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Content archived on 2024-05-29

UV photochemical bleaching of phytoplankton and Coloured Dissolved Organic Matter and the interactive effects on the inhibition of photosynthesis and the production of phytoplankton sunscreeens.


Phytoplankton is the most important biomass producer in aquatic ecosystems. Recent research has shown a pronounced sensitivity of phytoplankton to ultra-violet (UV) radiation as a consequence of the substantial decrease in stratospheric ozone over high and mid latitude waters, which can result in a significant inhibition of photosynthesis. Solar UV radiation (in particular UV-B) affects the marine ecosystem through various processes, from photo-damage of phytoplankton cells and photo-inhibition of photosynt hesis, to photochemical bleaching of the colored fraction of dissolved organic matter (CDOM). Phytoplankton has developed various strategies to prevent from photo-damage and photo-inhibition under high irradiance i) in the visible through the production of photo-protective pigments (e.g. xanthophylls cycle), and ii) in the UV spectral range through the production of UV-absorbing compounds such as mycosporine-like amino acids (MAAs) which act as sunscreens. Colored dissolved organic matter is one of the mai n components controlling light penetration in the water column at shorter wavelengths. CDOM photochemical bleaching will thus result in a deeper penetration of light in the visible and UV range, and consequently can affect phytoplankton photosynthesis. The interactive effects of UV radiation on CDOM photochemical bleaching, and phytoplankton photosynthesis and photoprotective mechanisms requires further study. This proposal aims at examining these interactive effects using laboratory experiments on phytopla nkton cultures and field studies in open ocean and coastal waters in the English Channel over a seasonal cycle. State-of-the-art of optical techniques will be used to characterize the underwater optical properties and phytoplankton photosynthesis and natur al samples will be incubated under different light intensities. The link between UV dosage and Chla and CDOM will be investigated using radiative transfer optical models and MODIS and MERIS satellite data.

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Prospect Place, West Hoe
United Kingdom

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