MICROENVIRONMENT IN OYSTER FARM AREA 1. On the Eutrophication and Raft Density in Geoje Bay

굴 양식장의 미세환경에 관한 연구 1. 거제만의 양식장밀도 및 부영양화에 관하여

After a great mortality owing to abnormal oceanographical condition and fungal disease in 1973 hanging cultch lines per raft has been reduced to 450 from 558, and oyster production per raft has also been decreased. It seems to be result of dense culture of oysters and its resulting accumulation of waste materials on the sea bottom in the farm area. The present study was carried out to investigate the effect of rearing density and the degree of eutrophication in Geoje Bay for 6 months from June through November in 1977. Total area of this bay is about $48.9\;km^2$, and the area of registered oyster farms as of November in 1977 is around $10.9\;km^2$, which is about $22.3\%$ of this bay. Water Quality during summer season was shown as transparency 5.5 m, COD 1.5ppm, degree of oxygen saturation $90.6\%$ in upper and middle layers and $82.2\%$ near bottom, chlorophyll-a 3.0 mg/m^3, and phytoplankton $8.7\times10^4\;cells/l$. In superficial mud in August COD was 35.4 mg/g, total sulphide 0.24 mg/g, and phaeophytin $43.7\;{\mu}g/g$dry mud. These values indicate that water qualify in this bay is so far excellent but quantities of chemical oxygen demend and sulphide in bottom mud show maximum level or a little over eutrophication standard.

굴 양식장의 환경연구중 거제만양식장의 밀도 및 노화정도에 관한 기초조사를 1977년 6월부터 11월까지 6개월간에 걸쳐 실시하였다. 1. 거제만해역의 면적은 $48.87km^2$이고 도수산국에 등록된 이 해역내의 양식장 수면적은 $10.91km^2$이다. 해역면적에 대한 면허면적은 $22.23\%$이고 면허면적과 해역면적의 비는 1 : 4.48이다. 2. 부영양화의 정도를 A,B,C로 구분하여 C단계를 과영양화로의 과도기단계라 할때, 거제만은 양식어장으로서 수질은 A단계로 양호한 편인데 비해 저질은 C단계로 부영양화의 한계치에 도달되었거나 또는 약간 상회하며 과영영화로 진입하고 있다.