Sagami Bay
Coordinates: 35 ° 7 ′ 0 ″ N , 139 ° 23 ′ 0 ″ E
The Sagami Bay ( Jap. 相模湾 , Sagami-wan , also known as Sagami Gulf or Sagamibucht ) is located south of Kanagawa Prefecture in Honshu in central Japan . The Miura Peninsula in the east separates it from Tokyo Bay , and the Izu Peninsula borders it in the west. It is located about 40 km southwest of the capital Tokyo . In her opening out Sagami .
The sea area lying in front of it between the Bōsō Peninsula in the east and the Izu Peninsula in the west with the island of Izu-Ōshima in between is called Sagami-nada ( 相 模 灘 , also Sagami Lake ).
Biological exploration
One of the richest marine fauna communities on earth is at home on an area measuring only 1000 km² with an average depth of 1000 m. Soil-dwelling organisms , which are otherwise only known from deeper regions of the Pacific Ocean , occur in great diversity in a limited space. Research into this special marine fauna began with the work of the German zoologist Ludwig Döderlein (1855–1936), who lectured in natural sciences at the University of Tokyo between 1879 and 1881 . It is his merit that he was the first to draw the world's attention to the unusual biodiversity of Sagami Bay. It was also he who suggested to his Japanese colleagues in Tokyo the establishment of a marine biological station to systematically explore the fauna of Sagami Bay. Misaki seemed to him to be a suitable place, as the peninsula between Tokyo and Sagami Bay offered logistical advantages and was easy to reach from the capital. In 1886 the construction project for the station was realized and Japan received a center for marine biological research for the first time.
After the Second World War , various groups of fauna in the Sagami Bay were processed on the initiative of Michi-no-miya Hirohito (1901–1989). Hirohito was better known in his capacity as the Japanese emperor (posthumously as Shōwa-tennō), but he also operated a private research station on the southern tip of the Izu Peninsula. Here, by processing his expedition yields, he gave Japanese scientists the opportunity to do taxonomic work. Extensive monographs on the crustaceans , hydroids and sponges were published by the Verlag des Kaiserliches Household . The Emperor's impressive collections are now housed in the Showa Memorial Institute in Tsukuba north of Tokyo, which was built under the most modern of conservation principles. Only in the last 20 years has the Sagami Bay moved back into the focus of multidisciplinary research. Japanese and international scientists presented new results on the geology, oceanography and biology of the region through undertakings such as the Kaiko project and the Sagami project. The use of manned submersibles in particular brought new light to the communities on the deep sea floor.
oceanography
One reason for the high biodiversity of Sagami Bay is the meeting of two ocean currents in this area. A sea current approx. 100 km wide and with an average temperature of 24 ° C flows in a north-easterly direction from the area of the Philippine Islands along the east coast of Japan. This current enters Sagami Bay on the northernmost coast of the island and leaves it in a sharp bend to the east into the open ocean. The dark blue color of the water observed in summer gave it the name Kuroshio - the black river. Warm water and high nutrient content create the conditions for rich phyto and zooplankton levels in the sea. From the north, the cold Kuril Current from the Bering Sea brushes the Japanese coast towards the southwest. Both currents overlap in the Sagami Bay, with the colder water rising in the northern part and the warm water of the Kuroshio dominating in the southern part. However, there is no sharp dividing line - it shifts seasonally, often within a few days or even hours. The temperature gradient causes a mass extinction of many plankton organisms, which sink into the depths as organic rain and form the basis of food for the bottom dwellers. Pacific deep water is exchanged via the Sagami Trench , an approx. 80 km long tectonic channel that connects the bay with the Pacific in a westerly direction .
