UVB radiation modifies protein and photosynthetic pigment content, volume and ultrastructure of marine diatoms

Abstract

Three marine diatom species (Cyclotella sp., Nitzschia closterium and Thalassiosira nor-densk~oldii) were exposed to a range of daily doses of ultraviolet B radiation (UVBR: 280-320 nm). The lowest UVBR treatments (c2000 J m-' d-!, DNA weighted biologically effective dose, normalised at 300 nm: daily BEDoh,\ nm) resulted in decreased division rates, volume enlargement and elevated cellular protein and pigment content levels. The highest UVBR treatments (between 2000 and 3800 J m-' d-' daily BEDnu, l rl i , , , ) resulted in complete growth inhibition, accompanied by only minor changes in protein, pigments and cell volume. Recovery of cell division after UVBR exposure was decreasingly successful with increasing UVBR dose rates. Ultrastructural examination of exposed Cyclotella cells indicated that high UVBR levels induced plasmolys~s and disol-ientation of cell organelles.