INFLUENCE OF ARTIFICIAL REEF SEDIMENT ON THE FORMATION OF THE TUBES OF SABELLARIID POLYCHAETES

Abstract

 There are two artificial reefs on the Iburi coast, Hokkaido, Japan. One is located off the coast of Shiraoi, where aggregations of Sabellariid polychaetes grow, and the other off the coast of Tomakomai, where this species is not found. We assessed and compared the characteristics of the bottom sediments of these two artificial reef areas. As a result, the silt and clay content rate in the seawater around the Tomakomai's artificial reef was 2.8 times higher than that around the Shiraoi's one. Laboratory experiments were carried out to investigate the ability to form the tube and the survival rate of this species in two different conditions. One is where the tube is buried in the bottom sediment and the other is where the tube stays in the suspended sand. The results showed that the survival rate of this species decreased significantly as the silt and clay content rate and the tube's burial depth increased. When the rate of sediment deposition into the tube exceeded the growth rate of the tube, it was speculated that this species died in it. The inhabit limit of this species was estimated using the estimating equation for the floating sand concentration in the breaker zone, which showed that the Tomakomai's artificial reef was an environment where the survival of this species was difficult.