Abstract

Hypoxic bottom $(\leq2.0ml/l),\;40\%\;oxygen\;saturation)$ is formed in the semi-closed Wonmun bay during summer and autumn early. This study was carried out to know seasonal distribution of marine bacteria and the role of marine bacteria for forming the hypoxic bottom at Wonmun bay during summer and autumn early, 1990. During the study periods, 170 bacterial strains were isolated from sea water and sediment. Viable cell counts were ranged between $10^5-10^7\;cells/ml$. The dominant species were Acinetobacter spp. in spring, Flavobacerium spp. in summer, Pseudomonas spp. in autumn, Serratia spp. in winter. Because ETSA(Electron Transport System Activity) reveals potential consumption of oxygen in the aquatic microorganisms, the ETSA was used as potential consumption of oxygen in this study. The potential consumption of oxygen was in the range of $232.4-637.5{\mu}l/O_2/l/day$ by marine organism and $142.6-432.4{\mu}l/O_2/l/day$ by marine bacteria during the study periods. The ratio of potential oxygen consumption of marine bacteria to total marine microorganism was 0.54. The potential consumption of oxygen by marine bacteria closely related with the number of viable cells. Consequently, bacteria play an important role to form Hypoxic bottom at marine environment.

반폐쇄만이며 하계동안 저층 빈산소수괴(Hypoxic bottom area)가 형성되는 진해만 일대 해역중의 하나인 원문만에서 해양세균의 계절적 분포와 해양세균이 용존산소소모에 미치는 영향을 알기 위하여 하계동안 미소생물의 전자전달계 활성도(Electron transport system activity)로서 잠재적 산소소모량(potential consumption of oxygen)을 구하였다. 해양세균의 계절별 우점종은 추계('89년 10월)에는 Pseudomonas spp., 동계 ('90년 2월)에는 Serratia spp., 춘계('90년 5월)에는 Acinetobacter spp., 하계('90년 8월)에는 Flavobacterium spp.가 우점하였다. 조사기간동안 생균수는 하계('90년 8월)에 표층, 저층, 저질의 평균치가 각각 $2.12\times10^6cells/ml,\;1.34\times10^6cells/ml,\;1.55\times10^7cells/ml$로 높은 분포치를, 동계에는 표층, 저층, 저질의 평균치가 각각 $2.08\times10^5cells/ml,\;1.54\times10^5cells/ml,\;1.28\times10^6cells/ml$로 낮은 분포치를 보여주었다. 또한 전자전달계 활성(Electron Transport System Activity)으로 잠재적 산소소모량을 조사한 결과 하계동안 수괴에서 미소생물군집의 잠재적 산소소모량은 $232.4-637.5{\mu}l/O_2/l/day$, 이중 세균의 잠재적 산소소모량은 $142.6-432.4{\mu}l/O_2/l/day$로서 수괴의 미소생물군집의 잠재적 산소소모량의 약 $55\%$를 차지하여, 하계동안 저층의 산소소모에 큰 영향을 미침을 알 수 있었으며, 세균의 잠재적 산소소모량은 생균수와 밀접한 관계가 있었다.

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