The tropical and subtropical oceans experience intense incident ultraviolet radiation (280-400 nm) while their water columns are thought to be highly transparent. This combination represents a high potential for harmful effects on organisms, yet only few reports on the UV penetration properties of oligotrophic tropical waters exist. Here, we present the pattern of UV attenuation over a wide latitudinal range of the oligotrophic Red Sea. We recorded spectroradiometer profiles of PAR and UV, together with chlorophyll-a (Chl-a) and light absorption by chromophoric dissolved organic matter (CDOM) to determine the contribution of phytoplankton and CDOM towards UV attenuation. Transparency to UV exhibited a distinct latitudinal gradient, with the lowest and highest diffuse attenuation coefficients at 313 nm (Kd (313)) of 0.130 m-1 and 0.357 m-1 observed at the northern coast off Duba, and in the south close to the Farasan islands, respectively. Phytoplankton and CDOM both modulated UV attenuation but CDOM was found to be the key driver despite the lack of riverine inputs. We confirm that ultraviolet radiation can reach deeper into the Red Sea than previously described, which means its potential to act as a stressor and selective driver for Red Sea organisms may have been underestimated to date. This article is protected by copyright. All rights reserved.
|Original language||English (US)|
|Number of pages||13|
|Journal||Photochemistry and Photobiology|
|State||Published - Jun 5 2019|
Bibliographical noteKAUST Repository Item: Exported on 2020-10-01
Acknowledged KAUST grant number(s): BAS/1/1072-01-01
Acknowledgements: We would like to express special thanks to the staff of the Coastal and Marine Resources Core Lab (CMOR) at King Abdullah University of Science and Technology (KAUST), and the crews of the R/V Thuwal and R/V Al Azizi for their expert support and assistance. The research reported in this publication was supported by baseline funding from KAUST under award number BAS/1/1072-01-01 to S. Agustí, and the KAUST RSRC Center Competitive Fund (CCF).