• The Korean Journal of Ecology
• /
• v.28 no.5
• /
• pp.335-345
• /
• 2005

A study on changes on the distribution of vascular hydrophytes and the growth pattern of Schenoplectus triqueter (Scirpus triqueter) was undertaken at the Nakdong River estuary from 2002 to 2004. The change was due to physical alteration of the estuary for the past 25 years. These plant species are the major food sources for winter waterfowl. A total of 32 species of vascular hydrophytes from 17 families were found in the West Nakdong River (freshwater), the main channel of Nakdong River (freshwater) and the Nakdong River Estuary (brackish water). After the construction of the barrage on the estuary in 1987, the number of hydrophytes has remarkably increased to 17 species (5 species in 1985) in the main channel of the River. In particular, a community of Eurale ferox was found at the backwater wetland of the Daejeo side of the main channel. The introduced species of Eichhornia crassipes and Pistia stratiotes that were epidemic in 2001 at West Nakdong River was not found any more. The other species such as Nymphoides indica, Myriophyllum spicatum, Ruppia spp. were rediscovered. The large area (about 1,300ha) of Zostera spp. was the main sources of food for swans, but disappeared because of direct and indirect impacts of reclamation in the River estuary. Currently, there remains a small patch of Zostera spp. and about 250ha of S. triqueter. Schenoplectus triqueter grew mostly between April-September and tuber formed, between September-October. The growth of S. triqueter up to $60\sim80cm$ in length was observed in 5 sites out of the 7 sites in brackish area. Tubers of S. triqueter were eaten by waterfowls such as swans as winter food. In five sites, tubers took $44\sim57%$ of total biomass in October. Tubers were found in deep layers; $5\sim15cm$ (9%), $15\sim25cm$ (28%), $25\sim40cm$ (55%), below 40cm $(6\sim7%)$. The distribution of vascular hydrophytes has remarkably changed in the Nakdong River Estuary due to the reclamation of the area. In order to determine the extent of changes of the distribution of these plants and the carrying capacity of the area for waterfowl, an intensive research is urgently needed.

• Journal of Environmental Impact Assessment
• /
• v.24 no.3
• /
• pp.287-299
• /
• 2015

If the Nakdong River estuary is to be sustainable, land use management practices need to consider bird habitat requirements, especially given that the area serves as an important migratory bird sanctuary. In this study, bird habitats found in the Nakdong River estuary were classified into 11 different types including Phragmites australiss, mud flat, farmland, open surface in freshwater, sand bar, riparian forest, Scirpus planiculmis, waterway, construction, grasslands, and open surface in sea or brackish water. Taking into consideration the regional characteristics, habitat properties, and landscape indices, a total of 12 study sites were analyzed. Mud flat, construction, farmland, and P. australis account for 80% of the total land area. The high area ratio of construction and farmland to other types of habitat revealed a high amount of historical human activity and intervention in the area. Both patch numbers as well as patch density were high in West Nakdong River, Samrak Waterfront, Maekdo River, and Daejeo Floodgate, with these areas showing the greatest fragmentation as well. Total numbers of species and individuals had a positive correlation with the area and the number of habitat types. Findings suggest that protecting the habitat area, especially in S. planiculmis, is the most important factor for bird habitat management and that future development could result in habitat loss, having a profoundly adverse impact on bird populations. Therefore, it is important that the total area should be carefully protected by land use regulations in order to ensure that the Nakdong River estuary maintains its functional integrity as a migratory bird sanctuary.

• Korean Journal of Environment and Ecology
• /
• v.20 no.3
• /
• pp.311-318
• /
• 2006

In an estuary, ecological dynamic is modified for a long time and memorized in soils and landscapes. As landscape memory, ecological motif is defined with dominance and rarity of vegetation. The purpose of the study is to investigate the existing vegetation character and to propose the ecological motif of this area. The present salt-water plants, community species composition and constancy degree around the estuary in Buandam watershed Buan-gun, Jeollabuk-do were analyzed. The results are as follows. The flora of the salt-water plants was listed as 16 taxa; 6 families,13 genera,14 species and 2 varieties. 5 taxa were Gramineae, 4 taxa Chenopodiaceae, and 4 taxa Comrositae. The salt-water plant communities are a total of 10 communities as listed; Zoysia sinica-Artemisia scoparia community, Phacelurus latifolius community, Artemisia scoparia Cnidium japonicum community, Limonium tetragonum -Artemisia scoparia community, Artemisia scoparia community, Suaeda japonica community, Elymus dahuricus community, Suaeda asparagoides community, Zoysia sinica community, and Zoysia sinica-Suaeda japonica community. Analyzed by the community classification species class of constancy degree, Phacelurus latifolius, Cnidium japonicum, Limonium tetragonum, Suaeda japonica, Elymus dahuricus and Suaeda asparagoides belong to I, Zoysia sinica and Artemisia scoparia to II. Elymus dahuricus, Setaria viridis var. pachystachys, Echinochloa crusgalli var. oryzicola, Phacelurus latifolius, Atriplex gmelini, Salicornia herbacea, Calystegia soldanella and Aster tripolium belong to the accompaniment species to I: Zoysia sinica, Suaeda asparagoides, Artemisia capillaris to II; Suaeda japonica, Artemisia scoparia to III ; Cnidium japonicum to IV: Limonium tetragonum, Artemisia fukudo to V. And the ecological motif is the Phacelurus latifolius community.

