Variability of Solar Radiation and CDOM in Surface Coastal Waters of the Northwestern Mediterranean Sea
Richard Sempéréa✉, Julien Paraa, Marc Tedettia, Bruno Charrìèrea b, Marc Malletc d
- aAix‐Marseille Université, Mediterranean Institute of Oceanography (M I O) Université de Toulon CNRS‐INSU/IRD Marseille France
- bCEFREM CNRS – Université de Perpignan Marseille France
- cCNRS Laboratoire d'Aérologie Toulouse France
- dUniversité Paul Sabatier de Toulouse Laboratoire d'Aérologie Toulouse France
- ✉Corresponding author
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Abstract
Atmospheric and in-water solar radiation, including UVR-B, UVR-A and PAR, as well as chromophoric dissolved organic matter absorption [aCDOM (λ)] in surface waters were monthly measured from November 2007 to December 2008 at a coastal station in the Northwestern Mediterranean Sea (Bay of Marseilles, France). Our results showed that the UVR-B/UVR-A ratio followed the same trend in the atmosphere and at 2 m depth in the water (P < 0.0001) with an increase (eight-fold higher) during summer. The low diffuse attenuation coefficients for downward irradiance [Kd (λ)] of UVR-B, UVR-A and PAR indicated that the waters were highly transparent throughout the year. The relationships between aCDOM (λ) and Kd (λ) in this oligotrophic system suggested that CDOM contributed to UVR attenuation in the UVA domain, but also played a significant role in PAR attenuation. Mean UV doses received in the mixed layer depth were higher by a factor 1.4-33 relative to doses received at fixed depths (5 and 10 m) in summer (stratified period), while the inverse pattern was found in winter (mixing period). This shows the importance of taking into account the vertical mixing in the evaluation of UVR effects on marine organisms.
TL;DRThe authors' results showed that the UVR‐B/UVR–A ratio followed the same trend in the atmosphere and at 2 m depth in the water (P < 0.0001) with an increase (eight‐fold higher) during summer, and the importance of taking into account the vertical mixing in the evaluation of UVR effects on marine organisms is shown. (Semantic Scholar)