Photochemical reaction and stability of marine fluorescent dissolved organic matter - a key process of bacterial long-term isolation of carbon

2016 Fiscal Year Final Research Report

• Project/Area Number: 15K13599
• Research Category: Grant-in-Aid for Challenging Exploratory Research
• Allocation Type: Multi-year Fund
• Research Field: Geochemistry/Cosmochemistry
• Research Institution: University of Tsukuba
• Principal Investigator: HAMA Takeo 筑波大学, 生命環境系, 教授 (30156385)
• Research Collaborator: IWASAWA Eri ; SAEKI Akira
• Project Period (FY): 2015-04-01 – 2017-03-31
• Keywords: 蛍光性溶存態有機物 / 微生物炭素ポンプ / 光化学反応

Outline of Final Research Achievements

Experimental analysis was carried out to elucidate the phochemical reactivity of marine fluorescent dissolved organic matter (FDOM) derived from bacteria.
Sea water sample collected from Shimda Bay, Shozuoka, was incubated under light and dark conditions for 24 h. The fluorescence intensity increased under the dark condition throughout the incubation, whereas it showed decrease under light condition in day time. These results confirmed that FDOM is produced by bacterial activity throughout the day and nighit time but quenching proceeds in the daytime in the oceanic surface layer.
Water sample collected was irradiated by a sun simulator corresponding. Fluorescence intensity decreased by 17-50% of the initial intensity showing the high photodegradability of the fluorosphore of FDOM. Organic carbon, on the other hand, exibited a little change during the exposure. This result strongly suggests that the lifetime of organic carbon of bacterial FDOM is much longer than its fluororescence.

Free Research Field

海洋物質循環