伊勢湾および三河湾の海底泥表層におけるAlexandrium属シストの現存量と分布

抄録

Abundance and distribution of resting cysts of toxic dinoflagellates, Alexandrium spp. (A. tamarense and/or A. catenella), were investigated in the surface sediments of Ise Bay and Mikawa Bay in June 2002, using primuline-staining direct count method. The cysts were abundant at innermost part and west of central part of Ise Bay, and eastern part of Mikawa Bay. The cyst density varied from 22 to 2,254 cysts cm^-3 wet sediment (mean=365 cysts cm^-3) and from 31 to 7,311 cysts cm^-3 wet sediment (mean=1,831 cysts cm^-3) in Ise Bay and Mikawa Bay, respectively, showing an increasing trend of cyst abundance from 1980’s when previous monitorings were conducted. It is also evident that, among bays reported so far in Japan, Ise Bay and Mikawa Bay are the ones having, respectively, the high and the highest cyst abundances. The cyst density in both bays tended to increase drastically where mud content exceeds ca. 70%, although this is not always the case. This may indicate that the selective mechanisms of sediment particles by physical factors, such as hydrographic and sedimentation processes, act on cysts strongly but the magnitude of cyst formation in the water column above the sediment also affects the cyst abundance simultaneously.