Influence of the Development and Destruction of Muddy Byssal Mats Made by a Mytilid Mussel, Musculista senhousia, on Seasonal Fluctuations of the Macrobenthic Community on Sandy Tidal Flats

Abstract

On the Midori River Tidal Flats, which face Ariake Bay in Kumamoto, Kyushu, Japan, the originally sandy sediment has recently become widely covered with muddy byssal mats created by mytilid musseles, Musculista senhousia. Since the formally dominant bivalves in the macrobenthic community, such as Tapes Ruditapes philippinarum, Mactra veneri-formis, and others, favor sandy sediment as their habitat, they have been excluded by the development of the muddy byssal mats. In this study, sediment covered such mats on the tidal flats was dug up to a depth of about 1 m with a power shovel fixed to a barge, with the aim of eliminating the muddy byssal mats, and restoring sandy surface sediment there. This operation was successful, and soon afterwards the two bivalves, T. R. philippinarum, and M. veneriformis, again became dominant in the macrobenthic community. The effect of digging up the sediment lasted through the year-long course of this study even though M. senhousia twice had a chance for dense recruitment of juveniles through reproduction. 56 m 2 ha 4 1994