• Journal of the Korean Society for Marine Environment & Energy
• /
• v.20 no.1
• /
• pp.1-11
• /
• 2017

Nakdong River Estuary is affected by the dam, barrage construction and dredge and reclaim worked artificially. So, we have studied the area input both freshwater and sea water to understand marine environment of Nakdong River estuary related to the effect of artificial work from 2013 to 2015. As a result, The discharge flow to the estuary remarkably decreased before barrage construction and the average of salinity at the estuary increased. So, the brackish water zone reduced under the influence of decreased discharge flow. The major sources of nitrate and silicate were freshwater, phosphate supplied from bottom and the open sea water. The concentration of phosphate and dissolved oxygen (DO) decreased remarkably in spring and summer. we investigated that phosphate in freshwater was removed under the influence of the estuary dam and phosphate in sea water was removed under the influence of phytoplankton. The low concentration of DO was due to decomposition of the organic compound by microorganism after phytoplankton blooms. Generally, the concentrations of chlorophyll-a in summer was higher than spring and fall. Therefore, the change of ecosystem in Nakdong river estuary was due to decrease of freshwater influx, the other change is facing because of the barrage.

• Journal of the Korean earth science society
• /
• v.27 no.1
• /
• pp.95-117
• /
• 2006

From the Tertiary Yeonil Group distributed in Songra and Cheongha areas, the northern part of the Pohang Basin, nine archaeomonad species belonging to two genera, and other three types of chryophycean cysts considered as stomatocysts, five endoskeletal dinoflagellate species belonging to three genera and eighteen ebridian species belonging to eleven genera were identified. Based on above siliceous microfossil assemblages, the Yeonil Group is corresponded to Middle Miocene age. The group is correlated with the Calvert Formation (Maryland in USA) and the Hojuji Formation (in Central Japan) by its archaeomonad cysts. And, the group is correlated with the intervals of Actiniscus elongatus to Middle Hermesinella conata zones in Southwest Pacific region and of Spongebria miocenica to Middle Hermesineila schulzii zones in $V{\o}ring$ Plateau, Norwegian Sea, based on the ebridian assemblages of the group. From the chrysophycean cyst including archaeomonad, endoskeletal dinoflagellate and ebridian assemblages in the Yeonil Group of the study area, it is inferred that cold water masses dominated during the deposition oi the group with occasional warm water. The upper part of the group might be somewhat colder than the lower one of the group in depositional condition. In addition, minute chrysopycean cysts considered as stomatocysts suggest the influence of fresh or brackish water during the deposition of the group.

• Korean Journal of Environmental Biology
• /
• v.27 no.4
• /
• pp.425-432
• /
• 2009

Mesozooplankton dynamics were studied in Watan stream which flows into the Yellow Sea in Yeonggwang, Korea. Samples were collected at eight stations bimonthly during April 2006~February 2007. Mesozooplankton community was consisted of 45 taxa (8 cladocerans and 29 cope-pods). The abundance varied between the highest one ($31{\sim}127,587\;indiv.m^{-3}$) in October, and the lowest ($12{\sim}233\;indiv.m^-3$) in December. Diversity index showed to be the highest value in July (0.671) and the lowest one in August (0.368). A euryhaline species, Acartia hongi was dominant in brackish water stations (the highest abundance at $13.4^{\circ}C$ and 14.1 psu). In freshwater stations of the upstream, two cladoceran species of Polyphemus pediculus and Moina weismani occurred in high abundance in August. Dominant taxa of copepod were clustered to two or three groups mainly due to the difference of salinity gradients. Spatial distribution of mesozooplankton revealed to be determined by salinity gradients which were affected by opening and closing of the artificial dam in Watan stream.

