We investigated the spatial distribution of heterotrophic bacteria associated with different water masses in the northern East China Sea (ECS) in summer. The surface water masses were divided into the Changjiang Diluted Water (CDW) and high salinity water (HSW). In the CDW region, the concentrations of dissolved inorganic nitrogen (DIN) and chlorophyll-a (Chl-a), and micro Chl-a contribution were high; and bacterial abundance (BA) and ciliate abundance (CA) were also high. In the HSW region with relatively low DIN concentrations, Chl-a concentration and micro Chl-a contribution were low, but pico Chl-a contribution was increased compared to those in the CDW region. BA did not show any significant difference from the CDW region, but CA was decreased. BA showed a positive correlation with Chl-a concentration in the CDW region; however, it did not show a significant correlation with Chl-a concentration in the HSW region. The ratio of bacterial carbon biomass/phytoplankton carbon biomass was exponentially increased with a decrease in the Chl-a concentration. Compared to the past (1990-2000s), the surface phosphate concentrations and the size of dominant phytoplankton have recently decreased in the ECS. Considering this trend of nutrient decrease and miniaturization of the phytoplankton, our results indicate that changes in the strength of the oligotrophic water mass could alter the function of the microbial food web.

From June 2007 to May 2008, seasonal variations of bacterial abundance and heterotrophic nanoflagellate (HNF), together with environmental factors, were investigated at weekly and monthly intervals in Kyeonggi Bay. During the study period, the water temperature and salinity varied from 1.9℃~29.0℃ and 31~35.1 psu, respectively. The concentration of ammonia, nitrate+nitrite, phosphate, and silicate ranged from 0.01 to 3.22 μM, 2.03 to 15.34 μM, 0.06 to 1.82 μM, and 0.03 to 18.3 μM, respectively. The annual average concentration of Chl. a varied from 0.86 μg L-1 to 37.70 μg L-1; the concentration was twice as much at the surface than at the deeper layers. The abundance of bacteria and HNF ranged from 0.29×106 to 7.62×106 cells mL-1 and 1.00×102 to 1.26×103 cells mL-1, respectively. In particular, there were significant correlations between bacteria and HNF abundance (p<0.05), and then the high abundance of HNF was frequently observed with an increase of bacterial abundance in summer (p<0.001). Our results therefore indicate that bacterial abundance in the bay was mainly controlled by resources supplied as organic and inorganic substances from Lake Shihwa due to the daily water exchange after dike construction. Also, the bacterial abundance was significantly controlled by HNF grazing pressure (top-down) in the warm seasons, i.e. excluding winter, in the Kyeonggi Bay.

To get more comprehensive understandings about the microbial diversity near the seawater of Ulleung Island, East sea of Korea, the bacterial identification base on 16S rDNA and their carbon source utilization patterns were analysed through the six surface water samples collected at June 23 to 25, 2007. The results are as follows; the population densities of aerobic heterotrophic and oligotrophic bacteria were from 1.9±0.6×104~6.3±0.7 ×104 cfu ml−1 and from 1.7±0.4×103~2.5±0.4×103 cfu ml−1 during sampling periods, respectively. Among 121 isolated stains, the dominant taxa are Pseudoalteromonas spp. (30 colonies) and Alteromonas spp. (17 colonies). Thirty-senven species-level strains base on 16S rDNA sequencing data are identified, which comprised Gammaproteobacteria (14 strains), Alphaproteobacteria (6 strains), Flavobacteria (6 strains), Actinobacteridae (4 strains), Firmicutes (4 strains), Deinococci (2 strains), Betaproteobacteria (1 strains). The carbon utilization patterns by assay of Biolog-microplate, α-D-glucose are used by 88.9% of the 27 strains of Gram-negative bacteria and more than 80% of them also consumed L-arabinose, D-trehalose, L-alanine, and pyruvic acid methyl ester. On the other hand, all the 10 strains of Gram-positive bacteria used α-D-glucose, and more than 80% of them also exploited maltose, palatinose, D-trehalose, turanose, D-xylose, and pyruvic acid.

Samples were taken from the surface waters around Dokdo Island to measure the physico-chemical and microbiological water qualities from June 23 to 26, 2007. Water temperature and dissolved oxygen were in the range of 20.7~20.9oC and 7.01~7.74, respectively. Salinity and pH were in the range of 34.5~34.8‰ and 8.23~8.37, respectively. Population densities of aerobic oligotrophic bacteria and heterotrophic bacteria by plate counting method were in the range of 2.4±0.5×103~3.0±0.3×103 and 4.4±0.6×103~6.0±0.9×103 cfu ml−1, respectively. Among thirty-seven isolates isolated from surface waters around Dokdo island by using 16S rDNA analysis, dominant species were closely related to Actionobacteria (7 clones), α-proteobacteria group (6 clones), and γ-proteobacteria group (4 clones).

본 연구는 경상남도 사천시 삼천포 항을 중심으로 인근의 40개의 조사정점을 선정하여 해수와 저질토에서 해양종속영양세균, E. coli, 그리고 Salmonella와 Shigella의 분포를 2003년 7월부터 12월가지 3차에 걸쳐 실시하였다. 본 연구의 조사기간(2003년 7~12월)중 삼천포만 인근해역의 조사정점에서 해양 종속영양세균의 분포는 1.7±0.9×103~2.4±0.9×105

2000년부터 2002년까지 통영 바다목장 해역 5개 정점표층수와 저층수에서 종속영양세균의 개체수를 평판계수법으로 측정하여 종속영양세균군집의 계절별 변동추이를 비교 분석하고, 우점종을 선별하여 동정하였다. 7월과 8월의 하절기에 채수한 해수에는 봄 혹은 가을 및 겨울에 채수한 해수에 비하여 모든 정점에서 훨씬 더 많은 종속영양세균이 검출되었다. 저층수에 비하여 표층수에서 종속영양세균의 수가 더 많았으나 동절기(2001년 12월과 2002년 2월)에는 해

This study was performed to evaluate the inactivation and microbial regrowth of heterotrophic and nitrifying bacteria using chloramine as a secondary disinfectant for drinking water distribution system. Three sets of the three reactors filled with the Cl2/NH3-N ratio of 3:1, 4:1 and 5:1 were used in these experiments. Chloramine concentration were applied to each set of the reactors with 1㎎/ℓ, 2㎎/ℓ and 3㎎/ℓ, respectively. For the set with 1㎎/ℓ was applied, all the reactors showed that the residual chloramine concentration gradually decreased with elapsed time and reached to zero level after 7 days. Heterotrophic bacteria remarkably increased and nitrification occurred after 11 days. For the sets with 2㎎/ℓ and 3㎎/ℓ, however, the residual chloramine was maintained through the experimenatal period (21 day). Furthermore the regrowth of heterotrophic bacteria and nitrification were not found. More than 2㎎/ℓ of chloramine with Cl2/NH3-N ratio of 3:1, the nitrification could be inhibited by 2 days of contact time.