Seasonality in the Benthic Foraminiferal Community and the Life History of Trochammina Hadai Uchio in Hamana Lake, Japan
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Trochammina hadai Uchio is a dominant species in brackish waters of Japan. The life history of this species was investigated in Hamana Lake, central Japan. Samples were collected by SCUBA diving at a fixed station and on a monthly basis from 1987 to 1989. On these occasions, we also monitored water temperature, salinity and dissolved oxygen content.
Trochammina hadai lives in the top 1 cm of the sediment throughout the year. Its population density drastically changed from nearly 0 individuals/10cm2 during the summer to 830 individuals/10cm2 in the winter. The change in the density was closely related to the environmental conditions of the lake. Lake water had stagnated during summer, forming a vertical stratification with a bottom layer of low oxygen values and a high concentration of hydrogen sulfide in sediment.
The life cycle of T. hadai is yearly and biphasic. The microspheric generation mainly rises in spring and summer, whereas the megalospheric generation was found mostly in autumn. In the laboratory, higher growth rates were observed in juvenile (58 µm/month) than in adult specimens (34 µm/month).
In both, micro and megalospheric specimens, two morphotypes were distinguished in T. hadai. One type is relatively high trochospiral, has a lobate periphery and 4–5 chambers in the final whorl. The other is low trochospiral, has a smooth periphery and 5–7 chambers in the final whorl. Transitional types produced both morphotypes during different stages of their development. The seasonal change in morphotypes within the same specimen suggests that environmental parameters control the gross morphology in T. hadai.
KeywordsBottom Water Benthic Foraminifera Dissolve Oxygen Content Dead Individual Test Diameter
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- Boltovskoy, E. (1966) Depth at which foraminifera can survive in sediments, Contr. Cushman. Found. Foram. Res., 17, 43–45.Google Scholar
- Hamanako Branch of the Shizuoka Prefectural Experimental Laboratory for Fisheries (1984–87) Annual reports, 1984–87, Shizuoka Prefecture, Shizuoka, Japan.Google Scholar
- Hirano, R. and Okamoto, K. (1980) Studies on population dynamics of red tide organisms in Lake Hamana, Report of Environmental Sciences, B. 148-R14–8, Monbusho, 47–54.Google Scholar
- Ikeya, N. (1970) Population ecology of benthonic foraminifera in Ishikari Bay, Hokkaido, Japan, Records of Océanographie Works in Japan, 10, 153–191.Google Scholar
- Ikeya, N. (1977) Ecology of foraminifera in the Hamana Lake region on the Pacific coast of Japan, Rep. Fac. Sci., Shizuoka Univ., 11, 131–159.Google Scholar
- Ishiwada, Y. (1958) Recent foraminifera from the brackish lake Hamana-ko. Study on the brackish water, 3, Geol. Surv. Japan, Rep., 180, 1–19.Google Scholar
- Kitazato, H. (1981) Observation of behavior and mode of life of benthic foraminifers in laboratory, Geosci. Rep., Shizuoka Univ., 6, 61–71.Google Scholar
- Langer, M., Hottinger, L., and Huber, B. (1989) Functional morphology in low-diverse benthic foraminiferal assemblages from tidal flats of the North Sea, Senckenbergiana mark., 20, 81–99.Google Scholar
- Matoba, Y. (1970) Distribution of recent shallow water foraminifera of Matushima Bay, Miyagi Prefecture, Northeast Japan, Sci. Rep. Tohoku Univ., 2nd ser. (Geol.), 42:1–85.Google Scholar
- Sliter, W. V. (1965) Laboratory experiments on the life cycle and écologie controls of Rosalinaglobulcais d’Orbigny, J. Protozool. 12, 210–215.Google Scholar
- Sliter, W.V. (1968) Shell-material variation in the agglutinated foraminifer Trochamminapacifioa Cushman, Tulane Stud. Geol. Paleontol., 6, 80–84.Google Scholar
- Uchio, T. (1962a) Recent foraminifera thanatocoenoses of beach and nearshore sediments along the coast of Wakayama-ken, Japan, Seto Mar. Biol. Lab., Pub., 10, 133–144.Google Scholar
- Uchio, T. (1962b) Influence of the River Shinano on foraminifera and sediment grain sizedistribution, Seto Mar. Biol. Lab., Pub., 10, 363–392.Google Scholar
- Watanabe, K., Hino, A., and Hirano, R. (1980) Some observations on 1978 red tide bloomsin Shonai estuary, Shizuoka Prefecture, Bull. Plankton Soc. Japan, 27, 87–98.Google Scholar