AN INVENTORY OF UV-ABSORBING MYCOSPORINE-LIKE AMINO-ACIDS IN MACROALGAE FROM POLAR TO WARM-TEMPERATE REGIONS

A qualitative and quantitative survey of 11 green, 27 brown and 30 red macroalgal species collected from polar (Spitsbergen), cold-temperate (Helgoland) and warm-temperate (southern Spain) regions revealed that all Rhodophyceae from the eulittoral zone contained several UV-absorb ing mycosporine-like amino acid compounds (MAAs), which are assumed to function as natural UV-sunscreens. In contrast, deep-water red algae, as well as the Chlorophyceae and Phaeophyceae did not contain MAAs or exhibited only trace concentrations. Within all species investigated 9 distinct compounds were found, of which 7 were identified as mycospo rine-glycine, shinorine, porphyra-334, palythine, asterina-330, palyth inol and palythene. The remaining two substances are unknown; they had different retention times under the chromatographic conditions used, but identical absorption spectra with a maximum at 357 nm. Both compou nds are restricted to a few polar red algae. In Polysiphonia arctica J . Agardh (Rhodophyta) from Spitsbergen the concentrations of MAAs decr eased from depths of 1 to 7 m. Shallow-water isolates contained > 5-fo ld higher total MAA amounts compared to deep-water samples. In additio n, the contents of all MAAs correlated with the biogeographic region i ndicating that the lower the natural solar irradiance in the respectiv e habitat the less MAAs are synthesised and accumulated. The red algal samples from Spain exhibited up to 2-fold higher MAA contents compare d to species from cold-temperate and polar waters supporting the idea of a UV-dose-dependent induction and/or concentration. The data suppor t the idea that MAAs represent a least for red macroalgae a natural de fense system against exposure to biologically harmful UV-radiation.