• Economic and Environmental Geology
• /
• v.27 no.1
• /
• pp.65-80
• /
• 1994

The Tertiary $Ch{\check{o}}ngja$ basin is located in the southeastern coastal area of the Korean Peninsula. It is a lozenge shaped fault-bounded basin with circa $5{\times}5km$ areal extent, isolated from other Tertiary basins by the Cretaceous Ulsan Formation in-between. The northwestern boundary of the basin is a domino/listric type normal fault trending $N30^{\circ}E$, whereas its southwestern boundary is a dextral strike-slip fault (trending $N20^{\circ}W$) with a lateral offset of more than 1 km. The basin is bounded by the East Sea on the eastern margin. Basin-fills consist of extrusive volcanic rock (Tangsa Andesites) of Early Miocene (16~22 Ma in radiometric age), unconsolidated fluviatile conglomerate (Kangdong Formation) and shallow brackish-water sandstone ($Sinhy{\check{o}}n$ Formation). The latter yields abundant Vicarya-Anadara molluscan fossils of early Middle Miocene age. The Tertiary strata become younger toward the northwestern boundary-fault of the basin, showing a zonal distribution pattern parallel to the fault: the younger sedimentary formations occupy a narrow zone of 2 km width along the northwestern boundary-fault, whereas the older Tangsa Andesites underlie them unconformably in the eastern and southeastern portions of the basin. The strata in the basin, including the Tangsa Andesites, are tilted (about $20^{\circ}$) toward the northwestern boundary-fault Sedimentary strata thicken toward the boundary-fault, forming a wedge shaped half-graben structure. A number of small-scale syndepositional normal growth faults and graben structures are observed in the sedimentary strata. These extensional structures have the same trend as the normal northwestern boundary-fault which we interpret as a pull-apart detachment fault. These characteristics imply persistent extension during the basin evolution, caused by a NW-SE directed tensional force. The $Ch{\check{o}}ngja$ basin is, thus, a kind of syndepositional tectonic basin evolved in a strike-slip (pull-apart) regime. The latter was caused by a dextral simple shear associated with the NNW-SSE opening of the East Sea. In view of the fact that the normal growth faults do not cut through the uppermost portion of the youngest $Sinhy{\check{o}}n$ Formation, it is inferred that the tensional force came to be inactive in the early Middle Miocene. This is coincident in timing with the termination of the East Sea opening (15 Ma).

• Parasites, Hosts and Diseases
• /
• v.27 no.4
• /
• pp.253-260
• /
• 1989

Metacercariae of the genus Stictodora encysted in the head tissue of Acanthogobius navimanus (the gobies) caught at Sachun-gun, Kyongnam Province, were identified to be Stictodora Zari Yamaguti, 1939 (Trematoda: Heterophyidae), a new parasite fauna in Korea. The metacercariae were 0.39∼,0.43 mm by 0.32∼0.35 mm in size, long elliptical, and with a thin and transparent cyst wall. Total 200 metacercariae were collected from 50 gobies. In order to obtain adult worms two kittens and a Puppy were infected each with 34∼100 metacercariae, and total 33 adults were recovered between the day 4 and day 8 post-infection. The S. sari adults measured 0.95∼1.18 mm long and 0.26∼0.32 mm wide and the eggs in uteri 0.028∼0.033 mm by 0.017∼0.020 mm. The most characteristic morphological feature of these flukes was the presence of a gonotyl and gonotyl spines arranged in two groups; densely crowded group of 30~40 spines and linearly-arranged one of 30∼40 spines, together of which made a comma(or reversed comma) shape along the lateral margin of the gonotyl. It has been proved by this study that 5. sari is distributed in southern coasts of Korea.

• Journal of Korean Society of Coastal and Ocean Engineers
• /
• v.18 no.3
• /
• pp.198-210
• /
• 2006

POM(Princeton Ocean Model) was utilized in this study because it took ${\sigma}-coordinate$ system which could predict the behavior of bottom water. The model has been increasingly applied to costal area although it was initially developed as the ocean flow model. The original POM did not correct computational errors in transformation of ${\sigma}-coordinate$ system. The trying to reduce conversional errors might improve accuracy of flow velocity in vicinities of bottom layer. Therefore, in this study it was proposed to modify the original POM by using error correction method suggested by $Sl{\Phi}rdal$(1997). The modified POM was applied to Young-rang Lake, one of the typical brackish lakes in Korea. It was found that the behavior of bottom water could be well predicted. Thus, it seems that the modified POM can be used as a useful tool to clarify the mechanism of formation and behavior of bottom water including oxygen-deficient water mass.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.21 no.7
• /
• pp.1-11
• /
• 2020

This study investigated the mesozooplankton community and the related environmental factors in the Nakdong River Estuary in May and early October shortly after passage of the typhoon "DUJUAN" in 2015. The mesozooplankton community was dominated by barnacle nauplii, foraminiferans, and Noctiluca scintillans, and the environmental characteristics were characterized by freshwater inflow through the Nakdong River barrage, the intrusion of warm currents, and the effect of typhoon passage in October. In May, cladocerans, such as Evadne nordmanni and Podon polyphemoides, as indicator species of brackish water, prevailed throughout the study area. The surface salinity was lowest on the inner side of the barrier-islands and increased gradually to the outer side during the study. The average concentration of total suspended solids in October was higher than that in May, while the averaged concentration of nitrate and chlorophyll-a in May was higher than those in October. On the other hand, there was no temporal difference in the total averaged abundance of mesozooplankton. In contrast, the distributional pattern of the mesozooplankton community was associated with the salinity gradient in both seasons. These results suggest that the temporal difference of the mesozooplankton community depended on the extent of freshwater inflow by barrage opening, the intrusion intensity of warm currents, and typhoon passage in the Nakdong River estuary in 2015.