• Korean Journal of Environmental Biology
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• v.27 no.2
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• pp.135-139
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• 2009

The abundance of earthworm in the agroecosystem of Sunyu Island was estimated on the basis of 1,025 individuals collected in August and October, 2007. Material were collected from litter layers and soils by hand sorting and digging. They encompassed 12 species, 4 genera, and 3 families. Species composition and abundance were as follows: Amynthas heteropodus 29.7%, Aporrectodea tuberculata 22.6%, Aporrectodea caliginosa 19.5%, Drawida japonica 11.3%, Amynthasagrestis 5.0%, Amynthas hupeiensis 3.6%, Aporrectodea sp. 3.5%, Amynthas corticis 2.0%, Bimastos parvus 1.6%, Amynthas koreanus 0.8%, Amynthas hilgendorfi 0.2%, and Amynthas sp. 0.2%. Of 537 individuals, A. heteropodus, and A. tuberculata were the most numerous members with abundance of 52.4%. The clitellate vs. aclitellate ratio of the earthworm was approximately 1:1.1.

• Ocean and Polar Research
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• v.30 no.4
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• pp.519-536
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• 2008

The relatively tranquil area within the Gogunsan Archipelago was for the first time investigated preliminarily with respect to modern sedimentological processes in association with the emplacement of the Saemangeum Dyke. Basic sedimentological observations, bathymetry and surface sediments were performed twice during 2006-2008 to compare the results and elaborate changes during that period of time. In addition, sediment dynamical observations were carried out with latest measuring equipment along two transects crossing the entrances of the archipelago, including 12-hour onboard measurements of current, suspended sediments, temperature, and salinity. This dataset was used to reveal hydrodynamic characteristics for spring season April-May and to estimate the direction and relative magnitude of the net flux of suspended sediments. There occurred three depositional areas (A to C) within the archipelago, where sediment texture was also changed. In area A, around Yami Island and the dyke, and area B, in the center of the archipelago, surface sediments became coarsened over the two-year period; sand content increased 5% at the expense of silt content in the former, whereas silt content increased 3% at the expense of clay content in the latter. By comparison, area C in the western entrance of the archipelago shows a textural trend of fining with more silt and clay (combined increase of 5%) at the expense of sand content. The accumulation of sediments in areas A and B is attributable to the sand and silt resuspended from the seabed sediments off sector 4 of the dyke during the winter. The origin of the fine materials depositing on area C is uncertain at present, although suspended sediments moving offshore around the archipelago may be one of the most likely candidates for the source. The temperature of seawater increased rapidly from $9-10^{\circ}C$ in April to $14-16^{\circ}C$ in May, whereas salinity remained more or less constant at 31-32%o during the two months. Both of these parameters showed little variations with depth through a tidal cycle, suggesting good mixing of seawater without any help of significant waves. The consistency of salinity during a tidal cycle also indicates no insignificant effects of freshwater from the rivers Mangyung and Donjin emitting through the opening gap near Sinsi Island. The suspended sediment concentrations were higher at the entrance between Sunyu and Sinsi islands than at the entrance between Hoenggyong and Sinsi islands, ranging from 20 and 30 mg/l and from 5 and 15 mg/l, respectively at the sea surface. Although tidal currents were variable across a transect between Sunyu and Sinsi islands, the currents across the entrance between Hoenggyong and Sinsi islands flowed consistently in the same direction all over the transect during a tidal cycle. The estimation of net flux of suspended sediments indicates that suspended sediments are transferred to the Gogunsan Archipelago mainly through a relatively deep trough adjacent to Sinsi Island toward the shallow area around Yami Island and the dyke.