• Journal of Korea Water Resources Association
• /
• v.42 no.4
• /
• pp.309-317
• /
• 2009

This study analyzed a hydrodynamic behavior using the EFDC model (Environmental Fluid Dynamics Code) in the downstream of the Nakdong River in the case of a storm surge and a localized torrential rainfall caused by a major typhoon, and the sea level rise caused by global warming. The study area is selected Gaduk island with the lower boundary and Jindong with the upper boundary, to investigate the total river hydrodynamic behavior including the estuary. In order to verify this numerical model, the calculated results was compared with the observed stage at each gauging point in case of the storm rainfall in 2003 and 2006. From the results, it was shown that the numerical model(EFDC) has high accuracy and is useful in simulating more various cases.

• Korean Journal of Ecology and Environment
• /
• v.51 no.4
• /
• pp.365-372
• /
• 2018

The Wintering Waterbird Census of Korea was started in 1999 and monitors 200 major migratory sites in South Korea. Waterfowl counts have been undertaken for more than 20 years since; however, a limited number of studies have analyzed the temporal patterns of waterfowl population. In this study, we analyzed population size changes of wintering whooper swan (Cygnus cygnus) at 112 monitoring sites from 2001 to 2018. The average number of whooper swans was $4,296{\pm}42.66$ and there was a trend for an increase in population size across the survey period. We found that the population in the Nakdong River Estuary, one of the major wintering sites over 18 years (26.22% of the national population), had rapidly decreased (-0.77% per year). Conversely, the whooper swan population in the Junam Reservoir and Sihwa Lake increased (+1.64%, +0.54% per year, respectively). Estuaries showed the highest dominance of whooper swans among the five different habitat types, accounting for 32.13% of the population. Reservoir/lakes had 30.60% of the total population and reclaimed lakes(18.24%), river (13.11%), and coast (5.93%) followed. The annual distribution of the whooper swan population in South Korea has been affected by various habitat conditions resulting from human activities and urbanization. To better understand the complex factors that can cause rapid changes in wintering waterfowl populations, it is necessary to integrate the data from the bird census program with environmental conditions to conduct in-depth pattern analyses over longer time periods.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
• /
• v.6 no.2
• /
• pp.93-102
• /
• 2001

Biomass and species composition of phytoplankton and zooplankton along the salinity gradients in the Seomjin River estuary were investigated in March, July, September and November, 1999. The locations of sampling sites were set based on the surface salinity during each cruise rather than geographic locations. A total of 96 phytoplankton species were identified with 60 diatom species in the study area. The species number of green algae was relatively high in low salinity region while the number of dinoflagellates increased in high salinity areas. Monthly mean of phytoplankton biomass ranged from 183 cells/ml to 833 cells/ml. There was a diatom bloom of Skeletonema costatum in November at the 5-15 psu salinity region and sharp decrease of biomass in very low salinity region occurred in March. During the rainy season in July with the salinity less than 8.1 psu, the green algae dominated in most of the study areas. Chroomonas spp. were highly dominant in March and September and the biomass increased towards the high salinity regions. A total of 83 zooplankton taxa were identified with 72 marine and 11 freshwater taxa. Major group of marine form was copepods with34 taxonomic groups. Most freshwater taxa were aquatic insects. Threshold salinities of freshwater zooplankton appearance were 8.1 psu in July, 4.7 psu in September, and 0.2 psu in November. The number of taxa appeared and abundances of zooplanktons were minimal in the middle of salinity gradients in this estuary.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
• /
• v.7 no.2
• /
• pp.51-59
• /
• 2002

The seasonal variation in species composition and abundance distribution of zooplankton was studied in the Seomjin river estuary along the salinity gradients. In this estuary, marine taxa predominated in all seasons and very limited number of freshwater species appeared. The total abundances showed a seasonal fluctuation. The highest total abundance appeared in spring with over 3,000 individuals/m$^3$. In summer, the high abundance was sustained although it decreased a little. The abundance was minimal in fall with about 500 individuals/m$^3$. When the study area was divided into three salinity regimes, oligohaline (salinity less than 5 psu), mesohaline (5${\sim}$18 psu), and polyhaline zone (over 18 psu), the zone of high abundance as well as the composition of zooplankton community in each salinity regime changed seasonally. In fall, marine copepods predominated in oligohaline zone while marine species other than crustaceans dominated in polyhaline zone. However, in winter copepods predominated in all area. In spring and summer, holozoic dinoflagellate Noctiluca scintillans dominated in higher salinity regimes. We listed major copepod species of each salinity regime for each season with the ranges of water temperatures (T) and salinities (S) of their occurrence. T, S's of maximum abundances of those major copepod species were also reported. The observed very wide tolerance ranges of major copepod species for salinity suggested that the concept of 'indicator species' should be used in quantitative context rather than qualitative.

