Variability in the Relative Penetration of Ultraviolet Radiation to Photosynthetically Available Radiation in Temperate Coastal Waters, Japan |
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| Authors: | Victor S Kuwahara Tatsuki Toda Koji Hamasaki Tomohiko Kikuchi Satoru Taguchi |
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| Institution: | (1) Faculty of Engineering, Soka University, 1-236 Tangi-cho, Hachioji, Tokyo, 192-8577, Japan;(2) Faculty of Engineering, Soka University, 1-236 Tangi-cho, Hachioji, Tokyo, 192-8577, Japan;(3) Faculty of Applied Biological Science, Hiroshima University, 1-4-1 Kagamiyama, Higashi-Hiroshima, 739-8528, Japan;(4) Faculty of Education and Human Sciences, Yokohama National University, 79-2 Tokiwadai, Hodogaya, Yokohama, 240-0067, Japan |
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| Abstract: | UVR and PAR wavelengths are attenuated to different extents within the water column, causing variations in spectral composition with depth. The present investigation (a) describes the variability of UVR and PAR penetration at a station in the temperate coastal waters of Sagami Bay and determines (b) the characteristics of relative UVR penetration to the euphotic zone. Examination of the seasonal irradiance profile measurements indicated eight measurements displaying two distinct attenuation coefficients (K
d) for specific UVR wavelengths and PAR. The two attenuation coefficients observed from specific wavelengths in the water column may be caused not only by chlorophyll pigments, but also by dissolved organic material in the upper layer. The 1% depth of surface UVR at 305, 320, 340, and 380 nm averaged 10.8 ± 5.7, 14.9 ± 9.5, 19.8 ± 12.1, and 30.4 ± 17.6 m, respectively. The depth of euphotic layer displayed less variability averaging 62 ± 15 m throughout the entire study. Relative UVR penetration within the euphotic zone averaged 17.8 ± 8.1, 22.9 ± 10, 30.5 ± 13.8, and 46 ± 46.9% for 305, 320, 340, and 380 nm, respectively. A large variation of the relative transmission of UVR within the euphotic zone was found although the spectral composition was relatively stable in the air throughout the study. |
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| Keywords: | Ultraviolet radiation light penetration irradiance temperate coastal water seasonal variation |
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