Effects of acute and chronic UV-B exposure on a green alga: a continuous culture study using a computer-controlled dynamic light regime

Abstract

The green alga Selenastrum capricornutum was grown in a specially developed continuous culture system to study long-term effects of chronic W-B exposure. The new system improves upon previous laboratory culture approaches. It is demonstrated that short-term experiments underestimate W-B effects. It is also shown that photoinhibition cannot explain the effects under chronic exposure. Under both nutrient-replete and phosphorus-limiting conditions a W-B mediated delay in cell division rate and an increase in the cellular content of proteins, carbohydrates and chlorophyll a was measured. Transition experiments showed that complete acclimatisation to UV-B took several cell cycles. DNA damage appears to be the major cause of the observed long-term W-B effects. [KEYWORDS: algal growth, algal photosynthesis, green alga, phosphorus limitation, UV-B inhibition]