• Journal of Environmental Science International
• /
• v.18 no.9
• /
• pp.1001-1010
• /
• 2009

To investigate the ichthyofauna and habitat type of the fish in Tamjin River system, Korea, fishes were collected with cast net ($5{\times}5\;mm$, $8{\times}8\;mm$) and dip net ($4{\times}4\;mm$) at eight stations seasonally during five years from 2000 to 2004. 56 species belonging to 18 families were collected and 15 Korean endemic species( 26.8%) were investigated. While Coreoperca kawamebari was occurred at every station, the number of individuals and composition were decreased. Anguilla marmorata was not collected and the exotic species didn't appeared. Dominant species were Zacco platypus(34.2%), Squalidus gracilis majimae (9.4%), Microphysogobio yaluensis(8.1%), Zacco temmincki(6.8%) and Acheilognathus lanceolatus(5.1%). The surveyed stations were clustered into 3 groups: up stream, main stream and estuary. With the cluster analysis using the relative abundance of major fishes at each habitat, fishes were separated into 5 habitat types: U (upstream type), UM (up and main stream type), M (main stream), ME (main stream and estuarine type), and E (estuarine type).

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
• /
• v.10 no.3
• /
• pp.164-170
• /
• 2005

To investigate the aquatic environmental factors and processes controlling primary production in the Seomjin River estuary, chlorophyll a, nutrients, pH, SS, DO, temperature, salinity and primary productivity were measured in February, April, August and October, 2001. Primary productivity values ranged between 50.7 and 14,120.3 mg C $m^{-3} day^{-1}$ during the sampling period. In contrast to other estuaries, light condition did not seem to be the important limiting factor far primary production due to high water-column transparency during most of the time. The autumn bloom occurred in regions where salinity values ranged between 10 and 20 psu. This phenomenon appeared to develop every year and deserves further investigation. The behavior of nutrients, which is one of the major factors controlling the primary productivity, appeared to be governed by salinity regimes. The main source of nitrogenous nutrients seemed to be the freshwater runoff from the Seomjin River. However, that of phosphorus seemed to be from the industrial wastewater in Gwangyang area. The primary pro-duction of phytoplankton in the study area varied with space and time, showing a close correlation with water column transparency, and exhibited higher values compared to those of adjacent coastal regions in Gwangyang Bay.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
• /
• v.16 no.2
• /
• pp.81-96
• /
• 2011

Sediment oxygen demand(SOD) and denitrification rates were measured in four major estuaries(Suncheon Bay, Seomjin river estuary, Goseong stream estuary and Masan Bay) in south coast of Korean peninsula from March of 2009 to May 2010 to estimate organic matter cleaning capacity. SOD was estimated from the temporal dissolved oxygen concentration change and isotopic pairing technique was employed to measure denitrification. Sediment oxygen demand(SOD) was ranged from -5.1 to 24.6 mmole $O_2m^{-2}d^{-1}$ and denitrification rate was ranged from 0.0 to 3.9 mmole $N_2m^{-2}d^{-1}$in the study area. SOD was the highest in Masan Bay(-2.2 to 19.2, average = 10.2 mmole $O_2m^{-2}d^{-1}$) and Suncheon, Goseong, Tae-an and Seomjin followed. Denitrification was also the highest in Masn Bay(0.0 to 3.9, average = 1.0 mmole $N_2m^{-2}d^{-1}$) and Goseong, Seomjin, Suncheon and Taean followed. The effect of benthic photosynthesis by microphytobenthos on denitrification was evident in some season of Tae-an, Seomjin, and Masn Bay. The increased oxygen level produced by photosynthesis stimulated nitrification without severe adverse effect on denitrification and, as a result, coupled nitrification and denitrification was enhanced in these areas. A difference of seasonal patterns of denitrification at each site depended on relative importance of denitrification on different nitrate source($D_w$: nitrate from water column and $D_n$: nitrated produced during nitrification). Denitrification was maximum during spring in Goseong, Suncheon and Masan Bay. On the contrary, denitrification was the highest during summer in Tae-an and Seomjin estuary.

• Journal of the Korean Society of Marine Environment & Safety
• /
• v.22 no.6
• /
• pp.694-707
• /
• 2016

This study investigated the community structure of macrobenthic assemblages in the Taehwa River Estuary, Ulsan, Korea. Macrobenthos were collected with a Van Veen Grab Sampler during February and November 2012. The total species number and mean density were $176species/9.6m^2$ and $1,992inds./m^2$, respectively. Polychaetes were the most dominant faunal group in terms of species (91 species) and abundance ($1,463inds./m^2$). The major dominant species were polychaetes Minuspio japonica ($609{\pm}1,221inds./m^2$), Hediste japonica ($174{\pm}318inds./m^2$), Tharyx sp.1 ($106{\pm}283inds/m^2$), Lumbrineris longifolia ($79{\pm}207inds./m^2$), bivalve Theora fragilis ($114{\pm}272inds./m^2$) and amphipod Grandidierella japonica ($88{\pm}223inds./m^2$). Based on community statistics (cluster analysis and non-metric multidimensional scaling (nMDS) ordination), the macrobenthic community was divided into three station groups. Group I(freshwater dominated stations 2-6 with coarse sediment) was characterized by a high abundance of polychaetes Minuspio japonica, Hediste japonica, Capitella capitata, Pseudopolydora kempi, amphipods Grandidierella japonica and Apocorophium acutum. Group II (ecotone, stations 7-9 with mixed sediment) was numerically dominated by bivalve Theora fragilis, polychaetes Cirriformia tentaculata, Tharyx sp.1, Lumbrineris longifolia and Chaetozone sp. Finally, Group III (seawater dominated stations 10-12 with fine sediment) was characterized by a high density of polychaete Magelona japonica. These results showed that changes in salinity gradient and sedimentary characteristics were the main factors behind spatial changes in the macrobenthic communities of the Taehwa River Estuary.

