Holocene relative sea-level changes in Hiroshima Bay were reconstructed from fossil ostracodes from a core, using a semi-quantitative method. In Hiroshima Bay, relative sea level rose rapidly (about 25 m) between ca. 9000 cal yr BP and ca. 5800 cal yr BP, after which it gradually fell (about 5 m) to its present level. The peak in relative sea level occurred at ca. 5800 cal yr BP. The sea-level curve for Hiroshima Bay is similar to curves for tectonically stable areas of Japan (e.g., Osaka Bay).

In Japan, a paralytic shellfish poison (PSP) event caused by Gymnodinium catenatum Graham, a naked, colonial and PSP dinoflagellate, was first reported from Senzaki Bay, western part of the Sea of Japan in 1986. Since then, the geographical distribution of this species seems to have expanded through West Japan. To clarify the possibility of its migration being due to anthropogenic agency the historical occurrence of G. catenatum in Japanese coastal waters was examined; core sediments that preserve an historical record of this species were collected from several coastal areas where it had been observed. From the cores collected from Imari Bay, smaller spherical cysts ornamented with fine reticulated structure and with epicystal archeopyle are found which are probably different from Gymnodinium nolleri. Low cyst concentrations of G. catenatum in these cores may have resulted from such a characteristic physiological feature as chain formation of its vegetative form. The earliest occurrence of this species was recorded in sediment of Omura Bay dated to ca. 1700 A.D. This fact strongly suggests that the occurrence of G. catenatum in Japan is natural and that it has not been artificially introduced from different areas.

Three brachiopod species, Marginatia burlingtonensis (Hall), Syringothyris transversa Minato and Rotaia hikoroichiensis sp. nov., are described from the Lower Carboniferous (Lower Visean) of the Shimoarisu, Yokota and Hikoroichi areas in the South Kitakami Belt (southern Kitakami Mountains), northeast Japan. The Marginatia-Syringothyris-Rotaia assemblage from the South Kitakami Belt indicates a palaeobiogeographical similarity between the South Kitakami Belt and the north Xinjiang-Inner Mongolia-Jilin region, i.e., the North China Province of S. Yang (1980) in Early Carboniferous time. Furthermore, the rugose corals Sugiyamaella, Yuanophyllum and Kueichouphyllum from the Lower Carboniferous (Upper Visean) of the South Kitakami Belt are strong evidence of a close connection between this region and the southern part of the North China Province, i.e., the Tianshan-Jilin Province of F. Yang (1994). These palaeobiogeographical data suggest that the South Kitakami region was the eastern extension of the Tianshan-Jilin Province, and located at the continental shelf bordering the eastern margin of North China (Sino-Korea) in the Early Carboniferous.

Live benthic foraminiferal assemblages from surface sediment in Osaka Bay collected in 1999 were analyzed to characterize the distribution of the modern foraminiferal assemblages. Foraminiferal assemblages were compared with those of previous studies to document environmental changes in Osaka Bay over the past 50 years.

Sixty-one species of foraminifera belonging to 37 genera were recognized from the 1999 surface sediment samples. An agglutinated assemblage containing Trochammina hadai and Eggerella advena is dominant in the inner part of the bay and is related to eutrophication. The foraminiferal assemblage in areas deeper than about 20 m is composed of Eggerella advena, Ammonia beccarii forma A, and Pseudorotalia gaimardii. This assemblage may be influenced by the large clockwise Okinose Circulation Current which extends throughout the western bay.

Foraminiferal assemblages in Osaka Bay have changed dramatically during the last 50 years. The Trochammina hadai-Eggerella advena assemblage became established in the inner part of the bay, reflecting eutrophication that progressed from the 1960s through the 1970s. This assemblage became dominant in 1983, and typically dominated the inner part of the bay. From 1983 to 1999, however, the abundance of taxa belonging to this assemblage decreased greatly following implementation of 1973 Osaka City bylaws that restricted wastewater discharge. Changes in benthic assemblages such as the decrease of Ammonia beccarii forma A and increase of Eggerella advena have occurred in response to decreased incidence of red tides, and floral change in the species that cause these tides. The results of this study demonstrate that the abundance and distribution of benthic foraminifers in Osaka Bay are intimately related to environmental changes related to the urbanization of coastal areas.

The Plio-Pleistocene Trophonopsis in northern Japan consists of seven species: T. kamchatkana (Dall), T. uyemurai (Yokoyama), T. sasae Sawada, T. vermeiji Amano, sp. nov., T. aff. densicostata Golikov in Golikov and Scarlato, T. aff. undocostata Golikov and Sirenko and T. sp.. Trophon toyamai Hatai and Nisiyama and T. kagaensis Hatai and Nisiyama are synonymous with Trophonopsis uyemurai. By the end of the early Pleistocene, T. uyemurai, T. sasae and T. vermeiji became extinct and T. aff. undocostata and T. sp. might have become extinct, owing to decrease of salinity in shallow water during the low stands of the glacial Pleistocene.