[A-CG57] 北極域の科学

[ACG57-P09] 北極海太平洋側の海洋物理場が生物源ケイ酸粒子の輸送に及ぼす影響

*小野寺 丈尚太郎¹、渡邉 英嗣¹、木村 仁¹、溝端 浩平²、田中 裕一郎³、原田 尚美¹ (1.海洋研究開発機構地球環境観測研究開発センター、2.東京海洋大学海洋科学部海洋環境学科、3.産業技術総合研究所地質調査総合センター)

キーワード：北極海、沈降粒子、珪藻

Under the changing physical oceanographic condition in the Arctic Ocean, transport condition of biogenic particles from shelf to basin in addition to vertical settlement of in situ biogenic particles may affect the ecosystems for deeper water mass and sea floor in the southwestern Canada Basin. In order to monitor the lower-trophic marine ecosystems in changing Arctic Ocean, we have studied the relationship between physical oceanographic condition and settling fluxes of biogenic particles mainly composed of diatom and silicoflagellate. Settling particle samples were collected using time-series sediment trap off the north of Barrow Canyon (NBC: 72.472N 155.407W, 2000 m water depth) and the northern part of Hanna Canyon (NHC: 73.303N 160.782W, 450 m water depth) in the southwestern Canada Basin from fall 2015 to summer 2017. Diatom settling flux increased in summer as a reflection of seasonal productivity increase. The assemblages of settling diatom particles at NBC for the first and second deployment periods was characterized by relative dominance of Thalassionema nitzschioides, which is sometimes observed in southwestern Canada Basin water, and sea-ice related species such as Fossula arctica, respectively. The relative abundance of sea-ice related species was higher at NHC, probably because of the NHC mooring position in more nutrient-rich condition compared to that at NBC. Diatom and silicoflagellate settling-fluxes at NBC also increased with particulate organic carbon in early winter 2016/2017. This reflected the temporal lateral advection of Pacific-origin waters from shelf to basin as the result of temporal changes in atmospheric and physical oceanographic condition.