The response of the early developmental stages of Laminaria japonica to enhanced ultraviolet-B radiation

The responses of the early development of Laminaria japonica collected from Kiaochow Bay in China to enhanced ultraviolet-B radiation (UV-B, 280–320 nm) were studied in the laboratory. The low UV-B radiations (11.7–23.4 J·m⁻²·d⁻¹) had no significant effects on zoospores attachment, but when the UV-B dose > 35.1 J·m⁻²·d⁻¹ the attachment decreased significantly compared with the control. Germination of embryospores was >93% under the low (11.7–35.1 J·m⁻²·d⁻¹) doses, and in the range of 78.5%–88.5% under the high (46.8–70.2 J·m⁻²·d⁻¹) UV-B doses, indicating a significant radiation effect. Under the higher UV-B exposure (35.1–70.2 J·m⁻²·d⁻¹), all of the few gametophytes formed from embryospores died 120 h post-release. After exposure to the low UV-B radiation (11.7–23.4 J·m⁻²·d⁻¹), the formation of sporophytes decreased and the female gametophyte clones increased compared with the control. However, the sex ratio and the relative growth of female gametophytes/sporophytes had not significantly changed. According to the results, enhanced UV-B radiation has a significant effect on the early development of L. japonica under laboratory conditions, suggesting that the UV-B radiation could not be overlooked as one of the important environmental factors influencing the ontogeny of macroalgae living in marine ecosystems. Supported by the Program for New Century Excellent Talents in University (Grant No. NCET-05-0597) and National Natural Science Foundation of China (Grant No. 30270258)