A submerged breakwater, its crest nearly coincided with the H.W.L., was constructed off Hagino, the Iburi Coast in Hokkaido. Echo-freindly units were used for this “high crest” submerged breakwater. The new units have large empty spaces to allow sunlight to go through onto the rock mound. A study on organisms attaching themselves and macrobenthos in the surroundings was performed over a period of 3 years. Kelp (Laminaria angustata) forests formed on the insidewalls of both units and the rock mound. The standing crop was 10-25 times that found on flat crest blocks (used as a control). This distinction was due to the complex unit structure and the variation in depth substrata. As the sand particle size on the landward side of the breakwater increased slightly with every year, macrobenthos such as annelida became more abundant. In addition, rock fish were seen to frequent the breakwater. The “high crest” submerged breakwater using the new units functioned not only protected the coast, but also acted as a rocky ecosystem and feeding point on the sandy bottom.
