• Ocean and Polar Research
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• v.42 no.3
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• pp.233-247
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• 2020

This study was carried out at 5 sites 11 times over two years to identify the variation of benthic environments and benthic polychaetous community and analyze the benthic healthiness in Dangdong Bay, a small semi-enclosed inner bay of Jinhae Bay. The temperature of bottom water showed the typical temporal fluctuation of a temperate zone and was in the range of 5.94 ~ 23.94℃. The salinity did not change significantly during the study period and was in the range of 32.93 ~ 35.72 psu. The concentration of dissolved oxygen of bottom water fluctuated a great deal and was in the range of 0.31 ~ 10.20 mg/L. The lowest DO value was recorded in July 2015, as 0.31±0.04 mg/L corresponding to the hypoxic water mass. The hypoxic water mass was formed continuously at some sites also in July and August 2016. The mean grain size was in the range of 7.57 ~ 9.81Ø and the average was 8.89±0.20Ø. The surface sediments were mainly composed of fine sediment (mud) above 85%. The mean of TOC was 3.09±0.22% and LOI was 13.30±0.47%, showing very high levels in Korean coastal waters. The concentration of AVS was in the range of 0.33 ~ 1.28 mgS/g-dry. The high values of organic contents and AVS indicated that there had been the serious organic enrichment in Dangdong Bay. The number of species and the density of the benthic polychaetous community in Dangdong Bay were in the range of 2 ~ 38 species and 2 ~ 2,185 ind./㎡ during the study period. The number of species and density were highly sustained in winter and spring, and then decreased gradually with the formation of a hypoxic water mass in summer, and the lowest number of species and density were recorded in autumn. In September and November 2015, the dead zone expanded to almost the whole study area. Dominant polychaetous species were Capitella capitata, Lumbrineris longifolia, Paraprionospio patiens and Sigambra tentaculata, each known as opportunistic species and potential organic pollutant indicator species. In particular, Paraprionospio patiens showed a very high population density of 2,019 ind./㎡ in December 2016. Polychaetous communities at each sampling time were classified into 4 temporal groups according to dominant species in each period by cluster analysis and nMDS. 'Period Group AI' was formed in winter and spring of 2015, dominated by Capitella capitata, 'Period AII' in summer dominated by Lumbrineris longifolia, 'Period B' in autumn with no fauna in the dead zone, and particularly 'Period C' in winter of 2016 dominated by Paraprionospio patiens. As a result of analysis of benthic healthiness, the study area was estimated to be in a Fair~Very Poor condition by AMBI and in a Poor~Very Poor condition by BPI during the study period. Both AMBI and BPI showed that the study area was in a Very Poor condition in September and November 2015, and when the dead zone occurred. In Dongdong Bay, the fact that the formation of a hypoxic water mass occurred in summer and a dead zone in autumn were confirmed. In addition, the dominance of opportunistic and organic pollutant indicator species was also observed clearly. The benthic healthiness indexes such as AMBI and BPI showed that organic enrichment was serious in Dangdong Bay.

• Korean Journal of Environmental Biology
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• v.24 no.4
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• pp.392-407
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• 2006