• The Korean Journal of Ecology
• /
• v.12 no.1
• /
• pp.51-65
• /
• 1989

Some aspects of limno-biology of the five dammed lakes such as Tamyang, Changsong, Kwangju, Naju, and Youngsan Lake along the Yongsan River were investigated from June 1986 to July 1988 for the comparison on the lentic ecosystems in relation to the fish fauna. Sixty four fish species representing 48 genera and 21 families of fishes were collected in these dammed areas, which included 29 species of the family Cyprinidea and 40 speaies of the primary fresh-water fishes. Among, these, 12 species such as Rhodeus Acheilognothus yamatsutae, A canathorhodeus gracilis, Sarcocheilichthys nigripinis morii, S. variegatus wakiyae, Gnathopogon strigatus, Squalidus gracilis majimae, Microphysogobio yaluensis, Cobitis longicorpus sp, Liobagrus mediadiposalis and Odontobutis platycephala are enddmic to Korea. Leiocassis nitidus and Gasterosteus aculeatus which occur in these water areas take note of the zooge rographic study of Korea. The fish species in each of the dammed lakes is in proportion of the scale of the lakes such as 32 species in Thamyang, 40 species in Changsong, 24 species in Kwangju, 35 species in Jaju, and 52 species in Yongsan Lake. The dominant fish species of the 4 upper dammed lakes of Thamyang, Changsong, Kwangju and Naju Lake are Zacco platypus and Rhodeus uyekii, while those of Youngsan Lake are Hemiculter eigenmanni and Carassius auratus. This difference of fish species of those areas suggests that the upper damed lake differ from the lower dammed lakes in the habitable condition of fishes. The migratory fish species have significantly declined and will continue to decline in both population size and number of species in the dammed lakes in near future as a result of the dam construction barriers in the river estuary. The major migratory fishes of this water area are as follows; Anguilla japonica, Plecoglossus altivelis, Hypomesus olidus, Gasterosteus aculeatus, Konosirus Punctatus, Coilia ectens, Hemirhampus sajori, Mugil cephalus. Acanthogobius flavimanus, and Takifugu ocellatus.

• Journal of the Korean Society for Marine Environment & Energy
• /
• v.12 no.1
• /
• pp.35-46
• /
• 2009

In order to investigate spatial and temporal distributional characteristics of major water qualities in the Saemangeum area during the Saemangeum dike construction, salinity, COD, dissolved nutrients(DIN, Silicate) and heavy metals were analyzed from the surface water collected in April, May, August and November 2002. The overall value of Salinity, COD, DIN, and silicate in surface waters were in the range of $13.08{\sim}31.96\;psu$, $0.12{\sim}3.43\;mg/L$, $0.001{\sim}2.638\;mg/L$, and $0.010{\sim}3.181\;mg/L$, respectively. The COD and DIN in each survey showed the highest concentration at the mouth of Mangyeong river estuary(St. 1) where freshwater flow into the Saemangeum area. The concentrations of nutrients were high in the inner part of the Saemangeum dike with low-salinity, and low nutrients in the outer part of the dike with high-salinity, which strongly indicated that concentrations were adjusted by physical mixing. The ranges of dissolved metals and acid-soluble Hg in surface seawater were $0.006{\sim}0.115{\mu}g/L$ for Co, $0.26{\sim}0.114{\mu}g/L$ for Ni, $0.14{\sim}0.93{\mu}g/L$ for Cu, $0.04{\sim}0.53{\mu}g/L$ for Zn, $0.010{\sim}0.043{\mu}g/L$ for Cd, $0.010{\sim}0.795{\mu}g/L$ for Pb, and $0.25{\sim}4.16{\mu}g/L$ for Hg. The highest concentrations of some metals except for Cd were found at the estuary(Sts. 1 or 3). In most cases, a decreasing order of metal concentrations towards open sea(low-salinity$\rightarrow$high-salinity) was observed and showed positive relationship with DIN and silicate caused by land base pollutants input. On the other hand, due to Cd desorption from suspended solids in saline water, dissolved Cd concentrations were high in high-salinity area and low in low-salinity. In November, Co, Zn, Cu and Pb were relatively high in the northern area of the outer-side of Saemangeum, which was only influenced by the Geum river discharge. The concentrations of most dissolved metals of this study were lower than those of the past data in this area, but higher than those in Lena river estuary under the pristine environment.