12:00 〜 12:15
[MIS21-P03_PG] 日本海内部における腐植様蛍光物質の蓄積
ポスター講演3分口頭発表枠
キーワード：日本海, 溶存有機物, 腐植様蛍光物質
Marine dissolved organic matter (DOM) is the largest reduced carbon reservoir in ocean. Most marine DOM is produced by marine biota and is resistant to rapid microbial degradation. Thus, it is crucial to know the dynamics of recalcitrant DOM for determining whether the marine DOM reservoir is stable or not. Even though there have been several hypotheses regarding with the recalcitrant mechanism of marine DOM, the microbial production of recalcitrant DOM (defined as microbial carbon pump) has been considered as the main process. Humic-like fluorescent DOM (FDOMH) has found to produce during microbial incubation. Even though FDOMH has known to easily degrade by sunlight, linear relationships between fluorescence intensity of FDOMH and indicators of microbial remineralization, e.g., apparent oxygen utilization (AOU), have been observed throughout the ocean. These experimental and observational results imply that FDOMH is a product of microbial carbon pump. Another important source of FDOMH, especially in coastal environments and marginal seas, is riverine supply. Even though the major fractions of FDOMH have been considered to be photo-degraded in coastal environments, substantial contribution of terrestrial FDOMH into ocean interior has been suggested. Thus, in addition to accumulation of in situ produced FDOMH, recalcitrant terrestrial FDOMH might occur in deep ocean, especially in marginal seas. However, it is not clear whether recalcitrant autochthonous and/or terrestrial FDOMH is accumulated in deep ocean of marginal seas or not.
We determined vertical profiles of FDOMH at 5 stations in the Japan Sea and 5 stations in the western North Pacific using excitation emission matrix fluorescence with parallel factor analysis (EEM-PARAFAC). Seawater samples from surface to bottom waters of the Japan Sea and the western North Pacific were collected during T/S Oshoro-maru (C184) and R/V Tansei-Maru (KT-11-17) cruises, respectively. Two FDOMH were obtained after EEM-PARAFAC and assigned as traditional terrestrial and marine (microbial) FDOMH, respectively. In the Japan Sea, levels of both FDOMH were lowest in surface waters, gradually increased with depth below surface waters, and were highest in waters distributed depths greater than 2000 m that were corresponding to the lower part of Japan Sea Proper Water (JSPW), i.e., lower part of the Japan Sea Deep Water (JSDW) and the Japan Sea Bottom Water (JSBW). Levels of both FDOMH were linearly correlated with AOU in the JSPW, suggesting that both FDOMH were produced in situ in the JSPW. Interestingly, levels of both FDOMH in the JSPW were similar or slightly higher compared with those in deep waters of the western North Pacific, even though AOU in the JSPW were significantly lower than those in deep waters of the western North Pacific. Such distributional characteristics of FDOMH in the JSPW imply that FDOMH is accumulated in the interior of the Japan Sea. We will discuss possible origin and accumulation mechanism of FDOMH in the Japan Sea interior.
We determined vertical profiles of FDOMH at 5 stations in the Japan Sea and 5 stations in the western North Pacific using excitation emission matrix fluorescence with parallel factor analysis (EEM-PARAFAC). Seawater samples from surface to bottom waters of the Japan Sea and the western North Pacific were collected during T/S Oshoro-maru (C184) and R/V Tansei-Maru (KT-11-17) cruises, respectively. Two FDOMH were obtained after EEM-PARAFAC and assigned as traditional terrestrial and marine (microbial) FDOMH, respectively. In the Japan Sea, levels of both FDOMH were lowest in surface waters, gradually increased with depth below surface waters, and were highest in waters distributed depths greater than 2000 m that were corresponding to the lower part of Japan Sea Proper Water (JSPW), i.e., lower part of the Japan Sea Deep Water (JSDW) and the Japan Sea Bottom Water (JSBW). Levels of both FDOMH were linearly correlated with AOU in the JSPW, suggesting that both FDOMH were produced in situ in the JSPW. Interestingly, levels of both FDOMH in the JSPW were similar or slightly higher compared with those in deep waters of the western North Pacific, even though AOU in the JSPW were significantly lower than those in deep waters of the western North Pacific. Such distributional characteristics of FDOMH in the JSPW imply that FDOMH is accumulated in the interior of the Japan Sea. We will discuss possible origin and accumulation mechanism of FDOMH in the Japan Sea interior.