This study was seasonally undertaken to investigate the benthic polychaetous community along the South-eastern coast of Geoje Is., in February 2004 to November. The macrobenthic fauna showed mean density of 953 md. $m^{-2}$ in February, 1,193 ind. $m^{-2}$ in May, 1,130 ind. $m^{-2}$ in September and 991 ind. $m^{-2}$ in November. Major faunal groups are polychaetes, crustaceans and mollusks, corresponding to 81.6%, 7.9%, 7.0% in total mean density during the sampling seasons, respectively. There was significant difference (two-way ANOVA, p<0.001) among stations in densities of polychaetes. But no significant relationship could be found between the densities of polychaetes and sampling seasons (two-way ANOVA, p>0.05). The density and the species number of polychaetes were high in the coastal area near the Jisepo port, independent of sampling seasons. Several indicator species for the organically enriched environments such as Lumbrineris longifolia, Tharyx sp., Heteromastus filiformis showed high densities during all study periods. Also Magelona japonica included in Ecolgical group I was the most abundant in the whole study period except for February. Cluster analysis on the basis of the species composition showed that the study area could be divided into 3 regions. The density of benthic polychaetes in the coastal area near Jisepo was higher than that in the other assemblages of the study area, due to some predominant opportunistic species, such as Lumbrineris longifolia, Tharyx sp. and Heteromastus filiformis. In addition, the two-way ANOVA showed significant differences among the distribution of AMBI (AZTI's Marine Biotic Index) values, both in sampling stations (p<0.001) and seasons (p<0.01). According to the classification proposed by Borja et at. (2000), the study area was slightly disturbed site.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.32 no.3
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• pp.320-332
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• 1999

Investigations were made on the community structure of macrobenthos in the subtidal soft bottom around semi-enclosed Youngsan River estuarine bay, southwest coast of Korea during the period from April 1995 to February 1996. Three macrobenthos samples were collected at 40 stations using a van Veen grab(0.1 m^2) during the study period. A total of 206 species of macrobenthos was identified. Their mean density and biomass (wet-weight, wwt) were $1,137 ind./m^2$ and $65.28 gwwt/m^2$, respectively. Of these, there were 74 species of polychaetes ($36\%$), 60 molluscs ($39\%$), 51 crustaceans ($25\%$) and 21 miscellaneous taxa. Molluscs were represented as a density- and biomass-dominant faunal group with a mean density of $601 ind./m^2$($53\%$ of the total benthic animals) and biomass of $25.37 gwwt/m^2$($39\%$ of total biomass): It was followed by polychaetes with $405 ind./m^2$($40\%$ of the total density). Total number of species and diversity were Bow in the inner estuarine bay containing high mud content and organic matter, whereas they were high in the outer stations containing low mud content and organic matter. Major dominant species were one biralve, Theora fragilis and three Polychaetes, Tharyx sp., Poeciloceatus johnonni and Lumbrineris lontifolia whose mean densities were $490ind./m^2$, $96ind./m^2$, $74ind./m^2$and $52 ind./m^2$, respectively. Cluster analysis indicated that the study area could be divided into four station groups: two innermost station groups, a central bay and an outer station group. The species diversity increased from the inner station group toward the outer groups. These results were discussed in terms of both the environmental factors and distribution of benthic community.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.7 no.1
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• pp.20-31
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• 2002

This study was carried out to investigate the composition and the distribution of the benthic polychaetous communities in Deugryang Bay, semi-enclosed bays, on the southern coast of Korea and to deduce temporal changes in community with the comparison of the past studies. In Deugryang Bay, benthic polychaetous community structure was investigated on the base of the samples from 98 stations in 1996 and 1997. The main facies of surface sediment was clayey silt. The overall benthic macrofaunal density was 871 ind./m$^{2}$. The density was highest in the middle part of the bay because Musculus senhousia (Bivalvia) and cumaceans (Crustacea) had their highest densities in some stations. Benthic polychaetes were comprised of 100 species with a mean density of 138 ind./m$^{2}$. Their abundances were higher in the inner bay, in the middle bay, and in the mouth of bay, but poor community structures were established in the whole bay. The dominant species over 1.0 percentage were composed of the total 21 species, and they occupied 78.3% of the total abundance of the benthic polychaetes. The most dominant species was Lumbrineris longifolia (9.3%), followed by Eteone longa (7.3%), Heteromastus filifomis (7.1%), Sternaspis scutata (6.1%). From the cluster analysis, the study area could be divided into three station groups. Station group AI was located in the inner bay and in the shallow coastal region, and its most dominant species was Heteromastus filiformis. At the station group AII in the mouth of bay and in some channel region, its most dominant species were Lumbrineris longifolia and Eteone longa. And at the station group B located in middle part of the bay, the most dominant specis was Sternaspis scutata. In comparison with previous studies, the benthic polychaetous community experienced great change in the view of species number, density and dominant species. The dominant species were Sternaspis scutata and Eteone longa, but their densities declined greatly. Instead of these species, Lumbrineris longifolia and Heteromastus filiformis, known as the potential organic enrichment indicator species, appeared to the new dominant species even if their low densities. These facts mean that Deugryang Bay was maintained yet as little organic enriched area compared to other bays on the coast of Korea, but needed some caution of marine environmental management.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.31 no.4
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• pp.453-462
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• 1998