tectonics
Another favorable condition for the rich bottom fauna is the extremely structured soil relief of the Sagami Bay, which was already mentioned during the Challenger Expedition (1872–1876) and which owes its origin to the geological features. On the east coast of the main island of Honshu , two continental and oceanic plates meet - the Eurasian and Okhotsk and the Philippine and Pacific plates that slide underneath. In this collision zone , increased and sustained volcanic and seismic activity has been recorded since the Mesozoic , which ultimately formed the Japanese Islands. Dangers to humans arise from the side effects of the tectonic movements, which manifest themselves in volcanic eruptions , earthquakes and the floods known as tsunami . In the northwest of the bay was the epicenter of the Great Kanto earthquake of 1923, which almost completely destroyed the Yokohama-Tokyo conurbation. The tsunami alone reached a height of 11 meters and completely buried the Enoshima peninsula in the northern part of the bay under the water masses. The Sagami Bay and the Sagami Trench are part of the aforementioned subduction zone , which has been subject to subsidence at this point since the early Pleistocene , around 1.6 million years ago.
ecology
The 20th century probably brought about the most fundamental change for Sagami Bay, which did not remain without effects on deep-sea life. The formation of a gigantic economic center and the associated increase in population density changed the region dramatically. In addition, the water quality is impaired by the high intake of nutrients from the shallow Tokyo Bay in the south-east . Overfishing of coastal waters and the use of ground nets is another serious problem. Today, the dangers to biodiversity lie less in natural conditions than in humans themselves.
Individual evidence
literature
- EJH Corner: His Majesty Emperor Hirohito of Japan, KG April 29, 1901- January 7, 1989. In: Biographical Memoirs of Fellows of the Royal Society. 36. pp. 242-272, 1990.
- L. Döderlein: (1883): Faunistic studies in Japan. Enoshima and the Sagami-Bai. In: Archive for Natural History 49. 1883, pp. 102–123.
- F. Doflein: The deep sea fauna of the Sagami Bay. In: East Asia trip. Experiences and observations of a naturalist in China, Japan and Ceylon. Teubner, Leipzig / Berlin 1906, pp. 238-274.
- C. Eckert, D. Janussen: The glass sponges of the Sagami Bay and their exploration. In: Nature and Museum (Frankfurt) 135 (5/6). 2005, pp. 105-116.
- M. Hasyimoto (Ed.): Geology of Japan. In: Developments in Earth and Planetary Sciences. 8th 1991.
- Hirohito, his Majesty the Emperor of Japan: The hydrocorals and scleractinian corals of Sagami Bay. Ed. by Biological Laboratory, Imperial Household, Maruzen, Tokyo 1968.
- I. Ijima: Studies on the Hexactinellida. Contribution I. In: Journal of the College of Science. 15, Imperial University of Tokyo, 1901, pp. 1-299.
- I. Ijima: About the Hexactinellids I collected in the Sagami Sea. In: Negotiations of the 5th International Zoological Congress in Berlin: 1–4. Fischer, Jena 1902.
- H. Kitazato: “The project Sagami” - dynamic sedimentary processes of both organic and inorganic materials at continental margins with active tectonic forcing. In: Progress in Oceanography. 57. 2003, pp. 1-2.
- T. Kuroda: The Sea Shells of Sagami Bay, collected by His Majesty the Emperor of Japan. Biological Laboratory, Imperial Household, 741. Maruzen Co., Tokyo 1971.
- X. Le Pichon, K. Kobayashi, J.-P. Cadet, T. Iiyama, K. Nakamura, V. Pautot, Kaiko Scientific Crew: Project Kaiko - Introduction. In: Earth and Planetary Science Letters. 83. 1987, pp. 183-185.
- M. Matsuyama, H. Ishidoya, S. Iwata, Y. Kitade, H. Nagamatsu: Kyucho induced by intrusion of Kuroshio water in Sagami Bay, Japan. In: Continental Shelf Research. 19 (12). 1999, pp. 1561-1575.
- G. Müller (Ed.): The Challenger Expedition. To the deepest point of the world's oceans 1872–1876. Thienemann Edition Erdmann, Stuttgart 1984.
- I. Mutsu: Kamakura. Fact and Legend. Times Publ., Tokyo 1930.
- T. Sakai: The crabs of Sagami Bay, collected by His Majesty the Emperor of Japan. Ed. by the Biological Laboratory, Imperial Household. East-West Center Press, Honolulu / Tokyo 1965.
