Short- and Long-term Effects of Typhoon 0418 on Macrobenthic Community in Tidal Flats on the Coast of Iwakuni in Hiroshima Bay

Abstract

The objective of this study is to clarify the effects of typhoon 0418 on the macrobenthic community in the tidal flats on the coast of Iwakuni in Hiroshima Bay, using monitoring data from 2001 to 2016. Zostera beds disappeared after typhoon 0418 hit in September 2004. The distribution area of the beds recovered to the pretyphoon level after more than eight years, because of two consecutive years of disturbance by typhoons. The bottom sediment of the tidal flats showed large fluctuations in the mud content, COD （ Chemical Oxygen Demand ） and IL （ Ignition Loss ） regardless of changes in the Zostera bed area. Macrobenthic communities showed a drastic decrease in number of species, number of individuals, wet weight and diversity （ H’ ） after typhoon 0418. These values were low during the deterioration period （ from just after typhoon 0418 to 2008 ） of Zostera beds, but became high during the recovery period （ 2009 and later ） . These results show that the presence of Zostera beds is important to the macrobenthic community in tidal flats and that typhoon 0418 had both short- and long-term effects on the macrobenthic community in the tidal flats as it caused physical disturbance and subsequent loss of Zostera beds.