Growth, artificial seedling raising and cultivation of Sargassum confusum (Fucales, Phaeophyceae) inhabiting the coast of Shandong Peninsula, China

The seasonal growth, seedling raising and artificial cultivation of Sargassum confusum were studied along the coast of Dong Chudao at the mouth of Sanggou Bay (37°02′12″N, 122°33′51″E). We also compared the growth of juveniles at different temperatures (15, 18, 21, and 24 °C) and irradiances (60, 95, and 130 μmol photons m −2 s −1 ) when seedlings were raised in a greenhouse. Sargassum confusum in Sanggou Bay began to develop receptacles in early April when the seawater temperature reached 10.8 °C. The receptacles matured in July and released the eggs when the seawater temperature reached 21 °C. The S . confusum thallus grew to maximum mean length (126.6 ± 19.8 cm) and reached the highest mean biomass yield (192.2 ± 40 g dwt thallus −1 ) in July and then rapidly decayed. Both temperature and irradiance significantly affected the growth of S . confusum seedlings ( p < 0.05). The seedlings reached 1005 ± 47.6 μm at 21 °C and under 95 μmol photons m −2 s −1 in 2 weeks. The seedlings grew to approximately 0.5 cm in length in the seedling raising pools in approximately 5 weeks and reached 6 cm in the open sea nursery after an additional 4 months. The seedlings were then separated and inserted between the strands of vinylon ropes and cultivated in the open sea until early July when the seawater temperature reached approximately 21 °C and the maximum thalli length reached 116.4 cm on average. The dry weight of S . confusum harvested from a 4-m cultivation rope was 1.48 kg on average, and the dry weight yield was approximately 8.9 t ha −1 .