Mycosporine-like amino acids in the marine dinoflagellate Gyrodinium dorsum: induction by ultraviolet irradiation

Cultures of the marine dinoflagellate Gyrodinium dorsum have been exposed t o polychromatic radiation (photosynthetically active radiation and UV) from a solar simulator for up to 72 h. Different irradiance spectra in the ultr aviolet are produced by inserting cut-off filters between lamp and samples. The mycosporine-like amino acid (MAA) content and composition are investig ated by spectroscopic and chromatographic analysis. The study reveals that G. dorsum contains a complex mixture of several aminocyclohexenimine-MAAs a nd one aminocyclohexenone-MAA. UV irradiation around 320 nm induces an incr ease in the concentration of all MAAs in the samples. In contrast, exposure to short-wavelength W-B radiation results in decreased overall MAA product ion. Furthermore, there is a spectral shift in the absorption of the MAA mi xture towards shorter wavelengths, indicating that short-wavelength UV-B in duces an altered MAA composition. The amount of MAAs is normalized to the c hlorophyll a concentration. (C) 2000 Elsevier Science S.A. All rights reser ved.