Vertical distribution of fluorescent organic matter in the North Pacific

• Published in: Marine chemistry 1988-12, Vol.25 (4), p.373-381
• Main Authors: Hayase, Kohji, Tsubota, Hiroyuki, Sunada, Isao, Goda, Shiro, Yamazaki, Hideo
• Format: Article
• Language: English
• Subjects: Earth, ocean, space; Exact sciences and technology; External geophysics; Marine; Marine optics and underwater sound; Physics of the oceans
• ISSN: 0304-4203; 1872-7581
• DOI: 10.1016/0304-4203(88)90117-X

The vertical distributions of fluorescent organic matter were investigated at three stations in the North Pacific. Fluorescence intensity was low in the upper layer, and increased rapidly to a maximum at ∼ 1000-m depth. This vertical profile is similar to that of phosphate and nitrate; in the water column above the fluorescence maximum, fluorescence varies linearly with phosphate, nitrate and silicate. This is the same trend that has been reported for fluorescence and nutrients in the coastal seas of Japan. It is suggested that fluorescent organic matter is degraded in the euphotic zone and regenerated in the water column by degradation of organic matter on the settling particles as in the case of the nutrients. When deeper water was irradiated with UV light, the intensity of fluorescence decreased rapidly with time, implying that photodegradation may be primarily responsible for degradation of the fluorescent substances in the upper layers.