Macrobenthic community structure was studied at thirteen stations in Taebudo subtidal area, Korea, from July to October 1996. Triple macrobenthos samples were collected using a van Veen grab (0.1 $m^2$) at each station during the study period. A total of 209 species of macrobenthos was sampled with a mean density of 1,093 ind./$m^2$ and biomass of 134,86 g/$m^2$. Of these, there were 72 species of polychaetes ($34.5\%$), 69 crustaceans ($33.0\%$) and 49 molluscs ($23.4\%$). Polyalaetes were represented as a density-dominant faunal group with a mean density of 608 ind./$m^2$, comprising $55.6\%$ of the total benthic animals. It was followed by crustaceans with 307 ind./$m^2$($28.1\%$ of the total density), Echinoderms were represented as a biomass-dominant faunal group with a mean biomass of 54.21 g/$m^2$($40.2\%$ of total biomass). Total number of species and diversity were low in the inner part of the study area with high mud content and high in the offshore stations of mixed sediments. Major dominant species were three polychaetes, Heteromastus filifomis, Scoloplos armiger and Tharyx sp. whose mean densities were 70 ind./$m^2$, 67 ind./$m^2$, and 66 ind./$m^2$, respectively. Cluster analysis showed that the study area could be divided into five stational groups based on the faunal composition, that is, the innermost stations, coastal stations, transitional stations and two offshore station groups. The species diversity of these groups increased from the inner stational group toward the outer groups.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.31 no.3
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• pp.343-352
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• 1998

The relationship between summer hypoxia in bottom water layer and benthic community structure was discussed at forty sampling stations in semi-enclosed Youngsan River estuarine bay, Korea. The oxygen deficient layer less than $2.0 mg/\ell$ was widely developed in the inner estuarine stations in summer due to the summer stratification. A total of 141 species was occurred, with a mean density of $1,923 ind./m^2$ and biomass of $79.44\;g/m^2$ in summer season. The species number was significantly increased with the increment of the bottom dissolved oxygen, whereas density and biomass were partially correlated within the low oxygen level of $2.0\;mg/\ell$. These results imply that benthic community structures are affected by bottom oxygen depletion in summer. Cluster analysis showed that the benthic community could be classified into three station groups. These station groups from the species composition coincided with the groups based on the environmental factors. This fact suggests that the overall spatial distribution of macrozoobenthos in Youngsan River estuarine bay in summer should be controlled by the summer hypoxia and clay content of the area. Group-I was located the innermost estunrine bay from Mokpo Harbour to near the dike, where summer hypoxia was developed and one bivalve Theora fragilis, two polychaetes, Tharyx sp. and Lumbrineris longifolia were dominated. Group-II, the central transitory area of the estuarine bay between two another stational groups, where two bivalves Theora fragilis, Raetellops pulchella and a polychaete Tharyx sp. predominated with relatively low density compared to that of Group-I. Group-III, the mouth part of the estunrine bay exposed to the open sea, where a polychaetes Poecilochaetus johnsoni and a bivalve Yoldia Johanni predominated.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.19 no.4
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• pp.243-255
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• 2014

