MEPS 246:61-71 (2003)  -  doi:10.3354/meps246061

ABSTRACT: Emiliania huxleyi is an important component of the global carbon and sulfur cycles and is known to be sensitive to ultraviolet (UV) radiation. We investigated the influence of radiation intensity and of short-term exposure to UV radiation on the per-cell amount and intracellular concentration of dimethylsulfoniopropionate (DMSP). E. huxleyi (strain L) was exposed to artificial radiation intensities similar to those at 15 m (700 µmol PAR [photosynthetically active radiation] m^-2 s^-1) and 25 m depth (400 µmol PAR m^-2 s^-1) in the subtropical Atlantic Ocean. Exposure to UV radiation led to a 10 to 25% increase in the per-cell amount of DMSP as compared to E. huxleyi exposed to only PAR, whereas photosynthetic activity (measured via oxygen production) of UV-exposed E. huxleyi was reduced by 18 to 22%. Furthermore, the intracellular DMSP concentration was always higher in PAR+UV-exposed E. huxleyi than in PAR-exposed E. huxleyi, despite the small but significant increase in cell volume of E. huxleyi after exposure to PAR+UV as compared to PAR exposure only. A shift of the radiation conditions to higher levels resulted in a short-term increase in the per-cell amount and intracellular concentration of DMSP. E. huxleyi cultured in turbidostats under different radiation intensities (ranging from 5.6 to 400 µmol PAR m^-2 s^-1) revealed a significant monotonical increase in the per-cell amount and the intracellular concentration of DMSP with increasing radiation intensity.

KEY WORDS: Coccolithophorida · Emiliania huxleyi · Ultraviolet radiation (UV) · DMSP · DMS · Marine sulfur cycle