2003 Volume 57 Issue 1-2 Pages 31-48
The authors studied the benthic fauna living on the tidal flat at six survey locations in Matsukawa-ura, Fukushima Prefecture: the north side of Junihonmatsu (A), the west side of Kikaijima (B), Ushirowada (C), the mouth of Udagawa River (D), northwest of Unoosaki (E) and the north-west side of Oosu bar (F). Their composition and exo- and endogenic lebensspuren were observed. A quadrangle survey of the benthic fauna was carried out to determine weight of biomass, population density, co-existent fauna and depositional environment of the substratum of the lebensspuren at each survey point. Thirty-two species benthic animals were identified at A-E survey points. On the mouth of the Udagawa River (D) and northwest of Unoosaki (E), numbers of species is smaller than those at the other three locations. Ten bio-zones are recognized by dominant species (dominant benthos zones) from low to high tidal levels. The Scopimera globosa zone occurred at high tidal level has fewer biomass, while the Ilyoplax pusillus and Macrophthalmus (Mareotis) japonicus zones occurred at low tidal level have more biomass. The authors described the lebensspuren of nine kinds of benthic fauna, including crustaceans, bivalves, gastropods and nereids in terms of their apertures, digging structures, feeding pellets, vertical sections, surface of inner walls and lining of burrows and relationship between burrows and substrates. These data cannot be obtained by plaster casting method. The authors studied not only individual lebensspuren but also following related subjects: comparing the similarly-shaped burrows, for example, Macrophthalmus (Mareotis) japonicus and Helice tridens tridens, Scopimera globosa and Ilyoplax pusillus; difference in population density; modification of Ilyoplax pusillus burrows in the Ilyoplax pusillus-Helice tridens tridens zone; population density in the Ilyoplax pusillus-Macrophthalmus (Mareotis) japonicus zone; the existence of lining of inner walls. Conceptual model was made to show a cross-section of the lebensspuren assemblage. Diatom flora were preliminarily investigated on the portions of lebensspuren (aperture, lining material, digging structures, feeding pellets) and their surrounding bottom material.
