Sunscreens, marine organisms

Across diverse taxonomic groups of marine organisms there are several classes of compounds that absorb UV and act as putative sunscreens. These include scytonemin (Figure 15.9), an extracellular cyanobacterial sheath pigment, and the mycosporine-like amino acids (MAAs, Figures 15.3-15.6) that are usually located intracellularly in cyanobacteria, algae, invertebrates, and fish. These compounds are the major focus of this chapter and will be discussed in detail below. 

Functional roles treated above are strictly organismal responses to biotic stresses. The use of chemical means to address physical stresses is largely nonexistent. A notable exception to this is the response many organisms make to harmful ultraviolet (UV) radiation. Sunscreens are small organic molecules which absorb UV radiation so that damage to DNA via cross-linking219 225 is prevented. Production of micosporin-like amino acids (MAA) appears to be widespread in shallow-water Antarctic marine invertebrates and macroalgae,223,224 which may be particularly adaptive at present because of the Antarctic ozone hole. 

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