• Journal of Korean Society of Environmental Engineers
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• v.34 no.6
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• pp.421-429
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• 2012

This study was aimed to analyze the water quality characteristics of the Hwapocheon Stream and to be utilized in the further related research. Water in the upper stream became a dammed pool due to the existence of 14 weirs, and pollutants such as both sewage and irrigation water were introduced into the mainstream passing through farming settlements and agricultural land. For these reasons, filamentous cyanobacteria (Oscillatoria sp.) bloomed at the bottom of the dammed pool. Also in the midstream and downstream, tributaries with high pollutant concentrations [e.g., Comocheon (T3) and Yongdeokcheon (T8)] were inflowed, and had a negative impact on water quality of the mainstream, especially nitrogen and phosphorus. In the Hwapocheon Stream, dissolved oxygen (DO) decreased, and suspended solid (SS) increased toward the downstream. The result showed that hydraulic retention time, SS, COD, and concentration of $NH_4{^+}$ were important water quality factors of the Hwapocheon Stream. The high concentration of benthic organic matter and rich in attached algae in the core of Hwapo-wetland were expected to give impact on the water quality of the mainstream. In the spatial manner, water quality showed increasing trend in the weir zone, and it was constant or decreased trend in wetland. In the seasonal manner, the nutrient concentrations were high in the winter dry season, however, the organic matter concentrations were high in spring and summer. Generally, the concentrations of phytoplankton value were $40{\mu}g\;chl-{\alpha}/L$ or less in all reaches except for the high concentrations in the weir and wetland area in June.

• Journal of the Korean Society of Marine Environment & Safety
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• v.28 no.spc
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• pp.37-43
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• 2022

Post-spill monitoring of hazardous noxious substances accidents is essential in the event of a spillage of significant quantities of pollutants and for the management of the marine environment resulting from the long-term effects of the persistent toxic substances. The accidental introduction of a sinker into the marine environment can create harmful anaerobic conditions in the benthic ecosystem and spread over the seafloor by the topography and currents. Through case studies, most post-spill monitoring includes modeling, remote sensing, and chemical analyses of the sediment and benthic organisms. The monitoring also evaluates the effectiveness of restoration and recovery activities and assesses damages and compensation.

• Ocean and Polar Research
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• v.24 no.4
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• pp.419-427
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• 2002

Meiobenthic community structure near Dokdo was investigated during two survey periods of June, 1999 and October 2000. Meiobenthos were separated from the sediment core samples collected from eight stations. A total of 19 meiobenthic animal groups were identified from those core samples. The most abundant meiobenthic animals belonged to Phylum Nematoda in both seasons and all stations. Sarcomastigophorans, nauplius of crustaceans, and benthic harpactiocoids were the next abundant meiobenthos. Vertical distribution of meiobenthic animals showed the highest individual numbers in the surface sediment layers of 0-1cm depth with a steep decreasing trend with depth for the three sampling stations (A0, A9', A19) located in the continental slope. Horizontal distribution of meiobenthic animals for the study area near Dokdo showed lower density at the sampling stations near Dokdo and the lowest density of meiobenthos in A19 (depth-2261 m). For size distribution, analysis showed that animals which fit onto the mesh size of 0.125mm were abundant. This study suggested that the continental shelf near Dokdo have a more unstable environment fo meiobenthos than the continental slope.

• Journal of the Korean Society of Environmental Restoration Technology
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• v.2 no.3
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• pp.1-9
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• 1999

This paper described the results of the characteristics of the near-bottom flow and field analysis of the tidal flats sediment. It was the aim of this paper to grasp current flow of tidal flat's environment and influence factor for environmental change forecast of tidal flats. Field measurement of water velocity, water elevation, bed materials test, and temperature distribution of tidal flat were conducted. Thereafter, current flow, turbidity and temperature distribution of tidal flat sediment have been discussed. The field research results showed that the fluctuating velocity near the seabed before and after its appearance at low tide was strongly affected by the wind wave. The resuspension of the sea-bottom sediment took place with great intensity before and after the appearance of the seabed at low tide. Both the sea water level and the weather condition were a significant influential factors. Such as, temperature and turbidity just on the surface and the shallow layer of seabed sediments were varied largely with time and weather conditions, but that its deeper layers was almost constant. Temperature on the seabed sediments was strongly influenced by irradiance and water depth. The temperature variation of the tidal flat and the variation characteristics of the current flow and turbidity depend greatly on the inhabiting environment of the tidal flat benthic organism.

• Korean Journal of Environmental Biology
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• v.39 no.4
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• pp.507-514
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• 2021

A new free-living marine nematode species of the genus Pseudosteineria Wieser, 1956 affiliated with the family Xyalidae is described based on specimens collected from the sediment of a subtidal benthic environmental habitat in the East Sea, Korea. Pseudosteineria varisetis sp. nov differed from its congeners by the combination of the following characteristics: a relatively long body (1,628-1,691 ㎛ long in males), a circular amphideal fovea situated behind the subcephalic setae, the presence of lateral cuticular alae starting from behind the nerve ring, the presence of eight groups of long subcephalic setae, the presence of irregularly distributed variable lengths of somatic setae on the body, solid spicules (43.2-43.9 ㎛ long) with a cephalated proximal end, a long tubular shaped gubernaculum with dorsal swelling, and a conico-cylindrical tail with two to four terminal setae. In this report, we provide a taxonomic description and illustrations of a new species of the genus Pseudosteineria by differential interference contrast microscopy.

