explained by this abiotic factor. The results suggest that spatial (between habitats) variation is an important and consistent component of subtidal algal assemblages in Geumo Archipelago and should be explained before any differences between localities are assessed.

• Earthquakes and Structures
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• v.22 no.2
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• pp.203-218
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• 2022

In this paper, quasi-static tests were carried out on three prefabricated reinforced concrete column-steel beam (RCS) sub-assemblages with floor slabs and one comparison specimen without floor slab. The effects of axial compression and floor slab on the seismic performance were studied, and finite element simulations were conducted using ABAQUS. The results showed that the failure of prefabricated RCS sub-assemblages with floor occurred as a joint beam and column failure mode, while failure of sub-assemblages without floor occurred due to beam plastic hinge formation. Compared to the prefabricated RCS sub-assemblages without floor slab, the overall stiffness of the sub-assemblages with floor slab was between 19.2% and 45.4% higher, and the maximum load bearing capacity increased by 26.8%. However, the equivalent viscosity coefficient was essentially unchanged. When the axial compression ratio increased from 0.24 to 0.36, the hysteretic loops of the sub-assemblages with floor became fuller, and the load bearing capacity, ductility, and energy dissipation capacity increased by 12.1%, 12.9% and 8.9%, respectively. Also, the initial stiffness increased by 10.2%, but the stiffness degradation accelerated. The proportion of column drift caused by beam end plastic bending and column end bending changed from 35% and 46% to 47% and 36%, respectively. Comparative finite element analyses indicated that the numerical simulation outcomes agreed well with the experimental results.

• 한국해양학회지
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• v.23 no.4
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• pp.169-183
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• 1989

Polychaete assemblages and their responses to habitat conditions were investigated in the southeastern continental shelf of Korea. The result of cluster analysis revealed that the study area could be divided into two regions, one including the shallow coastal region and the other the offshore region. The shallow coastal region sustained 4 polychaete assemblages: Nothria holobranchiata assemblage in the most northern part of fine sediments off Pohang, Magelona-Maldane assemblage off Gampo, Ophelina acuminata assemblage in the middle coastal area off Ulsan, Nothria conchylega assemblage in the south part off Pusan. These coastal polychaete assemblages contained less than 10 species per station and showed very low species diversity (H' = 1.22-1.52). The offshore also contained 4 assemblages: Terebellides-Aglaophamus assemblage in the northern and deep area of very fine sediments, Myriochele oculata and Spiophanes kroyeri assemblages in the central area of sandy bottoms, and Ninoe palmata assemblage in the southern offshore of sandy bottom. The offshore assemblages showed rather more species and higher diversity than coastal assemblages (H' = 1.90-2.26). The offshore region consisting of sandy sediment showed very low population densities. Some dominant species showed specific preference to sediment types and this phenomenon could be detected through their feeding modes. Depth or bottom temperature seems to be related to the distribution of most dominant worms. Thus the polychaete assemblages of the study area are found to be under the control of both a gradient of sedimentary properties and that of bottom temperature.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.50 no.4
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• pp.429-436
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• 2017

The seasonal and interannual variations in fish assemblages in the coastal waters off Gijang were examined with an otter trawl from 2015 to 2016. A total of 59 fish species was collected during the study period. The dominant species were Caelorinchus multispinulosus, Clupea pallasii pallasii and Chelidonichthys spinosus. Seasonal changes in fish assemblages appeared to be distinct in the study area. The fish assemblages in summer and autumn were clearly distinguishable from those in other seasons, and the largest numbers of species and individuals were captured in winter and summer, respectively. Because fish assemblages are closely related to changes in water temperature, long-term changes in water temperature can have a significant impact on the productivity of offshore fisheries by changing fish species composition, habitat migration, and growth rate of fish.

• Proceedings of the Korea Society of Costume Conference
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• 2004.08a
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• pp.306-307
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• 2004

• Proceedings of the Korean Quaternary Association Conference
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• 2002.06a
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• pp.9-9
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• 2002

• Journal of the Korean Society of Environmental Restoration Technology
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• v.15 no.2
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• pp.19-29
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• 2012

