Relationship between ultraviolet (UV) radiation and mycosporine-like amino acids (MAAS) in marine organisms.

Abstract

Although only about 5-7% of solar radiation reaching the earth's surface is composed of UV-A (320-400 nm) and UV-B (286-320 nm), the biological significance of these wavelengths is disproportionate due to the higher energy content of quanta in the UV compared to the visible portion of the spectrum (Moseley, 1988). Exposure of shallow-water benthic organisms to high fluxes of solar irradiance requires a trade-off between maintaining high rates of photosynthesis while preventing damage from UV radiation. Biochemical defenses against the effects of UV may include the presence ofmycosporine-like amino acids (MAAs) (Dunlap and Shick, 1998 and refs therein). These compounds have been found in a variety of marine organisms spanning from cyanobacteria (Shibata, 1969) to teleosts (Dunlap et al., 1989) and from tropical (Dunlap et al., 1986) to Antarctic waters (Karentz et al., 1991). Some tropical and temperate open ocean waters have low attenuation coefficients of UV and photosynthetically active radiation (PAR, 400-700 nm) due to the low levels of particulates and humic substances which absorb or scatter these wavelengths (Kirk, 1994). In other waters, such as around mangroves and estuaries, dissolved organic matter or gilvin and particulates decrease the transparency of the water column resulting in reduced penetration of PAR and even greater reduction of UV with increasing depth (Kirk, 1994). The purpose of this study was to survey for the presence of MAAs in macrophytes and invertebrates from habitats differing in water quality to determine the relationship between the concentration of these compounds and incident UV radiation.