LAUSR

Cobalt (Co), an essential element that is toxic in excess amounts, is a major component of wastewater that has accidentally been released from nuclear power plants. However, the effects of Co in seawater on the life cycle of macroalgae have seldom been investigated. Here, we tested the effects of different Co concentrations (1, 10, 50, 100, 200, 500, and 1000 μg L−1) on spore germination, gametophyte growth and development, and juvenile sporophyte growth of the brown alga Saccharina japonica. Sterilized natural seawater with a known Co concentration was used as the control. The spore germination percentage in the 1000 μg L−1 group was significantly reduced after 1 and 2 days of exposure. The gametophyte growth in the 1 μg L−1 group was significantly accelerated, while that of the ≥ 50 μg L−1 groups was significantly inhibited after 9 days of exposure. The relative growth rate and maximum quantum yield (Fv/Fm) of photosystem II of the juvenile sporophytes in the 1 μg L−1 group were significantly higher, while those of the ≥ 10 μg L−1 groups were significantly lower after 2 weeks of exposure. By culturing the sporophytes in the control medium, Fv/Fm values recovered from Co stress within 4 days. These results highlight the potentially severe impact of accidentally released Co from nuclear power plants on the life cycle of S. japonica. Further studies should focus on the toxic mechanism of Co in S. japonica and the phytoremediation potential of seaweeds to alleviate Co pollution.