Numerous studies suggested that fish assemblage structure reflects the status of stream ecosystems. The status of streams integrity, including various trophic levels, water quality and habitat degradation, can be assessed by fish assemblages. In this study, we investigated the relationships between fish assemblages and streamline geometry of streams. Previous studies suggested that geomorphologic parameter can be a critical factor of permeability between adjacent two systems. From a landscape ecological perspective, edges may partially control the flow rate of energy between two adjacent systems. Thus, the Streamline geometry can be a geomorphologic parameter that exhibits the integrity of stream. We selected the Nakdong river for study areas, which is one of major rivers and the longest (525 km) River in South Korea. We used the revised IBI representing overall ecological characteristics of Korean fish assemblages and eight sub-assessment criteria of IBI, collected from 82 sampling sites in the Nakdong River. For calculating the Streamline geometry, we measured fractal dimension index that generally used in biology, ecology and landscape ecology. We used the digital land-use/land-cover map and generated a 1-km buffer for each sampling site and refined the shape of the Streamlines. Pearson correlation analyses were performed between Streamline geometry and IBI and sub-assessment criteria of IBI. The results show that IBI and eight sub-assessments of fish are significantly correlated with geometry of Streamline. The fractal dimension of Streamline geometry were related with IBI (r = 0.48) and six sub-assessments of IBI, including total number of native fish and native species, the number of riffle benthic species, sensitive species, tolerant species and native insectivore. Especially, the number of tolerant species(r = -0.52) and native insectivore(r = 0.52) show strong correlation with geometry of Streamline. These results indicate that lower Streamline geometry can result in poor fish assemblages, while higher geometry of Streamline can enhance fish assemblages by potentially supplying insects and better habitat conditions. We expect the results of our study to be useful for stream restoration and management. However, we see the necessity of study investigating the mechanisms how Streamline geometry affect fish assemblages.

• 한국해양학회지
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• v.18 no.2
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• pp.125-141
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• 1983

Micropaleontological analyses of the bathic foraminifera of 132 subtidal surface samples of Asan Bay located in the middle of the western coast of Korea, fringing the Yellow Sea collected during late May-early June 1982, shows the results as follows; -Forainiferal numbers of total assemblages are influenced by hydrodynamic and ecologic factors as well as by the sedimentation in the study area. -Badly preserved faunas including replaced faunas seemed to be fossils, all having living counterparts in the study area and showing a somewhat similar type of wall structures with those of the total assemblages and showing no characteristic bathymetric occurrence compared to that of the biocoenose s.1. of the species, lead to infer theirprobable derivation from the environment without a remarkable environmental difference from the study area. But this inference demands further study in consideration of the physical conditions of the study area. -Living/total ratios show a strong negative correlation with the total foraminiferal numbers excluding replaced faunas. But this trend is somewhat deviated in the relatively high ratios. -Fisher-alpha diversity indices of the total assemblages excluding replaced faunas are lying between 1.7 and 3.7. Totals assemblages are mainly composed of hyaline forms with limited porcelaneous and agglutinated ones.

• Korean Journal of Ecology and Environment
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• v.53 no.2
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• pp.156-164
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• 2020

The accurate estimation of fish assemblages is highly dependent on the sampling gear used for sampling. We used data from 15 sampling sites along the Nakdong River, which is a large river in South Korea, to identify differences in assemblages and sizes of freshwater fishes collected with either cast nets or gill nets, the two most commonly used sampling gear in South Korea. The two gears differed in the fish assemblages they captured, with more species caught by gill nets. Further, due to its tighter mesh size, the cast net caught significantly smaller fishes than the gill nets(independent t-test, p<0.05). We found the cast net to be appropriate for species that inhabit shallow (less than 2 m) and open water, but inappropriate for deep water, habitats with plant beds, and nocturnal species. Thus, cast net sampling is not efficient in a large river environment, and a combination of sampling methods is more suitable for understanding fish assemblages in such habitats. In general, appropriate selection of fishing methods to specific habitats is necessary to improve data quality and minimize the misrepresentation of environmental conditions.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.43 no.5
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• pp.510-520
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• 2010

This study investigated the community structure and seasonal variation of the fish assemblages on Jangbong tidal flat, Incheon, Korea. Fish were collected monthly using a small otter trawl from November 1999 to January 2001. Thirty-six fish species were recorded, with a mean density of 185 individuals and biomass of 2,594.3 gWWt. The most abundant species by number were Johnius grypotus (23.7%), Acanthogobius hasta (17.8%), and Cynoglossus joyneri (10.7%), while the dominant species by catch weight were Acanthogobius hasta (21.2%), Sebastes schlegeli (16.2%), J. grypotus (14.0%), and C. joyneri (10.8%). Cluster analysis and non-metric multi-dimensional scaling (nMDS) were applied to assess the seasonal fluctuation in the fish assemblages. Based on the result of the cluster analysis and nMDS ordination, the faunal group could be divided into cold- and warm-water specialist groups. The cold-water specialists included A. hasta, Acanthogobius luridus, Triaenopogon barbatus, Tridentiger trigonocephalus, and Liza haematocheila. The warm-water specialists were J. grypotus, C. joyneri, S. schlegeli, and Hexagrammos otakii. In conclusion, the community structure showed a distinct seasonal trend, which seemed to be related to the seasonal fluctuations in water temperature.