This study was investigated to estimate the relations between benthic environments and benthic polychaetous community from April 2012 to February 2013. Twenty four stations were selected sequentially with Seomjin River Estuary from the northern part of Gwangyang Bay. The study area could be divided into three characteristic zones based on salinity, water temperature, dissolved oxygen and pH such as Saline Water Zone (SWZ), Brackish Water Zone (BWZ), and Fresh Water Zone (FWZ). Salinity was above 30.0 psu in SWZ, drastically decreased toward inland in BWZ, and nearly zero psu in FWZ. SWZ showed its specific environmental characters like that water temperature fluctuated with little seasonal change and DO showed the lowest values among three zones, and pH maintained as consistent value without seasonal fluctuation. In FWZ, on the other hand, water temperature showed high seasonal fluctuation, DO showed the highest values among three zones, and pH fluctuated greatly. In sedimentary environment, mud, sand and sand/gravel were found as dominant sedimentary deposits in SWZ, BWZ and FWZ, respectively. Organic matter content and AVS in surface sediment were high in SWZ, while Chl-a content high in FWZ. This study area showed a marked environmental difference between FWZ and SWZ as follows: FWZ has coarse sediment and low salinity, low organic matter content, low AVS in FWZ but SWZ has fine sediment and high salinity, high organic matter content and AVS. Species number and mean density of benthic polychaete community was highest in Saline Water Zone (SWZ), drastically decreased in Brackish Water Zone (BWZ), and lowest in Fresh Water Zone (FWZ). Dominant polychates above 5.0% of individual numbers were 6 taxa. Lumbrineris longifolia, Prionospio cirrifera, Tharyx sp. occurred as main dominant species of all study periods, and Hediste sp., Praxillella affinis, Tylorrhynchus sp. dominantly occurred at some seasons. Inhabiting areas of dominant species were separated characteristically. Representative species in SWZ were Lumbrineris longifolia, Tharyx sp., Mediomastus sp.. Wide-appearing species between SWZ and BWZ were Prionospio cirrifera, Heteromastus filiformis, Aricidea sp.. Characteristic species in FWZ were Tylorrhynchus sp. and Hediste sp.. As the results of cluster analysis and nMDS based on the species composition of polychaetous community, unique station groups were established in SWZ and FWZ. Stations in BWZ were sub-divided into several groups with season. Pearson's correlation analysis and PCA between benthic environments and ecological characteristics of polychaetous community showed that salinity, sediment composition, organic content and dissolved oxygen played a role to determine the temporal and spatial distribution of the ecological characteristics as species number, mean density, abundance of main species, and ecological indices.

• Korean Journal of Environmental Biology
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• v.27 no.4
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• pp.341-352
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• 2009

This study was carried out to investigated community structure of macrobenthic assemblages around the Wolseong Nuclear Power Plant, East Sea of Korea and seasonal sampling was performed from October 2007 to July 2008. A total of 163 macrobenthic fauna were collected. The overall average macrobenthos density and biomass were 1,005 individuals $m^{-2}$ and $21.81\;gWWt\;m^{-2}$, respectively. Based on the LeBris (1988) index, there were 10 dominant species accounting for approximately 69.00% of total individuals. The major dominant species were the polychaetes Spiophanes bombyx (349 inds. $m^{-2}$), Mediomastus californiensis (82 inds. $m^{-2}$), Sigambra tentaculata (55 inds. $m^{-2}$), Magelona japonica (50 inds. $m^{-2}$), Scoletoma longifolia (33 inds. $m^{-2}$) and the Unidentified amphipod (Amphipoda spp., 72 inds. $m^{-2}$). The conventional multi-variate statistics (cluster analysis and non-metric multi-dimensional scaling) applied to assess spatial variation in macrobenthic assemblages. Cluster analysis and nMDS ordination analysis based on the Bray-Curtis similarity identified 2 major station groups. The major group 1 was associated with sand dominated stations and was characterized by high abundance of the bivalves Mactra chinensis, Siliqua pulchella and the polychaete Protodorvillea egena. On the other hand, major group 2 was connected with mud dominated stations and was numerically dominated by the polychaetes M. californiensis, M. japonica, Sternaspis scutata, S. longifolia and the bivalves Thyasira tokunagai and Theora fragilis. However, macrobenthic community structure were no significant differences between the environmental variables (sediment type and depth) and heated discharge.

