Abstract
The effective function as anchoring materials of pebbles (mean diameter 30mm) or oyster shells (mean diameter 30mm) for enhancing the adhering strength of Zostera marina plants was clarified. The Z. marina plants collected at Mitsukuchi Bay, Hiroshima Prefecture, Seto Inland Sea, Japan were set for our experiments on the bottom of an outdoor 20ton capacity concrete water tank, by using commercial pebbles (mean diameter 30mm) or coarsely ground oyster shells (mean diameter 30mm) as anchoring material at a volume ratio 10%, 20%, 50% and 100% with sand or mud as the substrate. Test of the adhering strength by pulling out the rhizome of Z. marina plants was examined after the tank cultivation during periods of 3 months and 1.5 years. Maximum values of adhering strength in Z. marina plants were observed in the cases of mixing rate 20% of pebbles or oyster shells. On the other hand, the minimum values were confirmed for the cases of 100% pebbles or 100% oyster shells. These quantitative results on effective anchoring materials for artificial sandy bottoms for Zostera beds, indicate that improved design of actual sandy shallow bottom restoration for artificial sea coasts would be useful to enhance Z. marina beds.
