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Latitudinal Gradient of UV Attenuation Along the Highly Transparent Red Sea Basin
Author(s) -
Overmans Sebastian,
Agustí Susana
Publication year - 2019
Publication title -
photochemistry and photobiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.818
H-Index - 131
eISSN - 1751-1097
pISSN - 0031-8655
DOI - 10.1111/php.13112
Subject(s) - colored dissolved organic matter , attenuation , environmental science , phytoplankton , oceanography , ultraviolet , chlorophyll a , spectroradiometer , ocean color , atmospheric sciences , chemistry , geology , ecology , physics , biology , nutrient , optics , reflectivity , biochemistry , satellite , astronomy
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 toward UV attenuation. Transparency to UV exhibited a distinct latitudinal gradient, with the lowest and highest diffuse attenuation coefficients at 313 nm ( K d (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.