S-1 SUPPORTING INFORMATION Novel Fluorometric Method for the Determination of Production Rate and Steady-State Concentration of Pho- tochemically Generated Superoxide Radical in Seawater Using 3',6'-(Diphenylphosphinyl)fluorescein Adebanjo Jacob Anifowose, Kazuhiko Takeda, and Hiroshi Sakugawa* Graduate School of Biosphere Science, Department of Environmental Dynamics and Management, Hiroshima Univer- sity, 1-7-1 Kagamiyama, Higashi-Hiroshima, Hiroshima 739-8521, Japan *Email: hsakuga@hiroshima-u.ac.jp. Phone: 81 82 424 6504. Fax: 81 82 424 6504.