日本地球惑星科学連合2014年大会

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インターナショナルセッション(口頭発表)

セッション記号 B (地球生命科学) » B-PT 古生物学・古生態学

[B-PT02_1AM2] Biocalcification and the Geochemistry of Proxies

2014年5月1日(木) 11:00 〜 12:45 421 (4F)

コンビーナ:*豊福 高志(独立行政法人海洋研究開発機構)、北里 洋(独立行政法人海洋研究開発機構海洋・極限環境生物圏領域)、Bijma Jelle(アルフレッドウェゲナー極域海洋研究所)、座長:豊福 高志(独立行政法人海洋研究開発機構)

12:15 〜 12:30

[BPT02-12] カリブ海のサンゴ骨格に記録される北大西洋の窒素固定量の変動

*山崎 敦子1Hetzinger Steffen2Reumont Jonas V.2Manfrino Carrie3角皆 潤4渡邊 剛5 (1.東京大学大気海洋研究所、2.GEOMAR Helmholtz-Zentrum fur Ozeanforschung Kiel、3.Central Caribbean Marine Institute、4.名古屋大学大学院環境学研究科、5.北海道大学理学研究院)

キーワード:Coral skeletons, nitrogen isotopes, nitrogen fixation, Caribbean Sea, North Atlantic Ocean

Oceanic nitrogen fixation is important as new nitrogen in oligotrophic oceans and balances with denitrification in global nitrogen cycle controlling primary production. North Atlantic ocean is known to have higher nitrogen fixation rates, although the controlling factors have been debated by modern observations and sediment cores in geological time scales. Reef corals have been widely used as paleo-environmental proxy in oligotrophic oceans. Recent studies suggested that nitrogen isotopes of organic matter preserved in coral skeletons δ15Ncoral have the potential to record coral nitrogen sources on decadal to millennia scale. In this study, we report recent 90-year records of nitrogen isotopes in Diploria sp. coral cores from Cayman Islands. δ15Ncoral values were +1.9±2.6 (σ)‰ (n=139), which suggested that the variation of δ15Ncoral was controlled by nitrogen fixation (~0‰) in ambient seawater. The trend line of δ15Ncoral increased ~4‰ from 1920s to 2010s. This result suggests that nitrogen fixation rate in Caribbean Sea decreased during the past 90 years. Detrended δ15Ncoral showed a negative correlation between Atlantic Multi-decadal Oscillation (AMO) index (R=-0.71, P‹‹0.001), which suggested that nitrogen fixation rate increased in higher SST condition leading an index for hurricane activity on multi-decadal scales. In this presentation, we discuss the relationship between nitrogen fixation and hurricane activity in global warming state.