Various laboratory experiments were performed to examine the effects of H2S (Hydrogen Sulfide) on R. philippinarum in this study. These results were as follows. 1) Most of clam closed its shell, in case was placed in the anoxic water. However, the number of clam that opened its shell increased with time. 20 hours later, the dying clam appeared after the clam extended the siphon and pelecypod. 2) H2S exposure had an insignificant effect on the clam, they closed shells. However, the clam was significantly affected by H2S exposure when they opened its shell and extended siphon and pelecypod. 3) When the water was hypoxic or anoxic before Blue tide occurrence (Aoshio), the clam would directly suffer severe effects of H2S because the extended soft tissue from the inside of shell was exposed.