• 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 Ecology and Environment
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• v.52 no.4
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• pp.385-393
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• 2019

Chironomid communities are indicators of water pollution because of their ability to thrive under freshwater conditions. However, it is difficult to distinguish between chironomid larvae based on morphology. DNA barcoding, based on nucleotide sequences of marker genes, can be used to identify chironomid larvae. Samples of chironomid larvae were collected from Gwangju Stream and Pungyeongjeong Stream, tributaries of the Yeongsan River in South Korea. We identified 3 subfamilies, 13 genera, 16 species, and 1 cryptic species. There were 7 genera and 10 species from the subfamily Chironominae, 5 genera and 5 species from subfamily Orthocladiinae, 1 genus and 1 species from subfamily Tanipodinae, and the cryptic chironomid species of the family Chironomidae. There were 21 individuals from, 7 species and 1 cryptic species from the Gwangju Stream and 24 individuals, belonging to 10 species from the Pungyeongjeong Stream. The only species detected in both streams was Cricotopus bicinctus. The relationship between water quality and the species detected was difficult to explain, but the number of species showed a tendency to increase at sites where water quality was poor. Additional investigations and studies are needed to understand the relationship between water quality and the chironomid species occurring in these two streams.

• Journal of Korean Society on Water Environment
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• v.34 no.3
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• pp.301-307
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• 2018

This study investigated the effects of sediment removal on water quality and phytoplankton development by setting up mesocosms at Uiam Lake, South Korea, and analyzing the environmental parameters and phytoplankton communities between June and October 2015. The comparison between testbed without sediment removal (TB-1) and testbed after sediment removal (TB-2) gave similar values for water temperature, pH, dissolved oxygen (DO), and electrical conductivity. Nevertheless, the average electrical conductivities of the two testbeds were $139{\mu}S/cm$ and $135{\mu}S/cm$, which were lower than the value obtained from the external control point (TB-con; $154{\mu}S/cm$). The small difference in total phosphorus (TP) and total nitrogen (TN) concentrations between the two testbeds implied that sediment removal did not greatly reduce nutrients; however, the phytoplankton cell count had decreased by approximately 37 % in TB-2 (average 1,663 cells/mL) compared to TB-1 (average 2,625 cells/mL). Compared to TB-con, the phosphorus and nitrogen concentrations of the two testbeds had decreased by 39 % and 30 %, respectively, whereas the phytoplankton abundance had decreased by up to 73 %, perhaps because of the blocked inflow of nutrients and the stabilized body of water caused by the installation of the mesocosm. The concentration of geosmin was lower in testbeds than in the external point, because installation of the structures had reduced the cyanobacteria biomass.

• Journal of Environmental Science International
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• v.29 no.3
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• pp.273-282
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• 2020

Residence time is defined as the time taken for a material in a system to leave the system. The residence time characteristics in shellfish aquaculture determine the dispersion of excretion from aquaculture farms, along with the supply of food by seawater exchange. In this study, we estimated the spatial distribution of average residence time in the shellfish farming area using a particle tracking model. As a result, a relatively short average residence time of about 20 days or less was calculated in most areas, but an average residence time of more than 40 days was calculated in the inner areas. Relatively long average residence times were calculated along the west coast compared to the east coast, with the longest average residence time of more than 50 days in the northwestern areas. It can be inferred that the disturbance of the benthic ecosystem caused by shellfish farms is likely to be large because of the relatively weak dispersion of excrement from shellfish farms located on the west coast, especially in the northwest region. This distribution of average residence time is important for understanding the potential effects of seawater exchange on the environmental sustainability of shellfish farms, along with the seawater circulation characteristics of Jaran Bay.

• ALGAE
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• v.22 no.4
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• pp.297-304
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• 2007

This study is intended to clarify the effects of heated effluents on intertidal benthic marine algal community in Korea. The species composition and biomass of marine algae at the discharge canal of Gori nuclear power plant on the southeastern coast of Korea were investigated seasonally from February 2001 to October 2006. As a result, 54 species (7 blue-green, 12 green, 9 brown and 26 red algae) of marine algae were found at the discharge canal during the past six years. In general, the number of species observed was abundant during winter to spring and less in autumn. Enteromorpha compressa, E. intestinalis, E. prolifera and Caulacanthus ustulatus were common species found more than 80% frequency during the study period. Seasonal fluctuations of mean biomass were 1-440 g dry wt m–2 and dominant species in biomass were Enteromorpha spp. (contribution to a total biomass proportion 28%), Sargassum horneri (14%) and Amphiroa beauvoisii (14%). It is evident from the floristic composition and biomass data that unique micro-environment of the discharge canal support different communities from those on the intake or control area. Results from the large numbers of surveys before and during plant operation showed that, in the regions influenced by thermal effluents such as the discharge canal of power plants, the process of ecological succession has been proceeded. It is assumed that the uni-directional water flow and the time of overhaul largely affect the development and succession of benthic marine algal communities of the discharge canal.