Comparing the response of Antarctic, tropical and temperate microalgae to ultraviolet radiation (UVR) stress

The response of Antarctic, tropical and temperate microalgae of similar taxonomic grouping to ultraviolet radiation (UVR) stress was compared based on their growth and fatty acid profiles. Microalgae of similar taxa from the Antarctic (Chlamydomonas UMACC 229, Chlorella UMACC 237 and Navicula UMACC 231), tropical (Chlamydomonas augustae UMACC 246, Chlorella vulgaris UMACC 001 and Amphiprora UMACC 259) and temperate (Chlamydomonas augustae UMACC 247, Chlorella vulgaris UMACC 248 and Navicula incerta UMACC 249) regions were exposed to different UVR conditions. The cultures were exposed to the following conditions: PAR (42 mu mol photons m(-2) s(-1)), PAR + UVA (854 mu W cm(-2)) and PAR + UVA + UVB (117 mu W cm(-2)). The cultures were subjected to UVA doses of 46.1, 92.2 and 184.4 J cm(-2) and UVB doses of 6.3, 12.6 and 25.2 J cm(-2) by Varying the duration of their exposure (1.5, 3 and 6 h) to UVR during the light period (12:12 h light-dark cycle). UVA did not affect the growth of the microalgae, even at the highest dose. In contrast, growth was adversely affected by UVB, especially at the highest dose. The dose that caused 50% inhibition (ID50) in growth was used to assess the sensitivity of the microalgae to UVB. Sensitivity of the microalgae to UVB was species-dependent and also dependent on their biogeographic origin. Of the nine microalgae, the Antarctic Chlorella was most tolerant to UVB stress (ID50=21.0 J cm(-2)). Except for this Chlorella, the percentage of polyunsaturated fatty acids of the microalgae decreased in response to high doses of UVB. Fatty acid profile is a useful biomarker for UVB stress for some microalgae.