No abstract

No abstract

SUMMARY Sediment loading by human activities has increased in recent years and sedimentation in coastal areas is problematic because it removes seaweed forests. In this study, we examined the effects of different sediment quantities (0, 2, 4, and 6 mg cm−2) and particles sizes (<100, 100–250, and 250–600 μm) on zygote attachment, and germling survival and growth of Sargassum thunbergii, an economically and ecologically important species. Zygote attachment was negatively correlated with increased sediment quantities. However, it was not significantly different among sediment particle sizes. In addition, survival and growth of germlings were significantly inhibited by increased sediment quantity. Smaller particle size (< 100 μm) had greater negative impact on the survival and growth than bigger ones. Results of the present study suggest that early development of S. thunbergii is significantly inhibited by sediment. This might be a vital factor that results in forest depletion in Korea.

Anthropogenic disturbances such as shoreline development and sediment loading can reduce or eliminate Nereocystis luetkeana populations and commercially important species associated with N. luetkeana. Hence, kelp restoration will become increasingly important in urbanized nearshore areas. Techniques to establish N. luetkeana populations in the northwestern waters of Washington State, USA, were examined and compared: (1) out-planting recently settled zoospores and microscopic sporophytes (0.5 to 1.0 mm blade length) grown in laboratory culture, in the field onto natural substrate, and at elevated positions, and (2) transplanting juvenile sporophytes (<15 cm stipe length) from natural populations, bypassing the culturing phase. Juvenile transplants were found to be more successful than cultured out-plants. The restoration cost for juvenile transplants was 12 US dollars (USD) per installed plant with a maximum cost estimate of 200 USD m -2 . These had a 10 to 30% higher survival rate than previously reported kelp transplant efforts using larger individuals. The collection of smaller individuals for transplanting imposes smaller ecological costs to natural populations than does the collection of larger, established plants. Stipe breakage caused by the grazing gastropod Lacuna vincta posed the largest limiting factor on transplant survival. Lack of survival among the out-planted zoospores and microscopic sporophytes indicates that other methods will be more successful. Restoration efforts in the nearshore marine environment will benefit from an adaptive management approach in which techniques can be tailored to the specific physical and biological conditions at the restoration site.

Twelve morphological characters and the biochemical composition of Undaria pinnatifida f. distans sporophytes growing on the rocky shores of Jindo and Wando and on cultivation ropes in Kijang were measured to determine whether each population could be characterized by morphological features and biochemical composition. The goal of this study was to compare phenotypic variations between populations as they relate to environmental conditions. The sporophytes of the Kijang population were two times longer and 19 times heavier than those at Jindo. Sporophylls of the Jindo U. pinnatifida population were significantly smaller in length, width, frill number, and weight than those at Wando and Kijang. Kijang Undaria plants showed the highest contents of total protein, crude fiber, total amino acids, the amount of essential amino acids, the proportion of total unsaturated fatty acids, and eicosapentaenoic acid. However, the Jindo population showed the greatest content of carbohydrates, lipids, and minerals (Zn and Ca) of the three U. pinnatifida populations. In particular, Zn content of Jindo plants was 30 times greater than that of Kijang plants. Thus, the proximate composition, mineral composition, amino acids, and fatty acids of Undaria pinnatifida plants were distinguishable among the three representative Undaria populations evaluated. These results suggest that morphological and biochemical differences of the three U. pinnatifida populations can be attributed to differences in environmental conditions of their habitats.