• Korean Journal of Environmental Biology
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• v.28 no.4
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• pp.179-187
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• 2010

The Theory of Island Biogeography describes that the number of species on an island affected by island area and distance from the mainland. This study was performed to compare and analyze the community structure of the macro-invertebrates in three isolated islands, around Korean waters in terms of the Theory of Island Biogeography. Macrobenthic animals were collected using a modified underwater quadrat in August 2009. A total of 104 macrobenthic species were sampled with a mean density of 399 individuals $m^{-2}$ and biomass of 1,506.70 g $m^{-2}$. Based on the abundance and biomass data, there were 10 dominant species accounting for approximately 67.17% of total individuals. The highest densities were found in the amphipoda Amphipoda spp., the bivalvia Modiolus agripetus and Mytilus coruscus, the Sipunculida Phascolosoma scolops and the polychaeta Syllidae unid.. On the contrary, the top ten species made up 95.66% of the total biomass while the three most abundant, the bivalves M. coruscus, Streostria circumpicta and M. agripetus. The conventional multi-variate statistics (cluster analysis and non-metric multi-dimensional scaling) applied to assess spatial variation in macrobenthic assemblages. Cluster analysis and nMDS ordination analysis based on the Bray-Curtis similarity identified 2 station groups. The group 1 was consisted with Gageodo (except for lower station at Transect 2) and Dokdo station and was numerically dominated by the polychaetes Eunice antennata and Syllidae unid., the cirripedia Megabalanus rosa and the bivalvia M. coruscus. However, group 2 was associated with Sohwado station and was characterized by high abundance of the anomura Petrolisthes japonicus, the gastropoda Lirularia pygmaea and the brachiopoda Coptothyris grayi. In conclusion, these results suggested that the species diversity and community structure of macrobenthos in three isolated island seemed slightly related to island area and distance from the mainland.

• Korean Journal of Environmental Biology
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• v.27 no.1
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• pp.124-133
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• 2009

The study was performed to investigate the community structure of macrobenthic fauna during June 2005, in Hallyeohaesang National Park from Korea Strait. A total of 284 macrobenthic fauna were collected. The overall average macrobenthic density and biomass were 2,002 individuals m$^{-2}$ and 154.92 gWWt m$^{-2}$, respectively. Based on the Lebris (1988) index, there were 20 species accounting for approximately 47.64% of total individuals. And the highest densities were found in the polychaetes Scoletoma longifolia, Isolda pulchella, Mediomastus californiensis, Minuspio multibranchia, Tharyx sp. 1 and the bivalve Theora fragilis. On the other hand, the top twenty species made up 70.47% of the total biomass while the three most abundant, the echinoderms Schizaster lacunosus, Amphiura vadicola and the bivalve Fulvia mutica. The conventional multivariate statistics (cluster analysis and non-metric Multi-Dimensional Scaling) applied to assess spatial variation in macrobenthic assemblages. As a result of cluster analysis and nMDS ordination, this study area was divided into two different groups of stations and species. In case of station, there are two groups: one is a mud dominated station group and the other is dead shell and sand dominated group. And the 2 faunistic groups were established as follows: 1) a group of relatively higher abundances in mud dominated sediment. There were numerically dominated by the polychaetes Magelona japonica, Sternaspis scutata, Paraprionospio pinnata, Tharyx sp. 1 and the amphipods Monocorophium sinense and Eriopisella sechellensis. 2) a group of relatively higher densities dead shell and sand dominated sediment. These groups were characterized by the polychaetes I. pulchella, M. multibranchiata, the amphipods M. acherusicum, Gammaropsis japonicus and the echinoderm A. vadicola.