共同研究報告書


研究区分 一般研究

研究課題

 アイス・アルジー群集初期形成過程の実験的解明
研究代表者／所属 創価大学・工学部・生物工学科
研究代表者／職名 教授
研究代表者／氏名 田口　哲

研究分担者／氏名／所属／職名
　
氏　　名
所　　属
職　　名

1

 田口哲 創価大学 教授

2

 柴田晃 創価大学 助手

3

 服部寛 北海道東海大学 教授

4

 濱崎恒二 広島大学 講師

5

 高橋一生 東北海区水産研究所 研究員

6

 白澤邦男 北大低温研

研究目的 The microbial loops in ice algal community are dominated often by large cell diatoms. Based on our previous study， small cells in picoplankton size were abundant at the beginning of ice formation. This comparison strongly suggests the occurrence of species succession as sea ice grows. Our novel method to study the ice formation and incorporation of organisms into sea ice was applied to study on the species succession of ice algal community.
　　
研究内容・成果 Water temperature indicated a daily fluctuation due to daily variation of solar incident radiation and ranged from -1.8 to -1.1 oC. Salinity of newly formed sea ice ranged from 12.9 to 28.3 PSU. The accumulation compared to the seawater at the maximum concentration of phosphate and nitrate in the newly formed sea ice was 17 and 23 %， respectively while it was 60 % for silicate and 77 % for nitrite. The accumulation of chlorophyll a in the newly formed sea ice compared to one in the seawater ranged from 28 to 43 % during the present experiments. Chlorophyll a concentration in a size range of > 2 m occupied more than 67 % in the seawater under the newly formed sea ice while one in size range of < 2 m occupied more than 60 % in the newly formed sea ice. A weight ratio of C/N in the sea ice did not show much variation with mean of 7.1  0.3. All groups of organisms were incorporated into the newly formed sea ice. Their abundance was 1.7  0.95 x 102 for bacteria， 4.6  3.6 x 102 for viruses， and less than 1.0 x 10-3 cell ml-1 for nanoflagellates， respectively.
A ratio of viruses to bacteria at the abundance plateau was 10 in the newly formed sea ice compared to 100 in the seawater. Those low ratios may suggest that microbial community reach to a stable condition in the sea ice. A ratio of nanoflagellates to bacteria at the abundance plateau was 10-4 which might indicate that nanoflagellates were still in the progress of development in the sea ice. Overall significant relationships among bacteria， viruses， and nanoflagellates were maintained during the different stages of habitat from seawater to sea ice. Since the slopes of those relationships were different among three relations， maintenance of nonoflagellate abundance might require more bacteria than viruses.